void LLVMInitializeCore(LLVMPassRegistryRef R);
void LLVMInitializeTransformUtils(LLVMPassRegistryRef R);
void LLVMInitializeScalarOpts(LLVMPassRegistryRef R);
+void LLVMInitializeObjCARCOpts(LLVMPassRegistryRef R);
void LLVMInitializeVectorization(LLVMPassRegistryRef R);
void LLVMInitializeInstCombine(LLVMPassRegistryRef R);
void LLVMInitializeIPO(LLVMPassRegistryRef R);
/// ScalarOpts library.
void initializeScalarOpts(PassRegistry&);
+/// initializeObjCARCOpts - Initialize all passes linked into the ObjCARCOpts
+/// library.
+void initializeObjCARCOpts(PassRegistry&);
+
/// initializeVectorization - Initialize all passes linked into the
/// Vectorize library.
void initializeVectorization(PassRegistry&);
#include "llvm/IR/Function.h"
#include "llvm/Transforms/IPO.h"
#include "llvm/Transforms/Instrumentation.h"
+#include "llvm/Transforms/ObjCARC.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/UnifyFunctionExitNodes.h"
#include "llvm/Transforms/Vectorize.h"
--- /dev/null
+//===-- ObjCARC.h - ObjCARC Scalar Transformations --------------*- C++ -*-===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This header file defines prototypes for accessor functions that expose passes
+// in the ObjCARC Scalar Transformations library.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TRANSFORMS_OBJCARC_H
+#define LLVM_TRANSFORMS_OBJCARC_H
+
+namespace llvm {
+
+class Pass;
+
+//===----------------------------------------------------------------------===//
+//
+// ObjCARCAPElim - ObjC ARC autorelease pool elimination.
+//
+Pass *createObjCARCAPElimPass();
+
+//===----------------------------------------------------------------------===//
+//
+// ObjCARCExpand - ObjC ARC preliminary simplifications.
+//
+Pass *createObjCARCExpandPass();
+
+//===----------------------------------------------------------------------===//
+//
+// ObjCARCContract - Late ObjC ARC cleanups.
+//
+Pass *createObjCARCContractPass();
+
+//===----------------------------------------------------------------------===//
+//
+// ObjCARCOpt - ObjC ARC optimization.
+//
+Pass *createObjCARCOptPass();
+
+} // End llvm namespace
+
+#endif
+
//
Pass *createCorrelatedValuePropagationPass();
-//===----------------------------------------------------------------------===//
-//
-// ObjCARCAPElim - ObjC ARC autorelease pool elimination.
-//
-Pass *createObjCARCAPElimPass();
-
-//===----------------------------------------------------------------------===//
-//
-// ObjCARCExpand - ObjC ARC preliminary simplifications.
-//
-Pass *createObjCARCExpandPass();
-
-//===----------------------------------------------------------------------===//
-//
-// ObjCARCContract - Late ObjC ARC cleanups.
-//
-Pass *createObjCARCContractPass();
-
-//===----------------------------------------------------------------------===//
-//
-// ObjCARCOpt - ObjC ARC optimization.
-//
-Pass *createObjCARCOptPass();
-
//===----------------------------------------------------------------------===//
//
// InstructionSimplifier - Remove redundant instructions.
type = Library
name = CodeGen
parent = Libraries
-required_libraries = Analysis Core MC Scalar Support Target TransformUtils
+required_libraries = Analysis Core MC Scalar Support Target TransformUtils ObjCARC
add_subdirectory(IPO)
add_subdirectory(Vectorize)
add_subdirectory(Hello)
+add_subdirectory(ObjCARC)
name = IPO
parent = Transforms
library_name = ipo
-required_libraries = Analysis Core IPA InstCombine Scalar Vectorize Support Target TransformUtils
+required_libraries = Analysis Core IPA InstCombine Scalar Vectorize Support Target TransformUtils ObjCARC
;===------------------------------------------------------------------------===;
[common]
-subdirectories = IPO InstCombine Instrumentation Scalar Utils Vectorize
+subdirectories = IPO InstCombine Instrumentation Scalar Utils Vectorize ObjCARC
[component_0]
type = Group
##===----------------------------------------------------------------------===##
LEVEL = ../..
-PARALLEL_DIRS = Utils Instrumentation Scalar InstCombine IPO Vectorize Hello
+PARALLEL_DIRS = Utils Instrumentation Scalar InstCombine IPO Vectorize Hello ObjCARC
include $(LEVEL)/Makefile.config
--- /dev/null
+add_llvm_library(LLVMObjCARCOpts
+ ObjCARC.cpp
+ ObjCARCOpts.cpp
+ )
+
+add_dependencies(LLVMObjCARCOpts intrinsics_gen)
--- /dev/null
+;===- ./lib/Transforms/ObjCARC/LLVMBuild.txt --- ---------*- Conf -*--===;
+;
+; The LLVM Compiler Infrastructure
+;
+; This file is distributed under the University of Illinois Open Source
+; License. See LICENSE.TXT for details.
+;
+;===------------------------------------------------------------------------===;
+;
+; This is an LLVMBuild description file for the components in this subdirectory.
+;
+; For more information on the LLVMBuild system, please see:
+;
+; http://llvm.org/docs/LLVMBuild.html
+;
+;===------------------------------------------------------------------------===;
+
+[component_0]
+type = Library
+name = ObjCARC
+parent = Transforms
+library_name = ObjCARCOpts
+required_libraries = Analysis Core InstCombine Support Target TransformUtils
--- /dev/null
+##===- lib/Transforms/ObjCARC/Makefile ---------------------*- Makefile -*-===##
+#
+# The LLVM Compiler Infrastructure
+#
+# This file is distributed under the University of Illinois Open Source
+# License. See LICENSE.TXT for details.
+#
+##===----------------------------------------------------------------------===##
+
+LEVEL = ../../..
+LIBRARYNAME = LLVMObjCARCOpts
+BUILD_ARCHIVE = 1
+
+include $(LEVEL)/Makefile.common
+
--- /dev/null
+//===-- ObjCARC.cpp --------------------------------------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements common infrastructure for libLLVMObjCARCOpts.a, which
+// implements several scalar transformations over the LLVM intermediate
+// representation, including the C bindings for that library.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Transforms/ObjCARC.h"
+#include "llvm-c/Initialization.h"
+#include "llvm/Analysis/Passes.h"
+#include "llvm/Analysis/Verifier.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/PassManager.h"
+
+using namespace llvm;
+
+/// initializeObjCARCOptsPasses - Initialize all passes linked into the
+/// ObjCARCOpts library.
+void llvm::initializeObjCARCOpts(PassRegistry &Registry) {
+ initializeObjCARCAliasAnalysisPass(Registry);
+ initializeObjCARCAPElimPass(Registry);
+ initializeObjCARCExpandPass(Registry);
+ initializeObjCARCContractPass(Registry);
+ initializeObjCARCOptPass(Registry);
+}
+
+void LLVMInitializeObjCARCOpts(LLVMPassRegistryRef R) {
+ initializeObjCARCOpts(*unwrap(R));
+}
--- /dev/null
+//===- ObjCARCOpts.cpp - ObjC ARC Optimization ----------------------------===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+/// \file
+/// This file defines ObjC ARC optimizations. ARC stands for Automatic
+/// Reference Counting and is a system for managing reference counts for objects
+/// in Objective C.
+///
+/// The optimizations performed include elimination of redundant, partially
+/// redundant, and inconsequential reference count operations, elimination of
+/// redundant weak pointer operations, pattern-matching and replacement of
+/// low-level operations into higher-level operations, and numerous minor
+/// simplifications.
+///
+/// This file also defines a simple ARC-aware AliasAnalysis.
+///
+/// WARNING: This file knows about certain library functions. It recognizes them
+/// by name, and hardwires knowledge of their semantics.
+///
+/// WARNING: This file knows about how certain Objective-C library functions are
+/// used. Naive LLVM IR transformations which would otherwise be
+/// behavior-preserving may break these assumptions.
+///
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "objc-arc"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/raw_ostream.h"
+using namespace llvm;
+
+/// \brief A handy option to enable/disable all optimizations in this file.
+static cl::opt<bool> EnableARCOpts("enable-objc-arc-opts", cl::init(true));
+
+/// \defgroup MiscUtils Miscellaneous utilities that are not ARC specific.
+/// @{
+
+namespace {
+ /// \brief An associative container with fast insertion-order (deterministic)
+ /// iteration over its elements. Plus the special blot operation.
+ template<class KeyT, class ValueT>
+ class MapVector {
+ /// Map keys to indices in Vector.
+ typedef DenseMap<KeyT, size_t> MapTy;
+ MapTy Map;
+
+ typedef std::vector<std::pair<KeyT, ValueT> > VectorTy;
+ /// Keys and values.
+ VectorTy Vector;
+
+ public:
+ typedef typename VectorTy::iterator iterator;
+ typedef typename VectorTy::const_iterator const_iterator;
+ iterator begin() { return Vector.begin(); }
+ iterator end() { return Vector.end(); }
+ const_iterator begin() const { return Vector.begin(); }
+ const_iterator end() const { return Vector.end(); }
+
+#ifdef XDEBUG
+ ~MapVector() {
+ assert(Vector.size() >= Map.size()); // May differ due to blotting.
+ for (typename MapTy::const_iterator I = Map.begin(), E = Map.end();
+ I != E; ++I) {
+ assert(I->second < Vector.size());
+ assert(Vector[I->second].first == I->first);
+ }
+ for (typename VectorTy::const_iterator I = Vector.begin(),
+ E = Vector.end(); I != E; ++I)
+ assert(!I->first ||
+ (Map.count(I->first) &&
+ Map[I->first] == size_t(I - Vector.begin())));
+ }
+#endif
+
+ ValueT &operator[](const KeyT &Arg) {
+ std::pair<typename MapTy::iterator, bool> Pair =
+ Map.insert(std::make_pair(Arg, size_t(0)));
+ if (Pair.second) {
+ size_t Num = Vector.size();
+ Pair.first->second = Num;
+ Vector.push_back(std::make_pair(Arg, ValueT()));
+ return Vector[Num].second;
+ }
+ return Vector[Pair.first->second].second;
+ }
+
+ std::pair<iterator, bool>
+ insert(const std::pair<KeyT, ValueT> &InsertPair) {
+ std::pair<typename MapTy::iterator, bool> Pair =
+ Map.insert(std::make_pair(InsertPair.first, size_t(0)));
+ if (Pair.second) {
+ size_t Num = Vector.size();
+ Pair.first->second = Num;
+ Vector.push_back(InsertPair);
+ return std::make_pair(Vector.begin() + Num, true);
+ }
+ return std::make_pair(Vector.begin() + Pair.first->second, false);
+ }
+
+ const_iterator find(const KeyT &Key) const {
+ typename MapTy::const_iterator It = Map.find(Key);
+ if (It == Map.end()) return Vector.end();
+ return Vector.begin() + It->second;
+ }
+
+ /// This is similar to erase, but instead of removing the element from the
+ /// vector, it just zeros out the key in the vector. This leaves iterators
+ /// intact, but clients must be prepared for zeroed-out keys when iterating.
+ void blot(const KeyT &Key) {
+ typename MapTy::iterator It = Map.find(Key);
+ if (It == Map.end()) return;
+ Vector[It->second].first = KeyT();
+ Map.erase(It);
+ }
+
+ void clear() {
+ Map.clear();
+ Vector.clear();
+ }
+ };
+}
+
+/// @}
+///
+/// \defgroup ARCUtilities Utility declarations/definitions specific to ARC.
+/// @{
+
+#include "llvm/ADT/StringSwitch.h"
+#include "llvm/Analysis/ValueTracking.h"
+#include "llvm/IR/Intrinsics.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Support/CallSite.h"
+#include "llvm/Transforms/Utils/Local.h"
+
+namespace {
+ /// \enum InstructionClass
+ /// \brief A simple classification for instructions.
+ enum InstructionClass {
+ IC_Retain, ///< objc_retain
+ IC_RetainRV, ///< objc_retainAutoreleasedReturnValue
+ IC_RetainBlock, ///< objc_retainBlock
+ IC_Release, ///< objc_release
+ IC_Autorelease, ///< objc_autorelease
+ IC_AutoreleaseRV, ///< objc_autoreleaseReturnValue
+ IC_AutoreleasepoolPush, ///< objc_autoreleasePoolPush
+ IC_AutoreleasepoolPop, ///< objc_autoreleasePoolPop
+ IC_NoopCast, ///< objc_retainedObject, etc.
+ IC_FusedRetainAutorelease, ///< objc_retainAutorelease
+ IC_FusedRetainAutoreleaseRV, ///< objc_retainAutoreleaseReturnValue
+ IC_LoadWeakRetained, ///< objc_loadWeakRetained (primitive)
+ IC_StoreWeak, ///< objc_storeWeak (primitive)
+ IC_InitWeak, ///< objc_initWeak (derived)
+ IC_LoadWeak, ///< objc_loadWeak (derived)
+ IC_MoveWeak, ///< objc_moveWeak (derived)
+ IC_CopyWeak, ///< objc_copyWeak (derived)
+ IC_DestroyWeak, ///< objc_destroyWeak (derived)
+ IC_StoreStrong, ///< objc_storeStrong (derived)
+ IC_CallOrUser, ///< could call objc_release and/or "use" pointers
+ IC_Call, ///< could call objc_release
+ IC_User, ///< could "use" a pointer
+ IC_None ///< anything else
+ };
+
+ raw_ostream &operator<<(raw_ostream &OS, const InstructionClass Class)
+ LLVM_ATTRIBUTE_USED;
+ raw_ostream &operator<<(raw_ostream &OS, const InstructionClass Class) {
+ switch (Class) {
+ case IC_Retain:
+ return OS << "IC_Retain";
+ case IC_RetainRV:
+ return OS << "IC_RetainRV";
+ case IC_RetainBlock:
+ return OS << "IC_RetainBlock";
+ case IC_Release:
+ return OS << "IC_Release";
+ case IC_Autorelease:
+ return OS << "IC_Autorelease";
+ case IC_AutoreleaseRV:
+ return OS << "IC_AutoreleaseRV";
+ case IC_AutoreleasepoolPush:
+ return OS << "IC_AutoreleasepoolPush";
+ case IC_AutoreleasepoolPop:
+ return OS << "IC_AutoreleasepoolPop";
+ case IC_NoopCast:
+ return OS << "IC_NoopCast";
+ case IC_FusedRetainAutorelease:
+ return OS << "IC_FusedRetainAutorelease";
+ case IC_FusedRetainAutoreleaseRV:
+ return OS << "IC_FusedRetainAutoreleaseRV";
+ case IC_LoadWeakRetained:
+ return OS << "IC_LoadWeakRetained";
+ case IC_StoreWeak:
+ return OS << "IC_StoreWeak";
+ case IC_InitWeak:
+ return OS << "IC_InitWeak";
+ case IC_LoadWeak:
+ return OS << "IC_LoadWeak";
+ case IC_MoveWeak:
+ return OS << "IC_MoveWeak";
+ case IC_CopyWeak:
+ return OS << "IC_CopyWeak";
+ case IC_DestroyWeak:
+ return OS << "IC_DestroyWeak";
+ case IC_StoreStrong:
+ return OS << "IC_StoreStrong";
+ case IC_CallOrUser:
+ return OS << "IC_CallOrUser";
+ case IC_Call:
+ return OS << "IC_Call";
+ case IC_User:
+ return OS << "IC_User";
+ case IC_None:
+ return OS << "IC_None";
+ }
+ llvm_unreachable("Unknown instruction class!");
+ }
+}
+
+/// \brief Test whether the given value is possible a retainable object pointer.
+static bool IsPotentialRetainableObjPtr(const Value *Op) {
+ // Pointers to static or stack storage are not valid retainable object pointers.
+ if (isa<Constant>(Op) || isa<AllocaInst>(Op))
+ return false;
+ // Special arguments can not be a valid retainable object pointer.
+ if (const Argument *Arg = dyn_cast<Argument>(Op))
+ if (Arg->hasByValAttr() ||
+ Arg->hasNestAttr() ||
+ Arg->hasStructRetAttr())
+ return false;
+ // Only consider values with pointer types.
+ //
+ // It seemes intuitive to exclude function pointer types as well, since
+ // functions are never retainable object pointers, however clang occasionally
+ // bitcasts retainable object pointers to function-pointer type temporarily.
+ PointerType *Ty = dyn_cast<PointerType>(Op->getType());
+ if (!Ty)
+ return false;
+ // Conservatively assume anything else is a potential retainable object pointer.
+ return true;
+}
+
+/// \brief Helper for GetInstructionClass. Determines what kind of construct CS
+/// is.
+static InstructionClass GetCallSiteClass(ImmutableCallSite CS) {
+ for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
+ I != E; ++I)
+ if (IsPotentialRetainableObjPtr(*I))
+ return CS.onlyReadsMemory() ? IC_User : IC_CallOrUser;
+
+ return CS.onlyReadsMemory() ? IC_None : IC_Call;
+}
+
+/// \brief Determine if F is one of the special known Functions. If it isn't,
+/// return IC_CallOrUser.
+static InstructionClass GetFunctionClass(const Function *F) {
+ Function::const_arg_iterator AI = F->arg_begin(), AE = F->arg_end();
+
+ // No arguments.
+ if (AI == AE)
+ return StringSwitch<InstructionClass>(F->getName())
+ .Case("objc_autoreleasePoolPush", IC_AutoreleasepoolPush)
+ .Default(IC_CallOrUser);
+
+ // One argument.
+ const Argument *A0 = AI++;
+ if (AI == AE)
+ // Argument is a pointer.
+ if (PointerType *PTy = dyn_cast<PointerType>(A0->getType())) {
+ Type *ETy = PTy->getElementType();
+ // Argument is i8*.
+ if (ETy->isIntegerTy(8))
+ return StringSwitch<InstructionClass>(F->getName())
+ .Case("objc_retain", IC_Retain)
+ .Case("objc_retainAutoreleasedReturnValue", IC_RetainRV)
+ .Case("objc_retainBlock", IC_RetainBlock)
+ .Case("objc_release", IC_Release)
+ .Case("objc_autorelease", IC_Autorelease)
+ .Case("objc_autoreleaseReturnValue", IC_AutoreleaseRV)
+ .Case("objc_autoreleasePoolPop", IC_AutoreleasepoolPop)
+ .Case("objc_retainedObject", IC_NoopCast)
+ .Case("objc_unretainedObject", IC_NoopCast)
+ .Case("objc_unretainedPointer", IC_NoopCast)
+ .Case("objc_retain_autorelease", IC_FusedRetainAutorelease)
+ .Case("objc_retainAutorelease", IC_FusedRetainAutorelease)
+ .Case("objc_retainAutoreleaseReturnValue",IC_FusedRetainAutoreleaseRV)
+ .Default(IC_CallOrUser);
+
+ // Argument is i8**
+ if (PointerType *Pte = dyn_cast<PointerType>(ETy))
+ if (Pte->getElementType()->isIntegerTy(8))
+ return StringSwitch<InstructionClass>(F->getName())
+ .Case("objc_loadWeakRetained", IC_LoadWeakRetained)
+ .Case("objc_loadWeak", IC_LoadWeak)
+ .Case("objc_destroyWeak", IC_DestroyWeak)
+ .Default(IC_CallOrUser);
+ }
+
+ // Two arguments, first is i8**.
+ const Argument *A1 = AI++;
+ if (AI == AE)
+ if (PointerType *PTy = dyn_cast<PointerType>(A0->getType()))
+ if (PointerType *Pte = dyn_cast<PointerType>(PTy->getElementType()))
+ if (Pte->getElementType()->isIntegerTy(8))
+ if (PointerType *PTy1 = dyn_cast<PointerType>(A1->getType())) {
+ Type *ETy1 = PTy1->getElementType();
+ // Second argument is i8*
+ if (ETy1->isIntegerTy(8))
+ return StringSwitch<InstructionClass>(F->getName())
+ .Case("objc_storeWeak", IC_StoreWeak)
+ .Case("objc_initWeak", IC_InitWeak)
+ .Case("objc_storeStrong", IC_StoreStrong)
+ .Default(IC_CallOrUser);
+ // Second argument is i8**.
+ if (PointerType *Pte1 = dyn_cast<PointerType>(ETy1))
+ if (Pte1->getElementType()->isIntegerTy(8))
+ return StringSwitch<InstructionClass>(F->getName())
+ .Case("objc_moveWeak", IC_MoveWeak)
+ .Case("objc_copyWeak", IC_CopyWeak)
+ .Default(IC_CallOrUser);
+ }
+
+ // Anything else.
+ return IC_CallOrUser;
+}
+
+/// \brief Determine what kind of construct V is.
+static InstructionClass GetInstructionClass(const Value *V) {
+ if (const Instruction *I = dyn_cast<Instruction>(V)) {
+ // Any instruction other than bitcast and gep with a pointer operand have a
+ // use of an objc pointer. Bitcasts, GEPs, Selects, PHIs transfer a pointer
+ // to a subsequent use, rather than using it themselves, in this sense.
+ // As a short cut, several other opcodes are known to have no pointer
+ // operands of interest. And ret is never followed by a release, so it's
+ // not interesting to examine.
+ switch (I->getOpcode()) {
+ case Instruction::Call: {
+ const CallInst *CI = cast<CallInst>(I);
+ // Check for calls to special functions.
+ if (const Function *F = CI->getCalledFunction()) {
+ InstructionClass Class = GetFunctionClass(F);
+ if (Class != IC_CallOrUser)
+ return Class;
+
+ // None of the intrinsic functions do objc_release. For intrinsics, the
+ // only question is whether or not they may be users.
+ switch (F->getIntrinsicID()) {
+ case Intrinsic::returnaddress: case Intrinsic::frameaddress:
+ case Intrinsic::stacksave: case Intrinsic::stackrestore:
+ case Intrinsic::vastart: case Intrinsic::vacopy: case Intrinsic::vaend:
+ case Intrinsic::objectsize: case Intrinsic::prefetch:
+ case Intrinsic::stackprotector:
+ case Intrinsic::eh_return_i32: case Intrinsic::eh_return_i64:
+ case Intrinsic::eh_typeid_for: case Intrinsic::eh_dwarf_cfa:
+ case Intrinsic::eh_sjlj_lsda: case Intrinsic::eh_sjlj_functioncontext:
+ case Intrinsic::init_trampoline: case Intrinsic::adjust_trampoline:
+ case Intrinsic::lifetime_start: case Intrinsic::lifetime_end:
+ case Intrinsic::invariant_start: case Intrinsic::invariant_end:
+ // Don't let dbg info affect our results.
+ case Intrinsic::dbg_declare: case Intrinsic::dbg_value:
+ // Short cut: Some intrinsics obviously don't use ObjC pointers.
+ return IC_None;
+ default:
+ break;
+ }
+ }
+ return GetCallSiteClass(CI);
+ }
+ case Instruction::Invoke:
+ return GetCallSiteClass(cast<InvokeInst>(I));
+ case Instruction::BitCast:
+ case Instruction::GetElementPtr:
+ case Instruction::Select: case Instruction::PHI:
+ case Instruction::Ret: case Instruction::Br:
+ case Instruction::Switch: case Instruction::IndirectBr:
+ case Instruction::Alloca: case Instruction::VAArg:
+ case Instruction::Add: case Instruction::FAdd:
+ case Instruction::Sub: case Instruction::FSub:
+ case Instruction::Mul: case Instruction::FMul:
+ case Instruction::SDiv: case Instruction::UDiv: case Instruction::FDiv:
+ case Instruction::SRem: case Instruction::URem: case Instruction::FRem:
+ case Instruction::Shl: case Instruction::LShr: case Instruction::AShr:
+ case Instruction::And: case Instruction::Or: case Instruction::Xor:
+ case Instruction::SExt: case Instruction::ZExt: case Instruction::Trunc:
+ case Instruction::IntToPtr: case Instruction::FCmp:
+ case Instruction::FPTrunc: case Instruction::FPExt:
+ case Instruction::FPToUI: case Instruction::FPToSI:
+ case Instruction::UIToFP: case Instruction::SIToFP:
+ case Instruction::InsertElement: case Instruction::ExtractElement:
+ case Instruction::ShuffleVector:
+ case Instruction::ExtractValue:
+ break;
+ case Instruction::ICmp:
+ // Comparing a pointer with null, or any other constant, isn't an
+ // interesting use, because we don't care what the pointer points to, or
+ // about the values of any other dynamic reference-counted pointers.
+ if (IsPotentialRetainableObjPtr(I->getOperand(1)))
+ return IC_User;
+ break;
+ default:
+ // For anything else, check all the operands.
+ // Note that this includes both operands of a Store: while the first
+ // operand isn't actually being dereferenced, it is being stored to
+ // memory where we can no longer track who might read it and dereference
+ // it, so we have to consider it potentially used.
+ for (User::const_op_iterator OI = I->op_begin(), OE = I->op_end();
+ OI != OE; ++OI)
+ if (IsPotentialRetainableObjPtr(*OI))
+ return IC_User;
+ }
+ }
+
+ // Otherwise, it's totally inert for ARC purposes.
+ return IC_None;
+}
+
+/// \brief Determine which objc runtime call instruction class V belongs to.
+///
+/// This is similar to GetInstructionClass except that it only detects objc
+/// runtime calls. This allows it to be faster.
+///
+static InstructionClass GetBasicInstructionClass(const Value *V) {
+ if (const CallInst *CI = dyn_cast<CallInst>(V)) {
+ if (const Function *F = CI->getCalledFunction())
+ return GetFunctionClass(F);
+ // Otherwise, be conservative.
+ return IC_CallOrUser;
+ }
+
+ // Otherwise, be conservative.
+ return isa<InvokeInst>(V) ? IC_CallOrUser : IC_User;
+}
+
+/// \brief Test if the given class is objc_retain or equivalent.
+static bool IsRetain(InstructionClass Class) {
+ return Class == IC_Retain ||
+ Class == IC_RetainRV;
+}
+
+/// \brief Test if the given class is objc_autorelease or equivalent.
+static bool IsAutorelease(InstructionClass Class) {
+ return Class == IC_Autorelease ||
+ Class == IC_AutoreleaseRV;
+}
+
+/// \brief Test if the given class represents instructions which return their
+/// argument verbatim.
+static bool IsForwarding(InstructionClass Class) {
+ // objc_retainBlock technically doesn't always return its argument
+ // verbatim, but it doesn't matter for our purposes here.
+ return Class == IC_Retain ||
+ Class == IC_RetainRV ||
+ Class == IC_Autorelease ||
+ Class == IC_AutoreleaseRV ||
+ Class == IC_RetainBlock ||
+ Class == IC_NoopCast;
+}
+
+/// \brief Test if the given class represents instructions which do nothing if
+/// passed a null pointer.
+static bool IsNoopOnNull(InstructionClass Class) {
+ return Class == IC_Retain ||
+ Class == IC_RetainRV ||
+ Class == IC_Release ||
+ Class == IC_Autorelease ||
+ Class == IC_AutoreleaseRV ||
+ Class == IC_RetainBlock;
+}
+
+/// \brief Test if the given class represents instructions which are always safe
+/// to mark with the "tail" keyword.
+static bool IsAlwaysTail(InstructionClass Class) {
+ // IC_RetainBlock may be given a stack argument.
+ return Class == IC_Retain ||
+ Class == IC_RetainRV ||
+ Class == IC_AutoreleaseRV;
+}
+
+/// \brief Test if the given class represents instructions which are never safe
+/// to mark with the "tail" keyword.
+static bool IsNeverTail(InstructionClass Class) {
+ /// It is never safe to tail call objc_autorelease since by tail calling
+ /// objc_autorelease, we also tail call -[NSObject autorelease] which supports
+ /// fast autoreleasing causing our object to be potentially reclaimed from the
+ /// autorelease pool which violates the semantics of __autoreleasing types in
+ /// ARC.
+ return Class == IC_Autorelease;
+}
+
+/// \brief Test if the given class represents instructions which are always safe
+/// to mark with the nounwind attribute.
+static bool IsNoThrow(InstructionClass Class) {
+ // objc_retainBlock is not nounwind because it calls user copy constructors
+ // which could theoretically throw.
+ return Class == IC_Retain ||
+ Class == IC_RetainRV ||
+ Class == IC_Release ||
+ Class == IC_Autorelease ||
+ Class == IC_AutoreleaseRV ||
+ Class == IC_AutoreleasepoolPush ||
+ Class == IC_AutoreleasepoolPop;
+}
+
+/// \brief Erase the given instruction.
+///
+/// Many ObjC calls return their argument verbatim,
+/// so if it's such a call and the return value has users, replace them with the
+/// argument value.
+///
+static void EraseInstruction(Instruction *CI) {
+ Value *OldArg = cast<CallInst>(CI)->getArgOperand(0);
+
+ bool Unused = CI->use_empty();
+
+ if (!Unused) {
+ // Replace the return value with the argument.
+ assert(IsForwarding(GetBasicInstructionClass(CI)) &&
+ "Can't delete non-forwarding instruction with users!");
+ CI->replaceAllUsesWith(OldArg);
+ }
+
+ CI->eraseFromParent();
+
+ if (Unused)
+ RecursivelyDeleteTriviallyDeadInstructions(OldArg);
+}
+
+/// \brief This is a wrapper around getUnderlyingObject which also knows how to
+/// look through objc_retain and objc_autorelease calls, which we know to return
+/// their argument verbatim.
+static const Value *GetUnderlyingObjCPtr(const Value *V) {
+ for (;;) {
+ V = GetUnderlyingObject(V);
+ if (!IsForwarding(GetBasicInstructionClass(V)))
+ break;
+ V = cast<CallInst>(V)->getArgOperand(0);
+ }
+
+ return V;
+}
+
+/// \brief This is a wrapper around Value::stripPointerCasts which also knows
+/// how to look through objc_retain and objc_autorelease calls, which we know to
+/// return their argument verbatim.
+static const Value *StripPointerCastsAndObjCCalls(const Value *V) {
+ for (;;) {
+ V = V->stripPointerCasts();
+ if (!IsForwarding(GetBasicInstructionClass(V)))
+ break;
+ V = cast<CallInst>(V)->getArgOperand(0);
+ }
+ return V;
+}
+
+/// \brief This is a wrapper around Value::stripPointerCasts which also knows
+/// how to look through objc_retain and objc_autorelease calls, which we know to
+/// return their argument verbatim.
+static Value *StripPointerCastsAndObjCCalls(Value *V) {
+ for (;;) {
+ V = V->stripPointerCasts();
+ if (!IsForwarding(GetBasicInstructionClass(V)))
+ break;
+ V = cast<CallInst>(V)->getArgOperand(0);
+ }
+ return V;
+}
+
+/// \brief Assuming the given instruction is one of the special calls such as
+/// objc_retain or objc_release, return the argument value, stripped of no-op
+/// casts and forwarding calls.
+static Value *GetObjCArg(Value *Inst) {
+ return StripPointerCastsAndObjCCalls(cast<CallInst>(Inst)->getArgOperand(0));
+}
+
+/// \brief Return true if this value refers to a distinct and identifiable
+/// object.
+///
+/// This is similar to AliasAnalysis's isIdentifiedObject, except that it uses
+/// special knowledge of ObjC conventions.
+static bool IsObjCIdentifiedObject(const Value *V) {
+ // Assume that call results and arguments have their own "provenance".
+ // Constants (including GlobalVariables) and Allocas are never
+ // reference-counted.
+ if (isa<CallInst>(V) || isa<InvokeInst>(V) ||
+ isa<Argument>(V) || isa<Constant>(V) ||
+ isa<AllocaInst>(V))
+ return true;
+
+ if (const LoadInst *LI = dyn_cast<LoadInst>(V)) {
+ const Value *Pointer =
+ StripPointerCastsAndObjCCalls(LI->getPointerOperand());
+ if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Pointer)) {
+ // A constant pointer can't be pointing to an object on the heap. It may
+ // be reference-counted, but it won't be deleted.
+ if (GV->isConstant())
+ return true;
+ StringRef Name = GV->getName();
+ // These special variables are known to hold values which are not
+ // reference-counted pointers.
+ if (Name.startswith("\01L_OBJC_SELECTOR_REFERENCES_") ||
+ Name.startswith("\01L_OBJC_CLASSLIST_REFERENCES_") ||
+ Name.startswith("\01L_OBJC_CLASSLIST_SUP_REFS_$_") ||
+ Name.startswith("\01L_OBJC_METH_VAR_NAME_") ||
+ Name.startswith("\01l_objc_msgSend_fixup_"))
+ return true;
+ }
+ }
+
+ return false;
+}
+
+/// \brief This is similar to StripPointerCastsAndObjCCalls but it stops as soon
+/// as it finds a value with multiple uses.
+static const Value *FindSingleUseIdentifiedObject(const Value *Arg) {
+ if (Arg->hasOneUse()) {
+ if (const BitCastInst *BC = dyn_cast<BitCastInst>(Arg))
+ return FindSingleUseIdentifiedObject(BC->getOperand(0));
+ if (const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Arg))
+ if (GEP->hasAllZeroIndices())
+ return FindSingleUseIdentifiedObject(GEP->getPointerOperand());
+ if (IsForwarding(GetBasicInstructionClass(Arg)))
+ return FindSingleUseIdentifiedObject(
+ cast<CallInst>(Arg)->getArgOperand(0));
+ if (!IsObjCIdentifiedObject(Arg))
+ return 0;
+ return Arg;
+ }
+
+ // If we found an identifiable object but it has multiple uses, but they are
+ // trivial uses, we can still consider this to be a single-use value.
+ if (IsObjCIdentifiedObject(Arg)) {
+ for (Value::const_use_iterator UI = Arg->use_begin(), UE = Arg->use_end();
+ UI != UE; ++UI) {
+ const User *U = *UI;
+ if (!U->use_empty() || StripPointerCastsAndObjCCalls(U) != Arg)
+ return 0;
+ }
+
+ return Arg;
+ }
+
+ return 0;
+}
+
+/// \brief Test if the given module looks interesting to run ARC optimization
+/// on.
+static bool ModuleHasARC(const Module &M) {
+ return
+ M.getNamedValue("objc_retain") ||
+ M.getNamedValue("objc_release") ||
+ M.getNamedValue("objc_autorelease") ||
+ M.getNamedValue("objc_retainAutoreleasedReturnValue") ||
+ M.getNamedValue("objc_retainBlock") ||
+ M.getNamedValue("objc_autoreleaseReturnValue") ||
+ M.getNamedValue("objc_autoreleasePoolPush") ||
+ M.getNamedValue("objc_loadWeakRetained") ||
+ M.getNamedValue("objc_loadWeak") ||
+ M.getNamedValue("objc_destroyWeak") ||
+ M.getNamedValue("objc_storeWeak") ||
+ M.getNamedValue("objc_initWeak") ||
+ M.getNamedValue("objc_moveWeak") ||
+ M.getNamedValue("objc_copyWeak") ||
+ M.getNamedValue("objc_retainedObject") ||
+ M.getNamedValue("objc_unretainedObject") ||
+ M.getNamedValue("objc_unretainedPointer");
+}
+
+/// \brief Test whether the given pointer, which is an Objective C block
+/// pointer, does not "escape".
+///
+/// This differs from regular escape analysis in that a use as an
+/// argument to a call is not considered an escape.
+///
+static bool DoesObjCBlockEscape(const Value *BlockPtr) {
+
+ DEBUG(dbgs() << "DoesObjCBlockEscape: Target: " << *BlockPtr << "\n");
+
+ // Walk the def-use chains.
+ SmallVector<const Value *, 4> Worklist;
+ Worklist.push_back(BlockPtr);
+
+ // Ensure we do not visit any value twice.
+ SmallPtrSet<const Value *, 4> VisitedSet;
+
+ do {
+ const Value *V = Worklist.pop_back_val();
+
+ DEBUG(dbgs() << "DoesObjCBlockEscape: Visiting: " << *V << "\n");
+
+ for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end();
+ UI != UE; ++UI) {
+ const User *UUser = *UI;
+
+ DEBUG(dbgs() << "DoesObjCBlockEscape: User: " << *UUser << "\n");
+
+ // Special - Use by a call (callee or argument) is not considered
+ // to be an escape.
+ switch (GetBasicInstructionClass(UUser)) {
+ case IC_StoreWeak:
+ case IC_InitWeak:
+ case IC_StoreStrong:
+ case IC_Autorelease:
+ case IC_AutoreleaseRV: {
+ DEBUG(dbgs() << "DoesObjCBlockEscape: User copies pointer arguments. "
+ "Block Escapes!\n");
+ // These special functions make copies of their pointer arguments.
+ return true;
+ }
+ case IC_User:
+ case IC_None:
+ // Use by an instruction which copies the value is an escape if the
+ // result is an escape.
+ if (isa<BitCastInst>(UUser) || isa<GetElementPtrInst>(UUser) ||
+ isa<PHINode>(UUser) || isa<SelectInst>(UUser)) {
+
+ if (!VisitedSet.insert(UUser)) {
+ DEBUG(dbgs() << "DoesObjCBlockEscape: User copies value. Escapes "
+ "if result escapes. Adding to list.\n");
+ Worklist.push_back(UUser);
+ } else {
+ DEBUG(dbgs() << "DoesObjCBlockEscape: Already visited node.\n");
+ }
+ continue;
+ }
+ // Use by a load is not an escape.
+ if (isa<LoadInst>(UUser))
+ continue;
+ // Use by a store is not an escape if the use is the address.
+ if (const StoreInst *SI = dyn_cast<StoreInst>(UUser))
+ if (V != SI->getValueOperand())
+ continue;
+ break;
+ default:
+ // Regular calls and other stuff are not considered escapes.
+ continue;
+ }
+ // Otherwise, conservatively assume an escape.
+ DEBUG(dbgs() << "DoesObjCBlockEscape: Assuming block escapes.\n");
+ return true;
+ }
+ } while (!Worklist.empty());
+
+ // No escapes found.
+ DEBUG(dbgs() << "DoesObjCBlockEscape: Block does not escape.\n");
+ return false;
+}
+
+/// @}
+///
+/// \defgroup ARCAA Extends alias analysis using ObjC specific knowledge.
+/// @{
+
+#include "llvm/Analysis/AliasAnalysis.h"
+#include "llvm/Analysis/Passes.h"
+#include "llvm/Pass.h"
+
+namespace {
+ /// \brief This is a simple alias analysis implementation that uses knowledge
+ /// of ARC constructs to answer queries.
+ ///
+ /// TODO: This class could be generalized to know about other ObjC-specific
+ /// tricks. Such as knowing that ivars in the non-fragile ABI are non-aliasing
+ /// even though their offsets are dynamic.
+ class ObjCARCAliasAnalysis : public ImmutablePass,
+ public AliasAnalysis {
+ public:
+ static char ID; // Class identification, replacement for typeinfo
+ ObjCARCAliasAnalysis() : ImmutablePass(ID) {
+ initializeObjCARCAliasAnalysisPass(*PassRegistry::getPassRegistry());
+ }
+
+ private:
+ virtual void initializePass() {
+ InitializeAliasAnalysis(this);
+ }
+
+ /// This method is used when a pass implements an analysis interface through
+ /// multiple inheritance. If needed, it should override this to adjust the
+ /// this pointer as needed for the specified pass info.
+ virtual void *getAdjustedAnalysisPointer(const void *PI) {
+ if (PI == &AliasAnalysis::ID)
+ return static_cast<AliasAnalysis *>(this);
+ return this;
+ }
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+ virtual AliasResult alias(const Location &LocA, const Location &LocB);
+ virtual bool pointsToConstantMemory(const Location &Loc, bool OrLocal);
+ virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS);
+ virtual ModRefBehavior getModRefBehavior(const Function *F);
+ virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
+ const Location &Loc);
+ virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
+ ImmutableCallSite CS2);
+ };
+} // End of anonymous namespace
+
+// Register this pass...
+char ObjCARCAliasAnalysis::ID = 0;
+INITIALIZE_AG_PASS(ObjCARCAliasAnalysis, AliasAnalysis, "objc-arc-aa",
+ "ObjC-ARC-Based Alias Analysis", false, true, false)
+
+ImmutablePass *llvm::createObjCARCAliasAnalysisPass() {
+ return new ObjCARCAliasAnalysis();
+}
+
+void
+ObjCARCAliasAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesAll();
+ AliasAnalysis::getAnalysisUsage(AU);
+}
+
+AliasAnalysis::AliasResult
+ObjCARCAliasAnalysis::alias(const Location &LocA, const Location &LocB) {
+ if (!EnableARCOpts)
+ return AliasAnalysis::alias(LocA, LocB);
+
+ // First, strip off no-ops, including ObjC-specific no-ops, and try making a
+ // precise alias query.
+ const Value *SA = StripPointerCastsAndObjCCalls(LocA.Ptr);
+ const Value *SB = StripPointerCastsAndObjCCalls(LocB.Ptr);
+ AliasResult Result =
+ AliasAnalysis::alias(Location(SA, LocA.Size, LocA.TBAATag),
+ Location(SB, LocB.Size, LocB.TBAATag));
+ if (Result != MayAlias)
+ return Result;
+
+ // If that failed, climb to the underlying object, including climbing through
+ // ObjC-specific no-ops, and try making an imprecise alias query.
+ const Value *UA = GetUnderlyingObjCPtr(SA);
+ const Value *UB = GetUnderlyingObjCPtr(SB);
+ if (UA != SA || UB != SB) {
+ Result = AliasAnalysis::alias(Location(UA), Location(UB));
+ // We can't use MustAlias or PartialAlias results here because
+ // GetUnderlyingObjCPtr may return an offsetted pointer value.
+ if (Result == NoAlias)
+ return NoAlias;
+ }
+
+ // If that failed, fail. We don't need to chain here, since that's covered
+ // by the earlier precise query.
+ return MayAlias;
+}
+
+bool
+ObjCARCAliasAnalysis::pointsToConstantMemory(const Location &Loc,
+ bool OrLocal) {
+ if (!EnableARCOpts)
+ return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
+
+ // First, strip off no-ops, including ObjC-specific no-ops, and try making
+ // a precise alias query.
+ const Value *S = StripPointerCastsAndObjCCalls(Loc.Ptr);
+ if (AliasAnalysis::pointsToConstantMemory(Location(S, Loc.Size, Loc.TBAATag),
+ OrLocal))
+ return true;
+
+ // If that failed, climb to the underlying object, including climbing through
+ // ObjC-specific no-ops, and try making an imprecise alias query.
+ const Value *U = GetUnderlyingObjCPtr(S);
+ if (U != S)
+ return AliasAnalysis::pointsToConstantMemory(Location(U), OrLocal);
+
+ // If that failed, fail. We don't need to chain here, since that's covered
+ // by the earlier precise query.
+ return false;
+}
+
+AliasAnalysis::ModRefBehavior
+ObjCARCAliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
+ // We have nothing to do. Just chain to the next AliasAnalysis.
+ return AliasAnalysis::getModRefBehavior(CS);
+}
+
+AliasAnalysis::ModRefBehavior
+ObjCARCAliasAnalysis::getModRefBehavior(const Function *F) {
+ if (!EnableARCOpts)
+ return AliasAnalysis::getModRefBehavior(F);
+
+ switch (GetFunctionClass(F)) {
+ case IC_NoopCast:
+ return DoesNotAccessMemory;
+ default:
+ break;
+ }
+
+ return AliasAnalysis::getModRefBehavior(F);
+}
+
+AliasAnalysis::ModRefResult
+ObjCARCAliasAnalysis::getModRefInfo(ImmutableCallSite CS, const Location &Loc) {
+ if (!EnableARCOpts)
+ return AliasAnalysis::getModRefInfo(CS, Loc);
+
+ switch (GetBasicInstructionClass(CS.getInstruction())) {
+ case IC_Retain:
+ case IC_RetainRV:
+ case IC_Autorelease:
+ case IC_AutoreleaseRV:
+ case IC_NoopCast:
+ case IC_AutoreleasepoolPush:
+ case IC_FusedRetainAutorelease:
+ case IC_FusedRetainAutoreleaseRV:
+ // These functions don't access any memory visible to the compiler.
+ // Note that this doesn't include objc_retainBlock, because it updates
+ // pointers when it copies block data.
+ return NoModRef;
+ default:
+ break;
+ }
+
+ return AliasAnalysis::getModRefInfo(CS, Loc);
+}
+
+AliasAnalysis::ModRefResult
+ObjCARCAliasAnalysis::getModRefInfo(ImmutableCallSite CS1,
+ ImmutableCallSite CS2) {
+ // TODO: Theoretically we could check for dependencies between objc_* calls
+ // and OnlyAccessesArgumentPointees calls or other well-behaved calls.
+ return AliasAnalysis::getModRefInfo(CS1, CS2);
+}
+
+/// @}
+///
+/// \defgroup ARCExpansion Early ARC Optimizations.
+/// @{
+
+#include "llvm/Support/InstIterator.h"
+#include "llvm/Transforms/ObjCARC.h"
+
+namespace {
+ /// \brief Early ARC transformations.
+ class ObjCARCExpand : public FunctionPass {
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+ virtual bool doInitialization(Module &M);
+ virtual bool runOnFunction(Function &F);
+
+ /// A flag indicating whether this optimization pass should run.
+ bool Run;
+
+ public:
+ static char ID;
+ ObjCARCExpand() : FunctionPass(ID) {
+ initializeObjCARCExpandPass(*PassRegistry::getPassRegistry());
+ }
+ };
+}
+
+char ObjCARCExpand::ID = 0;
+INITIALIZE_PASS(ObjCARCExpand,
+ "objc-arc-expand", "ObjC ARC expansion", false, false)
+
+Pass *llvm::createObjCARCExpandPass() {
+ return new ObjCARCExpand();
+}
+
+void ObjCARCExpand::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesCFG();
+}
+
+bool ObjCARCExpand::doInitialization(Module &M) {
+ Run = ModuleHasARC(M);
+ return false;
+}
+
+bool ObjCARCExpand::runOnFunction(Function &F) {
+ if (!EnableARCOpts)
+ return false;
+
+ // If nothing in the Module uses ARC, don't do anything.
+ if (!Run)
+ return false;
+
+ bool Changed = false;
+
+ DEBUG(dbgs() << "ObjCARCExpand: Visiting Function: " << F.getName() << "\n");
+
+ for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ++I) {
+ Instruction *Inst = &*I;
+
+ DEBUG(dbgs() << "ObjCARCExpand: Visiting: " << *Inst << "\n");
+
+ switch (GetBasicInstructionClass(Inst)) {
+ case IC_Retain:
+ case IC_RetainRV:
+ case IC_Autorelease:
+ case IC_AutoreleaseRV:
+ case IC_FusedRetainAutorelease:
+ case IC_FusedRetainAutoreleaseRV: {
+ // These calls return their argument verbatim, as a low-level
+ // optimization. However, this makes high-level optimizations
+ // harder. Undo any uses of this optimization that the front-end
+ // emitted here. We'll redo them in the contract pass.
+ Changed = true;
+ Value *Value = cast<CallInst>(Inst)->getArgOperand(0);
+ DEBUG(dbgs() << "ObjCARCExpand: Old = " << *Inst << "\n"
+ " New = " << *Value << "\n");
+ Inst->replaceAllUsesWith(Value);
+ break;
+ }
+ default:
+ break;
+ }
+ }
+
+ DEBUG(dbgs() << "ObjCARCExpand: Finished List.\n\n");
+
+ return Changed;
+}
+
+/// @}
+///
+/// \defgroup ARCAPElim ARC Autorelease Pool Elimination.
+/// @{
+
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/IR/Constants.h"
+
+namespace {
+ /// \brief Autorelease pool elimination.
+ class ObjCARCAPElim : public ModulePass {
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+ virtual bool runOnModule(Module &M);
+
+ static bool MayAutorelease(ImmutableCallSite CS, unsigned Depth = 0);
+ static bool OptimizeBB(BasicBlock *BB);
+
+ public:
+ static char ID;
+ ObjCARCAPElim() : ModulePass(ID) {
+ initializeObjCARCAPElimPass(*PassRegistry::getPassRegistry());
+ }
+ };
+}
+
+char ObjCARCAPElim::ID = 0;
+INITIALIZE_PASS(ObjCARCAPElim,
+ "objc-arc-apelim",
+ "ObjC ARC autorelease pool elimination",
+ false, false)
+
+Pass *llvm::createObjCARCAPElimPass() {
+ return new ObjCARCAPElim();
+}
+
+void ObjCARCAPElim::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.setPreservesCFG();
+}
+
+/// Interprocedurally determine if calls made by the given call site can
+/// possibly produce autoreleases.
+bool ObjCARCAPElim::MayAutorelease(ImmutableCallSite CS, unsigned Depth) {
+ if (const Function *Callee = CS.getCalledFunction()) {
+ if (Callee->isDeclaration() || Callee->mayBeOverridden())
+ return true;
+ for (Function::const_iterator I = Callee->begin(), E = Callee->end();
+ I != E; ++I) {
+ const BasicBlock *BB = I;
+ for (BasicBlock::const_iterator J = BB->begin(), F = BB->end();
+ J != F; ++J)
+ if (ImmutableCallSite JCS = ImmutableCallSite(J))
+ // This recursion depth limit is arbitrary. It's just great
+ // enough to cover known interesting testcases.
+ if (Depth < 3 &&
+ !JCS.onlyReadsMemory() &&
+ MayAutorelease(JCS, Depth + 1))
+ return true;
+ }
+ return false;
+ }
+
+ return true;
+}
+
+bool ObjCARCAPElim::OptimizeBB(BasicBlock *BB) {
+ bool Changed = false;
+
+ Instruction *Push = 0;
+ for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
+ Instruction *Inst = I++;
+ switch (GetBasicInstructionClass(Inst)) {
+ case IC_AutoreleasepoolPush:
+ Push = Inst;
+ break;
+ case IC_AutoreleasepoolPop:
+ // If this pop matches a push and nothing in between can autorelease,
+ // zap the pair.
+ if (Push && cast<CallInst>(Inst)->getArgOperand(0) == Push) {
+ Changed = true;
+ DEBUG(dbgs() << "ObjCARCAPElim::OptimizeBB: Zapping push pop "
+ "autorelease pair:\n"
+ " Pop: " << *Inst << "\n"
+ << " Push: " << *Push << "\n");
+ Inst->eraseFromParent();
+ Push->eraseFromParent();
+ }
+ Push = 0;
+ break;
+ case IC_CallOrUser:
+ if (MayAutorelease(ImmutableCallSite(Inst)))
+ Push = 0;
+ break;
+ default:
+ break;
+ }
+ }
+
+ return Changed;
+}
+
+bool ObjCARCAPElim::runOnModule(Module &M) {
+ if (!EnableARCOpts)
+ return false;
+
+ // If nothing in the Module uses ARC, don't do anything.
+ if (!ModuleHasARC(M))
+ return false;
+
+ // Find the llvm.global_ctors variable, as the first step in
+ // identifying the global constructors. In theory, unnecessary autorelease
+ // pools could occur anywhere, but in practice it's pretty rare. Global
+ // ctors are a place where autorelease pools get inserted automatically,
+ // so it's pretty common for them to be unnecessary, and it's pretty
+ // profitable to eliminate them.
+ GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors");
+ if (!GV)
+ return false;
+
+ assert(GV->hasDefinitiveInitializer() &&
+ "llvm.global_ctors is uncooperative!");
+
+ bool Changed = false;
+
+ // Dig the constructor functions out of GV's initializer.
+ ConstantArray *Init = cast<ConstantArray>(GV->getInitializer());
+ for (User::op_iterator OI = Init->op_begin(), OE = Init->op_end();
+ OI != OE; ++OI) {
+ Value *Op = *OI;
+ // llvm.global_ctors is an array of pairs where the second members
+ // are constructor functions.
+ Function *F = dyn_cast<Function>(cast<ConstantStruct>(Op)->getOperand(1));
+ // If the user used a constructor function with the wrong signature and
+ // it got bitcasted or whatever, look the other way.
+ if (!F)
+ continue;
+ // Only look at function definitions.
+ if (F->isDeclaration())
+ continue;
+ // Only look at functions with one basic block.
+ if (llvm::next(F->begin()) != F->end())
+ continue;
+ // Ok, a single-block constructor function definition. Try to optimize it.
+ Changed |= OptimizeBB(F->begin());
+ }
+
+ return Changed;
+}
+
+/// @}
+///
+/// \defgroup ARCOpt ARC Optimization.
+/// @{
+
+// TODO: On code like this:
+//
+// objc_retain(%x)
+// stuff_that_cannot_release()
+// objc_autorelease(%x)
+// stuff_that_cannot_release()
+// objc_retain(%x)
+// stuff_that_cannot_release()
+// objc_autorelease(%x)
+//
+// The second retain and autorelease can be deleted.
+
+// TODO: It should be possible to delete
+// objc_autoreleasePoolPush and objc_autoreleasePoolPop
+// pairs if nothing is actually autoreleased between them. Also, autorelease
+// calls followed by objc_autoreleasePoolPop calls (perhaps in ObjC++ code
+// after inlining) can be turned into plain release calls.
+
+// TODO: Critical-edge splitting. If the optimial insertion point is
+// a critical edge, the current algorithm has to fail, because it doesn't
+// know how to split edges. It should be possible to make the optimizer
+// think in terms of edges, rather than blocks, and then split critical
+// edges on demand.
+
+// TODO: OptimizeSequences could generalized to be Interprocedural.
+
+// TODO: Recognize that a bunch of other objc runtime calls have
+// non-escaping arguments and non-releasing arguments, and may be
+// non-autoreleasing.
+
+// TODO: Sink autorelease calls as far as possible. Unfortunately we
+// usually can't sink them past other calls, which would be the main
+// case where it would be useful.
+
+// TODO: The pointer returned from objc_loadWeakRetained is retained.
+
+// TODO: Delete release+retain pairs (rare).
+
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/Support/CFG.h"
+
+STATISTIC(NumNoops, "Number of no-op objc calls eliminated");
+STATISTIC(NumPartialNoops, "Number of partially no-op objc calls eliminated");
+STATISTIC(NumAutoreleases,"Number of autoreleases converted to releases");
+STATISTIC(NumRets, "Number of return value forwarding "
+ "retain+autoreleaes eliminated");
+STATISTIC(NumRRs, "Number of retain+release paths eliminated");
+STATISTIC(NumPeeps, "Number of calls peephole-optimized");
+
+namespace {
+ /// \brief This is similar to BasicAliasAnalysis, and it uses many of the same
+ /// techniques, except it uses special ObjC-specific reasoning about pointer
+ /// relationships.
+ ///
+ /// In this context ``Provenance'' is defined as the history of an object's
+ /// ownership. Thus ``Provenance Analysis'' is defined by using the notion of
+ /// an ``independent provenance source'' of a pointer to determine whether or
+ /// not two pointers have the same provenance source and thus could
+ /// potentially be related.
+ class ProvenanceAnalysis {
+ AliasAnalysis *AA;
+
+ typedef std::pair<const Value *, const Value *> ValuePairTy;
+ typedef DenseMap<ValuePairTy, bool> CachedResultsTy;
+ CachedResultsTy CachedResults;
+
+ bool relatedCheck(const Value *A, const Value *B);
+ bool relatedSelect(const SelectInst *A, const Value *B);
+ bool relatedPHI(const PHINode *A, const Value *B);
+
+ void operator=(const ProvenanceAnalysis &) LLVM_DELETED_FUNCTION;
+ ProvenanceAnalysis(const ProvenanceAnalysis &) LLVM_DELETED_FUNCTION;
+
+ public:
+ ProvenanceAnalysis() {}
+
+ void setAA(AliasAnalysis *aa) { AA = aa; }
+
+ AliasAnalysis *getAA() const { return AA; }
+
+ bool related(const Value *A, const Value *B);
+
+ void clear() {
+ CachedResults.clear();
+ }
+ };
+}
+
+bool ProvenanceAnalysis::relatedSelect(const SelectInst *A, const Value *B) {
+ // If the values are Selects with the same condition, we can do a more precise
+ // check: just check for relations between the values on corresponding arms.
+ if (const SelectInst *SB = dyn_cast<SelectInst>(B))
+ if (A->getCondition() == SB->getCondition())
+ return related(A->getTrueValue(), SB->getTrueValue()) ||
+ related(A->getFalseValue(), SB->getFalseValue());
+
+ // Check both arms of the Select node individually.
+ return related(A->getTrueValue(), B) ||
+ related(A->getFalseValue(), B);
+}
+
+bool ProvenanceAnalysis::relatedPHI(const PHINode *A, const Value *B) {
+ // If the values are PHIs in the same block, we can do a more precise as well
+ // as efficient check: just check for relations between the values on
+ // corresponding edges.
+ if (const PHINode *PNB = dyn_cast<PHINode>(B))
+ if (PNB->getParent() == A->getParent()) {
+ for (unsigned i = 0, e = A->getNumIncomingValues(); i != e; ++i)
+ if (related(A->getIncomingValue(i),
+ PNB->getIncomingValueForBlock(A->getIncomingBlock(i))))
+ return true;
+ return false;
+ }
+
+ // Check each unique source of the PHI node against B.
+ SmallPtrSet<const Value *, 4> UniqueSrc;
+ for (unsigned i = 0, e = A->getNumIncomingValues(); i != e; ++i) {
+ const Value *PV1 = A->getIncomingValue(i);
+ if (UniqueSrc.insert(PV1) && related(PV1, B))
+ return true;
+ }
+
+ // All of the arms checked out.
+ return false;
+}
+
+/// Test if the value of P, or any value covered by its provenance, is ever
+/// stored within the function (not counting callees).
+static bool isStoredObjCPointer(const Value *P) {
+ SmallPtrSet<const Value *, 8> Visited;
+ SmallVector<const Value *, 8> Worklist;
+ Worklist.push_back(P);
+ Visited.insert(P);
+ do {
+ P = Worklist.pop_back_val();
+ for (Value::const_use_iterator UI = P->use_begin(), UE = P->use_end();
+ UI != UE; ++UI) {
+ const User *Ur = *UI;
+ if (isa<StoreInst>(Ur)) {
+ if (UI.getOperandNo() == 0)
+ // The pointer is stored.
+ return true;
+ // The pointed is stored through.
+ continue;
+ }
+ if (isa<CallInst>(Ur))
+ // The pointer is passed as an argument, ignore this.
+ continue;
+ if (isa<PtrToIntInst>(P))
+ // Assume the worst.
+ return true;
+ if (Visited.insert(Ur))
+ Worklist.push_back(Ur);
+ }
+ } while (!Worklist.empty());
+
+ // Everything checked out.
+ return false;
+}
+
+bool ProvenanceAnalysis::relatedCheck(const Value *A, const Value *B) {
+ // Skip past provenance pass-throughs.
+ A = GetUnderlyingObjCPtr(A);
+ B = GetUnderlyingObjCPtr(B);
+
+ // Quick check.
+ if (A == B)
+ return true;
+
+ // Ask regular AliasAnalysis, for a first approximation.
+ switch (AA->alias(A, B)) {
+ case AliasAnalysis::NoAlias:
+ return false;
+ case AliasAnalysis::MustAlias:
+ case AliasAnalysis::PartialAlias:
+ return true;
+ case AliasAnalysis::MayAlias:
+ break;
+ }
+
+ bool AIsIdentified = IsObjCIdentifiedObject(A);
+ bool BIsIdentified = IsObjCIdentifiedObject(B);
+
+ // An ObjC-Identified object can't alias a load if it is never locally stored.
+ if (AIsIdentified) {
+ // Check for an obvious escape.
+ if (isa<LoadInst>(B))
+ return isStoredObjCPointer(A);
+ if (BIsIdentified) {
+ // Check for an obvious escape.
+ if (isa<LoadInst>(A))
+ return isStoredObjCPointer(B);
+ // Both pointers are identified and escapes aren't an evident problem.
+ return false;
+ }
+ } else if (BIsIdentified) {
+ // Check for an obvious escape.
+ if (isa<LoadInst>(A))
+ return isStoredObjCPointer(B);
+ }
+
+ // Special handling for PHI and Select.
+ if (const PHINode *PN = dyn_cast<PHINode>(A))
+ return relatedPHI(PN, B);
+ if (const PHINode *PN = dyn_cast<PHINode>(B))
+ return relatedPHI(PN, A);
+ if (const SelectInst *S = dyn_cast<SelectInst>(A))
+ return relatedSelect(S, B);
+ if (const SelectInst *S = dyn_cast<SelectInst>(B))
+ return relatedSelect(S, A);
+
+ // Conservative.
+ return true;
+}
+
+bool ProvenanceAnalysis::related(const Value *A, const Value *B) {
+ // Begin by inserting a conservative value into the map. If the insertion
+ // fails, we have the answer already. If it succeeds, leave it there until we
+ // compute the real answer to guard against recursive queries.
+ if (A > B) std::swap(A, B);
+ std::pair<CachedResultsTy::iterator, bool> Pair =
+ CachedResults.insert(std::make_pair(ValuePairTy(A, B), true));
+ if (!Pair.second)
+ return Pair.first->second;
+
+ bool Result = relatedCheck(A, B);
+ CachedResults[ValuePairTy(A, B)] = Result;
+ return Result;
+}
+
+namespace {
+ /// \enum Sequence
+ ///
+ /// \brief A sequence of states that a pointer may go through in which an
+ /// objc_retain and objc_release are actually needed.
+ enum Sequence {
+ S_None,
+ S_Retain, ///< objc_retain(x)
+ S_CanRelease, ///< foo(x) -- x could possibly see a ref count decrement
+ S_Use, ///< any use of x
+ S_Stop, ///< like S_Release, but code motion is stopped
+ S_Release, ///< objc_release(x)
+ S_MovableRelease ///< objc_release(x), !clang.imprecise_release
+ };
+}
+
+static Sequence MergeSeqs(Sequence A, Sequence B, bool TopDown) {
+ // The easy cases.
+ if (A == B)
+ return A;
+ if (A == S_None || B == S_None)
+ return S_None;
+
+ if (A > B) std::swap(A, B);
+ if (TopDown) {
+ // Choose the side which is further along in the sequence.
+ if ((A == S_Retain || A == S_CanRelease) &&
+ (B == S_CanRelease || B == S_Use))
+ return B;
+ } else {
+ // Choose the side which is further along in the sequence.
+ if ((A == S_Use || A == S_CanRelease) &&
+ (B == S_Use || B == S_Release || B == S_Stop || B == S_MovableRelease))
+ return A;
+ // If both sides are releases, choose the more conservative one.
+ if (A == S_Stop && (B == S_Release || B == S_MovableRelease))
+ return A;
+ if (A == S_Release && B == S_MovableRelease)
+ return A;
+ }
+
+ return S_None;
+}
+
+namespace {
+ /// \brief Unidirectional information about either a
+ /// retain-decrement-use-release sequence or release-use-decrement-retain
+ /// reverese sequence.
+ struct RRInfo {
+ /// After an objc_retain, the reference count of the referenced
+ /// object is known to be positive. Similarly, before an objc_release, the
+ /// reference count of the referenced object is known to be positive. If
+ /// there are retain-release pairs in code regions where the retain count
+ /// is known to be positive, they can be eliminated, regardless of any side
+ /// effects between them.
+ ///
+ /// Also, a retain+release pair nested within another retain+release
+ /// pair all on the known same pointer value can be eliminated, regardless
+ /// of any intervening side effects.
+ ///
+ /// KnownSafe is true when either of these conditions is satisfied.
+ bool KnownSafe;
+
+ /// True if the Calls are objc_retainBlock calls (as opposed to objc_retain
+ /// calls).
+ bool IsRetainBlock;
+
+ /// True of the objc_release calls are all marked with the "tail" keyword.
+ bool IsTailCallRelease;
+
+ /// If the Calls are objc_release calls and they all have a
+ /// clang.imprecise_release tag, this is the metadata tag.
+ MDNode *ReleaseMetadata;
+
+ /// For a top-down sequence, the set of objc_retains or
+ /// objc_retainBlocks. For bottom-up, the set of objc_releases.
+ SmallPtrSet<Instruction *, 2> Calls;
+
+ /// The set of optimal insert positions for moving calls in the opposite
+ /// sequence.
+ SmallPtrSet<Instruction *, 2> ReverseInsertPts;
+
+ RRInfo() :
+ KnownSafe(false), IsRetainBlock(false),
+ IsTailCallRelease(false),
+ ReleaseMetadata(0) {}
+
+ void clear();
+ };
+}
+
+void RRInfo::clear() {
+ KnownSafe = false;
+ IsRetainBlock = false;
+ IsTailCallRelease = false;
+ ReleaseMetadata = 0;
+ Calls.clear();
+ ReverseInsertPts.clear();
+}
+
+namespace {
+ /// \brief This class summarizes several per-pointer runtime properties which
+ /// are propogated through the flow graph.
+ class PtrState {
+ /// True if the reference count is known to be incremented.
+ bool KnownPositiveRefCount;
+
+ /// True of we've seen an opportunity for partial RR elimination, such as
+ /// pushing calls into a CFG triangle or into one side of a CFG diamond.
+ bool Partial;
+
+ /// The current position in the sequence.
+ Sequence Seq : 8;
+
+ public:
+ /// Unidirectional information about the current sequence.
+ ///
+ /// TODO: Encapsulate this better.
+ RRInfo RRI;
+
+ PtrState() : KnownPositiveRefCount(false), Partial(false),
+ Seq(S_None) {}
+
+ void SetKnownPositiveRefCount() {
+ KnownPositiveRefCount = true;
+ }
+
+ void ClearRefCount() {
+ KnownPositiveRefCount = false;
+ }
+
+ bool IsKnownIncremented() const {
+ return KnownPositiveRefCount;
+ }
+
+ void SetSeq(Sequence NewSeq) {
+ Seq = NewSeq;
+ }
+
+ Sequence GetSeq() const {
+ return Seq;
+ }
+
+ void ClearSequenceProgress() {
+ ResetSequenceProgress(S_None);
+ }
+
+ void ResetSequenceProgress(Sequence NewSeq) {
+ Seq = NewSeq;
+ Partial = false;
+ RRI.clear();
+ }
+
+ void Merge(const PtrState &Other, bool TopDown);
+ };
+}
+
+void
+PtrState::Merge(const PtrState &Other, bool TopDown) {
+ Seq = MergeSeqs(Seq, Other.Seq, TopDown);
+ KnownPositiveRefCount = KnownPositiveRefCount && Other.KnownPositiveRefCount;
+
+ // We can't merge a plain objc_retain with an objc_retainBlock.
+ if (RRI.IsRetainBlock != Other.RRI.IsRetainBlock)
+ Seq = S_None;
+
+ // If we're not in a sequence (anymore), drop all associated state.
+ if (Seq == S_None) {
+ Partial = false;
+ RRI.clear();
+ } else if (Partial || Other.Partial) {
+ // If we're doing a merge on a path that's previously seen a partial
+ // merge, conservatively drop the sequence, to avoid doing partial
+ // RR elimination. If the branch predicates for the two merge differ,
+ // mixing them is unsafe.
+ ClearSequenceProgress();
+ } else {
+ // Conservatively merge the ReleaseMetadata information.
+ if (RRI.ReleaseMetadata != Other.RRI.ReleaseMetadata)
+ RRI.ReleaseMetadata = 0;
+
+ RRI.KnownSafe = RRI.KnownSafe && Other.RRI.KnownSafe;
+ RRI.IsTailCallRelease = RRI.IsTailCallRelease &&
+ Other.RRI.IsTailCallRelease;
+ RRI.Calls.insert(Other.RRI.Calls.begin(), Other.RRI.Calls.end());
+
+ // Merge the insert point sets. If there are any differences,
+ // that makes this a partial merge.
+ Partial = RRI.ReverseInsertPts.size() != Other.RRI.ReverseInsertPts.size();
+ for (SmallPtrSet<Instruction *, 2>::const_iterator
+ I = Other.RRI.ReverseInsertPts.begin(),
+ E = Other.RRI.ReverseInsertPts.end(); I != E; ++I)
+ Partial |= RRI.ReverseInsertPts.insert(*I);
+ }
+}
+
+namespace {
+ /// \brief Per-BasicBlock state.
+ class BBState {
+ /// The number of unique control paths from the entry which can reach this
+ /// block.
+ unsigned TopDownPathCount;
+
+ /// The number of unique control paths to exits from this block.
+ unsigned BottomUpPathCount;
+
+ /// A type for PerPtrTopDown and PerPtrBottomUp.
+ typedef MapVector<const Value *, PtrState> MapTy;
+
+ /// The top-down traversal uses this to record information known about a
+ /// pointer at the bottom of each block.
+ MapTy PerPtrTopDown;
+
+ /// The bottom-up traversal uses this to record information known about a
+ /// pointer at the top of each block.
+ MapTy PerPtrBottomUp;
+
+ /// Effective predecessors of the current block ignoring ignorable edges and
+ /// ignored backedges.
+ SmallVector<BasicBlock *, 2> Preds;
+ /// Effective successors of the current block ignoring ignorable edges and
+ /// ignored backedges.
+ SmallVector<BasicBlock *, 2> Succs;
+
+ public:
+ BBState() : TopDownPathCount(0), BottomUpPathCount(0) {}
+
+ typedef MapTy::iterator ptr_iterator;
+ typedef MapTy::const_iterator ptr_const_iterator;
+
+ ptr_iterator top_down_ptr_begin() { return PerPtrTopDown.begin(); }
+ ptr_iterator top_down_ptr_end() { return PerPtrTopDown.end(); }
+ ptr_const_iterator top_down_ptr_begin() const {
+ return PerPtrTopDown.begin();
+ }
+ ptr_const_iterator top_down_ptr_end() const {
+ return PerPtrTopDown.end();
+ }
+
+ ptr_iterator bottom_up_ptr_begin() { return PerPtrBottomUp.begin(); }
+ ptr_iterator bottom_up_ptr_end() { return PerPtrBottomUp.end(); }
+ ptr_const_iterator bottom_up_ptr_begin() const {
+ return PerPtrBottomUp.begin();
+ }
+ ptr_const_iterator bottom_up_ptr_end() const {
+ return PerPtrBottomUp.end();
+ }
+
+ /// Mark this block as being an entry block, which has one path from the
+ /// entry by definition.
+ void SetAsEntry() { TopDownPathCount = 1; }
+
+ /// Mark this block as being an exit block, which has one path to an exit by
+ /// definition.
+ void SetAsExit() { BottomUpPathCount = 1; }
+
+ PtrState &getPtrTopDownState(const Value *Arg) {
+ return PerPtrTopDown[Arg];
+ }
+
+ PtrState &getPtrBottomUpState(const Value *Arg) {
+ return PerPtrBottomUp[Arg];
+ }
+
+ void clearBottomUpPointers() {
+ PerPtrBottomUp.clear();
+ }
+
+ void clearTopDownPointers() {
+ PerPtrTopDown.clear();
+ }
+
+ void InitFromPred(const BBState &Other);
+ void InitFromSucc(const BBState &Other);
+ void MergePred(const BBState &Other);
+ void MergeSucc(const BBState &Other);
+
+ /// Return the number of possible unique paths from an entry to an exit
+ /// which pass through this block. This is only valid after both the
+ /// top-down and bottom-up traversals are complete.
+ unsigned GetAllPathCount() const {
+ assert(TopDownPathCount != 0);
+ assert(BottomUpPathCount != 0);
+ return TopDownPathCount * BottomUpPathCount;
+ }
+
+ // Specialized CFG utilities.
+ typedef SmallVectorImpl<BasicBlock *>::const_iterator edge_iterator;
+ edge_iterator pred_begin() { return Preds.begin(); }
+ edge_iterator pred_end() { return Preds.end(); }
+ edge_iterator succ_begin() { return Succs.begin(); }
+ edge_iterator succ_end() { return Succs.end(); }
+
+ void addSucc(BasicBlock *Succ) { Succs.push_back(Succ); }
+ void addPred(BasicBlock *Pred) { Preds.push_back(Pred); }
+
+ bool isExit() const { return Succs.empty(); }
+ };
+}
+
+void BBState::InitFromPred(const BBState &Other) {
+ PerPtrTopDown = Other.PerPtrTopDown;
+ TopDownPathCount = Other.TopDownPathCount;
+}
+
+void BBState::InitFromSucc(const BBState &Other) {
+ PerPtrBottomUp = Other.PerPtrBottomUp;
+ BottomUpPathCount = Other.BottomUpPathCount;
+}
+
+/// The top-down traversal uses this to merge information about predecessors to
+/// form the initial state for a new block.
+void BBState::MergePred(const BBState &Other) {
+ // Other.TopDownPathCount can be 0, in which case it is either dead or a
+ // loop backedge. Loop backedges are special.
+ TopDownPathCount += Other.TopDownPathCount;
+
+ // Check for overflow. If we have overflow, fall back to conservative
+ // behavior.
+ if (TopDownPathCount < Other.TopDownPathCount) {
+ clearTopDownPointers();
+ return;
+ }
+
+ // For each entry in the other set, if our set has an entry with the same key,
+ // merge the entries. Otherwise, copy the entry and merge it with an empty
+ // entry.
+ for (ptr_const_iterator MI = Other.top_down_ptr_begin(),
+ ME = Other.top_down_ptr_end(); MI != ME; ++MI) {
+ std::pair<ptr_iterator, bool> Pair = PerPtrTopDown.insert(*MI);
+ Pair.first->second.Merge(Pair.second ? PtrState() : MI->second,
+ /*TopDown=*/true);
+ }
+
+ // For each entry in our set, if the other set doesn't have an entry with the
+ // same key, force it to merge with an empty entry.
+ for (ptr_iterator MI = top_down_ptr_begin(),
+ ME = top_down_ptr_end(); MI != ME; ++MI)
+ if (Other.PerPtrTopDown.find(MI->first) == Other.PerPtrTopDown.end())
+ MI->second.Merge(PtrState(), /*TopDown=*/true);
+}
+
+/// The bottom-up traversal uses this to merge information about successors to
+/// form the initial state for a new block.
+void BBState::MergeSucc(const BBState &Other) {
+ // Other.BottomUpPathCount can be 0, in which case it is either dead or a
+ // loop backedge. Loop backedges are special.
+ BottomUpPathCount += Other.BottomUpPathCount;
+
+ // Check for overflow. If we have overflow, fall back to conservative
+ // behavior.
+ if (BottomUpPathCount < Other.BottomUpPathCount) {
+ clearBottomUpPointers();
+ return;
+ }
+
+ // For each entry in the other set, if our set has an entry with the
+ // same key, merge the entries. Otherwise, copy the entry and merge
+ // it with an empty entry.
+ for (ptr_const_iterator MI = Other.bottom_up_ptr_begin(),
+ ME = Other.bottom_up_ptr_end(); MI != ME; ++MI) {
+ std::pair<ptr_iterator, bool> Pair = PerPtrBottomUp.insert(*MI);
+ Pair.first->second.Merge(Pair.second ? PtrState() : MI->second,
+ /*TopDown=*/false);
+ }
+
+ // For each entry in our set, if the other set doesn't have an entry
+ // with the same key, force it to merge with an empty entry.
+ for (ptr_iterator MI = bottom_up_ptr_begin(),
+ ME = bottom_up_ptr_end(); MI != ME; ++MI)
+ if (Other.PerPtrBottomUp.find(MI->first) == Other.PerPtrBottomUp.end())
+ MI->second.Merge(PtrState(), /*TopDown=*/false);
+}
+
+namespace {
+ /// \brief The main ARC optimization pass.
+ class ObjCARCOpt : public FunctionPass {
+ bool Changed;
+ ProvenanceAnalysis PA;
+
+ /// A flag indicating whether this optimization pass should run.
+ bool Run;
+
+ /// Declarations for ObjC runtime functions, for use in creating calls to
+ /// them. These are initialized lazily to avoid cluttering up the Module
+ /// with unused declarations.
+
+ /// Declaration for ObjC runtime function
+ /// objc_retainAutoreleasedReturnValue.
+ Constant *RetainRVCallee;
+ /// Declaration for ObjC runtime function objc_autoreleaseReturnValue.
+ Constant *AutoreleaseRVCallee;
+ /// Declaration for ObjC runtime function objc_release.
+ Constant *ReleaseCallee;
+ /// Declaration for ObjC runtime function objc_retain.
+ Constant *RetainCallee;
+ /// Declaration for ObjC runtime function objc_retainBlock.
+ Constant *RetainBlockCallee;
+ /// Declaration for ObjC runtime function objc_autorelease.
+ Constant *AutoreleaseCallee;
+
+ /// Flags which determine whether each of the interesting runtine functions
+ /// is in fact used in the current function.
+ unsigned UsedInThisFunction;
+
+ /// The Metadata Kind for clang.imprecise_release metadata.
+ unsigned ImpreciseReleaseMDKind;
+
+ /// The Metadata Kind for clang.arc.copy_on_escape metadata.
+ unsigned CopyOnEscapeMDKind;
+
+ /// The Metadata Kind for clang.arc.no_objc_arc_exceptions metadata.
+ unsigned NoObjCARCExceptionsMDKind;
+
+ Constant *getRetainRVCallee(Module *M);
+ Constant *getAutoreleaseRVCallee(Module *M);
+ Constant *getReleaseCallee(Module *M);
+ Constant *getRetainCallee(Module *M);
+ Constant *getRetainBlockCallee(Module *M);
+ Constant *getAutoreleaseCallee(Module *M);
+
+ bool IsRetainBlockOptimizable(const Instruction *Inst);
+
+ void OptimizeRetainCall(Function &F, Instruction *Retain);
+ bool OptimizeRetainRVCall(Function &F, Instruction *RetainRV);
+ void OptimizeAutoreleaseRVCall(Function &F, Instruction *AutoreleaseRV,
+ InstructionClass &Class);
+ void OptimizeIndividualCalls(Function &F);
+
+ void CheckForCFGHazards(const BasicBlock *BB,
+ DenseMap<const BasicBlock *, BBState> &BBStates,
+ BBState &MyStates) const;
+ bool VisitInstructionBottomUp(Instruction *Inst,
+ BasicBlock *BB,
+ MapVector<Value *, RRInfo> &Retains,
+ BBState &MyStates);
+ bool VisitBottomUp(BasicBlock *BB,
+ DenseMap<const BasicBlock *, BBState> &BBStates,
+ MapVector<Value *, RRInfo> &Retains);
+ bool VisitInstructionTopDown(Instruction *Inst,
+ DenseMap<Value *, RRInfo> &Releases,
+ BBState &MyStates);
+ bool VisitTopDown(BasicBlock *BB,
+ DenseMap<const BasicBlock *, BBState> &BBStates,
+ DenseMap<Value *, RRInfo> &Releases);
+ bool Visit(Function &F,
+ DenseMap<const BasicBlock *, BBState> &BBStates,
+ MapVector<Value *, RRInfo> &Retains,
+ DenseMap<Value *, RRInfo> &Releases);
+
+ void MoveCalls(Value *Arg, RRInfo &RetainsToMove, RRInfo &ReleasesToMove,
+ MapVector<Value *, RRInfo> &Retains,
+ DenseMap<Value *, RRInfo> &Releases,
+ SmallVectorImpl<Instruction *> &DeadInsts,
+ Module *M);
+
+ bool ConnectTDBUTraversals(DenseMap<const BasicBlock *, BBState> &BBStates,
+ MapVector<Value *, RRInfo> &Retains,
+ DenseMap<Value *, RRInfo> &Releases,
+ Module *M,
+ SmallVector<Instruction *, 4> &NewRetains,
+ SmallVector<Instruction *, 4> &NewReleases,
+ SmallVector<Instruction *, 8> &DeadInsts,
+ RRInfo &RetainsToMove,
+ RRInfo &ReleasesToMove,
+ Value *Arg,
+ bool KnownSafe,
+ bool &AnyPairsCompletelyEliminated);
+
+ bool PerformCodePlacement(DenseMap<const BasicBlock *, BBState> &BBStates,
+ MapVector<Value *, RRInfo> &Retains,
+ DenseMap<Value *, RRInfo> &Releases,
+ Module *M);
+
+ void OptimizeWeakCalls(Function &F);
+
+ bool OptimizeSequences(Function &F);
+
+ void OptimizeReturns(Function &F);
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+ virtual bool doInitialization(Module &M);
+ virtual bool runOnFunction(Function &F);
+ virtual void releaseMemory();
+
+ public:
+ static char ID;
+ ObjCARCOpt() : FunctionPass(ID) {
+ initializeObjCARCOptPass(*PassRegistry::getPassRegistry());
+ }
+ };
+}
+
+char ObjCARCOpt::ID = 0;
+INITIALIZE_PASS_BEGIN(ObjCARCOpt,
+ "objc-arc", "ObjC ARC optimization", false, false)
+INITIALIZE_PASS_DEPENDENCY(ObjCARCAliasAnalysis)
+INITIALIZE_PASS_END(ObjCARCOpt,
+ "objc-arc", "ObjC ARC optimization", false, false)
+
+Pass *llvm::createObjCARCOptPass() {
+ return new ObjCARCOpt();
+}
+
+void ObjCARCOpt::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<ObjCARCAliasAnalysis>();
+ AU.addRequired<AliasAnalysis>();
+ // ARC optimization doesn't currently split critical edges.
+ AU.setPreservesCFG();
+}
+
+bool ObjCARCOpt::IsRetainBlockOptimizable(const Instruction *Inst) {
+ // Without the magic metadata tag, we have to assume this might be an
+ // objc_retainBlock call inserted to convert a block pointer to an id,
+ // in which case it really is needed.
+ if (!Inst->getMetadata(CopyOnEscapeMDKind))
+ return false;
+
+ // If the pointer "escapes" (not including being used in a call),
+ // the copy may be needed.
+ if (DoesObjCBlockEscape(Inst))
+ return false;
+
+ // Otherwise, it's not needed.
+ return true;
+}
+
+Constant *ObjCARCOpt::getRetainRVCallee(Module *M) {
+ if (!RetainRVCallee) {
+ LLVMContext &C = M->getContext();
+ Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
+ Type *Params[] = { I8X };
+ FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
+ AttributeSet Attribute =
+ AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
+ Attribute::NoUnwind);
+ RetainRVCallee =
+ M->getOrInsertFunction("objc_retainAutoreleasedReturnValue", FTy,
+ Attribute);
+ }
+ return RetainRVCallee;
+}
+
+Constant *ObjCARCOpt::getAutoreleaseRVCallee(Module *M) {
+ if (!AutoreleaseRVCallee) {
+ LLVMContext &C = M->getContext();
+ Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
+ Type *Params[] = { I8X };
+ FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
+ AttributeSet Attribute =
+ AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
+ Attribute::NoUnwind);
+ AutoreleaseRVCallee =
+ M->getOrInsertFunction("objc_autoreleaseReturnValue", FTy,
+ Attribute);
+ }
+ return AutoreleaseRVCallee;
+}
+
+Constant *ObjCARCOpt::getReleaseCallee(Module *M) {
+ if (!ReleaseCallee) {
+ LLVMContext &C = M->getContext();
+ Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
+ AttributeSet Attribute =
+ AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
+ Attribute::NoUnwind);
+ ReleaseCallee =
+ M->getOrInsertFunction(
+ "objc_release",
+ FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false),
+ Attribute);
+ }
+ return ReleaseCallee;
+}
+
+Constant *ObjCARCOpt::getRetainCallee(Module *M) {
+ if (!RetainCallee) {
+ LLVMContext &C = M->getContext();
+ Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
+ AttributeSet Attribute =
+ AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
+ Attribute::NoUnwind);
+ RetainCallee =
+ M->getOrInsertFunction(
+ "objc_retain",
+ FunctionType::get(Params[0], Params, /*isVarArg=*/false),
+ Attribute);
+ }
+ return RetainCallee;
+}
+
+Constant *ObjCARCOpt::getRetainBlockCallee(Module *M) {
+ if (!RetainBlockCallee) {
+ LLVMContext &C = M->getContext();
+ Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
+ // objc_retainBlock is not nounwind because it calls user copy constructors
+ // which could theoretically throw.
+ RetainBlockCallee =
+ M->getOrInsertFunction(
+ "objc_retainBlock",
+ FunctionType::get(Params[0], Params, /*isVarArg=*/false),
+ AttributeSet());
+ }
+ return RetainBlockCallee;
+}
+
+Constant *ObjCARCOpt::getAutoreleaseCallee(Module *M) {
+ if (!AutoreleaseCallee) {
+ LLVMContext &C = M->getContext();
+ Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
+ AttributeSet Attribute =
+ AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
+ Attribute::NoUnwind);
+ AutoreleaseCallee =
+ M->getOrInsertFunction(
+ "objc_autorelease",
+ FunctionType::get(Params[0], Params, /*isVarArg=*/false),
+ Attribute);
+ }
+ return AutoreleaseCallee;
+}
+
+/// Test whether the given value is possible a reference-counted pointer,
+/// including tests which utilize AliasAnalysis.
+static bool IsPotentialRetainableObjPtr(const Value *Op, AliasAnalysis &AA) {
+ // First make the rudimentary check.
+ if (!IsPotentialRetainableObjPtr(Op))
+ return false;
+
+ // Objects in constant memory are not reference-counted.
+ if (AA.pointsToConstantMemory(Op))
+ return false;
+
+ // Pointers in constant memory are not pointing to reference-counted objects.
+ if (const LoadInst *LI = dyn_cast<LoadInst>(Op))
+ if (AA.pointsToConstantMemory(LI->getPointerOperand()))
+ return false;
+
+ // Otherwise assume the worst.
+ return true;
+}
+
+/// Test whether the given instruction can result in a reference count
+/// modification (positive or negative) for the pointer's object.
+static bool
+CanAlterRefCount(const Instruction *Inst, const Value *Ptr,
+ ProvenanceAnalysis &PA, InstructionClass Class) {
+ switch (Class) {
+ case IC_Autorelease:
+ case IC_AutoreleaseRV:
+ case IC_User:
+ // These operations never directly modify a reference count.
+ return false;
+ default: break;
+ }
+
+ ImmutableCallSite CS = static_cast<const Value *>(Inst);
+ assert(CS && "Only calls can alter reference counts!");
+
+ // See if AliasAnalysis can help us with the call.
+ AliasAnalysis::ModRefBehavior MRB = PA.getAA()->getModRefBehavior(CS);
+ if (AliasAnalysis::onlyReadsMemory(MRB))
+ return false;
+ if (AliasAnalysis::onlyAccessesArgPointees(MRB)) {
+ for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
+ I != E; ++I) {
+ const Value *Op = *I;
+ if (IsPotentialRetainableObjPtr(Op, *PA.getAA()) && PA.related(Ptr, Op))
+ return true;
+ }
+ return false;
+ }
+
+ // Assume the worst.
+ return true;
+}
+
+/// Test whether the given instruction can "use" the given pointer's object in a
+/// way that requires the reference count to be positive.
+static bool
+CanUse(const Instruction *Inst, const Value *Ptr, ProvenanceAnalysis &PA,
+ InstructionClass Class) {
+ // IC_Call operations (as opposed to IC_CallOrUser) never "use" objc pointers.
+ if (Class == IC_Call)
+ return false;
+
+ // Consider various instructions which may have pointer arguments which are
+ // not "uses".
+ if (const ICmpInst *ICI = dyn_cast<ICmpInst>(Inst)) {
+ // Comparing a pointer with null, or any other constant, isn't really a use,
+ // because we don't care what the pointer points to, or about the values
+ // of any other dynamic reference-counted pointers.
+ if (!IsPotentialRetainableObjPtr(ICI->getOperand(1), *PA.getAA()))
+ return false;
+ } else if (ImmutableCallSite CS = static_cast<const Value *>(Inst)) {
+ // For calls, just check the arguments (and not the callee operand).
+ for (ImmutableCallSite::arg_iterator OI = CS.arg_begin(),
+ OE = CS.arg_end(); OI != OE; ++OI) {
+ const Value *Op = *OI;
+ if (IsPotentialRetainableObjPtr(Op, *PA.getAA()) && PA.related(Ptr, Op))
+ return true;
+ }
+ return false;
+ } else if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
+ // Special-case stores, because we don't care about the stored value, just
+ // the store address.
+ const Value *Op = GetUnderlyingObjCPtr(SI->getPointerOperand());
+ // If we can't tell what the underlying object was, assume there is a
+ // dependence.
+ return IsPotentialRetainableObjPtr(Op, *PA.getAA()) && PA.related(Op, Ptr);
+ }
+
+ // Check each operand for a match.
+ for (User::const_op_iterator OI = Inst->op_begin(), OE = Inst->op_end();
+ OI != OE; ++OI) {
+ const Value *Op = *OI;
+ if (IsPotentialRetainableObjPtr(Op, *PA.getAA()) && PA.related(Ptr, Op))
+ return true;
+ }
+ return false;
+}
+
+/// Test whether the given instruction can autorelease any pointer or cause an
+/// autoreleasepool pop.
+static bool
+CanInterruptRV(InstructionClass Class) {
+ switch (Class) {
+ case IC_AutoreleasepoolPop:
+ case IC_CallOrUser:
+ case IC_Call:
+ case IC_Autorelease:
+ case IC_AutoreleaseRV:
+ case IC_FusedRetainAutorelease:
+ case IC_FusedRetainAutoreleaseRV:
+ return true;
+ default:
+ return false;
+ }
+}
+
+namespace {
+ /// \enum DependenceKind
+ /// \brief Defines different dependence kinds among various ARC constructs.
+ ///
+ /// There are several kinds of dependence-like concepts in use here.
+ ///
+ enum DependenceKind {
+ NeedsPositiveRetainCount,
+ AutoreleasePoolBoundary,
+ CanChangeRetainCount,
+ RetainAutoreleaseDep, ///< Blocks objc_retainAutorelease.
+ RetainAutoreleaseRVDep, ///< Blocks objc_retainAutoreleaseReturnValue.
+ RetainRVDep ///< Blocks objc_retainAutoreleasedReturnValue.
+ };
+}
+
+/// Test if there can be dependencies on Inst through Arg. This function only
+/// tests dependencies relevant for removing pairs of calls.
+static bool
+Depends(DependenceKind Flavor, Instruction *Inst, const Value *Arg,
+ ProvenanceAnalysis &PA) {
+ // If we've reached the definition of Arg, stop.
+ if (Inst == Arg)
+ return true;
+
+ switch (Flavor) {
+ case NeedsPositiveRetainCount: {
+ InstructionClass Class = GetInstructionClass(Inst);
+ switch (Class) {
+ case IC_AutoreleasepoolPop:
+ case IC_AutoreleasepoolPush:
+ case IC_None:
+ return false;
+ default:
+ return CanUse(Inst, Arg, PA, Class);
+ }
+ }
+
+ case AutoreleasePoolBoundary: {
+ InstructionClass Class = GetInstructionClass(Inst);
+ switch (Class) {
+ case IC_AutoreleasepoolPop:
+ case IC_AutoreleasepoolPush:
+ // These mark the end and begin of an autorelease pool scope.
+ return true;
+ default:
+ // Nothing else does this.
+ return false;
+ }
+ }
+
+ case CanChangeRetainCount: {
+ InstructionClass Class = GetInstructionClass(Inst);
+ switch (Class) {
+ case IC_AutoreleasepoolPop:
+ // Conservatively assume this can decrement any count.
+ return true;
+ case IC_AutoreleasepoolPush:
+ case IC_None:
+ return false;
+ default:
+ return CanAlterRefCount(Inst, Arg, PA, Class);
+ }
+ }
+
+ case RetainAutoreleaseDep:
+ switch (GetBasicInstructionClass(Inst)) {
+ case IC_AutoreleasepoolPop:
+ case IC_AutoreleasepoolPush:
+ // Don't merge an objc_autorelease with an objc_retain inside a different
+ // autoreleasepool scope.
+ return true;
+ case IC_Retain:
+ case IC_RetainRV:
+ // Check for a retain of the same pointer for merging.
+ return GetObjCArg(Inst) == Arg;
+ default:
+ // Nothing else matters for objc_retainAutorelease formation.
+ return false;
+ }
+
+ case RetainAutoreleaseRVDep: {
+ InstructionClass Class = GetBasicInstructionClass(Inst);
+ switch (Class) {
+ case IC_Retain:
+ case IC_RetainRV:
+ // Check for a retain of the same pointer for merging.
+ return GetObjCArg(Inst) == Arg;
+ default:
+ // Anything that can autorelease interrupts
+ // retainAutoreleaseReturnValue formation.
+ return CanInterruptRV(Class);
+ }
+ }
+
+ case RetainRVDep:
+ return CanInterruptRV(GetBasicInstructionClass(Inst));
+ }
+
+ llvm_unreachable("Invalid dependence flavor");
+}
+
+/// Walk up the CFG from StartPos (which is in StartBB) and find local and
+/// non-local dependencies on Arg.
+///
+/// TODO: Cache results?
+static void
+FindDependencies(DependenceKind Flavor,
+ const Value *Arg,
+ BasicBlock *StartBB, Instruction *StartInst,
+ SmallPtrSet<Instruction *, 4> &DependingInstructions,
+ SmallPtrSet<const BasicBlock *, 4> &Visited,
+ ProvenanceAnalysis &PA) {
+ BasicBlock::iterator StartPos = StartInst;
+
+ SmallVector<std::pair<BasicBlock *, BasicBlock::iterator>, 4> Worklist;
+ Worklist.push_back(std::make_pair(StartBB, StartPos));
+ do {
+ std::pair<BasicBlock *, BasicBlock::iterator> Pair =
+ Worklist.pop_back_val();
+ BasicBlock *LocalStartBB = Pair.first;
+ BasicBlock::iterator LocalStartPos = Pair.second;
+ BasicBlock::iterator StartBBBegin = LocalStartBB->begin();
+ for (;;) {
+ if (LocalStartPos == StartBBBegin) {
+ pred_iterator PI(LocalStartBB), PE(LocalStartBB, false);
+ if (PI == PE)
+ // If we've reached the function entry, produce a null dependence.
+ DependingInstructions.insert(0);
+ else
+ // Add the predecessors to the worklist.
+ do {
+ BasicBlock *PredBB = *PI;
+ if (Visited.insert(PredBB))
+ Worklist.push_back(std::make_pair(PredBB, PredBB->end()));
+ } while (++PI != PE);
+ break;
+ }
+
+ Instruction *Inst = --LocalStartPos;
+ if (Depends(Flavor, Inst, Arg, PA)) {
+ DependingInstructions.insert(Inst);
+ break;
+ }
+ }
+ } while (!Worklist.empty());
+
+ // Determine whether the original StartBB post-dominates all of the blocks we
+ // visited. If not, insert a sentinal indicating that most optimizations are
+ // not safe.
+ for (SmallPtrSet<const BasicBlock *, 4>::const_iterator I = Visited.begin(),
+ E = Visited.end(); I != E; ++I) {
+ const BasicBlock *BB = *I;
+ if (BB == StartBB)
+ continue;
+ const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
+ for (succ_const_iterator SI(TI), SE(TI, false); SI != SE; ++SI) {
+ const BasicBlock *Succ = *SI;
+ if (Succ != StartBB && !Visited.count(Succ)) {
+ DependingInstructions.insert(reinterpret_cast<Instruction *>(-1));
+ return;
+ }
+ }
+ }
+}
+
+static bool isNullOrUndef(const Value *V) {
+ return isa<ConstantPointerNull>(V) || isa<UndefValue>(V);
+}
+
+static bool isNoopInstruction(const Instruction *I) {
+ return isa<BitCastInst>(I) ||
+ (isa<GetElementPtrInst>(I) &&
+ cast<GetElementPtrInst>(I)->hasAllZeroIndices());
+}
+
+/// Turn objc_retain into objc_retainAutoreleasedReturnValue if the operand is a
+/// return value.
+void
+ObjCARCOpt::OptimizeRetainCall(Function &F, Instruction *Retain) {
+ ImmutableCallSite CS(GetObjCArg(Retain));
+ const Instruction *Call = CS.getInstruction();
+ if (!Call) return;
+ if (Call->getParent() != Retain->getParent()) return;
+
+ // Check that the call is next to the retain.
+ BasicBlock::const_iterator I = Call;
+ ++I;
+ while (isNoopInstruction(I)) ++I;
+ if (&*I != Retain)
+ return;
+
+ // Turn it to an objc_retainAutoreleasedReturnValue..
+ Changed = true;
+ ++NumPeeps;
+
+ DEBUG(dbgs() << "ObjCARCOpt::OptimizeRetainCall: Transforming "
+ "objc_retain => objc_retainAutoreleasedReturnValue"
+ " since the operand is a return value.\n"
+ " Old: "
+ << *Retain << "\n");
+
+ cast<CallInst>(Retain)->setCalledFunction(getRetainRVCallee(F.getParent()));
+
+ DEBUG(dbgs() << " New: "
+ << *Retain << "\n");
+}
+
+/// Turn objc_retainAutoreleasedReturnValue into objc_retain if the operand is
+/// not a return value. Or, if it can be paired with an
+/// objc_autoreleaseReturnValue, delete the pair and return true.
+bool
+ObjCARCOpt::OptimizeRetainRVCall(Function &F, Instruction *RetainRV) {
+ // Check for the argument being from an immediately preceding call or invoke.
+ const Value *Arg = GetObjCArg(RetainRV);
+ ImmutableCallSite CS(Arg);
+ if (const Instruction *Call = CS.getInstruction()) {
+ if (Call->getParent() == RetainRV->getParent()) {
+ BasicBlock::const_iterator I = Call;
+ ++I;
+ while (isNoopInstruction(I)) ++I;
+ if (&*I == RetainRV)
+ return false;
+ } else if (const InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
+ BasicBlock *RetainRVParent = RetainRV->getParent();
+ if (II->getNormalDest() == RetainRVParent) {
+ BasicBlock::const_iterator I = RetainRVParent->begin();
+ while (isNoopInstruction(I)) ++I;
+ if (&*I == RetainRV)
+ return false;
+ }
+ }
+ }
+
+ // Check for being preceded by an objc_autoreleaseReturnValue on the same
+ // pointer. In this case, we can delete the pair.
+ BasicBlock::iterator I = RetainRV, Begin = RetainRV->getParent()->begin();
+ if (I != Begin) {
+ do --I; while (I != Begin && isNoopInstruction(I));
+ if (GetBasicInstructionClass(I) == IC_AutoreleaseRV &&
+ GetObjCArg(I) == Arg) {
+ Changed = true;
+ ++NumPeeps;
+
+ DEBUG(dbgs() << "ObjCARCOpt::OptimizeRetainRVCall: Erasing " << *I << "\n"
+ << " Erasing " << *RetainRV
+ << "\n");
+
+ EraseInstruction(I);
+ EraseInstruction(RetainRV);
+ return true;
+ }
+ }
+
+ // Turn it to a plain objc_retain.
+ Changed = true;
+ ++NumPeeps;
+
+ DEBUG(dbgs() << "ObjCARCOpt::OptimizeRetainRVCall: Transforming "
+ "objc_retainAutoreleasedReturnValue => "
+ "objc_retain since the operand is not a return value.\n"
+ " Old: "
+ << *RetainRV << "\n");
+
+ cast<CallInst>(RetainRV)->setCalledFunction(getRetainCallee(F.getParent()));
+
+ DEBUG(dbgs() << " New: "
+ << *RetainRV << "\n");
+
+ return false;
+}
+
+/// Turn objc_autoreleaseReturnValue into objc_autorelease if the result is not
+/// used as a return value.
+void
+ObjCARCOpt::OptimizeAutoreleaseRVCall(Function &F, Instruction *AutoreleaseRV,
+ InstructionClass &Class) {
+ // Check for a return of the pointer value.
+ const Value *Ptr = GetObjCArg(AutoreleaseRV);
+ SmallVector<const Value *, 2> Users;
+ Users.push_back(Ptr);
+ do {
+ Ptr = Users.pop_back_val();
+ for (Value::const_use_iterator UI = Ptr->use_begin(), UE = Ptr->use_end();
+ UI != UE; ++UI) {
+ const User *I = *UI;
+ if (isa<ReturnInst>(I) || GetBasicInstructionClass(I) == IC_RetainRV)
+ return;
+ if (isa<BitCastInst>(I))
+ Users.push_back(I);
+ }
+ } while (!Users.empty());
+
+ Changed = true;
+ ++NumPeeps;
+
+ DEBUG(dbgs() << "ObjCARCOpt::OptimizeAutoreleaseRVCall: Transforming "
+ "objc_autoreleaseReturnValue => "
+ "objc_autorelease since its operand is not used as a return "
+ "value.\n"
+ " Old: "
+ << *AutoreleaseRV << "\n");
+
+ CallInst *AutoreleaseRVCI = cast<CallInst>(AutoreleaseRV);
+ AutoreleaseRVCI->
+ setCalledFunction(getAutoreleaseCallee(F.getParent()));
+ AutoreleaseRVCI->setTailCall(false); // Never tail call objc_autorelease.
+ Class = IC_Autorelease;
+
+ DEBUG(dbgs() << " New: "
+ << *AutoreleaseRV << "\n");
+
+}
+
+/// Visit each call, one at a time, and make simplifications without doing any
+/// additional analysis.
+void ObjCARCOpt::OptimizeIndividualCalls(Function &F) {
+ // Reset all the flags in preparation for recomputing them.
+ UsedInThisFunction = 0;
+
+ // Visit all objc_* calls in F.
+ for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
+ Instruction *Inst = &*I++;
+
+ InstructionClass Class = GetBasicInstructionClass(Inst);
+
+ DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Visiting: Class: "
+ << Class << "; " << *Inst << "\n");
+
+ switch (Class) {
+ default: break;
+
+ // Delete no-op casts. These function calls have special semantics, but
+ // the semantics are entirely implemented via lowering in the front-end,
+ // so by the time they reach the optimizer, they are just no-op calls
+ // which return their argument.
+ //
+ // There are gray areas here, as the ability to cast reference-counted
+ // pointers to raw void* and back allows code to break ARC assumptions,
+ // however these are currently considered to be unimportant.
+ case IC_NoopCast:
+ Changed = true;
+ ++NumNoops;
+ DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Erasing no-op cast:"
+ " " << *Inst << "\n");
+ EraseInstruction(Inst);
+ continue;
+
+ // If the pointer-to-weak-pointer is null, it's undefined behavior.
+ case IC_StoreWeak:
+ case IC_LoadWeak:
+ case IC_LoadWeakRetained:
+ case IC_InitWeak:
+ case IC_DestroyWeak: {
+ CallInst *CI = cast<CallInst>(Inst);
+ if (isNullOrUndef(CI->getArgOperand(0))) {
+ Changed = true;
+ Type *Ty = CI->getArgOperand(0)->getType();
+ new StoreInst(UndefValue::get(cast<PointerType>(Ty)->getElementType()),
+ Constant::getNullValue(Ty),
+ CI);
+ llvm::Value *NewValue = UndefValue::get(CI->getType());
+ DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: A null "
+ "pointer-to-weak-pointer is undefined behavior.\n"
+ " Old = " << *CI <<
+ "\n New = " <<
+ *NewValue << "\n");
+ CI->replaceAllUsesWith(NewValue);
+ CI->eraseFromParent();
+ continue;
+ }
+ break;
+ }
+ case IC_CopyWeak:
+ case IC_MoveWeak: {
+ CallInst *CI = cast<CallInst>(Inst);
+ if (isNullOrUndef(CI->getArgOperand(0)) ||
+ isNullOrUndef(CI->getArgOperand(1))) {
+ Changed = true;
+ Type *Ty = CI->getArgOperand(0)->getType();
+ new StoreInst(UndefValue::get(cast<PointerType>(Ty)->getElementType()),
+ Constant::getNullValue(Ty),
+ CI);
+
+ llvm::Value *NewValue = UndefValue::get(CI->getType());
+ DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: A null "
+ "pointer-to-weak-pointer is undefined behavior.\n"
+ " Old = " << *CI <<
+ "\n New = " <<
+ *NewValue << "\n");
+
+ CI->replaceAllUsesWith(NewValue);
+ CI->eraseFromParent();
+ continue;
+ }
+ break;
+ }
+ case IC_Retain:
+ OptimizeRetainCall(F, Inst);
+ break;
+ case IC_RetainRV:
+ if (OptimizeRetainRVCall(F, Inst))
+ continue;
+ break;
+ case IC_AutoreleaseRV:
+ OptimizeAutoreleaseRVCall(F, Inst, Class);
+ break;
+ }
+
+ // objc_autorelease(x) -> objc_release(x) if x is otherwise unused.
+ if (IsAutorelease(Class) && Inst->use_empty()) {
+ CallInst *Call = cast<CallInst>(Inst);
+ const Value *Arg = Call->getArgOperand(0);
+ Arg = FindSingleUseIdentifiedObject(Arg);
+ if (Arg) {
+ Changed = true;
+ ++NumAutoreleases;
+
+ // Create the declaration lazily.
+ LLVMContext &C = Inst->getContext();
+ CallInst *NewCall =
+ CallInst::Create(getReleaseCallee(F.getParent()),
+ Call->getArgOperand(0), "", Call);
+ NewCall->setMetadata(ImpreciseReleaseMDKind,
+ MDNode::get(C, ArrayRef<Value *>()));
+
+ DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Replacing "
+ "objc_autorelease(x) with objc_release(x) since x is "
+ "otherwise unused.\n"
+ " Old: " << *Call <<
+ "\n New: " <<
+ *NewCall << "\n");
+
+ EraseInstruction(Call);
+ Inst = NewCall;
+ Class = IC_Release;
+ }
+ }
+
+ // For functions which can never be passed stack arguments, add
+ // a tail keyword.
+ if (IsAlwaysTail(Class)) {
+ Changed = true;
+ DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Adding tail keyword"
+ " to function since it can never be passed stack args: " << *Inst <<
+ "\n");
+ cast<CallInst>(Inst)->setTailCall();
+ }
+
+ // Ensure that functions that can never have a "tail" keyword due to the
+ // semantics of ARC truly do not do so.
+ if (IsNeverTail(Class)) {
+ Changed = true;
+ DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Removing tail "
+ "keyword from function: " << *Inst <<
+ "\n");
+ cast<CallInst>(Inst)->setTailCall(false);
+ }
+
+ // Set nounwind as needed.
+ if (IsNoThrow(Class)) {
+ Changed = true;
+ DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Found no throw"
+ " class. Setting nounwind on: " << *Inst << "\n");
+ cast<CallInst>(Inst)->setDoesNotThrow();
+ }
+
+ if (!IsNoopOnNull(Class)) {
+ UsedInThisFunction |= 1 << Class;
+ continue;
+ }
+
+ const Value *Arg = GetObjCArg(Inst);
+
+ // ARC calls with null are no-ops. Delete them.
+ if (isNullOrUndef(Arg)) {
+ Changed = true;
+ ++NumNoops;
+ DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: ARC calls with "
+ " null are no-ops. Erasing: " << *Inst << "\n");
+ EraseInstruction(Inst);
+ continue;
+ }
+
+ // Keep track of which of retain, release, autorelease, and retain_block
+ // are actually present in this function.
+ UsedInThisFunction |= 1 << Class;
+
+ // If Arg is a PHI, and one or more incoming values to the
+ // PHI are null, and the call is control-equivalent to the PHI, and there
+ // are no relevant side effects between the PHI and the call, the call
+ // could be pushed up to just those paths with non-null incoming values.
+ // For now, don't bother splitting critical edges for this.
+ SmallVector<std::pair<Instruction *, const Value *>, 4> Worklist;
+ Worklist.push_back(std::make_pair(Inst, Arg));
+ do {
+ std::pair<Instruction *, const Value *> Pair = Worklist.pop_back_val();
+ Inst = Pair.first;
+ Arg = Pair.second;
+
+ const PHINode *PN = dyn_cast<PHINode>(Arg);
+ if (!PN) continue;
+
+ // Determine if the PHI has any null operands, or any incoming
+ // critical edges.
+ bool HasNull = false;
+ bool HasCriticalEdges = false;
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+ Value *Incoming =
+ StripPointerCastsAndObjCCalls(PN->getIncomingValue(i));
+ if (isNullOrUndef(Incoming))
+ HasNull = true;
+ else if (cast<TerminatorInst>(PN->getIncomingBlock(i)->back())
+ .getNumSuccessors() != 1) {
+ HasCriticalEdges = true;
+ break;
+ }
+ }
+ // If we have null operands and no critical edges, optimize.
+ if (!HasCriticalEdges && HasNull) {
+ SmallPtrSet<Instruction *, 4> DependingInstructions;
+ SmallPtrSet<const BasicBlock *, 4> Visited;
+
+ // Check that there is nothing that cares about the reference
+ // count between the call and the phi.
+ switch (Class) {
+ case IC_Retain:
+ case IC_RetainBlock:
+ // These can always be moved up.
+ break;
+ case IC_Release:
+ // These can't be moved across things that care about the retain
+ // count.
+ FindDependencies(NeedsPositiveRetainCount, Arg,
+ Inst->getParent(), Inst,
+ DependingInstructions, Visited, PA);
+ break;
+ case IC_Autorelease:
+ // These can't be moved across autorelease pool scope boundaries.
+ FindDependencies(AutoreleasePoolBoundary, Arg,
+ Inst->getParent(), Inst,
+ DependingInstructions, Visited, PA);
+ break;
+ case IC_RetainRV:
+ case IC_AutoreleaseRV:
+ // Don't move these; the RV optimization depends on the autoreleaseRV
+ // being tail called, and the retainRV being immediately after a call
+ // (which might still happen if we get lucky with codegen layout, but
+ // it's not worth taking the chance).
+ continue;
+ default:
+ llvm_unreachable("Invalid dependence flavor");
+ }
+
+ if (DependingInstructions.size() == 1 &&
+ *DependingInstructions.begin() == PN) {
+ Changed = true;
+ ++NumPartialNoops;
+ // Clone the call into each predecessor that has a non-null value.
+ CallInst *CInst = cast<CallInst>(Inst);
+ Type *ParamTy = CInst->getArgOperand(0)->getType();
+ for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+ Value *Incoming =
+ StripPointerCastsAndObjCCalls(PN->getIncomingValue(i));
+ if (!isNullOrUndef(Incoming)) {
+ CallInst *Clone = cast<CallInst>(CInst->clone());
+ Value *Op = PN->getIncomingValue(i);
+ Instruction *InsertPos = &PN->getIncomingBlock(i)->back();
+ if (Op->getType() != ParamTy)
+ Op = new BitCastInst(Op, ParamTy, "", InsertPos);
+ Clone->setArgOperand(0, Op);
+ Clone->insertBefore(InsertPos);
+
+ DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Cloning "
+ << *CInst << "\n"
+ " And inserting "
+ "clone at " << *InsertPos << "\n");
+ Worklist.push_back(std::make_pair(Clone, Incoming));
+ }
+ }
+ // Erase the original call.
+ DEBUG(dbgs() << "Erasing: " << *CInst << "\n");
+ EraseInstruction(CInst);
+ continue;
+ }
+ }
+ } while (!Worklist.empty());
+ }
+ DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Finished List.\n");
+}
+
+/// Check for critical edges, loop boundaries, irreducible control flow, or
+/// other CFG structures where moving code across the edge would result in it
+/// being executed more.
+void
+ObjCARCOpt::CheckForCFGHazards(const BasicBlock *BB,
+ DenseMap<const BasicBlock *, BBState> &BBStates,
+ BBState &MyStates) const {
+ // If any top-down local-use or possible-dec has a succ which is earlier in
+ // the sequence, forget it.
+ for (BBState::ptr_iterator I = MyStates.top_down_ptr_begin(),
+ E = MyStates.top_down_ptr_end(); I != E; ++I)
+ switch (I->second.GetSeq()) {
+ default: break;
+ case S_Use: {
+ const Value *Arg = I->first;
+ const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
+ bool SomeSuccHasSame = false;
+ bool AllSuccsHaveSame = true;
+ PtrState &S = I->second;
+ succ_const_iterator SI(TI), SE(TI, false);
+
+ for (; SI != SE; ++SI) {
+ Sequence SuccSSeq = S_None;
+ bool SuccSRRIKnownSafe = false;
+ // If VisitBottomUp has pointer information for this successor, take
+ // what we know about it.
+ DenseMap<const BasicBlock *, BBState>::iterator BBI =
+ BBStates.find(*SI);
+ assert(BBI != BBStates.end());
+ const PtrState &SuccS = BBI->second.getPtrBottomUpState(Arg);
+ SuccSSeq = SuccS.GetSeq();
+ SuccSRRIKnownSafe = SuccS.RRI.KnownSafe;
+ switch (SuccSSeq) {
+ case S_None:
+ case S_CanRelease: {
+ if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe) {
+ S.ClearSequenceProgress();
+ break;
+ }
+ continue;
+ }
+ case S_Use:
+ SomeSuccHasSame = true;
+ break;
+ case S_Stop:
+ case S_Release:
+ case S_MovableRelease:
+ if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe)
+ AllSuccsHaveSame = false;
+ break;
+ case S_Retain:
+ llvm_unreachable("bottom-up pointer in retain state!");
+ }
+ }
+ // If the state at the other end of any of the successor edges
+ // matches the current state, require all edges to match. This
+ // guards against loops in the middle of a sequence.
+ if (SomeSuccHasSame && !AllSuccsHaveSame)
+ S.ClearSequenceProgress();
+ break;
+ }
+ case S_CanRelease: {
+ const Value *Arg = I->first;
+ const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
+ bool SomeSuccHasSame = false;
+ bool AllSuccsHaveSame = true;
+ PtrState &S = I->second;
+ succ_const_iterator SI(TI), SE(TI, false);
+
+ for (; SI != SE; ++SI) {
+ Sequence SuccSSeq = S_None;
+ bool SuccSRRIKnownSafe = false;
+ // If VisitBottomUp has pointer information for this successor, take
+ // what we know about it.
+ DenseMap<const BasicBlock *, BBState>::iterator BBI =
+ BBStates.find(*SI);
+ assert(BBI != BBStates.end());
+ const PtrState &SuccS = BBI->second.getPtrBottomUpState(Arg);
+ SuccSSeq = SuccS.GetSeq();
+ SuccSRRIKnownSafe = SuccS.RRI.KnownSafe;
+ switch (SuccSSeq) {
+ case S_None: {
+ if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe) {
+ S.ClearSequenceProgress();
+ break;
+ }
+ continue;
+ }
+ case S_CanRelease:
+ SomeSuccHasSame = true;
+ break;
+ case S_Stop:
+ case S_Release:
+ case S_MovableRelease:
+ case S_Use:
+ if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe)
+ AllSuccsHaveSame = false;
+ break;
+ case S_Retain:
+ llvm_unreachable("bottom-up pointer in retain state!");
+ }
+ }
+ // If the state at the other end of any of the successor edges
+ // matches the current state, require all edges to match. This
+ // guards against loops in the middle of a sequence.
+ if (SomeSuccHasSame && !AllSuccsHaveSame)
+ S.ClearSequenceProgress();
+ break;
+ }
+ }
+}
+
+bool
+ObjCARCOpt::VisitInstructionBottomUp(Instruction *Inst,
+ BasicBlock *BB,
+ MapVector<Value *, RRInfo> &Retains,
+ BBState &MyStates) {
+ bool NestingDetected = false;
+ InstructionClass Class = GetInstructionClass(Inst);
+ const Value *Arg = 0;
+
+ switch (Class) {
+ case IC_Release: {
+ Arg = GetObjCArg(Inst);
+
+ PtrState &S = MyStates.getPtrBottomUpState(Arg);
+
+ // If we see two releases in a row on the same pointer. If so, make
+ // a note, and we'll cicle back to revisit it after we've
+ // hopefully eliminated the second release, which may allow us to
+ // eliminate the first release too.
+ // Theoretically we could implement removal of nested retain+release
+ // pairs by making PtrState hold a stack of states, but this is
+ // simple and avoids adding overhead for the non-nested case.
+ if (S.GetSeq() == S_Release || S.GetSeq() == S_MovableRelease) {
+ DEBUG(dbgs() << "ObjCARCOpt::VisitInstructionBottomUp: Found nested "
+ "releases (i.e. a release pair)\n");
+ NestingDetected = true;
+ }
+
+ MDNode *ReleaseMetadata = Inst->getMetadata(ImpreciseReleaseMDKind);
+ S.ResetSequenceProgress(ReleaseMetadata ? S_MovableRelease : S_Release);
+ S.RRI.ReleaseMetadata = ReleaseMetadata;
+ S.RRI.KnownSafe = S.IsKnownIncremented();
+ S.RRI.IsTailCallRelease = cast<CallInst>(Inst)->isTailCall();
+ S.RRI.Calls.insert(Inst);
+
+ S.SetKnownPositiveRefCount();
+ break;
+ }
+ case IC_RetainBlock:
+ // An objc_retainBlock call with just a use may need to be kept,
+ // because it may be copying a block from the stack to the heap.
+ if (!IsRetainBlockOptimizable(Inst))
+ break;
+ // FALLTHROUGH
+ case IC_Retain:
+ case IC_RetainRV: {
+ Arg = GetObjCArg(Inst);
+
+ PtrState &S = MyStates.getPtrBottomUpState(Arg);
+ S.SetKnownPositiveRefCount();
+
+ switch (S.GetSeq()) {
+ case S_Stop:
+ case S_Release:
+ case S_MovableRelease:
+ case S_Use:
+ S.RRI.ReverseInsertPts.clear();
+ // FALL THROUGH
+ case S_CanRelease:
+ // Don't do retain+release tracking for IC_RetainRV, because it's
+ // better to let it remain as the first instruction after a call.
+ if (Class != IC_RetainRV) {
+ S.RRI.IsRetainBlock = Class == IC_RetainBlock;
+ Retains[Inst] = S.RRI;
+ }
+ S.ClearSequenceProgress();
+ break;
+ case S_None:
+ break;
+ case S_Retain:
+ llvm_unreachable("bottom-up pointer in retain state!");
+ }
+ return NestingDetected;
+ }
+ case IC_AutoreleasepoolPop:
+ // Conservatively, clear MyStates for all known pointers.
+ MyStates.clearBottomUpPointers();
+ return NestingDetected;
+ case IC_AutoreleasepoolPush:
+ case IC_None:
+ // These are irrelevant.
+ return NestingDetected;
+ default:
+ break;
+ }
+
+ // Consider any other possible effects of this instruction on each
+ // pointer being tracked.
+ for (BBState::ptr_iterator MI = MyStates.bottom_up_ptr_begin(),
+ ME = MyStates.bottom_up_ptr_end(); MI != ME; ++MI) {
+ const Value *Ptr = MI->first;
+ if (Ptr == Arg)
+ continue; // Handled above.
+ PtrState &S = MI->second;
+ Sequence Seq = S.GetSeq();
+
+ // Check for possible releases.
+ if (CanAlterRefCount(Inst, Ptr, PA, Class)) {
+ S.ClearRefCount();
+ switch (Seq) {
+ case S_Use:
+ S.SetSeq(S_CanRelease);
+ continue;
+ case S_CanRelease:
+ case S_Release:
+ case S_MovableRelease:
+ case S_Stop:
+ case S_None:
+ break;
+ case S_Retain:
+ llvm_unreachable("bottom-up pointer in retain state!");
+ }
+ }
+
+ // Check for possible direct uses.
+ switch (Seq) {
+ case S_Release:
+ case S_MovableRelease:
+ if (CanUse(Inst, Ptr, PA, Class)) {
+ assert(S.RRI.ReverseInsertPts.empty());
+ // If this is an invoke instruction, we're scanning it as part of
+ // one of its successor blocks, since we can't insert code after it
+ // in its own block, and we don't want to split critical edges.
+ if (isa<InvokeInst>(Inst))
+ S.RRI.ReverseInsertPts.insert(BB->getFirstInsertionPt());
+ else
+ S.RRI.ReverseInsertPts.insert(llvm::next(BasicBlock::iterator(Inst)));
+ S.SetSeq(S_Use);
+ } else if (Seq == S_Release &&
+ (Class == IC_User || Class == IC_CallOrUser)) {
+ // Non-movable releases depend on any possible objc pointer use.
+ S.SetSeq(S_Stop);
+ assert(S.RRI.ReverseInsertPts.empty());
+ // As above; handle invoke specially.
+ if (isa<InvokeInst>(Inst))
+ S.RRI.ReverseInsertPts.insert(BB->getFirstInsertionPt());
+ else
+ S.RRI.ReverseInsertPts.insert(llvm::next(BasicBlock::iterator(Inst)));
+ }
+ break;
+ case S_Stop:
+ if (CanUse(Inst, Ptr, PA, Class))
+ S.SetSeq(S_Use);
+ break;
+ case S_CanRelease:
+ case S_Use:
+ case S_None:
+ break;
+ case S_Retain:
+ llvm_unreachable("bottom-up pointer in retain state!");
+ }
+ }
+
+ return NestingDetected;
+}
+
+bool
+ObjCARCOpt::VisitBottomUp(BasicBlock *BB,
+ DenseMap<const BasicBlock *, BBState> &BBStates,
+ MapVector<Value *, RRInfo> &Retains) {
+ bool NestingDetected = false;
+ BBState &MyStates = BBStates[BB];
+
+ // Merge the states from each successor to compute the initial state
+ // for the current block.
+ BBState::edge_iterator SI(MyStates.succ_begin()),
+ SE(MyStates.succ_end());
+ if (SI != SE) {
+ const BasicBlock *Succ = *SI;
+ DenseMap<const BasicBlock *, BBState>::iterator I = BBStates.find(Succ);
+ assert(I != BBStates.end());
+ MyStates.InitFromSucc(I->second);
+ ++SI;
+ for (; SI != SE; ++SI) {
+ Succ = *SI;
+ I = BBStates.find(Succ);
+ assert(I != BBStates.end());
+ MyStates.MergeSucc(I->second);
+ }
+ }
+
+ // Visit all the instructions, bottom-up.
+ for (BasicBlock::iterator I = BB->end(), E = BB->begin(); I != E; --I) {
+ Instruction *Inst = llvm::prior(I);
+
+ // Invoke instructions are visited as part of their successors (below).
+ if (isa<InvokeInst>(Inst))
+ continue;
+
+ DEBUG(dbgs() << "ObjCARCOpt::VisitButtonUp: Visiting " << *Inst << "\n");
+
+ NestingDetected |= VisitInstructionBottomUp(Inst, BB, Retains, MyStates);
+ }
+
+ // If there's a predecessor with an invoke, visit the invoke as if it were
+ // part of this block, since we can't insert code after an invoke in its own
+ // block, and we don't want to split critical edges.
+ for (BBState::edge_iterator PI(MyStates.pred_begin()),
+ PE(MyStates.pred_end()); PI != PE; ++PI) {
+ BasicBlock *Pred = *PI;
+ if (InvokeInst *II = dyn_cast<InvokeInst>(&Pred->back()))
+ NestingDetected |= VisitInstructionBottomUp(II, BB, Retains, MyStates);
+ }
+
+ return NestingDetected;
+}
+
+bool
+ObjCARCOpt::VisitInstructionTopDown(Instruction *Inst,
+ DenseMap<Value *, RRInfo> &Releases,
+ BBState &MyStates) {
+ bool NestingDetected = false;
+ InstructionClass Class = GetInstructionClass(Inst);
+ const Value *Arg = 0;
+
+ switch (Class) {
+ case IC_RetainBlock:
+ // An objc_retainBlock call with just a use may need to be kept,
+ // because it may be copying a block from the stack to the heap.
+ if (!IsRetainBlockOptimizable(Inst))
+ break;
+ // FALLTHROUGH
+ case IC_Retain:
+ case IC_RetainRV: {
+ Arg = GetObjCArg(Inst);
+
+ PtrState &S = MyStates.getPtrTopDownState(Arg);
+
+ // Don't do retain+release tracking for IC_RetainRV, because it's
+ // better to let it remain as the first instruction after a call.
+ if (Class != IC_RetainRV) {
+ // If we see two retains in a row on the same pointer. If so, make
+ // a note, and we'll cicle back to revisit it after we've
+ // hopefully eliminated the second retain, which may allow us to
+ // eliminate the first retain too.
+ // Theoretically we could implement removal of nested retain+release
+ // pairs by making PtrState hold a stack of states, but this is
+ // simple and avoids adding overhead for the non-nested case.
+ if (S.GetSeq() == S_Retain)
+ NestingDetected = true;
+
+ S.ResetSequenceProgress(S_Retain);
+ S.RRI.IsRetainBlock = Class == IC_RetainBlock;
+ S.RRI.KnownSafe = S.IsKnownIncremented();
+ S.RRI.Calls.insert(Inst);
+ }
+
+ S.SetKnownPositiveRefCount();
+
+ // A retain can be a potential use; procede to the generic checking
+ // code below.
+ break;
+ }
+ case IC_Release: {
+ Arg = GetObjCArg(Inst);
+
+ PtrState &S = MyStates.getPtrTopDownState(Arg);
+ S.ClearRefCount();
+
+ switch (S.GetSeq()) {
+ case S_Retain:
+ case S_CanRelease:
+ S.RRI.ReverseInsertPts.clear();
+ // FALL THROUGH
+ case S_Use:
+ S.RRI.ReleaseMetadata = Inst->getMetadata(ImpreciseReleaseMDKind);
+ S.RRI.IsTailCallRelease = cast<CallInst>(Inst)->isTailCall();
+ Releases[Inst] = S.RRI;
+ S.ClearSequenceProgress();
+ break;
+ case S_None:
+ break;
+ case S_Stop:
+ case S_Release:
+ case S_MovableRelease:
+ llvm_unreachable("top-down pointer in release state!");
+ }
+ break;
+ }
+ case IC_AutoreleasepoolPop:
+ // Conservatively, clear MyStates for all known pointers.
+ MyStates.clearTopDownPointers();
+ return NestingDetected;
+ case IC_AutoreleasepoolPush:
+ case IC_None:
+ // These are irrelevant.
+ return NestingDetected;
+ default:
+ break;
+ }
+
+ // Consider any other possible effects of this instruction on each
+ // pointer being tracked.
+ for (BBState::ptr_iterator MI = MyStates.top_down_ptr_begin(),
+ ME = MyStates.top_down_ptr_end(); MI != ME; ++MI) {
+ const Value *Ptr = MI->first;
+ if (Ptr == Arg)
+ continue; // Handled above.
+ PtrState &S = MI->second;
+ Sequence Seq = S.GetSeq();
+
+ // Check for possible releases.
+ if (CanAlterRefCount(Inst, Ptr, PA, Class)) {
+ S.ClearRefCount();
+ switch (Seq) {
+ case S_Retain:
+ S.SetSeq(S_CanRelease);
+ assert(S.RRI.ReverseInsertPts.empty());
+ S.RRI.ReverseInsertPts.insert(Inst);
+
+ // One call can't cause a transition from S_Retain to S_CanRelease
+ // and S_CanRelease to S_Use. If we've made the first transition,
+ // we're done.
+ continue;
+ case S_Use:
+ case S_CanRelease:
+ case S_None:
+ break;
+ case S_Stop:
+ case S_Release:
+ case S_MovableRelease:
+ llvm_unreachable("top-down pointer in release state!");
+ }
+ }
+
+ // Check for possible direct uses.
+ switch (Seq) {
+ case S_CanRelease:
+ if (CanUse(Inst, Ptr, PA, Class))
+ S.SetSeq(S_Use);
+ break;
+ case S_Retain:
+ case S_Use:
+ case S_None:
+ break;
+ case S_Stop:
+ case S_Release:
+ case S_MovableRelease:
+ llvm_unreachable("top-down pointer in release state!");
+ }
+ }
+
+ return NestingDetected;
+}
+
+bool
+ObjCARCOpt::VisitTopDown(BasicBlock *BB,
+ DenseMap<const BasicBlock *, BBState> &BBStates,
+ DenseMap<Value *, RRInfo> &Releases) {
+ bool NestingDetected = false;
+ BBState &MyStates = BBStates[BB];
+
+ // Merge the states from each predecessor to compute the initial state
+ // for the current block.
+ BBState::edge_iterator PI(MyStates.pred_begin()),
+ PE(MyStates.pred_end());
+ if (PI != PE) {
+ const BasicBlock *Pred = *PI;
+ DenseMap<const BasicBlock *, BBState>::iterator I = BBStates.find(Pred);
+ assert(I != BBStates.end());
+ MyStates.InitFromPred(I->second);
+ ++PI;
+ for (; PI != PE; ++PI) {
+ Pred = *PI;
+ I = BBStates.find(Pred);
+ assert(I != BBStates.end());
+ MyStates.MergePred(I->second);
+ }
+ }
+
+ // Visit all the instructions, top-down.
+ for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
+ Instruction *Inst = I;
+
+ DEBUG(dbgs() << "ObjCARCOpt::VisitTopDown: Visiting " << *Inst << "\n");
+
+ NestingDetected |= VisitInstructionTopDown(Inst, Releases, MyStates);
+ }
+
+ CheckForCFGHazards(BB, BBStates, MyStates);
+ return NestingDetected;
+}
+
+static void
+ComputePostOrders(Function &F,
+ SmallVectorImpl<BasicBlock *> &PostOrder,
+ SmallVectorImpl<BasicBlock *> &ReverseCFGPostOrder,
+ unsigned NoObjCARCExceptionsMDKind,
+ DenseMap<const BasicBlock *, BBState> &BBStates) {
+ /// The visited set, for doing DFS walks.
+ SmallPtrSet<BasicBlock *, 16> Visited;
+
+ // Do DFS, computing the PostOrder.
+ SmallPtrSet<BasicBlock *, 16> OnStack;
+ SmallVector<std::pair<BasicBlock *, succ_iterator>, 16> SuccStack;
+
+ // Functions always have exactly one entry block, and we don't have
+ // any other block that we treat like an entry block.
+ BasicBlock *EntryBB = &F.getEntryBlock();
+ BBState &MyStates = BBStates[EntryBB];
+ MyStates.SetAsEntry();
+ TerminatorInst *EntryTI = cast<TerminatorInst>(&EntryBB->back());
+ SuccStack.push_back(std::make_pair(EntryBB, succ_iterator(EntryTI)));
+ Visited.insert(EntryBB);
+ OnStack.insert(EntryBB);
+ do {
+ dfs_next_succ:
+ BasicBlock *CurrBB = SuccStack.back().first;
+ TerminatorInst *TI = cast<TerminatorInst>(&CurrBB->back());
+ succ_iterator SE(TI, false);
+
+ while (SuccStack.back().second != SE) {
+ BasicBlock *SuccBB = *SuccStack.back().second++;
+ if (Visited.insert(SuccBB)) {
+ TerminatorInst *TI = cast<TerminatorInst>(&SuccBB->back());
+ SuccStack.push_back(std::make_pair(SuccBB, succ_iterator(TI)));
+ BBStates[CurrBB].addSucc(SuccBB);
+ BBState &SuccStates = BBStates[SuccBB];
+ SuccStates.addPred(CurrBB);
+ OnStack.insert(SuccBB);
+ goto dfs_next_succ;
+ }
+
+ if (!OnStack.count(SuccBB)) {
+ BBStates[CurrBB].addSucc(SuccBB);
+ BBStates[SuccBB].addPred(CurrBB);
+ }
+ }
+ OnStack.erase(CurrBB);
+ PostOrder.push_back(CurrBB);
+ SuccStack.pop_back();
+ } while (!SuccStack.empty());
+
+ Visited.clear();
+
+ // Do reverse-CFG DFS, computing the reverse-CFG PostOrder.
+ // Functions may have many exits, and there also blocks which we treat
+ // as exits due to ignored edges.
+ SmallVector<std::pair<BasicBlock *, BBState::edge_iterator>, 16> PredStack;
+ for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) {
+ BasicBlock *ExitBB = I;
+ BBState &MyStates = BBStates[ExitBB];
+ if (!MyStates.isExit())
+ continue;
+
+ MyStates.SetAsExit();
+
+ PredStack.push_back(std::make_pair(ExitBB, MyStates.pred_begin()));
+ Visited.insert(ExitBB);
+ while (!PredStack.empty()) {
+ reverse_dfs_next_succ:
+ BBState::edge_iterator PE = BBStates[PredStack.back().first].pred_end();
+ while (PredStack.back().second != PE) {
+ BasicBlock *BB = *PredStack.back().second++;
+ if (Visited.insert(BB)) {
+ PredStack.push_back(std::make_pair(BB, BBStates[BB].pred_begin()));
+ goto reverse_dfs_next_succ;
+ }
+ }
+ ReverseCFGPostOrder.push_back(PredStack.pop_back_val().first);
+ }
+ }
+}
+
+// Visit the function both top-down and bottom-up.
+bool
+ObjCARCOpt::Visit(Function &F,
+ DenseMap<const BasicBlock *, BBState> &BBStates,
+ MapVector<Value *, RRInfo> &Retains,
+ DenseMap<Value *, RRInfo> &Releases) {
+
+ // Use reverse-postorder traversals, because we magically know that loops
+ // will be well behaved, i.e. they won't repeatedly call retain on a single
+ // pointer without doing a release. We can't use the ReversePostOrderTraversal
+ // class here because we want the reverse-CFG postorder to consider each
+ // function exit point, and we want to ignore selected cycle edges.
+ SmallVector<BasicBlock *, 16> PostOrder;
+ SmallVector<BasicBlock *, 16> ReverseCFGPostOrder;
+ ComputePostOrders(F, PostOrder, ReverseCFGPostOrder,
+ NoObjCARCExceptionsMDKind,
+ BBStates);
+
+ // Use reverse-postorder on the reverse CFG for bottom-up.
+ bool BottomUpNestingDetected = false;
+ for (SmallVectorImpl<BasicBlock *>::const_reverse_iterator I =
+ ReverseCFGPostOrder.rbegin(), E = ReverseCFGPostOrder.rend();
+ I != E; ++I)
+ BottomUpNestingDetected |= VisitBottomUp(*I, BBStates, Retains);
+
+ // Use reverse-postorder for top-down.
+ bool TopDownNestingDetected = false;
+ for (SmallVectorImpl<BasicBlock *>::const_reverse_iterator I =
+ PostOrder.rbegin(), E = PostOrder.rend();
+ I != E; ++I)
+ TopDownNestingDetected |= VisitTopDown(*I, BBStates, Releases);
+
+ return TopDownNestingDetected && BottomUpNestingDetected;
+}
+
+/// Move the calls in RetainsToMove and ReleasesToMove.
+void ObjCARCOpt::MoveCalls(Value *Arg,
+ RRInfo &RetainsToMove,
+ RRInfo &ReleasesToMove,
+ MapVector<Value *, RRInfo> &Retains,
+ DenseMap<Value *, RRInfo> &Releases,
+ SmallVectorImpl<Instruction *> &DeadInsts,
+ Module *M) {
+ Type *ArgTy = Arg->getType();
+ Type *ParamTy = PointerType::getUnqual(Type::getInt8Ty(ArgTy->getContext()));
+
+ // Insert the new retain and release calls.
+ for (SmallPtrSet<Instruction *, 2>::const_iterator
+ PI = ReleasesToMove.ReverseInsertPts.begin(),
+ PE = ReleasesToMove.ReverseInsertPts.end(); PI != PE; ++PI) {
+ Instruction *InsertPt = *PI;
+ Value *MyArg = ArgTy == ParamTy ? Arg :
+ new BitCastInst(Arg, ParamTy, "", InsertPt);
+ CallInst *Call =
+ CallInst::Create(RetainsToMove.IsRetainBlock ?
+ getRetainBlockCallee(M) : getRetainCallee(M),
+ MyArg, "", InsertPt);
+ Call->setDoesNotThrow();
+ if (RetainsToMove.IsRetainBlock)
+ Call->setMetadata(CopyOnEscapeMDKind,
+ MDNode::get(M->getContext(), ArrayRef<Value *>()));
+ else
+ Call->setTailCall();
+
+ DEBUG(dbgs() << "ObjCARCOpt::MoveCalls: Inserting new Release: " << *Call
+ << "\n"
+ " At insertion point: " << *InsertPt
+ << "\n");
+ }
+ for (SmallPtrSet<Instruction *, 2>::const_iterator
+ PI = RetainsToMove.ReverseInsertPts.begin(),
+ PE = RetainsToMove.ReverseInsertPts.end(); PI != PE; ++PI) {
+ Instruction *InsertPt = *PI;
+ Value *MyArg = ArgTy == ParamTy ? Arg :
+ new BitCastInst(Arg, ParamTy, "", InsertPt);
+ CallInst *Call = CallInst::Create(getReleaseCallee(M), MyArg,
+ "", InsertPt);
+ // Attach a clang.imprecise_release metadata tag, if appropriate.
+ if (MDNode *M = ReleasesToMove.ReleaseMetadata)
+ Call->setMetadata(ImpreciseReleaseMDKind, M);
+ Call->setDoesNotThrow();
+ if (ReleasesToMove.IsTailCallRelease)
+ Call->setTailCall();
+
+ DEBUG(dbgs() << "ObjCARCOpt::MoveCalls: Inserting new Retain: " << *Call
+ << "\n"
+ " At insertion point: " << *InsertPt
+ << "\n");
+ }
+
+ // Delete the original retain and release calls.
+ for (SmallPtrSet<Instruction *, 2>::const_iterator
+ AI = RetainsToMove.Calls.begin(),
+ AE = RetainsToMove.Calls.end(); AI != AE; ++AI) {
+ Instruction *OrigRetain = *AI;
+ Retains.blot(OrigRetain);
+ DeadInsts.push_back(OrigRetain);
+ DEBUG(dbgs() << "ObjCARCOpt::MoveCalls: Deleting retain: " << *OrigRetain <<
+ "\n");
+ }
+ for (SmallPtrSet<Instruction *, 2>::const_iterator
+ AI = ReleasesToMove.Calls.begin(),
+ AE = ReleasesToMove.Calls.end(); AI != AE; ++AI) {
+ Instruction *OrigRelease = *AI;
+ Releases.erase(OrigRelease);
+ DeadInsts.push_back(OrigRelease);
+ DEBUG(dbgs() << "ObjCARCOpt::MoveCalls: Deleting release: " << *OrigRelease
+ << "\n");
+ }
+}
+
+bool
+ObjCARCOpt::ConnectTDBUTraversals(DenseMap<const BasicBlock *, BBState>
+ &BBStates,
+ MapVector<Value *, RRInfo> &Retains,
+ DenseMap<Value *, RRInfo> &Releases,
+ Module *M,
+ SmallVector<Instruction *, 4> &NewRetains,
+ SmallVector<Instruction *, 4> &NewReleases,
+ SmallVector<Instruction *, 8> &DeadInsts,
+ RRInfo &RetainsToMove,
+ RRInfo &ReleasesToMove,
+ Value *Arg,
+ bool KnownSafe,
+ bool &AnyPairsCompletelyEliminated) {
+ // If a pair happens in a region where it is known that the reference count
+ // is already incremented, we can similarly ignore possible decrements.
+ bool KnownSafeTD = true, KnownSafeBU = true;
+
+ // Connect the dots between the top-down-collected RetainsToMove and
+ // bottom-up-collected ReleasesToMove to form sets of related calls.
+ // This is an iterative process so that we connect multiple releases
+ // to multiple retains if needed.
+ unsigned OldDelta = 0;
+ unsigned NewDelta = 0;
+ unsigned OldCount = 0;
+ unsigned NewCount = 0;
+ bool FirstRelease = true;
+ bool FirstRetain = true;
+ for (;;) {
+ for (SmallVectorImpl<Instruction *>::const_iterator
+ NI = NewRetains.begin(), NE = NewRetains.end(); NI != NE; ++NI) {
+ Instruction *NewRetain = *NI;
+ MapVector<Value *, RRInfo>::const_iterator It = Retains.find(NewRetain);
+ assert(It != Retains.end());
+ const RRInfo &NewRetainRRI = It->second;
+ KnownSafeTD &= NewRetainRRI.KnownSafe;
+ for (SmallPtrSet<Instruction *, 2>::const_iterator
+ LI = NewRetainRRI.Calls.begin(),
+ LE = NewRetainRRI.Calls.end(); LI != LE; ++LI) {
+ Instruction *NewRetainRelease = *LI;
+ DenseMap<Value *, RRInfo>::const_iterator Jt =
+ Releases.find(NewRetainRelease);
+ if (Jt == Releases.end())
+ return false;
+ const RRInfo &NewRetainReleaseRRI = Jt->second;
+ assert(NewRetainReleaseRRI.Calls.count(NewRetain));
+ if (ReleasesToMove.Calls.insert(NewRetainRelease)) {
+ OldDelta -=
+ BBStates[NewRetainRelease->getParent()].GetAllPathCount();
+
+ // Merge the ReleaseMetadata and IsTailCallRelease values.
+ if (FirstRelease) {
+ ReleasesToMove.ReleaseMetadata =
+ NewRetainReleaseRRI.ReleaseMetadata;
+ ReleasesToMove.IsTailCallRelease =
+ NewRetainReleaseRRI.IsTailCallRelease;
+ FirstRelease = false;
+ } else {
+ if (ReleasesToMove.ReleaseMetadata !=
+ NewRetainReleaseRRI.ReleaseMetadata)
+ ReleasesToMove.ReleaseMetadata = 0;
+ if (ReleasesToMove.IsTailCallRelease !=
+ NewRetainReleaseRRI.IsTailCallRelease)
+ ReleasesToMove.IsTailCallRelease = false;
+ }
+
+ // Collect the optimal insertion points.
+ if (!KnownSafe)
+ for (SmallPtrSet<Instruction *, 2>::const_iterator
+ RI = NewRetainReleaseRRI.ReverseInsertPts.begin(),
+ RE = NewRetainReleaseRRI.ReverseInsertPts.end();
+ RI != RE; ++RI) {
+ Instruction *RIP = *RI;
+ if (ReleasesToMove.ReverseInsertPts.insert(RIP))
+ NewDelta -= BBStates[RIP->getParent()].GetAllPathCount();
+ }
+ NewReleases.push_back(NewRetainRelease);
+ }
+ }
+ }
+ NewRetains.clear();
+ if (NewReleases.empty()) break;
+
+ // Back the other way.
+ for (SmallVectorImpl<Instruction *>::const_iterator
+ NI = NewReleases.begin(), NE = NewReleases.end(); NI != NE; ++NI) {
+ Instruction *NewRelease = *NI;
+ DenseMap<Value *, RRInfo>::const_iterator It =
+ Releases.find(NewRelease);
+ assert(It != Releases.end());
+ const RRInfo &NewReleaseRRI = It->second;
+ KnownSafeBU &= NewReleaseRRI.KnownSafe;
+ for (SmallPtrSet<Instruction *, 2>::const_iterator
+ LI = NewReleaseRRI.Calls.begin(),
+ LE = NewReleaseRRI.Calls.end(); LI != LE; ++LI) {
+ Instruction *NewReleaseRetain = *LI;
+ MapVector<Value *, RRInfo>::const_iterator Jt =
+ Retains.find(NewReleaseRetain);
+ if (Jt == Retains.end())
+ return false;
+ const RRInfo &NewReleaseRetainRRI = Jt->second;
+ assert(NewReleaseRetainRRI.Calls.count(NewRelease));
+ if (RetainsToMove.Calls.insert(NewReleaseRetain)) {
+ unsigned PathCount =
+ BBStates[NewReleaseRetain->getParent()].GetAllPathCount();
+ OldDelta += PathCount;
+ OldCount += PathCount;
+
+ // Merge the IsRetainBlock values.
+ if (FirstRetain) {
+ RetainsToMove.IsRetainBlock = NewReleaseRetainRRI.IsRetainBlock;
+ FirstRetain = false;
+ } else if (ReleasesToMove.IsRetainBlock !=
+ NewReleaseRetainRRI.IsRetainBlock)
+ // It's not possible to merge the sequences if one uses
+ // objc_retain and the other uses objc_retainBlock.
+ return false;
+
+ // Collect the optimal insertion points.
+ if (!KnownSafe)
+ for (SmallPtrSet<Instruction *, 2>::const_iterator
+ RI = NewReleaseRetainRRI.ReverseInsertPts.begin(),
+ RE = NewReleaseRetainRRI.ReverseInsertPts.end();
+ RI != RE; ++RI) {
+ Instruction *RIP = *RI;
+ if (RetainsToMove.ReverseInsertPts.insert(RIP)) {
+ PathCount = BBStates[RIP->getParent()].GetAllPathCount();
+ NewDelta += PathCount;
+ NewCount += PathCount;
+ }
+ }
+ NewRetains.push_back(NewReleaseRetain);
+ }
+ }
+ }
+ NewReleases.clear();
+ if (NewRetains.empty()) break;
+ }
+
+ // If the pointer is known incremented or nested, we can safely delete the
+ // pair regardless of what's between them.
+ if (KnownSafeTD || KnownSafeBU) {
+ RetainsToMove.ReverseInsertPts.clear();
+ ReleasesToMove.ReverseInsertPts.clear();
+ NewCount = 0;
+ } else {
+ // Determine whether the new insertion points we computed preserve the
+ // balance of retain and release calls through the program.
+ // TODO: If the fully aggressive solution isn't valid, try to find a
+ // less aggressive solution which is.
+ if (NewDelta != 0)
+ return false;
+ }
+
+ // Determine whether the original call points are balanced in the retain and
+ // release calls through the program. If not, conservatively don't touch
+ // them.
+ // TODO: It's theoretically possible to do code motion in this case, as
+ // long as the existing imbalances are maintained.
+ if (OldDelta != 0)
+ return false;
+
+ Changed = true;
+ assert(OldCount != 0 && "Unreachable code?");
+ NumRRs += OldCount - NewCount;
+ // Set to true if we completely removed any RR pairs.
+ AnyPairsCompletelyEliminated = NewCount == 0;
+
+ // We can move calls!
+ return true;
+}
+
+/// Identify pairings between the retains and releases, and delete and/or move
+/// them.
+bool
+ObjCARCOpt::PerformCodePlacement(DenseMap<const BasicBlock *, BBState>
+ &BBStates,
+ MapVector<Value *, RRInfo> &Retains,
+ DenseMap<Value *, RRInfo> &Releases,
+ Module *M) {
+ bool AnyPairsCompletelyEliminated = false;
+ RRInfo RetainsToMove;
+ RRInfo ReleasesToMove;
+ SmallVector<Instruction *, 4> NewRetains;
+ SmallVector<Instruction *, 4> NewReleases;
+ SmallVector<Instruction *, 8> DeadInsts;
+
+ // Visit each retain.
+ for (MapVector<Value *, RRInfo>::const_iterator I = Retains.begin(),
+ E = Retains.end(); I != E; ++I) {
+ Value *V = I->first;
+ if (!V) continue; // blotted
+
+ Instruction *Retain = cast<Instruction>(V);
+
+ DEBUG(dbgs() << "ObjCARCOpt::PerformCodePlacement: Visiting: " << *Retain
+ << "\n");
+
+ Value *Arg = GetObjCArg(Retain);
+
+ // If the object being released is in static or stack storage, we know it's
+ // not being managed by ObjC reference counting, so we can delete pairs
+ // regardless of what possible decrements or uses lie between them.
+ bool KnownSafe = isa<Constant>(Arg) || isa<AllocaInst>(Arg);
+
+ // A constant pointer can't be pointing to an object on the heap. It may
+ // be reference-counted, but it won't be deleted.
+ if (const LoadInst *LI = dyn_cast<LoadInst>(Arg))
+ if (const GlobalVariable *GV =
+ dyn_cast<GlobalVariable>(
+ StripPointerCastsAndObjCCalls(LI->getPointerOperand())))
+ if (GV->isConstant())
+ KnownSafe = true;
+
+ // Connect the dots between the top-down-collected RetainsToMove and
+ // bottom-up-collected ReleasesToMove to form sets of related calls.
+ NewRetains.push_back(Retain);
+ bool PerformMoveCalls =
+ ConnectTDBUTraversals(BBStates, Retains, Releases, M, NewRetains,
+ NewReleases, DeadInsts, RetainsToMove,
+ ReleasesToMove, Arg, KnownSafe,
+ AnyPairsCompletelyEliminated);
+
+ if (PerformMoveCalls) {
+ // Ok, everything checks out and we're all set. Let's move/delete some
+ // code!
+ MoveCalls(Arg, RetainsToMove, ReleasesToMove,
+ Retains, Releases, DeadInsts, M);
+ }
+
+ // Clean up state for next retain.
+ NewReleases.clear();
+ NewRetains.clear();
+ RetainsToMove.clear();
+ ReleasesToMove.clear();
+ }
+
+ // Now that we're done moving everything, we can delete the newly dead
+ // instructions, as we no longer need them as insert points.
+ while (!DeadInsts.empty())
+ EraseInstruction(DeadInsts.pop_back_val());
+
+ return AnyPairsCompletelyEliminated;
+}
+
+/// Weak pointer optimizations.
+void ObjCARCOpt::OptimizeWeakCalls(Function &F) {
+ // First, do memdep-style RLE and S2L optimizations. We can't use memdep
+ // itself because it uses AliasAnalysis and we need to do provenance
+ // queries instead.
+ for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
+ Instruction *Inst = &*I++;
+
+ DEBUG(dbgs() << "ObjCARCOpt::OptimizeWeakCalls: Visiting: " << *Inst <<
+ "\n");
+
+ InstructionClass Class = GetBasicInstructionClass(Inst);
+ if (Class != IC_LoadWeak && Class != IC_LoadWeakRetained)
+ continue;
+
+ // Delete objc_loadWeak calls with no users.
+ if (Class == IC_LoadWeak && Inst->use_empty()) {
+ Inst->eraseFromParent();
+ continue;
+ }
+
+ // TODO: For now, just look for an earlier available version of this value
+ // within the same block. Theoretically, we could do memdep-style non-local
+ // analysis too, but that would want caching. A better approach would be to
+ // use the technique that EarlyCSE uses.
+ inst_iterator Current = llvm::prior(I);
+ BasicBlock *CurrentBB = Current.getBasicBlockIterator();
+ for (BasicBlock::iterator B = CurrentBB->begin(),
+ J = Current.getInstructionIterator();
+ J != B; --J) {
+ Instruction *EarlierInst = &*llvm::prior(J);
+ InstructionClass EarlierClass = GetInstructionClass(EarlierInst);
+ switch (EarlierClass) {
+ case IC_LoadWeak:
+ case IC_LoadWeakRetained: {
+ // If this is loading from the same pointer, replace this load's value
+ // with that one.
+ CallInst *Call = cast<CallInst>(Inst);
+ CallInst *EarlierCall = cast<CallInst>(EarlierInst);
+ Value *Arg = Call->getArgOperand(0);
+ Value *EarlierArg = EarlierCall->getArgOperand(0);
+ switch (PA.getAA()->alias(Arg, EarlierArg)) {
+ case AliasAnalysis::MustAlias:
+ Changed = true;
+ // If the load has a builtin retain, insert a plain retain for it.
+ if (Class == IC_LoadWeakRetained) {
+ CallInst *CI =
+ CallInst::Create(getRetainCallee(F.getParent()), EarlierCall,
+ "", Call);
+ CI->setTailCall();
+ }
+ // Zap the fully redundant load.
+ Call->replaceAllUsesWith(EarlierCall);
+ Call->eraseFromParent();
+ goto clobbered;
+ case AliasAnalysis::MayAlias:
+ case AliasAnalysis::PartialAlias:
+ goto clobbered;
+ case AliasAnalysis::NoAlias:
+ break;
+ }
+ break;
+ }
+ case IC_StoreWeak:
+ case IC_InitWeak: {
+ // If this is storing to the same pointer and has the same size etc.
+ // replace this load's value with the stored value.
+ CallInst *Call = cast<CallInst>(Inst);
+ CallInst *EarlierCall = cast<CallInst>(EarlierInst);
+ Value *Arg = Call->getArgOperand(0);
+ Value *EarlierArg = EarlierCall->getArgOperand(0);
+ switch (PA.getAA()->alias(Arg, EarlierArg)) {
+ case AliasAnalysis::MustAlias:
+ Changed = true;
+ // If the load has a builtin retain, insert a plain retain for it.
+ if (Class == IC_LoadWeakRetained) {
+ CallInst *CI =
+ CallInst::Create(getRetainCallee(F.getParent()), EarlierCall,
+ "", Call);
+ CI->setTailCall();
+ }
+ // Zap the fully redundant load.
+ Call->replaceAllUsesWith(EarlierCall->getArgOperand(1));
+ Call->eraseFromParent();
+ goto clobbered;
+ case AliasAnalysis::MayAlias:
+ case AliasAnalysis::PartialAlias:
+ goto clobbered;
+ case AliasAnalysis::NoAlias:
+ break;
+ }
+ break;
+ }
+ case IC_MoveWeak:
+ case IC_CopyWeak:
+ // TOOD: Grab the copied value.
+ goto clobbered;
+ case IC_AutoreleasepoolPush:
+ case IC_None:
+ case IC_User:
+ // Weak pointers are only modified through the weak entry points
+ // (and arbitrary calls, which could call the weak entry points).
+ break;
+ default:
+ // Anything else could modify the weak pointer.
+ goto clobbered;
+ }
+ }
+ clobbered:;
+ }
+
+ // Then, for each destroyWeak with an alloca operand, check to see if
+ // the alloca and all its users can be zapped.
+ for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
+ Instruction *Inst = &*I++;
+ InstructionClass Class = GetBasicInstructionClass(Inst);
+ if (Class != IC_DestroyWeak)
+ continue;
+
+ CallInst *Call = cast<CallInst>(Inst);
+ Value *Arg = Call->getArgOperand(0);
+ if (AllocaInst *Alloca = dyn_cast<AllocaInst>(Arg)) {
+ for (Value::use_iterator UI = Alloca->use_begin(),
+ UE = Alloca->use_end(); UI != UE; ++UI) {
+ const Instruction *UserInst = cast<Instruction>(*UI);
+ switch (GetBasicInstructionClass(UserInst)) {
+ case IC_InitWeak:
+ case IC_StoreWeak:
+ case IC_DestroyWeak:
+ continue;
+ default:
+ goto done;
+ }
+ }
+ Changed = true;
+ for (Value::use_iterator UI = Alloca->use_begin(),
+ UE = Alloca->use_end(); UI != UE; ) {
+ CallInst *UserInst = cast<CallInst>(*UI++);
+ switch (GetBasicInstructionClass(UserInst)) {
+ case IC_InitWeak:
+ case IC_StoreWeak:
+ // These functions return their second argument.
+ UserInst->replaceAllUsesWith(UserInst->getArgOperand(1));
+ break;
+ case IC_DestroyWeak:
+ // No return value.
+ break;
+ default:
+ llvm_unreachable("alloca really is used!");
+ }
+ UserInst->eraseFromParent();
+ }
+ Alloca->eraseFromParent();
+ done:;
+ }
+ }
+
+ DEBUG(dbgs() << "ObjCARCOpt::OptimizeWeakCalls: Finished List.\n\n");
+
+}
+
+/// Identify program paths which execute sequences of retains and releases which
+/// can be eliminated.
+bool ObjCARCOpt::OptimizeSequences(Function &F) {
+ /// Releases, Retains - These are used to store the results of the main flow
+ /// analysis. These use Value* as the key instead of Instruction* so that the
+ /// map stays valid when we get around to rewriting code and calls get
+ /// replaced by arguments.
+ DenseMap<Value *, RRInfo> Releases;
+ MapVector<Value *, RRInfo> Retains;
+
+ /// This is used during the traversal of the function to track the
+ /// states for each identified object at each block.
+ DenseMap<const BasicBlock *, BBState> BBStates;
+
+ // Analyze the CFG of the function, and all instructions.
+ bool NestingDetected = Visit(F, BBStates, Retains, Releases);
+
+ // Transform.
+ return PerformCodePlacement(BBStates, Retains, Releases, F.getParent()) &&
+ NestingDetected;
+}
+
+/// Look for this pattern:
+/// \code
+/// %call = call i8* @something(...)
+/// %2 = call i8* @objc_retain(i8* %call)
+/// %3 = call i8* @objc_autorelease(i8* %2)
+/// ret i8* %3
+/// \endcode
+/// And delete the retain and autorelease.
+///
+/// Otherwise if it's just this:
+/// \code
+/// %3 = call i8* @objc_autorelease(i8* %2)
+/// ret i8* %3
+/// \endcode
+/// convert the autorelease to autoreleaseRV.
+void ObjCARCOpt::OptimizeReturns(Function &F) {
+ if (!F.getReturnType()->isPointerTy())
+ return;
+
+ SmallPtrSet<Instruction *, 4> DependingInstructions;
+ SmallPtrSet<const BasicBlock *, 4> Visited;
+ for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI) {
+ BasicBlock *BB = FI;
+ ReturnInst *Ret = dyn_cast<ReturnInst>(&BB->back());
+
+ DEBUG(dbgs() << "ObjCARCOpt::OptimizeReturns: Visiting: " << *Ret << "\n");
+
+ if (!Ret) continue;
+
+ const Value *Arg = StripPointerCastsAndObjCCalls(Ret->getOperand(0));
+ FindDependencies(NeedsPositiveRetainCount, Arg,
+ BB, Ret, DependingInstructions, Visited, PA);
+ if (DependingInstructions.size() != 1)
+ goto next_block;
+
+ {
+ CallInst *Autorelease =
+ dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
+ if (!Autorelease)
+ goto next_block;
+ InstructionClass AutoreleaseClass = GetBasicInstructionClass(Autorelease);
+ if (!IsAutorelease(AutoreleaseClass))
+ goto next_block;
+ if (GetObjCArg(Autorelease) != Arg)
+ goto next_block;
+
+ DependingInstructions.clear();
+ Visited.clear();
+
+ // Check that there is nothing that can affect the reference
+ // count between the autorelease and the retain.
+ FindDependencies(CanChangeRetainCount, Arg,
+ BB, Autorelease, DependingInstructions, Visited, PA);
+ if (DependingInstructions.size() != 1)
+ goto next_block;
+
+ {
+ CallInst *Retain =
+ dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
+
+ // Check that we found a retain with the same argument.
+ if (!Retain ||
+ !IsRetain(GetBasicInstructionClass(Retain)) ||
+ GetObjCArg(Retain) != Arg)
+ goto next_block;
+
+ DependingInstructions.clear();
+ Visited.clear();
+
+ // Convert the autorelease to an autoreleaseRV, since it's
+ // returning the value.
+ if (AutoreleaseClass == IC_Autorelease) {
+ DEBUG(dbgs() << "ObjCARCOpt::OptimizeReturns: Converting autorelease "
+ "=> autoreleaseRV since it's returning a value.\n"
+ " In: " << *Autorelease
+ << "\n");
+ Autorelease->setCalledFunction(getAutoreleaseRVCallee(F.getParent()));
+ DEBUG(dbgs() << " Out: " << *Autorelease
+ << "\n");
+ Autorelease->setTailCall(); // Always tail call autoreleaseRV.
+ AutoreleaseClass = IC_AutoreleaseRV;
+ }
+
+ // Check that there is nothing that can affect the reference
+ // count between the retain and the call.
+ // Note that Retain need not be in BB.
+ FindDependencies(CanChangeRetainCount, Arg, Retain->getParent(), Retain,
+ DependingInstructions, Visited, PA);
+ if (DependingInstructions.size() != 1)
+ goto next_block;
+
+ {
+ CallInst *Call =
+ dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
+
+ // Check that the pointer is the return value of the call.
+ if (!Call || Arg != Call)
+ goto next_block;
+
+ // Check that the call is a regular call.
+ InstructionClass Class = GetBasicInstructionClass(Call);
+ if (Class != IC_CallOrUser && Class != IC_Call)
+ goto next_block;
+
+ // If so, we can zap the retain and autorelease.
+ Changed = true;
+ ++NumRets;
+ DEBUG(dbgs() << "ObjCARCOpt::OptimizeReturns: Erasing: " << *Retain
+ << "\n Erasing: "
+ << *Autorelease << "\n");
+ EraseInstruction(Retain);
+ EraseInstruction(Autorelease);
+ }
+ }
+ }
+
+ next_block:
+ DependingInstructions.clear();
+ Visited.clear();
+ }
+
+ DEBUG(dbgs() << "ObjCARCOpt::OptimizeReturns: Finished List.\n\n");
+
+}
+
+bool ObjCARCOpt::doInitialization(Module &M) {
+ if (!EnableARCOpts)
+ return false;
+
+ // If nothing in the Module uses ARC, don't do anything.
+ Run = ModuleHasARC(M);
+ if (!Run)
+ return false;
+
+ // Identify the imprecise release metadata kind.
+ ImpreciseReleaseMDKind =
+ M.getContext().getMDKindID("clang.imprecise_release");
+ CopyOnEscapeMDKind =
+ M.getContext().getMDKindID("clang.arc.copy_on_escape");
+ NoObjCARCExceptionsMDKind =
+ M.getContext().getMDKindID("clang.arc.no_objc_arc_exceptions");
+
+ // Intuitively, objc_retain and others are nocapture, however in practice
+ // they are not, because they return their argument value. And objc_release
+ // calls finalizers which can have arbitrary side effects.
+
+ // These are initialized lazily.
+ RetainRVCallee = 0;
+ AutoreleaseRVCallee = 0;
+ ReleaseCallee = 0;
+ RetainCallee = 0;
+ RetainBlockCallee = 0;
+ AutoreleaseCallee = 0;
+
+ return false;
+}
+
+bool ObjCARCOpt::runOnFunction(Function &F) {
+ if (!EnableARCOpts)
+ return false;
+
+ // If nothing in the Module uses ARC, don't do anything.
+ if (!Run)
+ return false;
+
+ Changed = false;
+
+ DEBUG(dbgs() << "ObjCARCOpt: Visiting Function: " << F.getName() << "\n");
+
+ PA.setAA(&getAnalysis<AliasAnalysis>());
+
+ // This pass performs several distinct transformations. As a compile-time aid
+ // when compiling code that isn't ObjC, skip these if the relevant ObjC
+ // library functions aren't declared.
+
+ // Preliminary optimizations. This also computs UsedInThisFunction.
+ OptimizeIndividualCalls(F);
+
+ // Optimizations for weak pointers.
+ if (UsedInThisFunction & ((1 << IC_LoadWeak) |
+ (1 << IC_LoadWeakRetained) |
+ (1 << IC_StoreWeak) |
+ (1 << IC_InitWeak) |
+ (1 << IC_CopyWeak) |
+ (1 << IC_MoveWeak) |
+ (1 << IC_DestroyWeak)))
+ OptimizeWeakCalls(F);
+
+ // Optimizations for retain+release pairs.
+ if (UsedInThisFunction & ((1 << IC_Retain) |
+ (1 << IC_RetainRV) |
+ (1 << IC_RetainBlock)))
+ if (UsedInThisFunction & (1 << IC_Release))
+ // Run OptimizeSequences until it either stops making changes or
+ // no retain+release pair nesting is detected.
+ while (OptimizeSequences(F)) {}
+
+ // Optimizations if objc_autorelease is used.
+ if (UsedInThisFunction & ((1 << IC_Autorelease) |
+ (1 << IC_AutoreleaseRV)))
+ OptimizeReturns(F);
+
+ DEBUG(dbgs() << "\n");
+
+ return Changed;
+}
+
+void ObjCARCOpt::releaseMemory() {
+ PA.clear();
+}
+
+/// @}
+///
+/// \defgroup ARCContract ARC Contraction.
+/// @{
+
+// TODO: ObjCARCContract could insert PHI nodes when uses aren't
+// dominated by single calls.
+
+#include "llvm/Analysis/Dominators.h"
+#include "llvm/IR/InlineAsm.h"
+#include "llvm/IR/Operator.h"
+
+STATISTIC(NumStoreStrongs, "Number objc_storeStrong calls formed");
+
+namespace {
+ /// \brief Late ARC optimizations
+ ///
+ /// These change the IR in a way that makes it difficult to be analyzed by
+ /// ObjCARCOpt, so it's run late.
+ class ObjCARCContract : public FunctionPass {
+ bool Changed;
+ AliasAnalysis *AA;
+ DominatorTree *DT;
+ ProvenanceAnalysis PA;
+
+ /// A flag indicating whether this optimization pass should run.
+ bool Run;
+
+ /// Declarations for ObjC runtime functions, for use in creating calls to
+ /// them. These are initialized lazily to avoid cluttering up the Module
+ /// with unused declarations.
+
+ /// Declaration for objc_storeStrong().
+ Constant *StoreStrongCallee;
+ /// Declaration for objc_retainAutorelease().
+ Constant *RetainAutoreleaseCallee;
+ /// Declaration for objc_retainAutoreleaseReturnValue().
+ Constant *RetainAutoreleaseRVCallee;
+
+ /// The inline asm string to insert between calls and RetainRV calls to make
+ /// the optimization work on targets which need it.
+ const MDString *RetainRVMarker;
+
+ /// The set of inserted objc_storeStrong calls. If at the end of walking the
+ /// function we have found no alloca instructions, these calls can be marked
+ /// "tail".
+ SmallPtrSet<CallInst *, 8> StoreStrongCalls;
+
+ Constant *getStoreStrongCallee(Module *M);
+ Constant *getRetainAutoreleaseCallee(Module *M);
+ Constant *getRetainAutoreleaseRVCallee(Module *M);
+
+ bool ContractAutorelease(Function &F, Instruction *Autorelease,
+ InstructionClass Class,
+ SmallPtrSet<Instruction *, 4>
+ &DependingInstructions,
+ SmallPtrSet<const BasicBlock *, 4>
+ &Visited);
+
+ void ContractRelease(Instruction *Release,
+ inst_iterator &Iter);
+
+ virtual void getAnalysisUsage(AnalysisUsage &AU) const;
+ virtual bool doInitialization(Module &M);
+ virtual bool runOnFunction(Function &F);
+
+ public:
+ static char ID;
+ ObjCARCContract() : FunctionPass(ID) {
+ initializeObjCARCContractPass(*PassRegistry::getPassRegistry());
+ }
+ };
+}
+
+char ObjCARCContract::ID = 0;
+INITIALIZE_PASS_BEGIN(ObjCARCContract,
+ "objc-arc-contract", "ObjC ARC contraction", false, false)
+INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
+INITIALIZE_PASS_DEPENDENCY(DominatorTree)
+INITIALIZE_PASS_END(ObjCARCContract,
+ "objc-arc-contract", "ObjC ARC contraction", false, false)
+
+Pass *llvm::createObjCARCContractPass() {
+ return new ObjCARCContract();
+}
+
+void ObjCARCContract::getAnalysisUsage(AnalysisUsage &AU) const {
+ AU.addRequired<AliasAnalysis>();
+ AU.addRequired<DominatorTree>();
+ AU.setPreservesCFG();
+}
+
+Constant *ObjCARCContract::getStoreStrongCallee(Module *M) {
+ if (!StoreStrongCallee) {
+ LLVMContext &C = M->getContext();
+ Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
+ Type *I8XX = PointerType::getUnqual(I8X);
+ Type *Params[] = { I8XX, I8X };
+
+ AttributeSet Attr = AttributeSet()
+ .addAttribute(M->getContext(), AttributeSet::FunctionIndex,
+ Attribute::NoUnwind)
+ .addAttribute(M->getContext(), 1, Attribute::NoCapture);
+
+ StoreStrongCallee =
+ M->getOrInsertFunction(
+ "objc_storeStrong",
+ FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false),
+ Attr);
+ }
+ return StoreStrongCallee;
+}
+
+Constant *ObjCARCContract::getRetainAutoreleaseCallee(Module *M) {
+ if (!RetainAutoreleaseCallee) {
+ LLVMContext &C = M->getContext();
+ Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
+ Type *Params[] = { I8X };
+ FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
+ AttributeSet Attribute =
+ AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
+ Attribute::NoUnwind);
+ RetainAutoreleaseCallee =
+ M->getOrInsertFunction("objc_retainAutorelease", FTy, Attribute);
+ }
+ return RetainAutoreleaseCallee;
+}
+
+Constant *ObjCARCContract::getRetainAutoreleaseRVCallee(Module *M) {
+ if (!RetainAutoreleaseRVCallee) {
+ LLVMContext &C = M->getContext();
+ Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
+ Type *Params[] = { I8X };
+ FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
+ AttributeSet Attribute =
+ AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
+ Attribute::NoUnwind);
+ RetainAutoreleaseRVCallee =
+ M->getOrInsertFunction("objc_retainAutoreleaseReturnValue", FTy,
+ Attribute);
+ }
+ return RetainAutoreleaseRVCallee;
+}
+
+/// Merge an autorelease with a retain into a fused call.
+bool
+ObjCARCContract::ContractAutorelease(Function &F, Instruction *Autorelease,
+ InstructionClass Class,
+ SmallPtrSet<Instruction *, 4>
+ &DependingInstructions,
+ SmallPtrSet<const BasicBlock *, 4>
+ &Visited) {
+ const Value *Arg = GetObjCArg(Autorelease);
+
+ // Check that there are no instructions between the retain and the autorelease
+ // (such as an autorelease_pop) which may change the count.
+ CallInst *Retain = 0;
+ if (Class == IC_AutoreleaseRV)
+ FindDependencies(RetainAutoreleaseRVDep, Arg,
+ Autorelease->getParent(), Autorelease,
+ DependingInstructions, Visited, PA);
+ else
+ FindDependencies(RetainAutoreleaseDep, Arg,
+ Autorelease->getParent(), Autorelease,
+ DependingInstructions, Visited, PA);
+
+ Visited.clear();
+ if (DependingInstructions.size() != 1) {
+ DependingInstructions.clear();
+ return false;
+ }
+
+ Retain = dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
+ DependingInstructions.clear();
+
+ if (!Retain ||
+ GetBasicInstructionClass(Retain) != IC_Retain ||
+ GetObjCArg(Retain) != Arg)
+ return false;
+
+ Changed = true;
+ ++NumPeeps;
+
+ DEBUG(dbgs() << "ObjCARCContract::ContractAutorelease: Fusing "
+ "retain/autorelease. Erasing: " << *Autorelease << "\n"
+ " Old Retain: "
+ << *Retain << "\n");
+
+ if (Class == IC_AutoreleaseRV)
+ Retain->setCalledFunction(getRetainAutoreleaseRVCallee(F.getParent()));
+ else
+ Retain->setCalledFunction(getRetainAutoreleaseCallee(F.getParent()));
+
+ DEBUG(dbgs() << " New Retain: "
+ << *Retain << "\n");
+
+ EraseInstruction(Autorelease);
+ return true;
+}
+
+/// Attempt to merge an objc_release with a store, load, and objc_retain to form
+/// an objc_storeStrong. This can be a little tricky because the instructions
+/// don't always appear in order, and there may be unrelated intervening
+/// instructions.
+void ObjCARCContract::ContractRelease(Instruction *Release,
+ inst_iterator &Iter) {
+ LoadInst *Load = dyn_cast<LoadInst>(GetObjCArg(Release));
+ if (!Load || !Load->isSimple()) return;
+
+ // For now, require everything to be in one basic block.
+ BasicBlock *BB = Release->getParent();
+ if (Load->getParent() != BB) return;
+
+ // Walk down to find the store and the release, which may be in either order.
+ BasicBlock::iterator I = Load, End = BB->end();
+ ++I;
+ AliasAnalysis::Location Loc = AA->getLocation(Load);
+ StoreInst *Store = 0;
+ bool SawRelease = false;
+ for (; !Store || !SawRelease; ++I) {
+ if (I == End)
+ return;
+
+ Instruction *Inst = I;
+ if (Inst == Release) {
+ SawRelease = true;
+ continue;
+ }
+
+ InstructionClass Class = GetBasicInstructionClass(Inst);
+
+ // Unrelated retains are harmless.
+ if (IsRetain(Class))
+ continue;
+
+ if (Store) {
+ // The store is the point where we're going to put the objc_storeStrong,
+ // so make sure there are no uses after it.
+ if (CanUse(Inst, Load, PA, Class))
+ return;
+ } else if (AA->getModRefInfo(Inst, Loc) & AliasAnalysis::Mod) {
+ // We are moving the load down to the store, so check for anything
+ // else which writes to the memory between the load and the store.
+ Store = dyn_cast<StoreInst>(Inst);
+ if (!Store || !Store->isSimple()) return;
+ if (Store->getPointerOperand() != Loc.Ptr) return;
+ }
+ }
+
+ Value *New = StripPointerCastsAndObjCCalls(Store->getValueOperand());
+
+ // Walk up to find the retain.
+ I = Store;
+ BasicBlock::iterator Begin = BB->begin();
+ while (I != Begin && GetBasicInstructionClass(I) != IC_Retain)
+ --I;
+ Instruction *Retain = I;
+ if (GetBasicInstructionClass(Retain) != IC_Retain) return;
+ if (GetObjCArg(Retain) != New) return;
+
+ Changed = true;
+ ++NumStoreStrongs;
+
+ LLVMContext &C = Release->getContext();
+ Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
+ Type *I8XX = PointerType::getUnqual(I8X);
+
+ Value *Args[] = { Load->getPointerOperand(), New };
+ if (Args[0]->getType() != I8XX)
+ Args[0] = new BitCastInst(Args[0], I8XX, "", Store);
+ if (Args[1]->getType() != I8X)
+ Args[1] = new BitCastInst(Args[1], I8X, "", Store);
+ CallInst *StoreStrong =
+ CallInst::Create(getStoreStrongCallee(BB->getParent()->getParent()),
+ Args, "", Store);
+ StoreStrong->setDoesNotThrow();
+ StoreStrong->setDebugLoc(Store->getDebugLoc());
+
+ // We can't set the tail flag yet, because we haven't yet determined
+ // whether there are any escaping allocas. Remember this call, so that
+ // we can set the tail flag once we know it's safe.
+ StoreStrongCalls.insert(StoreStrong);
+
+ if (&*Iter == Store) ++Iter;
+ Store->eraseFromParent();
+ Release->eraseFromParent();
+ EraseInstruction(Retain);
+ if (Load->use_empty())
+ Load->eraseFromParent();
+}
+
+bool ObjCARCContract::doInitialization(Module &M) {
+ // If nothing in the Module uses ARC, don't do anything.
+ Run = ModuleHasARC(M);
+ if (!Run)
+ return false;
+
+ // These are initialized lazily.
+ StoreStrongCallee = 0;
+ RetainAutoreleaseCallee = 0;
+ RetainAutoreleaseRVCallee = 0;
+
+ // Initialize RetainRVMarker.
+ RetainRVMarker = 0;
+ if (NamedMDNode *NMD =
+ M.getNamedMetadata("clang.arc.retainAutoreleasedReturnValueMarker"))
+ if (NMD->getNumOperands() == 1) {
+ const MDNode *N = NMD->getOperand(0);
+ if (N->getNumOperands() == 1)
+ if (const MDString *S = dyn_cast<MDString>(N->getOperand(0)))
+ RetainRVMarker = S;
+ }
+
+ return false;
+}
+
+bool ObjCARCContract::runOnFunction(Function &F) {
+ if (!EnableARCOpts)
+ return false;
+
+ // If nothing in the Module uses ARC, don't do anything.
+ if (!Run)
+ return false;
+
+ Changed = false;
+ AA = &getAnalysis<AliasAnalysis>();
+ DT = &getAnalysis<DominatorTree>();
+
+ PA.setAA(&getAnalysis<AliasAnalysis>());
+
+ // Track whether it's ok to mark objc_storeStrong calls with the "tail"
+ // keyword. Be conservative if the function has variadic arguments.
+ // It seems that functions which "return twice" are also unsafe for the
+ // "tail" argument, because they are setjmp, which could need to
+ // return to an earlier stack state.
+ bool TailOkForStoreStrongs = !F.isVarArg() &&
+ !F.callsFunctionThatReturnsTwice();
+
+ // For ObjC library calls which return their argument, replace uses of the
+ // argument with uses of the call return value, if it dominates the use. This
+ // reduces register pressure.
+ SmallPtrSet<Instruction *, 4> DependingInstructions;
+ SmallPtrSet<const BasicBlock *, 4> Visited;
+ for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
+ Instruction *Inst = &*I++;
+
+ DEBUG(dbgs() << "ObjCARCContract: Visiting: " << *Inst << "\n");
+
+ // Only these library routines return their argument. In particular,
+ // objc_retainBlock does not necessarily return its argument.
+ InstructionClass Class = GetBasicInstructionClass(Inst);
+ switch (Class) {
+ case IC_Retain:
+ case IC_FusedRetainAutorelease:
+ case IC_FusedRetainAutoreleaseRV:
+ break;
+ case IC_Autorelease:
+ case IC_AutoreleaseRV:
+ if (ContractAutorelease(F, Inst, Class, DependingInstructions, Visited))
+ continue;
+ break;
+ case IC_RetainRV: {
+ // If we're compiling for a target which needs a special inline-asm
+ // marker to do the retainAutoreleasedReturnValue optimization,
+ // insert it now.
+ if (!RetainRVMarker)
+ break;
+ BasicBlock::iterator BBI = Inst;
+ BasicBlock *InstParent = Inst->getParent();
+
+ // Step up to see if the call immediately precedes the RetainRV call.
+ // If it's an invoke, we have to cross a block boundary. And we have
+ // to carefully dodge no-op instructions.
+ do {
+ if (&*BBI == InstParent->begin()) {
+ BasicBlock *Pred = InstParent->getSinglePredecessor();
+ if (!Pred)
+ goto decline_rv_optimization;
+ BBI = Pred->getTerminator();
+ break;
+ }
+ --BBI;
+ } while (isNoopInstruction(BBI));
+
+ if (&*BBI == GetObjCArg(Inst)) {
+ DEBUG(dbgs() << "ObjCARCContract: Adding inline asm marker for "
+ "retainAutoreleasedReturnValue optimization.\n");
+ Changed = true;
+ InlineAsm *IA =
+ InlineAsm::get(FunctionType::get(Type::getVoidTy(Inst->getContext()),
+ /*isVarArg=*/false),
+ RetainRVMarker->getString(),
+ /*Constraints=*/"", /*hasSideEffects=*/true);
+ CallInst::Create(IA, "", Inst);
+ }
+ decline_rv_optimization:
+ break;
+ }
+ case IC_InitWeak: {
+ // objc_initWeak(p, null) => *p = null
+ CallInst *CI = cast<CallInst>(Inst);
+ if (isNullOrUndef(CI->getArgOperand(1))) {
+ Value *Null =
+ ConstantPointerNull::get(cast<PointerType>(CI->getType()));
+ Changed = true;
+ new StoreInst(Null, CI->getArgOperand(0), CI);
+
+ DEBUG(dbgs() << "OBJCARCContract: Old = " << *CI << "\n"
+ << " New = " << *Null << "\n");
+
+ CI->replaceAllUsesWith(Null);
+ CI->eraseFromParent();
+ }
+ continue;
+ }
+ case IC_Release:
+ ContractRelease(Inst, I);
+ continue;
+ case IC_User:
+ // Be conservative if the function has any alloca instructions.
+ // Technically we only care about escaping alloca instructions,
+ // but this is sufficient to handle some interesting cases.
+ if (isa<AllocaInst>(Inst))
+ TailOkForStoreStrongs = false;
+ continue;
+ default:
+ continue;
+ }
+
+ DEBUG(dbgs() << "ObjCARCContract: Finished List.\n\n");
+
+ // Don't use GetObjCArg because we don't want to look through bitcasts
+ // and such; to do the replacement, the argument must have type i8*.
+ const Value *Arg = cast<CallInst>(Inst)->getArgOperand(0);
+ for (;;) {
+ // If we're compiling bugpointed code, don't get in trouble.
+ if (!isa<Instruction>(Arg) && !isa<Argument>(Arg))
+ break;
+ // Look through the uses of the pointer.
+ for (Value::const_use_iterator UI = Arg->use_begin(), UE = Arg->use_end();
+ UI != UE; ) {
+ Use &U = UI.getUse();
+ unsigned OperandNo = UI.getOperandNo();
+ ++UI; // Increment UI now, because we may unlink its element.
+
+ // If the call's return value dominates a use of the call's argument
+ // value, rewrite the use to use the return value. We check for
+ // reachability here because an unreachable call is considered to
+ // trivially dominate itself, which would lead us to rewriting its
+ // argument in terms of its return value, which would lead to
+ // infinite loops in GetObjCArg.
+ if (DT->isReachableFromEntry(U) && DT->dominates(Inst, U)) {
+ Changed = true;
+ Instruction *Replacement = Inst;
+ Type *UseTy = U.get()->getType();
+ if (PHINode *PHI = dyn_cast<PHINode>(U.getUser())) {
+ // For PHI nodes, insert the bitcast in the predecessor block.
+ unsigned ValNo = PHINode::getIncomingValueNumForOperand(OperandNo);
+ BasicBlock *BB = PHI->getIncomingBlock(ValNo);
+ if (Replacement->getType() != UseTy)
+ Replacement = new BitCastInst(Replacement, UseTy, "",
+ &BB->back());
+ // While we're here, rewrite all edges for this PHI, rather
+ // than just one use at a time, to minimize the number of
+ // bitcasts we emit.
+ for (unsigned i = 0, e = PHI->getNumIncomingValues(); i != e; ++i)
+ if (PHI->getIncomingBlock(i) == BB) {
+ // Keep the UI iterator valid.
+ if (&PHI->getOperandUse(
+ PHINode::getOperandNumForIncomingValue(i)) ==
+ &UI.getUse())
+ ++UI;
+ PHI->setIncomingValue(i, Replacement);
+ }
+ } else {
+ if (Replacement->getType() != UseTy)
+ Replacement = new BitCastInst(Replacement, UseTy, "",
+ cast<Instruction>(U.getUser()));
+ U.set(Replacement);
+ }
+ }
+ }
+
+ // If Arg is a no-op casted pointer, strip one level of casts and iterate.
+ if (const BitCastInst *BI = dyn_cast<BitCastInst>(Arg))
+ Arg = BI->getOperand(0);
+ else if (isa<GEPOperator>(Arg) &&
+ cast<GEPOperator>(Arg)->hasAllZeroIndices())
+ Arg = cast<GEPOperator>(Arg)->getPointerOperand();
+ else if (isa<GlobalAlias>(Arg) &&
+ !cast<GlobalAlias>(Arg)->mayBeOverridden())
+ Arg = cast<GlobalAlias>(Arg)->getAliasee();
+ else
+ break;
+ }
+ }
+
+ // If this function has no escaping allocas or suspicious vararg usage,
+ // objc_storeStrong calls can be marked with the "tail" keyword.
+ if (TailOkForStoreStrongs)
+ for (SmallPtrSet<CallInst *, 8>::iterator I = StoreStrongCalls.begin(),
+ E = StoreStrongCalls.end(); I != E; ++I)
+ (*I)->setTailCall();
+ StoreStrongCalls.clear();
+
+ return Changed;
+}
+
+/// @}
+///
LoopUnswitch.cpp
LowerAtomic.cpp
MemCpyOptimizer.cpp
- ObjCARC.cpp
Reassociate.cpp
Reg2Mem.cpp
SCCP.cpp
+++ /dev/null
-//===- ObjCARC.cpp - ObjC ARC Optimization --------------------------------===//
-//
-// The LLVM Compiler Infrastructure
-//
-// This file is distributed under the University of Illinois Open Source
-// License. See LICENSE.TXT for details.
-//
-//===----------------------------------------------------------------------===//
-/// \file
-/// This file defines ObjC ARC optimizations. ARC stands for Automatic
-/// Reference Counting and is a system for managing reference counts for objects
-/// in Objective C.
-///
-/// The optimizations performed include elimination of redundant, partially
-/// redundant, and inconsequential reference count operations, elimination of
-/// redundant weak pointer operations, pattern-matching and replacement of
-/// low-level operations into higher-level operations, and numerous minor
-/// simplifications.
-///
-/// This file also defines a simple ARC-aware AliasAnalysis.
-///
-/// WARNING: This file knows about certain library functions. It recognizes them
-/// by name, and hardwires knowledge of their semantics.
-///
-/// WARNING: This file knows about how certain Objective-C library functions are
-/// used. Naive LLVM IR transformations which would otherwise be
-/// behavior-preserving may break these assumptions.
-///
-//===----------------------------------------------------------------------===//
-
-#define DEBUG_TYPE "objc-arc"
-#include "llvm/ADT/DenseMap.h"
-#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/Support/CommandLine.h"
-#include "llvm/Support/Debug.h"
-#include "llvm/Support/raw_ostream.h"
-using namespace llvm;
-
-/// \brief A handy option to enable/disable all optimizations in this file.
-static cl::opt<bool> EnableARCOpts("enable-objc-arc-opts", cl::init(true));
-
-/// \defgroup MiscUtils Miscellaneous utilities that are not ARC specific.
-/// @{
-
-namespace {
- /// \brief An associative container with fast insertion-order (deterministic)
- /// iteration over its elements. Plus the special blot operation.
- template<class KeyT, class ValueT>
- class MapVector {
- /// Map keys to indices in Vector.
- typedef DenseMap<KeyT, size_t> MapTy;
- MapTy Map;
-
- typedef std::vector<std::pair<KeyT, ValueT> > VectorTy;
- /// Keys and values.
- VectorTy Vector;
-
- public:
- typedef typename VectorTy::iterator iterator;
- typedef typename VectorTy::const_iterator const_iterator;
- iterator begin() { return Vector.begin(); }
- iterator end() { return Vector.end(); }
- const_iterator begin() const { return Vector.begin(); }
- const_iterator end() const { return Vector.end(); }
-
-#ifdef XDEBUG
- ~MapVector() {
- assert(Vector.size() >= Map.size()); // May differ due to blotting.
- for (typename MapTy::const_iterator I = Map.begin(), E = Map.end();
- I != E; ++I) {
- assert(I->second < Vector.size());
- assert(Vector[I->second].first == I->first);
- }
- for (typename VectorTy::const_iterator I = Vector.begin(),
- E = Vector.end(); I != E; ++I)
- assert(!I->first ||
- (Map.count(I->first) &&
- Map[I->first] == size_t(I - Vector.begin())));
- }
-#endif
-
- ValueT &operator[](const KeyT &Arg) {
- std::pair<typename MapTy::iterator, bool> Pair =
- Map.insert(std::make_pair(Arg, size_t(0)));
- if (Pair.second) {
- size_t Num = Vector.size();
- Pair.first->second = Num;
- Vector.push_back(std::make_pair(Arg, ValueT()));
- return Vector[Num].second;
- }
- return Vector[Pair.first->second].second;
- }
-
- std::pair<iterator, bool>
- insert(const std::pair<KeyT, ValueT> &InsertPair) {
- std::pair<typename MapTy::iterator, bool> Pair =
- Map.insert(std::make_pair(InsertPair.first, size_t(0)));
- if (Pair.second) {
- size_t Num = Vector.size();
- Pair.first->second = Num;
- Vector.push_back(InsertPair);
- return std::make_pair(Vector.begin() + Num, true);
- }
- return std::make_pair(Vector.begin() + Pair.first->second, false);
- }
-
- const_iterator find(const KeyT &Key) const {
- typename MapTy::const_iterator It = Map.find(Key);
- if (It == Map.end()) return Vector.end();
- return Vector.begin() + It->second;
- }
-
- /// This is similar to erase, but instead of removing the element from the
- /// vector, it just zeros out the key in the vector. This leaves iterators
- /// intact, but clients must be prepared for zeroed-out keys when iterating.
- void blot(const KeyT &Key) {
- typename MapTy::iterator It = Map.find(Key);
- if (It == Map.end()) return;
- Vector[It->second].first = KeyT();
- Map.erase(It);
- }
-
- void clear() {
- Map.clear();
- Vector.clear();
- }
- };
-}
-
-/// @}
-///
-/// \defgroup ARCUtilities Utility declarations/definitions specific to ARC.
-/// @{
-
-#include "llvm/ADT/StringSwitch.h"
-#include "llvm/Analysis/ValueTracking.h"
-#include "llvm/IR/Intrinsics.h"
-#include "llvm/IR/Module.h"
-#include "llvm/Support/CallSite.h"
-#include "llvm/Transforms/Utils/Local.h"
-
-namespace {
- /// \enum InstructionClass
- /// \brief A simple classification for instructions.
- enum InstructionClass {
- IC_Retain, ///< objc_retain
- IC_RetainRV, ///< objc_retainAutoreleasedReturnValue
- IC_RetainBlock, ///< objc_retainBlock
- IC_Release, ///< objc_release
- IC_Autorelease, ///< objc_autorelease
- IC_AutoreleaseRV, ///< objc_autoreleaseReturnValue
- IC_AutoreleasepoolPush, ///< objc_autoreleasePoolPush
- IC_AutoreleasepoolPop, ///< objc_autoreleasePoolPop
- IC_NoopCast, ///< objc_retainedObject, etc.
- IC_FusedRetainAutorelease, ///< objc_retainAutorelease
- IC_FusedRetainAutoreleaseRV, ///< objc_retainAutoreleaseReturnValue
- IC_LoadWeakRetained, ///< objc_loadWeakRetained (primitive)
- IC_StoreWeak, ///< objc_storeWeak (primitive)
- IC_InitWeak, ///< objc_initWeak (derived)
- IC_LoadWeak, ///< objc_loadWeak (derived)
- IC_MoveWeak, ///< objc_moveWeak (derived)
- IC_CopyWeak, ///< objc_copyWeak (derived)
- IC_DestroyWeak, ///< objc_destroyWeak (derived)
- IC_StoreStrong, ///< objc_storeStrong (derived)
- IC_CallOrUser, ///< could call objc_release and/or "use" pointers
- IC_Call, ///< could call objc_release
- IC_User, ///< could "use" a pointer
- IC_None ///< anything else
- };
-
- raw_ostream &operator<<(raw_ostream &OS, const InstructionClass Class)
- LLVM_ATTRIBUTE_USED;
- raw_ostream &operator<<(raw_ostream &OS, const InstructionClass Class) {
- switch (Class) {
- case IC_Retain:
- return OS << "IC_Retain";
- case IC_RetainRV:
- return OS << "IC_RetainRV";
- case IC_RetainBlock:
- return OS << "IC_RetainBlock";
- case IC_Release:
- return OS << "IC_Release";
- case IC_Autorelease:
- return OS << "IC_Autorelease";
- case IC_AutoreleaseRV:
- return OS << "IC_AutoreleaseRV";
- case IC_AutoreleasepoolPush:
- return OS << "IC_AutoreleasepoolPush";
- case IC_AutoreleasepoolPop:
- return OS << "IC_AutoreleasepoolPop";
- case IC_NoopCast:
- return OS << "IC_NoopCast";
- case IC_FusedRetainAutorelease:
- return OS << "IC_FusedRetainAutorelease";
- case IC_FusedRetainAutoreleaseRV:
- return OS << "IC_FusedRetainAutoreleaseRV";
- case IC_LoadWeakRetained:
- return OS << "IC_LoadWeakRetained";
- case IC_StoreWeak:
- return OS << "IC_StoreWeak";
- case IC_InitWeak:
- return OS << "IC_InitWeak";
- case IC_LoadWeak:
- return OS << "IC_LoadWeak";
- case IC_MoveWeak:
- return OS << "IC_MoveWeak";
- case IC_CopyWeak:
- return OS << "IC_CopyWeak";
- case IC_DestroyWeak:
- return OS << "IC_DestroyWeak";
- case IC_StoreStrong:
- return OS << "IC_StoreStrong";
- case IC_CallOrUser:
- return OS << "IC_CallOrUser";
- case IC_Call:
- return OS << "IC_Call";
- case IC_User:
- return OS << "IC_User";
- case IC_None:
- return OS << "IC_None";
- }
- llvm_unreachable("Unknown instruction class!");
- }
-}
-
-/// \brief Test whether the given value is possible a retainable object pointer.
-static bool IsPotentialRetainableObjPtr(const Value *Op) {
- // Pointers to static or stack storage are not valid retainable object pointers.
- if (isa<Constant>(Op) || isa<AllocaInst>(Op))
- return false;
- // Special arguments can not be a valid retainable object pointer.
- if (const Argument *Arg = dyn_cast<Argument>(Op))
- if (Arg->hasByValAttr() ||
- Arg->hasNestAttr() ||
- Arg->hasStructRetAttr())
- return false;
- // Only consider values with pointer types.
- //
- // It seemes intuitive to exclude function pointer types as well, since
- // functions are never retainable object pointers, however clang occasionally
- // bitcasts retainable object pointers to function-pointer type temporarily.
- PointerType *Ty = dyn_cast<PointerType>(Op->getType());
- if (!Ty)
- return false;
- // Conservatively assume anything else is a potential retainable object pointer.
- return true;
-}
-
-/// \brief Helper for GetInstructionClass. Determines what kind of construct CS
-/// is.
-static InstructionClass GetCallSiteClass(ImmutableCallSite CS) {
- for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
- I != E; ++I)
- if (IsPotentialRetainableObjPtr(*I))
- return CS.onlyReadsMemory() ? IC_User : IC_CallOrUser;
-
- return CS.onlyReadsMemory() ? IC_None : IC_Call;
-}
-
-/// \brief Determine if F is one of the special known Functions. If it isn't,
-/// return IC_CallOrUser.
-static InstructionClass GetFunctionClass(const Function *F) {
- Function::const_arg_iterator AI = F->arg_begin(), AE = F->arg_end();
-
- // No arguments.
- if (AI == AE)
- return StringSwitch<InstructionClass>(F->getName())
- .Case("objc_autoreleasePoolPush", IC_AutoreleasepoolPush)
- .Default(IC_CallOrUser);
-
- // One argument.
- const Argument *A0 = AI++;
- if (AI == AE)
- // Argument is a pointer.
- if (PointerType *PTy = dyn_cast<PointerType>(A0->getType())) {
- Type *ETy = PTy->getElementType();
- // Argument is i8*.
- if (ETy->isIntegerTy(8))
- return StringSwitch<InstructionClass>(F->getName())
- .Case("objc_retain", IC_Retain)
- .Case("objc_retainAutoreleasedReturnValue", IC_RetainRV)
- .Case("objc_retainBlock", IC_RetainBlock)
- .Case("objc_release", IC_Release)
- .Case("objc_autorelease", IC_Autorelease)
- .Case("objc_autoreleaseReturnValue", IC_AutoreleaseRV)
- .Case("objc_autoreleasePoolPop", IC_AutoreleasepoolPop)
- .Case("objc_retainedObject", IC_NoopCast)
- .Case("objc_unretainedObject", IC_NoopCast)
- .Case("objc_unretainedPointer", IC_NoopCast)
- .Case("objc_retain_autorelease", IC_FusedRetainAutorelease)
- .Case("objc_retainAutorelease", IC_FusedRetainAutorelease)
- .Case("objc_retainAutoreleaseReturnValue",IC_FusedRetainAutoreleaseRV)
- .Default(IC_CallOrUser);
-
- // Argument is i8**
- if (PointerType *Pte = dyn_cast<PointerType>(ETy))
- if (Pte->getElementType()->isIntegerTy(8))
- return StringSwitch<InstructionClass>(F->getName())
- .Case("objc_loadWeakRetained", IC_LoadWeakRetained)
- .Case("objc_loadWeak", IC_LoadWeak)
- .Case("objc_destroyWeak", IC_DestroyWeak)
- .Default(IC_CallOrUser);
- }
-
- // Two arguments, first is i8**.
- const Argument *A1 = AI++;
- if (AI == AE)
- if (PointerType *PTy = dyn_cast<PointerType>(A0->getType()))
- if (PointerType *Pte = dyn_cast<PointerType>(PTy->getElementType()))
- if (Pte->getElementType()->isIntegerTy(8))
- if (PointerType *PTy1 = dyn_cast<PointerType>(A1->getType())) {
- Type *ETy1 = PTy1->getElementType();
- // Second argument is i8*
- if (ETy1->isIntegerTy(8))
- return StringSwitch<InstructionClass>(F->getName())
- .Case("objc_storeWeak", IC_StoreWeak)
- .Case("objc_initWeak", IC_InitWeak)
- .Case("objc_storeStrong", IC_StoreStrong)
- .Default(IC_CallOrUser);
- // Second argument is i8**.
- if (PointerType *Pte1 = dyn_cast<PointerType>(ETy1))
- if (Pte1->getElementType()->isIntegerTy(8))
- return StringSwitch<InstructionClass>(F->getName())
- .Case("objc_moveWeak", IC_MoveWeak)
- .Case("objc_copyWeak", IC_CopyWeak)
- .Default(IC_CallOrUser);
- }
-
- // Anything else.
- return IC_CallOrUser;
-}
-
-/// \brief Determine what kind of construct V is.
-static InstructionClass GetInstructionClass(const Value *V) {
- if (const Instruction *I = dyn_cast<Instruction>(V)) {
- // Any instruction other than bitcast and gep with a pointer operand have a
- // use of an objc pointer. Bitcasts, GEPs, Selects, PHIs transfer a pointer
- // to a subsequent use, rather than using it themselves, in this sense.
- // As a short cut, several other opcodes are known to have no pointer
- // operands of interest. And ret is never followed by a release, so it's
- // not interesting to examine.
- switch (I->getOpcode()) {
- case Instruction::Call: {
- const CallInst *CI = cast<CallInst>(I);
- // Check for calls to special functions.
- if (const Function *F = CI->getCalledFunction()) {
- InstructionClass Class = GetFunctionClass(F);
- if (Class != IC_CallOrUser)
- return Class;
-
- // None of the intrinsic functions do objc_release. For intrinsics, the
- // only question is whether or not they may be users.
- switch (F->getIntrinsicID()) {
- case Intrinsic::returnaddress: case Intrinsic::frameaddress:
- case Intrinsic::stacksave: case Intrinsic::stackrestore:
- case Intrinsic::vastart: case Intrinsic::vacopy: case Intrinsic::vaend:
- case Intrinsic::objectsize: case Intrinsic::prefetch:
- case Intrinsic::stackprotector:
- case Intrinsic::eh_return_i32: case Intrinsic::eh_return_i64:
- case Intrinsic::eh_typeid_for: case Intrinsic::eh_dwarf_cfa:
- case Intrinsic::eh_sjlj_lsda: case Intrinsic::eh_sjlj_functioncontext:
- case Intrinsic::init_trampoline: case Intrinsic::adjust_trampoline:
- case Intrinsic::lifetime_start: case Intrinsic::lifetime_end:
- case Intrinsic::invariant_start: case Intrinsic::invariant_end:
- // Don't let dbg info affect our results.
- case Intrinsic::dbg_declare: case Intrinsic::dbg_value:
- // Short cut: Some intrinsics obviously don't use ObjC pointers.
- return IC_None;
- default:
- break;
- }
- }
- return GetCallSiteClass(CI);
- }
- case Instruction::Invoke:
- return GetCallSiteClass(cast<InvokeInst>(I));
- case Instruction::BitCast:
- case Instruction::GetElementPtr:
- case Instruction::Select: case Instruction::PHI:
- case Instruction::Ret: case Instruction::Br:
- case Instruction::Switch: case Instruction::IndirectBr:
- case Instruction::Alloca: case Instruction::VAArg:
- case Instruction::Add: case Instruction::FAdd:
- case Instruction::Sub: case Instruction::FSub:
- case Instruction::Mul: case Instruction::FMul:
- case Instruction::SDiv: case Instruction::UDiv: case Instruction::FDiv:
- case Instruction::SRem: case Instruction::URem: case Instruction::FRem:
- case Instruction::Shl: case Instruction::LShr: case Instruction::AShr:
- case Instruction::And: case Instruction::Or: case Instruction::Xor:
- case Instruction::SExt: case Instruction::ZExt: case Instruction::Trunc:
- case Instruction::IntToPtr: case Instruction::FCmp:
- case Instruction::FPTrunc: case Instruction::FPExt:
- case Instruction::FPToUI: case Instruction::FPToSI:
- case Instruction::UIToFP: case Instruction::SIToFP:
- case Instruction::InsertElement: case Instruction::ExtractElement:
- case Instruction::ShuffleVector:
- case Instruction::ExtractValue:
- break;
- case Instruction::ICmp:
- // Comparing a pointer with null, or any other constant, isn't an
- // interesting use, because we don't care what the pointer points to, or
- // about the values of any other dynamic reference-counted pointers.
- if (IsPotentialRetainableObjPtr(I->getOperand(1)))
- return IC_User;
- break;
- default:
- // For anything else, check all the operands.
- // Note that this includes both operands of a Store: while the first
- // operand isn't actually being dereferenced, it is being stored to
- // memory where we can no longer track who might read it and dereference
- // it, so we have to consider it potentially used.
- for (User::const_op_iterator OI = I->op_begin(), OE = I->op_end();
- OI != OE; ++OI)
- if (IsPotentialRetainableObjPtr(*OI))
- return IC_User;
- }
- }
-
- // Otherwise, it's totally inert for ARC purposes.
- return IC_None;
-}
-
-/// \brief Determine which objc runtime call instruction class V belongs to.
-///
-/// This is similar to GetInstructionClass except that it only detects objc
-/// runtime calls. This allows it to be faster.
-///
-static InstructionClass GetBasicInstructionClass(const Value *V) {
- if (const CallInst *CI = dyn_cast<CallInst>(V)) {
- if (const Function *F = CI->getCalledFunction())
- return GetFunctionClass(F);
- // Otherwise, be conservative.
- return IC_CallOrUser;
- }
-
- // Otherwise, be conservative.
- return isa<InvokeInst>(V) ? IC_CallOrUser : IC_User;
-}
-
-/// \brief Test if the given class is objc_retain or equivalent.
-static bool IsRetain(InstructionClass Class) {
- return Class == IC_Retain ||
- Class == IC_RetainRV;
-}
-
-/// \brief Test if the given class is objc_autorelease or equivalent.
-static bool IsAutorelease(InstructionClass Class) {
- return Class == IC_Autorelease ||
- Class == IC_AutoreleaseRV;
-}
-
-/// \brief Test if the given class represents instructions which return their
-/// argument verbatim.
-static bool IsForwarding(InstructionClass Class) {
- // objc_retainBlock technically doesn't always return its argument
- // verbatim, but it doesn't matter for our purposes here.
- return Class == IC_Retain ||
- Class == IC_RetainRV ||
- Class == IC_Autorelease ||
- Class == IC_AutoreleaseRV ||
- Class == IC_RetainBlock ||
- Class == IC_NoopCast;
-}
-
-/// \brief Test if the given class represents instructions which do nothing if
-/// passed a null pointer.
-static bool IsNoopOnNull(InstructionClass Class) {
- return Class == IC_Retain ||
- Class == IC_RetainRV ||
- Class == IC_Release ||
- Class == IC_Autorelease ||
- Class == IC_AutoreleaseRV ||
- Class == IC_RetainBlock;
-}
-
-/// \brief Test if the given class represents instructions which are always safe
-/// to mark with the "tail" keyword.
-static bool IsAlwaysTail(InstructionClass Class) {
- // IC_RetainBlock may be given a stack argument.
- return Class == IC_Retain ||
- Class == IC_RetainRV ||
- Class == IC_AutoreleaseRV;
-}
-
-/// \brief Test if the given class represents instructions which are never safe
-/// to mark with the "tail" keyword.
-static bool IsNeverTail(InstructionClass Class) {
- /// It is never safe to tail call objc_autorelease since by tail calling
- /// objc_autorelease, we also tail call -[NSObject autorelease] which supports
- /// fast autoreleasing causing our object to be potentially reclaimed from the
- /// autorelease pool which violates the semantics of __autoreleasing types in
- /// ARC.
- return Class == IC_Autorelease;
-}
-
-/// \brief Test if the given class represents instructions which are always safe
-/// to mark with the nounwind attribute.
-static bool IsNoThrow(InstructionClass Class) {
- // objc_retainBlock is not nounwind because it calls user copy constructors
- // which could theoretically throw.
- return Class == IC_Retain ||
- Class == IC_RetainRV ||
- Class == IC_Release ||
- Class == IC_Autorelease ||
- Class == IC_AutoreleaseRV ||
- Class == IC_AutoreleasepoolPush ||
- Class == IC_AutoreleasepoolPop;
-}
-
-/// \brief Erase the given instruction.
-///
-/// Many ObjC calls return their argument verbatim,
-/// so if it's such a call and the return value has users, replace them with the
-/// argument value.
-///
-static void EraseInstruction(Instruction *CI) {
- Value *OldArg = cast<CallInst>(CI)->getArgOperand(0);
-
- bool Unused = CI->use_empty();
-
- if (!Unused) {
- // Replace the return value with the argument.
- assert(IsForwarding(GetBasicInstructionClass(CI)) &&
- "Can't delete non-forwarding instruction with users!");
- CI->replaceAllUsesWith(OldArg);
- }
-
- CI->eraseFromParent();
-
- if (Unused)
- RecursivelyDeleteTriviallyDeadInstructions(OldArg);
-}
-
-/// \brief This is a wrapper around getUnderlyingObject which also knows how to
-/// look through objc_retain and objc_autorelease calls, which we know to return
-/// their argument verbatim.
-static const Value *GetUnderlyingObjCPtr(const Value *V) {
- for (;;) {
- V = GetUnderlyingObject(V);
- if (!IsForwarding(GetBasicInstructionClass(V)))
- break;
- V = cast<CallInst>(V)->getArgOperand(0);
- }
-
- return V;
-}
-
-/// \brief This is a wrapper around Value::stripPointerCasts which also knows
-/// how to look through objc_retain and objc_autorelease calls, which we know to
-/// return their argument verbatim.
-static const Value *StripPointerCastsAndObjCCalls(const Value *V) {
- for (;;) {
- V = V->stripPointerCasts();
- if (!IsForwarding(GetBasicInstructionClass(V)))
- break;
- V = cast<CallInst>(V)->getArgOperand(0);
- }
- return V;
-}
-
-/// \brief This is a wrapper around Value::stripPointerCasts which also knows
-/// how to look through objc_retain and objc_autorelease calls, which we know to
-/// return their argument verbatim.
-static Value *StripPointerCastsAndObjCCalls(Value *V) {
- for (;;) {
- V = V->stripPointerCasts();
- if (!IsForwarding(GetBasicInstructionClass(V)))
- break;
- V = cast<CallInst>(V)->getArgOperand(0);
- }
- return V;
-}
-
-/// \brief Assuming the given instruction is one of the special calls such as
-/// objc_retain or objc_release, return the argument value, stripped of no-op
-/// casts and forwarding calls.
-static Value *GetObjCArg(Value *Inst) {
- return StripPointerCastsAndObjCCalls(cast<CallInst>(Inst)->getArgOperand(0));
-}
-
-/// \brief Return true if this value refers to a distinct and identifiable
-/// object.
-///
-/// This is similar to AliasAnalysis's isIdentifiedObject, except that it uses
-/// special knowledge of ObjC conventions.
-static bool IsObjCIdentifiedObject(const Value *V) {
- // Assume that call results and arguments have their own "provenance".
- // Constants (including GlobalVariables) and Allocas are never
- // reference-counted.
- if (isa<CallInst>(V) || isa<InvokeInst>(V) ||
- isa<Argument>(V) || isa<Constant>(V) ||
- isa<AllocaInst>(V))
- return true;
-
- if (const LoadInst *LI = dyn_cast<LoadInst>(V)) {
- const Value *Pointer =
- StripPointerCastsAndObjCCalls(LI->getPointerOperand());
- if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(Pointer)) {
- // A constant pointer can't be pointing to an object on the heap. It may
- // be reference-counted, but it won't be deleted.
- if (GV->isConstant())
- return true;
- StringRef Name = GV->getName();
- // These special variables are known to hold values which are not
- // reference-counted pointers.
- if (Name.startswith("\01L_OBJC_SELECTOR_REFERENCES_") ||
- Name.startswith("\01L_OBJC_CLASSLIST_REFERENCES_") ||
- Name.startswith("\01L_OBJC_CLASSLIST_SUP_REFS_$_") ||
- Name.startswith("\01L_OBJC_METH_VAR_NAME_") ||
- Name.startswith("\01l_objc_msgSend_fixup_"))
- return true;
- }
- }
-
- return false;
-}
-
-/// \brief This is similar to StripPointerCastsAndObjCCalls but it stops as soon
-/// as it finds a value with multiple uses.
-static const Value *FindSingleUseIdentifiedObject(const Value *Arg) {
- if (Arg->hasOneUse()) {
- if (const BitCastInst *BC = dyn_cast<BitCastInst>(Arg))
- return FindSingleUseIdentifiedObject(BC->getOperand(0));
- if (const GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Arg))
- if (GEP->hasAllZeroIndices())
- return FindSingleUseIdentifiedObject(GEP->getPointerOperand());
- if (IsForwarding(GetBasicInstructionClass(Arg)))
- return FindSingleUseIdentifiedObject(
- cast<CallInst>(Arg)->getArgOperand(0));
- if (!IsObjCIdentifiedObject(Arg))
- return 0;
- return Arg;
- }
-
- // If we found an identifiable object but it has multiple uses, but they are
- // trivial uses, we can still consider this to be a single-use value.
- if (IsObjCIdentifiedObject(Arg)) {
- for (Value::const_use_iterator UI = Arg->use_begin(), UE = Arg->use_end();
- UI != UE; ++UI) {
- const User *U = *UI;
- if (!U->use_empty() || StripPointerCastsAndObjCCalls(U) != Arg)
- return 0;
- }
-
- return Arg;
- }
-
- return 0;
-}
-
-/// \brief Test if the given module looks interesting to run ARC optimization
-/// on.
-static bool ModuleHasARC(const Module &M) {
- return
- M.getNamedValue("objc_retain") ||
- M.getNamedValue("objc_release") ||
- M.getNamedValue("objc_autorelease") ||
- M.getNamedValue("objc_retainAutoreleasedReturnValue") ||
- M.getNamedValue("objc_retainBlock") ||
- M.getNamedValue("objc_autoreleaseReturnValue") ||
- M.getNamedValue("objc_autoreleasePoolPush") ||
- M.getNamedValue("objc_loadWeakRetained") ||
- M.getNamedValue("objc_loadWeak") ||
- M.getNamedValue("objc_destroyWeak") ||
- M.getNamedValue("objc_storeWeak") ||
- M.getNamedValue("objc_initWeak") ||
- M.getNamedValue("objc_moveWeak") ||
- M.getNamedValue("objc_copyWeak") ||
- M.getNamedValue("objc_retainedObject") ||
- M.getNamedValue("objc_unretainedObject") ||
- M.getNamedValue("objc_unretainedPointer");
-}
-
-/// \brief Test whether the given pointer, which is an Objective C block
-/// pointer, does not "escape".
-///
-/// This differs from regular escape analysis in that a use as an
-/// argument to a call is not considered an escape.
-///
-static bool DoesObjCBlockEscape(const Value *BlockPtr) {
-
- DEBUG(dbgs() << "DoesObjCBlockEscape: Target: " << *BlockPtr << "\n");
-
- // Walk the def-use chains.
- SmallVector<const Value *, 4> Worklist;
- Worklist.push_back(BlockPtr);
-
- // Ensure we do not visit any value twice.
- SmallPtrSet<const Value *, 4> VisitedSet;
-
- do {
- const Value *V = Worklist.pop_back_val();
-
- DEBUG(dbgs() << "DoesObjCBlockEscape: Visiting: " << *V << "\n");
-
- for (Value::const_use_iterator UI = V->use_begin(), UE = V->use_end();
- UI != UE; ++UI) {
- const User *UUser = *UI;
-
- DEBUG(dbgs() << "DoesObjCBlockEscape: User: " << *UUser << "\n");
-
- // Special - Use by a call (callee or argument) is not considered
- // to be an escape.
- switch (GetBasicInstructionClass(UUser)) {
- case IC_StoreWeak:
- case IC_InitWeak:
- case IC_StoreStrong:
- case IC_Autorelease:
- case IC_AutoreleaseRV: {
- DEBUG(dbgs() << "DoesObjCBlockEscape: User copies pointer arguments. "
- "Block Escapes!\n");
- // These special functions make copies of their pointer arguments.
- return true;
- }
- case IC_User:
- case IC_None:
- // Use by an instruction which copies the value is an escape if the
- // result is an escape.
- if (isa<BitCastInst>(UUser) || isa<GetElementPtrInst>(UUser) ||
- isa<PHINode>(UUser) || isa<SelectInst>(UUser)) {
-
- if (!VisitedSet.insert(UUser)) {
- DEBUG(dbgs() << "DoesObjCBlockEscape: User copies value. Escapes "
- "if result escapes. Adding to list.\n");
- Worklist.push_back(UUser);
- } else {
- DEBUG(dbgs() << "DoesObjCBlockEscape: Already visited node.\n");
- }
- continue;
- }
- // Use by a load is not an escape.
- if (isa<LoadInst>(UUser))
- continue;
- // Use by a store is not an escape if the use is the address.
- if (const StoreInst *SI = dyn_cast<StoreInst>(UUser))
- if (V != SI->getValueOperand())
- continue;
- break;
- default:
- // Regular calls and other stuff are not considered escapes.
- continue;
- }
- // Otherwise, conservatively assume an escape.
- DEBUG(dbgs() << "DoesObjCBlockEscape: Assuming block escapes.\n");
- return true;
- }
- } while (!Worklist.empty());
-
- // No escapes found.
- DEBUG(dbgs() << "DoesObjCBlockEscape: Block does not escape.\n");
- return false;
-}
-
-/// @}
-///
-/// \defgroup ARCAA Extends alias analysis using ObjC specific knowledge.
-/// @{
-
-#include "llvm/Analysis/AliasAnalysis.h"
-#include "llvm/Analysis/Passes.h"
-#include "llvm/Pass.h"
-
-namespace {
- /// \brief This is a simple alias analysis implementation that uses knowledge
- /// of ARC constructs to answer queries.
- ///
- /// TODO: This class could be generalized to know about other ObjC-specific
- /// tricks. Such as knowing that ivars in the non-fragile ABI are non-aliasing
- /// even though their offsets are dynamic.
- class ObjCARCAliasAnalysis : public ImmutablePass,
- public AliasAnalysis {
- public:
- static char ID; // Class identification, replacement for typeinfo
- ObjCARCAliasAnalysis() : ImmutablePass(ID) {
- initializeObjCARCAliasAnalysisPass(*PassRegistry::getPassRegistry());
- }
-
- private:
- virtual void initializePass() {
- InitializeAliasAnalysis(this);
- }
-
- /// This method is used when a pass implements an analysis interface through
- /// multiple inheritance. If needed, it should override this to adjust the
- /// this pointer as needed for the specified pass info.
- virtual void *getAdjustedAnalysisPointer(const void *PI) {
- if (PI == &AliasAnalysis::ID)
- return static_cast<AliasAnalysis *>(this);
- return this;
- }
-
- virtual void getAnalysisUsage(AnalysisUsage &AU) const;
- virtual AliasResult alias(const Location &LocA, const Location &LocB);
- virtual bool pointsToConstantMemory(const Location &Loc, bool OrLocal);
- virtual ModRefBehavior getModRefBehavior(ImmutableCallSite CS);
- virtual ModRefBehavior getModRefBehavior(const Function *F);
- virtual ModRefResult getModRefInfo(ImmutableCallSite CS,
- const Location &Loc);
- virtual ModRefResult getModRefInfo(ImmutableCallSite CS1,
- ImmutableCallSite CS2);
- };
-} // End of anonymous namespace
-
-// Register this pass...
-char ObjCARCAliasAnalysis::ID = 0;
-INITIALIZE_AG_PASS(ObjCARCAliasAnalysis, AliasAnalysis, "objc-arc-aa",
- "ObjC-ARC-Based Alias Analysis", false, true, false)
-
-ImmutablePass *llvm::createObjCARCAliasAnalysisPass() {
- return new ObjCARCAliasAnalysis();
-}
-
-void
-ObjCARCAliasAnalysis::getAnalysisUsage(AnalysisUsage &AU) const {
- AU.setPreservesAll();
- AliasAnalysis::getAnalysisUsage(AU);
-}
-
-AliasAnalysis::AliasResult
-ObjCARCAliasAnalysis::alias(const Location &LocA, const Location &LocB) {
- if (!EnableARCOpts)
- return AliasAnalysis::alias(LocA, LocB);
-
- // First, strip off no-ops, including ObjC-specific no-ops, and try making a
- // precise alias query.
- const Value *SA = StripPointerCastsAndObjCCalls(LocA.Ptr);
- const Value *SB = StripPointerCastsAndObjCCalls(LocB.Ptr);
- AliasResult Result =
- AliasAnalysis::alias(Location(SA, LocA.Size, LocA.TBAATag),
- Location(SB, LocB.Size, LocB.TBAATag));
- if (Result != MayAlias)
- return Result;
-
- // If that failed, climb to the underlying object, including climbing through
- // ObjC-specific no-ops, and try making an imprecise alias query.
- const Value *UA = GetUnderlyingObjCPtr(SA);
- const Value *UB = GetUnderlyingObjCPtr(SB);
- if (UA != SA || UB != SB) {
- Result = AliasAnalysis::alias(Location(UA), Location(UB));
- // We can't use MustAlias or PartialAlias results here because
- // GetUnderlyingObjCPtr may return an offsetted pointer value.
- if (Result == NoAlias)
- return NoAlias;
- }
-
- // If that failed, fail. We don't need to chain here, since that's covered
- // by the earlier precise query.
- return MayAlias;
-}
-
-bool
-ObjCARCAliasAnalysis::pointsToConstantMemory(const Location &Loc,
- bool OrLocal) {
- if (!EnableARCOpts)
- return AliasAnalysis::pointsToConstantMemory(Loc, OrLocal);
-
- // First, strip off no-ops, including ObjC-specific no-ops, and try making
- // a precise alias query.
- const Value *S = StripPointerCastsAndObjCCalls(Loc.Ptr);
- if (AliasAnalysis::pointsToConstantMemory(Location(S, Loc.Size, Loc.TBAATag),
- OrLocal))
- return true;
-
- // If that failed, climb to the underlying object, including climbing through
- // ObjC-specific no-ops, and try making an imprecise alias query.
- const Value *U = GetUnderlyingObjCPtr(S);
- if (U != S)
- return AliasAnalysis::pointsToConstantMemory(Location(U), OrLocal);
-
- // If that failed, fail. We don't need to chain here, since that's covered
- // by the earlier precise query.
- return false;
-}
-
-AliasAnalysis::ModRefBehavior
-ObjCARCAliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
- // We have nothing to do. Just chain to the next AliasAnalysis.
- return AliasAnalysis::getModRefBehavior(CS);
-}
-
-AliasAnalysis::ModRefBehavior
-ObjCARCAliasAnalysis::getModRefBehavior(const Function *F) {
- if (!EnableARCOpts)
- return AliasAnalysis::getModRefBehavior(F);
-
- switch (GetFunctionClass(F)) {
- case IC_NoopCast:
- return DoesNotAccessMemory;
- default:
- break;
- }
-
- return AliasAnalysis::getModRefBehavior(F);
-}
-
-AliasAnalysis::ModRefResult
-ObjCARCAliasAnalysis::getModRefInfo(ImmutableCallSite CS, const Location &Loc) {
- if (!EnableARCOpts)
- return AliasAnalysis::getModRefInfo(CS, Loc);
-
- switch (GetBasicInstructionClass(CS.getInstruction())) {
- case IC_Retain:
- case IC_RetainRV:
- case IC_Autorelease:
- case IC_AutoreleaseRV:
- case IC_NoopCast:
- case IC_AutoreleasepoolPush:
- case IC_FusedRetainAutorelease:
- case IC_FusedRetainAutoreleaseRV:
- // These functions don't access any memory visible to the compiler.
- // Note that this doesn't include objc_retainBlock, because it updates
- // pointers when it copies block data.
- return NoModRef;
- default:
- break;
- }
-
- return AliasAnalysis::getModRefInfo(CS, Loc);
-}
-
-AliasAnalysis::ModRefResult
-ObjCARCAliasAnalysis::getModRefInfo(ImmutableCallSite CS1,
- ImmutableCallSite CS2) {
- // TODO: Theoretically we could check for dependencies between objc_* calls
- // and OnlyAccessesArgumentPointees calls or other well-behaved calls.
- return AliasAnalysis::getModRefInfo(CS1, CS2);
-}
-
-/// @}
-///
-/// \defgroup ARCExpansion Early ARC Optimizations.
-/// @{
-
-#include "llvm/Support/InstIterator.h"
-#include "llvm/Transforms/Scalar.h"
-
-namespace {
- /// \brief Early ARC transformations.
- class ObjCARCExpand : public FunctionPass {
- virtual void getAnalysisUsage(AnalysisUsage &AU) const;
- virtual bool doInitialization(Module &M);
- virtual bool runOnFunction(Function &F);
-
- /// A flag indicating whether this optimization pass should run.
- bool Run;
-
- public:
- static char ID;
- ObjCARCExpand() : FunctionPass(ID) {
- initializeObjCARCExpandPass(*PassRegistry::getPassRegistry());
- }
- };
-}
-
-char ObjCARCExpand::ID = 0;
-INITIALIZE_PASS(ObjCARCExpand,
- "objc-arc-expand", "ObjC ARC expansion", false, false)
-
-Pass *llvm::createObjCARCExpandPass() {
- return new ObjCARCExpand();
-}
-
-void ObjCARCExpand::getAnalysisUsage(AnalysisUsage &AU) const {
- AU.setPreservesCFG();
-}
-
-bool ObjCARCExpand::doInitialization(Module &M) {
- Run = ModuleHasARC(M);
- return false;
-}
-
-bool ObjCARCExpand::runOnFunction(Function &F) {
- if (!EnableARCOpts)
- return false;
-
- // If nothing in the Module uses ARC, don't do anything.
- if (!Run)
- return false;
-
- bool Changed = false;
-
- DEBUG(dbgs() << "ObjCARCExpand: Visiting Function: " << F.getName() << "\n");
-
- for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ++I) {
- Instruction *Inst = &*I;
-
- DEBUG(dbgs() << "ObjCARCExpand: Visiting: " << *Inst << "\n");
-
- switch (GetBasicInstructionClass(Inst)) {
- case IC_Retain:
- case IC_RetainRV:
- case IC_Autorelease:
- case IC_AutoreleaseRV:
- case IC_FusedRetainAutorelease:
- case IC_FusedRetainAutoreleaseRV: {
- // These calls return their argument verbatim, as a low-level
- // optimization. However, this makes high-level optimizations
- // harder. Undo any uses of this optimization that the front-end
- // emitted here. We'll redo them in the contract pass.
- Changed = true;
- Value *Value = cast<CallInst>(Inst)->getArgOperand(0);
- DEBUG(dbgs() << "ObjCARCExpand: Old = " << *Inst << "\n"
- " New = " << *Value << "\n");
- Inst->replaceAllUsesWith(Value);
- break;
- }
- default:
- break;
- }
- }
-
- DEBUG(dbgs() << "ObjCARCExpand: Finished List.\n\n");
-
- return Changed;
-}
-
-/// @}
-///
-/// \defgroup ARCAPElim ARC Autorelease Pool Elimination.
-/// @{
-
-#include "llvm/ADT/STLExtras.h"
-#include "llvm/IR/Constants.h"
-
-namespace {
- /// \brief Autorelease pool elimination.
- class ObjCARCAPElim : public ModulePass {
- virtual void getAnalysisUsage(AnalysisUsage &AU) const;
- virtual bool runOnModule(Module &M);
-
- static bool MayAutorelease(ImmutableCallSite CS, unsigned Depth = 0);
- static bool OptimizeBB(BasicBlock *BB);
-
- public:
- static char ID;
- ObjCARCAPElim() : ModulePass(ID) {
- initializeObjCARCAPElimPass(*PassRegistry::getPassRegistry());
- }
- };
-}
-
-char ObjCARCAPElim::ID = 0;
-INITIALIZE_PASS(ObjCARCAPElim,
- "objc-arc-apelim",
- "ObjC ARC autorelease pool elimination",
- false, false)
-
-Pass *llvm::createObjCARCAPElimPass() {
- return new ObjCARCAPElim();
-}
-
-void ObjCARCAPElim::getAnalysisUsage(AnalysisUsage &AU) const {
- AU.setPreservesCFG();
-}
-
-/// Interprocedurally determine if calls made by the given call site can
-/// possibly produce autoreleases.
-bool ObjCARCAPElim::MayAutorelease(ImmutableCallSite CS, unsigned Depth) {
- if (const Function *Callee = CS.getCalledFunction()) {
- if (Callee->isDeclaration() || Callee->mayBeOverridden())
- return true;
- for (Function::const_iterator I = Callee->begin(), E = Callee->end();
- I != E; ++I) {
- const BasicBlock *BB = I;
- for (BasicBlock::const_iterator J = BB->begin(), F = BB->end();
- J != F; ++J)
- if (ImmutableCallSite JCS = ImmutableCallSite(J))
- // This recursion depth limit is arbitrary. It's just great
- // enough to cover known interesting testcases.
- if (Depth < 3 &&
- !JCS.onlyReadsMemory() &&
- MayAutorelease(JCS, Depth + 1))
- return true;
- }
- return false;
- }
-
- return true;
-}
-
-bool ObjCARCAPElim::OptimizeBB(BasicBlock *BB) {
- bool Changed = false;
-
- Instruction *Push = 0;
- for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ) {
- Instruction *Inst = I++;
- switch (GetBasicInstructionClass(Inst)) {
- case IC_AutoreleasepoolPush:
- Push = Inst;
- break;
- case IC_AutoreleasepoolPop:
- // If this pop matches a push and nothing in between can autorelease,
- // zap the pair.
- if (Push && cast<CallInst>(Inst)->getArgOperand(0) == Push) {
- Changed = true;
- DEBUG(dbgs() << "ObjCARCAPElim::OptimizeBB: Zapping push pop "
- "autorelease pair:\n"
- " Pop: " << *Inst << "\n"
- << " Push: " << *Push << "\n");
- Inst->eraseFromParent();
- Push->eraseFromParent();
- }
- Push = 0;
- break;
- case IC_CallOrUser:
- if (MayAutorelease(ImmutableCallSite(Inst)))
- Push = 0;
- break;
- default:
- break;
- }
- }
-
- return Changed;
-}
-
-bool ObjCARCAPElim::runOnModule(Module &M) {
- if (!EnableARCOpts)
- return false;
-
- // If nothing in the Module uses ARC, don't do anything.
- if (!ModuleHasARC(M))
- return false;
-
- // Find the llvm.global_ctors variable, as the first step in
- // identifying the global constructors. In theory, unnecessary autorelease
- // pools could occur anywhere, but in practice it's pretty rare. Global
- // ctors are a place where autorelease pools get inserted automatically,
- // so it's pretty common for them to be unnecessary, and it's pretty
- // profitable to eliminate them.
- GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors");
- if (!GV)
- return false;
-
- assert(GV->hasDefinitiveInitializer() &&
- "llvm.global_ctors is uncooperative!");
-
- bool Changed = false;
-
- // Dig the constructor functions out of GV's initializer.
- ConstantArray *Init = cast<ConstantArray>(GV->getInitializer());
- for (User::op_iterator OI = Init->op_begin(), OE = Init->op_end();
- OI != OE; ++OI) {
- Value *Op = *OI;
- // llvm.global_ctors is an array of pairs where the second members
- // are constructor functions.
- Function *F = dyn_cast<Function>(cast<ConstantStruct>(Op)->getOperand(1));
- // If the user used a constructor function with the wrong signature and
- // it got bitcasted or whatever, look the other way.
- if (!F)
- continue;
- // Only look at function definitions.
- if (F->isDeclaration())
- continue;
- // Only look at functions with one basic block.
- if (llvm::next(F->begin()) != F->end())
- continue;
- // Ok, a single-block constructor function definition. Try to optimize it.
- Changed |= OptimizeBB(F->begin());
- }
-
- return Changed;
-}
-
-/// @}
-///
-/// \defgroup ARCOpt ARC Optimization.
-/// @{
-
-// TODO: On code like this:
-//
-// objc_retain(%x)
-// stuff_that_cannot_release()
-// objc_autorelease(%x)
-// stuff_that_cannot_release()
-// objc_retain(%x)
-// stuff_that_cannot_release()
-// objc_autorelease(%x)
-//
-// The second retain and autorelease can be deleted.
-
-// TODO: It should be possible to delete
-// objc_autoreleasePoolPush and objc_autoreleasePoolPop
-// pairs if nothing is actually autoreleased between them. Also, autorelease
-// calls followed by objc_autoreleasePoolPop calls (perhaps in ObjC++ code
-// after inlining) can be turned into plain release calls.
-
-// TODO: Critical-edge splitting. If the optimial insertion point is
-// a critical edge, the current algorithm has to fail, because it doesn't
-// know how to split edges. It should be possible to make the optimizer
-// think in terms of edges, rather than blocks, and then split critical
-// edges on demand.
-
-// TODO: OptimizeSequences could generalized to be Interprocedural.
-
-// TODO: Recognize that a bunch of other objc runtime calls have
-// non-escaping arguments and non-releasing arguments, and may be
-// non-autoreleasing.
-
-// TODO: Sink autorelease calls as far as possible. Unfortunately we
-// usually can't sink them past other calls, which would be the main
-// case where it would be useful.
-
-// TODO: The pointer returned from objc_loadWeakRetained is retained.
-
-// TODO: Delete release+retain pairs (rare).
-
-#include "llvm/ADT/SmallPtrSet.h"
-#include "llvm/ADT/Statistic.h"
-#include "llvm/IR/LLVMContext.h"
-#include "llvm/Support/CFG.h"
-
-STATISTIC(NumNoops, "Number of no-op objc calls eliminated");
-STATISTIC(NumPartialNoops, "Number of partially no-op objc calls eliminated");
-STATISTIC(NumAutoreleases,"Number of autoreleases converted to releases");
-STATISTIC(NumRets, "Number of return value forwarding "
- "retain+autoreleaes eliminated");
-STATISTIC(NumRRs, "Number of retain+release paths eliminated");
-STATISTIC(NumPeeps, "Number of calls peephole-optimized");
-
-namespace {
- /// \brief This is similar to BasicAliasAnalysis, and it uses many of the same
- /// techniques, except it uses special ObjC-specific reasoning about pointer
- /// relationships.
- ///
- /// In this context ``Provenance'' is defined as the history of an object's
- /// ownership. Thus ``Provenance Analysis'' is defined by using the notion of
- /// an ``independent provenance source'' of a pointer to determine whether or
- /// not two pointers have the same provenance source and thus could
- /// potentially be related.
- class ProvenanceAnalysis {
- AliasAnalysis *AA;
-
- typedef std::pair<const Value *, const Value *> ValuePairTy;
- typedef DenseMap<ValuePairTy, bool> CachedResultsTy;
- CachedResultsTy CachedResults;
-
- bool relatedCheck(const Value *A, const Value *B);
- bool relatedSelect(const SelectInst *A, const Value *B);
- bool relatedPHI(const PHINode *A, const Value *B);
-
- void operator=(const ProvenanceAnalysis &) LLVM_DELETED_FUNCTION;
- ProvenanceAnalysis(const ProvenanceAnalysis &) LLVM_DELETED_FUNCTION;
-
- public:
- ProvenanceAnalysis() {}
-
- void setAA(AliasAnalysis *aa) { AA = aa; }
-
- AliasAnalysis *getAA() const { return AA; }
-
- bool related(const Value *A, const Value *B);
-
- void clear() {
- CachedResults.clear();
- }
- };
-}
-
-bool ProvenanceAnalysis::relatedSelect(const SelectInst *A, const Value *B) {
- // If the values are Selects with the same condition, we can do a more precise
- // check: just check for relations between the values on corresponding arms.
- if (const SelectInst *SB = dyn_cast<SelectInst>(B))
- if (A->getCondition() == SB->getCondition())
- return related(A->getTrueValue(), SB->getTrueValue()) ||
- related(A->getFalseValue(), SB->getFalseValue());
-
- // Check both arms of the Select node individually.
- return related(A->getTrueValue(), B) ||
- related(A->getFalseValue(), B);
-}
-
-bool ProvenanceAnalysis::relatedPHI(const PHINode *A, const Value *B) {
- // If the values are PHIs in the same block, we can do a more precise as well
- // as efficient check: just check for relations between the values on
- // corresponding edges.
- if (const PHINode *PNB = dyn_cast<PHINode>(B))
- if (PNB->getParent() == A->getParent()) {
- for (unsigned i = 0, e = A->getNumIncomingValues(); i != e; ++i)
- if (related(A->getIncomingValue(i),
- PNB->getIncomingValueForBlock(A->getIncomingBlock(i))))
- return true;
- return false;
- }
-
- // Check each unique source of the PHI node against B.
- SmallPtrSet<const Value *, 4> UniqueSrc;
- for (unsigned i = 0, e = A->getNumIncomingValues(); i != e; ++i) {
- const Value *PV1 = A->getIncomingValue(i);
- if (UniqueSrc.insert(PV1) && related(PV1, B))
- return true;
- }
-
- // All of the arms checked out.
- return false;
-}
-
-/// Test if the value of P, or any value covered by its provenance, is ever
-/// stored within the function (not counting callees).
-static bool isStoredObjCPointer(const Value *P) {
- SmallPtrSet<const Value *, 8> Visited;
- SmallVector<const Value *, 8> Worklist;
- Worklist.push_back(P);
- Visited.insert(P);
- do {
- P = Worklist.pop_back_val();
- for (Value::const_use_iterator UI = P->use_begin(), UE = P->use_end();
- UI != UE; ++UI) {
- const User *Ur = *UI;
- if (isa<StoreInst>(Ur)) {
- if (UI.getOperandNo() == 0)
- // The pointer is stored.
- return true;
- // The pointed is stored through.
- continue;
- }
- if (isa<CallInst>(Ur))
- // The pointer is passed as an argument, ignore this.
- continue;
- if (isa<PtrToIntInst>(P))
- // Assume the worst.
- return true;
- if (Visited.insert(Ur))
- Worklist.push_back(Ur);
- }
- } while (!Worklist.empty());
-
- // Everything checked out.
- return false;
-}
-
-bool ProvenanceAnalysis::relatedCheck(const Value *A, const Value *B) {
- // Skip past provenance pass-throughs.
- A = GetUnderlyingObjCPtr(A);
- B = GetUnderlyingObjCPtr(B);
-
- // Quick check.
- if (A == B)
- return true;
-
- // Ask regular AliasAnalysis, for a first approximation.
- switch (AA->alias(A, B)) {
- case AliasAnalysis::NoAlias:
- return false;
- case AliasAnalysis::MustAlias:
- case AliasAnalysis::PartialAlias:
- return true;
- case AliasAnalysis::MayAlias:
- break;
- }
-
- bool AIsIdentified = IsObjCIdentifiedObject(A);
- bool BIsIdentified = IsObjCIdentifiedObject(B);
-
- // An ObjC-Identified object can't alias a load if it is never locally stored.
- if (AIsIdentified) {
- // Check for an obvious escape.
- if (isa<LoadInst>(B))
- return isStoredObjCPointer(A);
- if (BIsIdentified) {
- // Check for an obvious escape.
- if (isa<LoadInst>(A))
- return isStoredObjCPointer(B);
- // Both pointers are identified and escapes aren't an evident problem.
- return false;
- }
- } else if (BIsIdentified) {
- // Check for an obvious escape.
- if (isa<LoadInst>(A))
- return isStoredObjCPointer(B);
- }
-
- // Special handling for PHI and Select.
- if (const PHINode *PN = dyn_cast<PHINode>(A))
- return relatedPHI(PN, B);
- if (const PHINode *PN = dyn_cast<PHINode>(B))
- return relatedPHI(PN, A);
- if (const SelectInst *S = dyn_cast<SelectInst>(A))
- return relatedSelect(S, B);
- if (const SelectInst *S = dyn_cast<SelectInst>(B))
- return relatedSelect(S, A);
-
- // Conservative.
- return true;
-}
-
-bool ProvenanceAnalysis::related(const Value *A, const Value *B) {
- // Begin by inserting a conservative value into the map. If the insertion
- // fails, we have the answer already. If it succeeds, leave it there until we
- // compute the real answer to guard against recursive queries.
- if (A > B) std::swap(A, B);
- std::pair<CachedResultsTy::iterator, bool> Pair =
- CachedResults.insert(std::make_pair(ValuePairTy(A, B), true));
- if (!Pair.second)
- return Pair.first->second;
-
- bool Result = relatedCheck(A, B);
- CachedResults[ValuePairTy(A, B)] = Result;
- return Result;
-}
-
-namespace {
- /// \enum Sequence
- ///
- /// \brief A sequence of states that a pointer may go through in which an
- /// objc_retain and objc_release are actually needed.
- enum Sequence {
- S_None,
- S_Retain, ///< objc_retain(x)
- S_CanRelease, ///< foo(x) -- x could possibly see a ref count decrement
- S_Use, ///< any use of x
- S_Stop, ///< like S_Release, but code motion is stopped
- S_Release, ///< objc_release(x)
- S_MovableRelease ///< objc_release(x), !clang.imprecise_release
- };
-}
-
-static Sequence MergeSeqs(Sequence A, Sequence B, bool TopDown) {
- // The easy cases.
- if (A == B)
- return A;
- if (A == S_None || B == S_None)
- return S_None;
-
- if (A > B) std::swap(A, B);
- if (TopDown) {
- // Choose the side which is further along in the sequence.
- if ((A == S_Retain || A == S_CanRelease) &&
- (B == S_CanRelease || B == S_Use))
- return B;
- } else {
- // Choose the side which is further along in the sequence.
- if ((A == S_Use || A == S_CanRelease) &&
- (B == S_Use || B == S_Release || B == S_Stop || B == S_MovableRelease))
- return A;
- // If both sides are releases, choose the more conservative one.
- if (A == S_Stop && (B == S_Release || B == S_MovableRelease))
- return A;
- if (A == S_Release && B == S_MovableRelease)
- return A;
- }
-
- return S_None;
-}
-
-namespace {
- /// \brief Unidirectional information about either a
- /// retain-decrement-use-release sequence or release-use-decrement-retain
- /// reverese sequence.
- struct RRInfo {
- /// After an objc_retain, the reference count of the referenced
- /// object is known to be positive. Similarly, before an objc_release, the
- /// reference count of the referenced object is known to be positive. If
- /// there are retain-release pairs in code regions where the retain count
- /// is known to be positive, they can be eliminated, regardless of any side
- /// effects between them.
- ///
- /// Also, a retain+release pair nested within another retain+release
- /// pair all on the known same pointer value can be eliminated, regardless
- /// of any intervening side effects.
- ///
- /// KnownSafe is true when either of these conditions is satisfied.
- bool KnownSafe;
-
- /// True if the Calls are objc_retainBlock calls (as opposed to objc_retain
- /// calls).
- bool IsRetainBlock;
-
- /// True of the objc_release calls are all marked with the "tail" keyword.
- bool IsTailCallRelease;
-
- /// If the Calls are objc_release calls and they all have a
- /// clang.imprecise_release tag, this is the metadata tag.
- MDNode *ReleaseMetadata;
-
- /// For a top-down sequence, the set of objc_retains or
- /// objc_retainBlocks. For bottom-up, the set of objc_releases.
- SmallPtrSet<Instruction *, 2> Calls;
-
- /// The set of optimal insert positions for moving calls in the opposite
- /// sequence.
- SmallPtrSet<Instruction *, 2> ReverseInsertPts;
-
- RRInfo() :
- KnownSafe(false), IsRetainBlock(false),
- IsTailCallRelease(false),
- ReleaseMetadata(0) {}
-
- void clear();
- };
-}
-
-void RRInfo::clear() {
- KnownSafe = false;
- IsRetainBlock = false;
- IsTailCallRelease = false;
- ReleaseMetadata = 0;
- Calls.clear();
- ReverseInsertPts.clear();
-}
-
-namespace {
- /// \brief This class summarizes several per-pointer runtime properties which
- /// are propogated through the flow graph.
- class PtrState {
- /// True if the reference count is known to be incremented.
- bool KnownPositiveRefCount;
-
- /// True of we've seen an opportunity for partial RR elimination, such as
- /// pushing calls into a CFG triangle or into one side of a CFG diamond.
- bool Partial;
-
- /// The current position in the sequence.
- Sequence Seq : 8;
-
- public:
- /// Unidirectional information about the current sequence.
- ///
- /// TODO: Encapsulate this better.
- RRInfo RRI;
-
- PtrState() : KnownPositiveRefCount(false), Partial(false),
- Seq(S_None) {}
-
- void SetKnownPositiveRefCount() {
- KnownPositiveRefCount = true;
- }
-
- void ClearRefCount() {
- KnownPositiveRefCount = false;
- }
-
- bool IsKnownIncremented() const {
- return KnownPositiveRefCount;
- }
-
- void SetSeq(Sequence NewSeq) {
- Seq = NewSeq;
- }
-
- Sequence GetSeq() const {
- return Seq;
- }
-
- void ClearSequenceProgress() {
- ResetSequenceProgress(S_None);
- }
-
- void ResetSequenceProgress(Sequence NewSeq) {
- Seq = NewSeq;
- Partial = false;
- RRI.clear();
- }
-
- void Merge(const PtrState &Other, bool TopDown);
- };
-}
-
-void
-PtrState::Merge(const PtrState &Other, bool TopDown) {
- Seq = MergeSeqs(Seq, Other.Seq, TopDown);
- KnownPositiveRefCount = KnownPositiveRefCount && Other.KnownPositiveRefCount;
-
- // We can't merge a plain objc_retain with an objc_retainBlock.
- if (RRI.IsRetainBlock != Other.RRI.IsRetainBlock)
- Seq = S_None;
-
- // If we're not in a sequence (anymore), drop all associated state.
- if (Seq == S_None) {
- Partial = false;
- RRI.clear();
- } else if (Partial || Other.Partial) {
- // If we're doing a merge on a path that's previously seen a partial
- // merge, conservatively drop the sequence, to avoid doing partial
- // RR elimination. If the branch predicates for the two merge differ,
- // mixing them is unsafe.
- ClearSequenceProgress();
- } else {
- // Conservatively merge the ReleaseMetadata information.
- if (RRI.ReleaseMetadata != Other.RRI.ReleaseMetadata)
- RRI.ReleaseMetadata = 0;
-
- RRI.KnownSafe = RRI.KnownSafe && Other.RRI.KnownSafe;
- RRI.IsTailCallRelease = RRI.IsTailCallRelease &&
- Other.RRI.IsTailCallRelease;
- RRI.Calls.insert(Other.RRI.Calls.begin(), Other.RRI.Calls.end());
-
- // Merge the insert point sets. If there are any differences,
- // that makes this a partial merge.
- Partial = RRI.ReverseInsertPts.size() != Other.RRI.ReverseInsertPts.size();
- for (SmallPtrSet<Instruction *, 2>::const_iterator
- I = Other.RRI.ReverseInsertPts.begin(),
- E = Other.RRI.ReverseInsertPts.end(); I != E; ++I)
- Partial |= RRI.ReverseInsertPts.insert(*I);
- }
-}
-
-namespace {
- /// \brief Per-BasicBlock state.
- class BBState {
- /// The number of unique control paths from the entry which can reach this
- /// block.
- unsigned TopDownPathCount;
-
- /// The number of unique control paths to exits from this block.
- unsigned BottomUpPathCount;
-
- /// A type for PerPtrTopDown and PerPtrBottomUp.
- typedef MapVector<const Value *, PtrState> MapTy;
-
- /// The top-down traversal uses this to record information known about a
- /// pointer at the bottom of each block.
- MapTy PerPtrTopDown;
-
- /// The bottom-up traversal uses this to record information known about a
- /// pointer at the top of each block.
- MapTy PerPtrBottomUp;
-
- /// Effective predecessors of the current block ignoring ignorable edges and
- /// ignored backedges.
- SmallVector<BasicBlock *, 2> Preds;
- /// Effective successors of the current block ignoring ignorable edges and
- /// ignored backedges.
- SmallVector<BasicBlock *, 2> Succs;
-
- public:
- BBState() : TopDownPathCount(0), BottomUpPathCount(0) {}
-
- typedef MapTy::iterator ptr_iterator;
- typedef MapTy::const_iterator ptr_const_iterator;
-
- ptr_iterator top_down_ptr_begin() { return PerPtrTopDown.begin(); }
- ptr_iterator top_down_ptr_end() { return PerPtrTopDown.end(); }
- ptr_const_iterator top_down_ptr_begin() const {
- return PerPtrTopDown.begin();
- }
- ptr_const_iterator top_down_ptr_end() const {
- return PerPtrTopDown.end();
- }
-
- ptr_iterator bottom_up_ptr_begin() { return PerPtrBottomUp.begin(); }
- ptr_iterator bottom_up_ptr_end() { return PerPtrBottomUp.end(); }
- ptr_const_iterator bottom_up_ptr_begin() const {
- return PerPtrBottomUp.begin();
- }
- ptr_const_iterator bottom_up_ptr_end() const {
- return PerPtrBottomUp.end();
- }
-
- /// Mark this block as being an entry block, which has one path from the
- /// entry by definition.
- void SetAsEntry() { TopDownPathCount = 1; }
-
- /// Mark this block as being an exit block, which has one path to an exit by
- /// definition.
- void SetAsExit() { BottomUpPathCount = 1; }
-
- PtrState &getPtrTopDownState(const Value *Arg) {
- return PerPtrTopDown[Arg];
- }
-
- PtrState &getPtrBottomUpState(const Value *Arg) {
- return PerPtrBottomUp[Arg];
- }
-
- void clearBottomUpPointers() {
- PerPtrBottomUp.clear();
- }
-
- void clearTopDownPointers() {
- PerPtrTopDown.clear();
- }
-
- void InitFromPred(const BBState &Other);
- void InitFromSucc(const BBState &Other);
- void MergePred(const BBState &Other);
- void MergeSucc(const BBState &Other);
-
- /// Return the number of possible unique paths from an entry to an exit
- /// which pass through this block. This is only valid after both the
- /// top-down and bottom-up traversals are complete.
- unsigned GetAllPathCount() const {
- assert(TopDownPathCount != 0);
- assert(BottomUpPathCount != 0);
- return TopDownPathCount * BottomUpPathCount;
- }
-
- // Specialized CFG utilities.
- typedef SmallVectorImpl<BasicBlock *>::const_iterator edge_iterator;
- edge_iterator pred_begin() { return Preds.begin(); }
- edge_iterator pred_end() { return Preds.end(); }
- edge_iterator succ_begin() { return Succs.begin(); }
- edge_iterator succ_end() { return Succs.end(); }
-
- void addSucc(BasicBlock *Succ) { Succs.push_back(Succ); }
- void addPred(BasicBlock *Pred) { Preds.push_back(Pred); }
-
- bool isExit() const { return Succs.empty(); }
- };
-}
-
-void BBState::InitFromPred(const BBState &Other) {
- PerPtrTopDown = Other.PerPtrTopDown;
- TopDownPathCount = Other.TopDownPathCount;
-}
-
-void BBState::InitFromSucc(const BBState &Other) {
- PerPtrBottomUp = Other.PerPtrBottomUp;
- BottomUpPathCount = Other.BottomUpPathCount;
-}
-
-/// The top-down traversal uses this to merge information about predecessors to
-/// form the initial state for a new block.
-void BBState::MergePred(const BBState &Other) {
- // Other.TopDownPathCount can be 0, in which case it is either dead or a
- // loop backedge. Loop backedges are special.
- TopDownPathCount += Other.TopDownPathCount;
-
- // Check for overflow. If we have overflow, fall back to conservative
- // behavior.
- if (TopDownPathCount < Other.TopDownPathCount) {
- clearTopDownPointers();
- return;
- }
-
- // For each entry in the other set, if our set has an entry with the same key,
- // merge the entries. Otherwise, copy the entry and merge it with an empty
- // entry.
- for (ptr_const_iterator MI = Other.top_down_ptr_begin(),
- ME = Other.top_down_ptr_end(); MI != ME; ++MI) {
- std::pair<ptr_iterator, bool> Pair = PerPtrTopDown.insert(*MI);
- Pair.first->second.Merge(Pair.second ? PtrState() : MI->second,
- /*TopDown=*/true);
- }
-
- // For each entry in our set, if the other set doesn't have an entry with the
- // same key, force it to merge with an empty entry.
- for (ptr_iterator MI = top_down_ptr_begin(),
- ME = top_down_ptr_end(); MI != ME; ++MI)
- if (Other.PerPtrTopDown.find(MI->first) == Other.PerPtrTopDown.end())
- MI->second.Merge(PtrState(), /*TopDown=*/true);
-}
-
-/// The bottom-up traversal uses this to merge information about successors to
-/// form the initial state for a new block.
-void BBState::MergeSucc(const BBState &Other) {
- // Other.BottomUpPathCount can be 0, in which case it is either dead or a
- // loop backedge. Loop backedges are special.
- BottomUpPathCount += Other.BottomUpPathCount;
-
- // Check for overflow. If we have overflow, fall back to conservative
- // behavior.
- if (BottomUpPathCount < Other.BottomUpPathCount) {
- clearBottomUpPointers();
- return;
- }
-
- // For each entry in the other set, if our set has an entry with the
- // same key, merge the entries. Otherwise, copy the entry and merge
- // it with an empty entry.
- for (ptr_const_iterator MI = Other.bottom_up_ptr_begin(),
- ME = Other.bottom_up_ptr_end(); MI != ME; ++MI) {
- std::pair<ptr_iterator, bool> Pair = PerPtrBottomUp.insert(*MI);
- Pair.first->second.Merge(Pair.second ? PtrState() : MI->second,
- /*TopDown=*/false);
- }
-
- // For each entry in our set, if the other set doesn't have an entry
- // with the same key, force it to merge with an empty entry.
- for (ptr_iterator MI = bottom_up_ptr_begin(),
- ME = bottom_up_ptr_end(); MI != ME; ++MI)
- if (Other.PerPtrBottomUp.find(MI->first) == Other.PerPtrBottomUp.end())
- MI->second.Merge(PtrState(), /*TopDown=*/false);
-}
-
-namespace {
- /// \brief The main ARC optimization pass.
- class ObjCARCOpt : public FunctionPass {
- bool Changed;
- ProvenanceAnalysis PA;
-
- /// A flag indicating whether this optimization pass should run.
- bool Run;
-
- /// Declarations for ObjC runtime functions, for use in creating calls to
- /// them. These are initialized lazily to avoid cluttering up the Module
- /// with unused declarations.
-
- /// Declaration for ObjC runtime function
- /// objc_retainAutoreleasedReturnValue.
- Constant *RetainRVCallee;
- /// Declaration for ObjC runtime function objc_autoreleaseReturnValue.
- Constant *AutoreleaseRVCallee;
- /// Declaration for ObjC runtime function objc_release.
- Constant *ReleaseCallee;
- /// Declaration for ObjC runtime function objc_retain.
- Constant *RetainCallee;
- /// Declaration for ObjC runtime function objc_retainBlock.
- Constant *RetainBlockCallee;
- /// Declaration for ObjC runtime function objc_autorelease.
- Constant *AutoreleaseCallee;
-
- /// Flags which determine whether each of the interesting runtine functions
- /// is in fact used in the current function.
- unsigned UsedInThisFunction;
-
- /// The Metadata Kind for clang.imprecise_release metadata.
- unsigned ImpreciseReleaseMDKind;
-
- /// The Metadata Kind for clang.arc.copy_on_escape metadata.
- unsigned CopyOnEscapeMDKind;
-
- /// The Metadata Kind for clang.arc.no_objc_arc_exceptions metadata.
- unsigned NoObjCARCExceptionsMDKind;
-
- Constant *getRetainRVCallee(Module *M);
- Constant *getAutoreleaseRVCallee(Module *M);
- Constant *getReleaseCallee(Module *M);
- Constant *getRetainCallee(Module *M);
- Constant *getRetainBlockCallee(Module *M);
- Constant *getAutoreleaseCallee(Module *M);
-
- bool IsRetainBlockOptimizable(const Instruction *Inst);
-
- void OptimizeRetainCall(Function &F, Instruction *Retain);
- bool OptimizeRetainRVCall(Function &F, Instruction *RetainRV);
- void OptimizeAutoreleaseRVCall(Function &F, Instruction *AutoreleaseRV,
- InstructionClass &Class);
- void OptimizeIndividualCalls(Function &F);
-
- void CheckForCFGHazards(const BasicBlock *BB,
- DenseMap<const BasicBlock *, BBState> &BBStates,
- BBState &MyStates) const;
- bool VisitInstructionBottomUp(Instruction *Inst,
- BasicBlock *BB,
- MapVector<Value *, RRInfo> &Retains,
- BBState &MyStates);
- bool VisitBottomUp(BasicBlock *BB,
- DenseMap<const BasicBlock *, BBState> &BBStates,
- MapVector<Value *, RRInfo> &Retains);
- bool VisitInstructionTopDown(Instruction *Inst,
- DenseMap<Value *, RRInfo> &Releases,
- BBState &MyStates);
- bool VisitTopDown(BasicBlock *BB,
- DenseMap<const BasicBlock *, BBState> &BBStates,
- DenseMap<Value *, RRInfo> &Releases);
- bool Visit(Function &F,
- DenseMap<const BasicBlock *, BBState> &BBStates,
- MapVector<Value *, RRInfo> &Retains,
- DenseMap<Value *, RRInfo> &Releases);
-
- void MoveCalls(Value *Arg, RRInfo &RetainsToMove, RRInfo &ReleasesToMove,
- MapVector<Value *, RRInfo> &Retains,
- DenseMap<Value *, RRInfo> &Releases,
- SmallVectorImpl<Instruction *> &DeadInsts,
- Module *M);
-
- bool ConnectTDBUTraversals(DenseMap<const BasicBlock *, BBState> &BBStates,
- MapVector<Value *, RRInfo> &Retains,
- DenseMap<Value *, RRInfo> &Releases,
- Module *M,
- SmallVector<Instruction *, 4> &NewRetains,
- SmallVector<Instruction *, 4> &NewReleases,
- SmallVector<Instruction *, 8> &DeadInsts,
- RRInfo &RetainsToMove,
- RRInfo &ReleasesToMove,
- Value *Arg,
- bool KnownSafe,
- bool &AnyPairsCompletelyEliminated);
-
- bool PerformCodePlacement(DenseMap<const BasicBlock *, BBState> &BBStates,
- MapVector<Value *, RRInfo> &Retains,
- DenseMap<Value *, RRInfo> &Releases,
- Module *M);
-
- void OptimizeWeakCalls(Function &F);
-
- bool OptimizeSequences(Function &F);
-
- void OptimizeReturns(Function &F);
-
- virtual void getAnalysisUsage(AnalysisUsage &AU) const;
- virtual bool doInitialization(Module &M);
- virtual bool runOnFunction(Function &F);
- virtual void releaseMemory();
-
- public:
- static char ID;
- ObjCARCOpt() : FunctionPass(ID) {
- initializeObjCARCOptPass(*PassRegistry::getPassRegistry());
- }
- };
-}
-
-char ObjCARCOpt::ID = 0;
-INITIALIZE_PASS_BEGIN(ObjCARCOpt,
- "objc-arc", "ObjC ARC optimization", false, false)
-INITIALIZE_PASS_DEPENDENCY(ObjCARCAliasAnalysis)
-INITIALIZE_PASS_END(ObjCARCOpt,
- "objc-arc", "ObjC ARC optimization", false, false)
-
-Pass *llvm::createObjCARCOptPass() {
- return new ObjCARCOpt();
-}
-
-void ObjCARCOpt::getAnalysisUsage(AnalysisUsage &AU) const {
- AU.addRequired<ObjCARCAliasAnalysis>();
- AU.addRequired<AliasAnalysis>();
- // ARC optimization doesn't currently split critical edges.
- AU.setPreservesCFG();
-}
-
-bool ObjCARCOpt::IsRetainBlockOptimizable(const Instruction *Inst) {
- // Without the magic metadata tag, we have to assume this might be an
- // objc_retainBlock call inserted to convert a block pointer to an id,
- // in which case it really is needed.
- if (!Inst->getMetadata(CopyOnEscapeMDKind))
- return false;
-
- // If the pointer "escapes" (not including being used in a call),
- // the copy may be needed.
- if (DoesObjCBlockEscape(Inst))
- return false;
-
- // Otherwise, it's not needed.
- return true;
-}
-
-Constant *ObjCARCOpt::getRetainRVCallee(Module *M) {
- if (!RetainRVCallee) {
- LLVMContext &C = M->getContext();
- Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
- Type *Params[] = { I8X };
- FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
- AttributeSet Attribute =
- AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
- Attribute::NoUnwind);
- RetainRVCallee =
- M->getOrInsertFunction("objc_retainAutoreleasedReturnValue", FTy,
- Attribute);
- }
- return RetainRVCallee;
-}
-
-Constant *ObjCARCOpt::getAutoreleaseRVCallee(Module *M) {
- if (!AutoreleaseRVCallee) {
- LLVMContext &C = M->getContext();
- Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
- Type *Params[] = { I8X };
- FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
- AttributeSet Attribute =
- AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
- Attribute::NoUnwind);
- AutoreleaseRVCallee =
- M->getOrInsertFunction("objc_autoreleaseReturnValue", FTy,
- Attribute);
- }
- return AutoreleaseRVCallee;
-}
-
-Constant *ObjCARCOpt::getReleaseCallee(Module *M) {
- if (!ReleaseCallee) {
- LLVMContext &C = M->getContext();
- Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
- AttributeSet Attribute =
- AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
- Attribute::NoUnwind);
- ReleaseCallee =
- M->getOrInsertFunction(
- "objc_release",
- FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false),
- Attribute);
- }
- return ReleaseCallee;
-}
-
-Constant *ObjCARCOpt::getRetainCallee(Module *M) {
- if (!RetainCallee) {
- LLVMContext &C = M->getContext();
- Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
- AttributeSet Attribute =
- AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
- Attribute::NoUnwind);
- RetainCallee =
- M->getOrInsertFunction(
- "objc_retain",
- FunctionType::get(Params[0], Params, /*isVarArg=*/false),
- Attribute);
- }
- return RetainCallee;
-}
-
-Constant *ObjCARCOpt::getRetainBlockCallee(Module *M) {
- if (!RetainBlockCallee) {
- LLVMContext &C = M->getContext();
- Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
- // objc_retainBlock is not nounwind because it calls user copy constructors
- // which could theoretically throw.
- RetainBlockCallee =
- M->getOrInsertFunction(
- "objc_retainBlock",
- FunctionType::get(Params[0], Params, /*isVarArg=*/false),
- AttributeSet());
- }
- return RetainBlockCallee;
-}
-
-Constant *ObjCARCOpt::getAutoreleaseCallee(Module *M) {
- if (!AutoreleaseCallee) {
- LLVMContext &C = M->getContext();
- Type *Params[] = { PointerType::getUnqual(Type::getInt8Ty(C)) };
- AttributeSet Attribute =
- AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
- Attribute::NoUnwind);
- AutoreleaseCallee =
- M->getOrInsertFunction(
- "objc_autorelease",
- FunctionType::get(Params[0], Params, /*isVarArg=*/false),
- Attribute);
- }
- return AutoreleaseCallee;
-}
-
-/// Test whether the given value is possible a reference-counted pointer,
-/// including tests which utilize AliasAnalysis.
-static bool IsPotentialRetainableObjPtr(const Value *Op, AliasAnalysis &AA) {
- // First make the rudimentary check.
- if (!IsPotentialRetainableObjPtr(Op))
- return false;
-
- // Objects in constant memory are not reference-counted.
- if (AA.pointsToConstantMemory(Op))
- return false;
-
- // Pointers in constant memory are not pointing to reference-counted objects.
- if (const LoadInst *LI = dyn_cast<LoadInst>(Op))
- if (AA.pointsToConstantMemory(LI->getPointerOperand()))
- return false;
-
- // Otherwise assume the worst.
- return true;
-}
-
-/// Test whether the given instruction can result in a reference count
-/// modification (positive or negative) for the pointer's object.
-static bool
-CanAlterRefCount(const Instruction *Inst, const Value *Ptr,
- ProvenanceAnalysis &PA, InstructionClass Class) {
- switch (Class) {
- case IC_Autorelease:
- case IC_AutoreleaseRV:
- case IC_User:
- // These operations never directly modify a reference count.
- return false;
- default: break;
- }
-
- ImmutableCallSite CS = static_cast<const Value *>(Inst);
- assert(CS && "Only calls can alter reference counts!");
-
- // See if AliasAnalysis can help us with the call.
- AliasAnalysis::ModRefBehavior MRB = PA.getAA()->getModRefBehavior(CS);
- if (AliasAnalysis::onlyReadsMemory(MRB))
- return false;
- if (AliasAnalysis::onlyAccessesArgPointees(MRB)) {
- for (ImmutableCallSite::arg_iterator I = CS.arg_begin(), E = CS.arg_end();
- I != E; ++I) {
- const Value *Op = *I;
- if (IsPotentialRetainableObjPtr(Op, *PA.getAA()) && PA.related(Ptr, Op))
- return true;
- }
- return false;
- }
-
- // Assume the worst.
- return true;
-}
-
-/// Test whether the given instruction can "use" the given pointer's object in a
-/// way that requires the reference count to be positive.
-static bool
-CanUse(const Instruction *Inst, const Value *Ptr, ProvenanceAnalysis &PA,
- InstructionClass Class) {
- // IC_Call operations (as opposed to IC_CallOrUser) never "use" objc pointers.
- if (Class == IC_Call)
- return false;
-
- // Consider various instructions which may have pointer arguments which are
- // not "uses".
- if (const ICmpInst *ICI = dyn_cast<ICmpInst>(Inst)) {
- // Comparing a pointer with null, or any other constant, isn't really a use,
- // because we don't care what the pointer points to, or about the values
- // of any other dynamic reference-counted pointers.
- if (!IsPotentialRetainableObjPtr(ICI->getOperand(1), *PA.getAA()))
- return false;
- } else if (ImmutableCallSite CS = static_cast<const Value *>(Inst)) {
- // For calls, just check the arguments (and not the callee operand).
- for (ImmutableCallSite::arg_iterator OI = CS.arg_begin(),
- OE = CS.arg_end(); OI != OE; ++OI) {
- const Value *Op = *OI;
- if (IsPotentialRetainableObjPtr(Op, *PA.getAA()) && PA.related(Ptr, Op))
- return true;
- }
- return false;
- } else if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
- // Special-case stores, because we don't care about the stored value, just
- // the store address.
- const Value *Op = GetUnderlyingObjCPtr(SI->getPointerOperand());
- // If we can't tell what the underlying object was, assume there is a
- // dependence.
- return IsPotentialRetainableObjPtr(Op, *PA.getAA()) && PA.related(Op, Ptr);
- }
-
- // Check each operand for a match.
- for (User::const_op_iterator OI = Inst->op_begin(), OE = Inst->op_end();
- OI != OE; ++OI) {
- const Value *Op = *OI;
- if (IsPotentialRetainableObjPtr(Op, *PA.getAA()) && PA.related(Ptr, Op))
- return true;
- }
- return false;
-}
-
-/// Test whether the given instruction can autorelease any pointer or cause an
-/// autoreleasepool pop.
-static bool
-CanInterruptRV(InstructionClass Class) {
- switch (Class) {
- case IC_AutoreleasepoolPop:
- case IC_CallOrUser:
- case IC_Call:
- case IC_Autorelease:
- case IC_AutoreleaseRV:
- case IC_FusedRetainAutorelease:
- case IC_FusedRetainAutoreleaseRV:
- return true;
- default:
- return false;
- }
-}
-
-namespace {
- /// \enum DependenceKind
- /// \brief Defines different dependence kinds among various ARC constructs.
- ///
- /// There are several kinds of dependence-like concepts in use here.
- ///
- enum DependenceKind {
- NeedsPositiveRetainCount,
- AutoreleasePoolBoundary,
- CanChangeRetainCount,
- RetainAutoreleaseDep, ///< Blocks objc_retainAutorelease.
- RetainAutoreleaseRVDep, ///< Blocks objc_retainAutoreleaseReturnValue.
- RetainRVDep ///< Blocks objc_retainAutoreleasedReturnValue.
- };
-}
-
-/// Test if there can be dependencies on Inst through Arg. This function only
-/// tests dependencies relevant for removing pairs of calls.
-static bool
-Depends(DependenceKind Flavor, Instruction *Inst, const Value *Arg,
- ProvenanceAnalysis &PA) {
- // If we've reached the definition of Arg, stop.
- if (Inst == Arg)
- return true;
-
- switch (Flavor) {
- case NeedsPositiveRetainCount: {
- InstructionClass Class = GetInstructionClass(Inst);
- switch (Class) {
- case IC_AutoreleasepoolPop:
- case IC_AutoreleasepoolPush:
- case IC_None:
- return false;
- default:
- return CanUse(Inst, Arg, PA, Class);
- }
- }
-
- case AutoreleasePoolBoundary: {
- InstructionClass Class = GetInstructionClass(Inst);
- switch (Class) {
- case IC_AutoreleasepoolPop:
- case IC_AutoreleasepoolPush:
- // These mark the end and begin of an autorelease pool scope.
- return true;
- default:
- // Nothing else does this.
- return false;
- }
- }
-
- case CanChangeRetainCount: {
- InstructionClass Class = GetInstructionClass(Inst);
- switch (Class) {
- case IC_AutoreleasepoolPop:
- // Conservatively assume this can decrement any count.
- return true;
- case IC_AutoreleasepoolPush:
- case IC_None:
- return false;
- default:
- return CanAlterRefCount(Inst, Arg, PA, Class);
- }
- }
-
- case RetainAutoreleaseDep:
- switch (GetBasicInstructionClass(Inst)) {
- case IC_AutoreleasepoolPop:
- case IC_AutoreleasepoolPush:
- // Don't merge an objc_autorelease with an objc_retain inside a different
- // autoreleasepool scope.
- return true;
- case IC_Retain:
- case IC_RetainRV:
- // Check for a retain of the same pointer for merging.
- return GetObjCArg(Inst) == Arg;
- default:
- // Nothing else matters for objc_retainAutorelease formation.
- return false;
- }
-
- case RetainAutoreleaseRVDep: {
- InstructionClass Class = GetBasicInstructionClass(Inst);
- switch (Class) {
- case IC_Retain:
- case IC_RetainRV:
- // Check for a retain of the same pointer for merging.
- return GetObjCArg(Inst) == Arg;
- default:
- // Anything that can autorelease interrupts
- // retainAutoreleaseReturnValue formation.
- return CanInterruptRV(Class);
- }
- }
-
- case RetainRVDep:
- return CanInterruptRV(GetBasicInstructionClass(Inst));
- }
-
- llvm_unreachable("Invalid dependence flavor");
-}
-
-/// Walk up the CFG from StartPos (which is in StartBB) and find local and
-/// non-local dependencies on Arg.
-///
-/// TODO: Cache results?
-static void
-FindDependencies(DependenceKind Flavor,
- const Value *Arg,
- BasicBlock *StartBB, Instruction *StartInst,
- SmallPtrSet<Instruction *, 4> &DependingInstructions,
- SmallPtrSet<const BasicBlock *, 4> &Visited,
- ProvenanceAnalysis &PA) {
- BasicBlock::iterator StartPos = StartInst;
-
- SmallVector<std::pair<BasicBlock *, BasicBlock::iterator>, 4> Worklist;
- Worklist.push_back(std::make_pair(StartBB, StartPos));
- do {
- std::pair<BasicBlock *, BasicBlock::iterator> Pair =
- Worklist.pop_back_val();
- BasicBlock *LocalStartBB = Pair.first;
- BasicBlock::iterator LocalStartPos = Pair.second;
- BasicBlock::iterator StartBBBegin = LocalStartBB->begin();
- for (;;) {
- if (LocalStartPos == StartBBBegin) {
- pred_iterator PI(LocalStartBB), PE(LocalStartBB, false);
- if (PI == PE)
- // If we've reached the function entry, produce a null dependence.
- DependingInstructions.insert(0);
- else
- // Add the predecessors to the worklist.
- do {
- BasicBlock *PredBB = *PI;
- if (Visited.insert(PredBB))
- Worklist.push_back(std::make_pair(PredBB, PredBB->end()));
- } while (++PI != PE);
- break;
- }
-
- Instruction *Inst = --LocalStartPos;
- if (Depends(Flavor, Inst, Arg, PA)) {
- DependingInstructions.insert(Inst);
- break;
- }
- }
- } while (!Worklist.empty());
-
- // Determine whether the original StartBB post-dominates all of the blocks we
- // visited. If not, insert a sentinal indicating that most optimizations are
- // not safe.
- for (SmallPtrSet<const BasicBlock *, 4>::const_iterator I = Visited.begin(),
- E = Visited.end(); I != E; ++I) {
- const BasicBlock *BB = *I;
- if (BB == StartBB)
- continue;
- const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
- for (succ_const_iterator SI(TI), SE(TI, false); SI != SE; ++SI) {
- const BasicBlock *Succ = *SI;
- if (Succ != StartBB && !Visited.count(Succ)) {
- DependingInstructions.insert(reinterpret_cast<Instruction *>(-1));
- return;
- }
- }
- }
-}
-
-static bool isNullOrUndef(const Value *V) {
- return isa<ConstantPointerNull>(V) || isa<UndefValue>(V);
-}
-
-static bool isNoopInstruction(const Instruction *I) {
- return isa<BitCastInst>(I) ||
- (isa<GetElementPtrInst>(I) &&
- cast<GetElementPtrInst>(I)->hasAllZeroIndices());
-}
-
-/// Turn objc_retain into objc_retainAutoreleasedReturnValue if the operand is a
-/// return value.
-void
-ObjCARCOpt::OptimizeRetainCall(Function &F, Instruction *Retain) {
- ImmutableCallSite CS(GetObjCArg(Retain));
- const Instruction *Call = CS.getInstruction();
- if (!Call) return;
- if (Call->getParent() != Retain->getParent()) return;
-
- // Check that the call is next to the retain.
- BasicBlock::const_iterator I = Call;
- ++I;
- while (isNoopInstruction(I)) ++I;
- if (&*I != Retain)
- return;
-
- // Turn it to an objc_retainAutoreleasedReturnValue..
- Changed = true;
- ++NumPeeps;
-
- DEBUG(dbgs() << "ObjCARCOpt::OptimizeRetainCall: Transforming "
- "objc_retain => objc_retainAutoreleasedReturnValue"
- " since the operand is a return value.\n"
- " Old: "
- << *Retain << "\n");
-
- cast<CallInst>(Retain)->setCalledFunction(getRetainRVCallee(F.getParent()));
-
- DEBUG(dbgs() << " New: "
- << *Retain << "\n");
-}
-
-/// Turn objc_retainAutoreleasedReturnValue into objc_retain if the operand is
-/// not a return value. Or, if it can be paired with an
-/// objc_autoreleaseReturnValue, delete the pair and return true.
-bool
-ObjCARCOpt::OptimizeRetainRVCall(Function &F, Instruction *RetainRV) {
- // Check for the argument being from an immediately preceding call or invoke.
- const Value *Arg = GetObjCArg(RetainRV);
- ImmutableCallSite CS(Arg);
- if (const Instruction *Call = CS.getInstruction()) {
- if (Call->getParent() == RetainRV->getParent()) {
- BasicBlock::const_iterator I = Call;
- ++I;
- while (isNoopInstruction(I)) ++I;
- if (&*I == RetainRV)
- return false;
- } else if (const InvokeInst *II = dyn_cast<InvokeInst>(Call)) {
- BasicBlock *RetainRVParent = RetainRV->getParent();
- if (II->getNormalDest() == RetainRVParent) {
- BasicBlock::const_iterator I = RetainRVParent->begin();
- while (isNoopInstruction(I)) ++I;
- if (&*I == RetainRV)
- return false;
- }
- }
- }
-
- // Check for being preceded by an objc_autoreleaseReturnValue on the same
- // pointer. In this case, we can delete the pair.
- BasicBlock::iterator I = RetainRV, Begin = RetainRV->getParent()->begin();
- if (I != Begin) {
- do --I; while (I != Begin && isNoopInstruction(I));
- if (GetBasicInstructionClass(I) == IC_AutoreleaseRV &&
- GetObjCArg(I) == Arg) {
- Changed = true;
- ++NumPeeps;
-
- DEBUG(dbgs() << "ObjCARCOpt::OptimizeRetainRVCall: Erasing " << *I << "\n"
- << " Erasing " << *RetainRV
- << "\n");
-
- EraseInstruction(I);
- EraseInstruction(RetainRV);
- return true;
- }
- }
-
- // Turn it to a plain objc_retain.
- Changed = true;
- ++NumPeeps;
-
- DEBUG(dbgs() << "ObjCARCOpt::OptimizeRetainRVCall: Transforming "
- "objc_retainAutoreleasedReturnValue => "
- "objc_retain since the operand is not a return value.\n"
- " Old: "
- << *RetainRV << "\n");
-
- cast<CallInst>(RetainRV)->setCalledFunction(getRetainCallee(F.getParent()));
-
- DEBUG(dbgs() << " New: "
- << *RetainRV << "\n");
-
- return false;
-}
-
-/// Turn objc_autoreleaseReturnValue into objc_autorelease if the result is not
-/// used as a return value.
-void
-ObjCARCOpt::OptimizeAutoreleaseRVCall(Function &F, Instruction *AutoreleaseRV,
- InstructionClass &Class) {
- // Check for a return of the pointer value.
- const Value *Ptr = GetObjCArg(AutoreleaseRV);
- SmallVector<const Value *, 2> Users;
- Users.push_back(Ptr);
- do {
- Ptr = Users.pop_back_val();
- for (Value::const_use_iterator UI = Ptr->use_begin(), UE = Ptr->use_end();
- UI != UE; ++UI) {
- const User *I = *UI;
- if (isa<ReturnInst>(I) || GetBasicInstructionClass(I) == IC_RetainRV)
- return;
- if (isa<BitCastInst>(I))
- Users.push_back(I);
- }
- } while (!Users.empty());
-
- Changed = true;
- ++NumPeeps;
-
- DEBUG(dbgs() << "ObjCARCOpt::OptimizeAutoreleaseRVCall: Transforming "
- "objc_autoreleaseReturnValue => "
- "objc_autorelease since its operand is not used as a return "
- "value.\n"
- " Old: "
- << *AutoreleaseRV << "\n");
-
- CallInst *AutoreleaseRVCI = cast<CallInst>(AutoreleaseRV);
- AutoreleaseRVCI->
- setCalledFunction(getAutoreleaseCallee(F.getParent()));
- AutoreleaseRVCI->setTailCall(false); // Never tail call objc_autorelease.
- Class = IC_Autorelease;
-
- DEBUG(dbgs() << " New: "
- << *AutoreleaseRV << "\n");
-
-}
-
-/// Visit each call, one at a time, and make simplifications without doing any
-/// additional analysis.
-void ObjCARCOpt::OptimizeIndividualCalls(Function &F) {
- // Reset all the flags in preparation for recomputing them.
- UsedInThisFunction = 0;
-
- // Visit all objc_* calls in F.
- for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
- Instruction *Inst = &*I++;
-
- InstructionClass Class = GetBasicInstructionClass(Inst);
-
- DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Visiting: Class: "
- << Class << "; " << *Inst << "\n");
-
- switch (Class) {
- default: break;
-
- // Delete no-op casts. These function calls have special semantics, but
- // the semantics are entirely implemented via lowering in the front-end,
- // so by the time they reach the optimizer, they are just no-op calls
- // which return their argument.
- //
- // There are gray areas here, as the ability to cast reference-counted
- // pointers to raw void* and back allows code to break ARC assumptions,
- // however these are currently considered to be unimportant.
- case IC_NoopCast:
- Changed = true;
- ++NumNoops;
- DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Erasing no-op cast:"
- " " << *Inst << "\n");
- EraseInstruction(Inst);
- continue;
-
- // If the pointer-to-weak-pointer is null, it's undefined behavior.
- case IC_StoreWeak:
- case IC_LoadWeak:
- case IC_LoadWeakRetained:
- case IC_InitWeak:
- case IC_DestroyWeak: {
- CallInst *CI = cast<CallInst>(Inst);
- if (isNullOrUndef(CI->getArgOperand(0))) {
- Changed = true;
- Type *Ty = CI->getArgOperand(0)->getType();
- new StoreInst(UndefValue::get(cast<PointerType>(Ty)->getElementType()),
- Constant::getNullValue(Ty),
- CI);
- llvm::Value *NewValue = UndefValue::get(CI->getType());
- DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: A null "
- "pointer-to-weak-pointer is undefined behavior.\n"
- " Old = " << *CI <<
- "\n New = " <<
- *NewValue << "\n");
- CI->replaceAllUsesWith(NewValue);
- CI->eraseFromParent();
- continue;
- }
- break;
- }
- case IC_CopyWeak:
- case IC_MoveWeak: {
- CallInst *CI = cast<CallInst>(Inst);
- if (isNullOrUndef(CI->getArgOperand(0)) ||
- isNullOrUndef(CI->getArgOperand(1))) {
- Changed = true;
- Type *Ty = CI->getArgOperand(0)->getType();
- new StoreInst(UndefValue::get(cast<PointerType>(Ty)->getElementType()),
- Constant::getNullValue(Ty),
- CI);
-
- llvm::Value *NewValue = UndefValue::get(CI->getType());
- DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: A null "
- "pointer-to-weak-pointer is undefined behavior.\n"
- " Old = " << *CI <<
- "\n New = " <<
- *NewValue << "\n");
-
- CI->replaceAllUsesWith(NewValue);
- CI->eraseFromParent();
- continue;
- }
- break;
- }
- case IC_Retain:
- OptimizeRetainCall(F, Inst);
- break;
- case IC_RetainRV:
- if (OptimizeRetainRVCall(F, Inst))
- continue;
- break;
- case IC_AutoreleaseRV:
- OptimizeAutoreleaseRVCall(F, Inst, Class);
- break;
- }
-
- // objc_autorelease(x) -> objc_release(x) if x is otherwise unused.
- if (IsAutorelease(Class) && Inst->use_empty()) {
- CallInst *Call = cast<CallInst>(Inst);
- const Value *Arg = Call->getArgOperand(0);
- Arg = FindSingleUseIdentifiedObject(Arg);
- if (Arg) {
- Changed = true;
- ++NumAutoreleases;
-
- // Create the declaration lazily.
- LLVMContext &C = Inst->getContext();
- CallInst *NewCall =
- CallInst::Create(getReleaseCallee(F.getParent()),
- Call->getArgOperand(0), "", Call);
- NewCall->setMetadata(ImpreciseReleaseMDKind,
- MDNode::get(C, ArrayRef<Value *>()));
-
- DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Replacing "
- "objc_autorelease(x) with objc_release(x) since x is "
- "otherwise unused.\n"
- " Old: " << *Call <<
- "\n New: " <<
- *NewCall << "\n");
-
- EraseInstruction(Call);
- Inst = NewCall;
- Class = IC_Release;
- }
- }
-
- // For functions which can never be passed stack arguments, add
- // a tail keyword.
- if (IsAlwaysTail(Class)) {
- Changed = true;
- DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Adding tail keyword"
- " to function since it can never be passed stack args: " << *Inst <<
- "\n");
- cast<CallInst>(Inst)->setTailCall();
- }
-
- // Ensure that functions that can never have a "tail" keyword due to the
- // semantics of ARC truly do not do so.
- if (IsNeverTail(Class)) {
- Changed = true;
- DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Removing tail "
- "keyword from function: " << *Inst <<
- "\n");
- cast<CallInst>(Inst)->setTailCall(false);
- }
-
- // Set nounwind as needed.
- if (IsNoThrow(Class)) {
- Changed = true;
- DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Found no throw"
- " class. Setting nounwind on: " << *Inst << "\n");
- cast<CallInst>(Inst)->setDoesNotThrow();
- }
-
- if (!IsNoopOnNull(Class)) {
- UsedInThisFunction |= 1 << Class;
- continue;
- }
-
- const Value *Arg = GetObjCArg(Inst);
-
- // ARC calls with null are no-ops. Delete them.
- if (isNullOrUndef(Arg)) {
- Changed = true;
- ++NumNoops;
- DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: ARC calls with "
- " null are no-ops. Erasing: " << *Inst << "\n");
- EraseInstruction(Inst);
- continue;
- }
-
- // Keep track of which of retain, release, autorelease, and retain_block
- // are actually present in this function.
- UsedInThisFunction |= 1 << Class;
-
- // If Arg is a PHI, and one or more incoming values to the
- // PHI are null, and the call is control-equivalent to the PHI, and there
- // are no relevant side effects between the PHI and the call, the call
- // could be pushed up to just those paths with non-null incoming values.
- // For now, don't bother splitting critical edges for this.
- SmallVector<std::pair<Instruction *, const Value *>, 4> Worklist;
- Worklist.push_back(std::make_pair(Inst, Arg));
- do {
- std::pair<Instruction *, const Value *> Pair = Worklist.pop_back_val();
- Inst = Pair.first;
- Arg = Pair.second;
-
- const PHINode *PN = dyn_cast<PHINode>(Arg);
- if (!PN) continue;
-
- // Determine if the PHI has any null operands, or any incoming
- // critical edges.
- bool HasNull = false;
- bool HasCriticalEdges = false;
- for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
- Value *Incoming =
- StripPointerCastsAndObjCCalls(PN->getIncomingValue(i));
- if (isNullOrUndef(Incoming))
- HasNull = true;
- else if (cast<TerminatorInst>(PN->getIncomingBlock(i)->back())
- .getNumSuccessors() != 1) {
- HasCriticalEdges = true;
- break;
- }
- }
- // If we have null operands and no critical edges, optimize.
- if (!HasCriticalEdges && HasNull) {
- SmallPtrSet<Instruction *, 4> DependingInstructions;
- SmallPtrSet<const BasicBlock *, 4> Visited;
-
- // Check that there is nothing that cares about the reference
- // count between the call and the phi.
- switch (Class) {
- case IC_Retain:
- case IC_RetainBlock:
- // These can always be moved up.
- break;
- case IC_Release:
- // These can't be moved across things that care about the retain
- // count.
- FindDependencies(NeedsPositiveRetainCount, Arg,
- Inst->getParent(), Inst,
- DependingInstructions, Visited, PA);
- break;
- case IC_Autorelease:
- // These can't be moved across autorelease pool scope boundaries.
- FindDependencies(AutoreleasePoolBoundary, Arg,
- Inst->getParent(), Inst,
- DependingInstructions, Visited, PA);
- break;
- case IC_RetainRV:
- case IC_AutoreleaseRV:
- // Don't move these; the RV optimization depends on the autoreleaseRV
- // being tail called, and the retainRV being immediately after a call
- // (which might still happen if we get lucky with codegen layout, but
- // it's not worth taking the chance).
- continue;
- default:
- llvm_unreachable("Invalid dependence flavor");
- }
-
- if (DependingInstructions.size() == 1 &&
- *DependingInstructions.begin() == PN) {
- Changed = true;
- ++NumPartialNoops;
- // Clone the call into each predecessor that has a non-null value.
- CallInst *CInst = cast<CallInst>(Inst);
- Type *ParamTy = CInst->getArgOperand(0)->getType();
- for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
- Value *Incoming =
- StripPointerCastsAndObjCCalls(PN->getIncomingValue(i));
- if (!isNullOrUndef(Incoming)) {
- CallInst *Clone = cast<CallInst>(CInst->clone());
- Value *Op = PN->getIncomingValue(i);
- Instruction *InsertPos = &PN->getIncomingBlock(i)->back();
- if (Op->getType() != ParamTy)
- Op = new BitCastInst(Op, ParamTy, "", InsertPos);
- Clone->setArgOperand(0, Op);
- Clone->insertBefore(InsertPos);
-
- DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Cloning "
- << *CInst << "\n"
- " And inserting "
- "clone at " << *InsertPos << "\n");
- Worklist.push_back(std::make_pair(Clone, Incoming));
- }
- }
- // Erase the original call.
- DEBUG(dbgs() << "Erasing: " << *CInst << "\n");
- EraseInstruction(CInst);
- continue;
- }
- }
- } while (!Worklist.empty());
- }
- DEBUG(dbgs() << "ObjCARCOpt::OptimizeIndividualCalls: Finished List.\n");
-}
-
-/// Check for critical edges, loop boundaries, irreducible control flow, or
-/// other CFG structures where moving code across the edge would result in it
-/// being executed more.
-void
-ObjCARCOpt::CheckForCFGHazards(const BasicBlock *BB,
- DenseMap<const BasicBlock *, BBState> &BBStates,
- BBState &MyStates) const {
- // If any top-down local-use or possible-dec has a succ which is earlier in
- // the sequence, forget it.
- for (BBState::ptr_iterator I = MyStates.top_down_ptr_begin(),
- E = MyStates.top_down_ptr_end(); I != E; ++I)
- switch (I->second.GetSeq()) {
- default: break;
- case S_Use: {
- const Value *Arg = I->first;
- const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
- bool SomeSuccHasSame = false;
- bool AllSuccsHaveSame = true;
- PtrState &S = I->second;
- succ_const_iterator SI(TI), SE(TI, false);
-
- for (; SI != SE; ++SI) {
- Sequence SuccSSeq = S_None;
- bool SuccSRRIKnownSafe = false;
- // If VisitBottomUp has pointer information for this successor, take
- // what we know about it.
- DenseMap<const BasicBlock *, BBState>::iterator BBI =
- BBStates.find(*SI);
- assert(BBI != BBStates.end());
- const PtrState &SuccS = BBI->second.getPtrBottomUpState(Arg);
- SuccSSeq = SuccS.GetSeq();
- SuccSRRIKnownSafe = SuccS.RRI.KnownSafe;
- switch (SuccSSeq) {
- case S_None:
- case S_CanRelease: {
- if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe) {
- S.ClearSequenceProgress();
- break;
- }
- continue;
- }
- case S_Use:
- SomeSuccHasSame = true;
- break;
- case S_Stop:
- case S_Release:
- case S_MovableRelease:
- if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe)
- AllSuccsHaveSame = false;
- break;
- case S_Retain:
- llvm_unreachable("bottom-up pointer in retain state!");
- }
- }
- // If the state at the other end of any of the successor edges
- // matches the current state, require all edges to match. This
- // guards against loops in the middle of a sequence.
- if (SomeSuccHasSame && !AllSuccsHaveSame)
- S.ClearSequenceProgress();
- break;
- }
- case S_CanRelease: {
- const Value *Arg = I->first;
- const TerminatorInst *TI = cast<TerminatorInst>(&BB->back());
- bool SomeSuccHasSame = false;
- bool AllSuccsHaveSame = true;
- PtrState &S = I->second;
- succ_const_iterator SI(TI), SE(TI, false);
-
- for (; SI != SE; ++SI) {
- Sequence SuccSSeq = S_None;
- bool SuccSRRIKnownSafe = false;
- // If VisitBottomUp has pointer information for this successor, take
- // what we know about it.
- DenseMap<const BasicBlock *, BBState>::iterator BBI =
- BBStates.find(*SI);
- assert(BBI != BBStates.end());
- const PtrState &SuccS = BBI->second.getPtrBottomUpState(Arg);
- SuccSSeq = SuccS.GetSeq();
- SuccSRRIKnownSafe = SuccS.RRI.KnownSafe;
- switch (SuccSSeq) {
- case S_None: {
- if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe) {
- S.ClearSequenceProgress();
- break;
- }
- continue;
- }
- case S_CanRelease:
- SomeSuccHasSame = true;
- break;
- case S_Stop:
- case S_Release:
- case S_MovableRelease:
- case S_Use:
- if (!S.RRI.KnownSafe && !SuccSRRIKnownSafe)
- AllSuccsHaveSame = false;
- break;
- case S_Retain:
- llvm_unreachable("bottom-up pointer in retain state!");
- }
- }
- // If the state at the other end of any of the successor edges
- // matches the current state, require all edges to match. This
- // guards against loops in the middle of a sequence.
- if (SomeSuccHasSame && !AllSuccsHaveSame)
- S.ClearSequenceProgress();
- break;
- }
- }
-}
-
-bool
-ObjCARCOpt::VisitInstructionBottomUp(Instruction *Inst,
- BasicBlock *BB,
- MapVector<Value *, RRInfo> &Retains,
- BBState &MyStates) {
- bool NestingDetected = false;
- InstructionClass Class = GetInstructionClass(Inst);
- const Value *Arg = 0;
-
- switch (Class) {
- case IC_Release: {
- Arg = GetObjCArg(Inst);
-
- PtrState &S = MyStates.getPtrBottomUpState(Arg);
-
- // If we see two releases in a row on the same pointer. If so, make
- // a note, and we'll cicle back to revisit it after we've
- // hopefully eliminated the second release, which may allow us to
- // eliminate the first release too.
- // Theoretically we could implement removal of nested retain+release
- // pairs by making PtrState hold a stack of states, but this is
- // simple and avoids adding overhead for the non-nested case.
- if (S.GetSeq() == S_Release || S.GetSeq() == S_MovableRelease) {
- DEBUG(dbgs() << "ObjCARCOpt::VisitInstructionBottomUp: Found nested "
- "releases (i.e. a release pair)\n");
- NestingDetected = true;
- }
-
- MDNode *ReleaseMetadata = Inst->getMetadata(ImpreciseReleaseMDKind);
- S.ResetSequenceProgress(ReleaseMetadata ? S_MovableRelease : S_Release);
- S.RRI.ReleaseMetadata = ReleaseMetadata;
- S.RRI.KnownSafe = S.IsKnownIncremented();
- S.RRI.IsTailCallRelease = cast<CallInst>(Inst)->isTailCall();
- S.RRI.Calls.insert(Inst);
-
- S.SetKnownPositiveRefCount();
- break;
- }
- case IC_RetainBlock:
- // An objc_retainBlock call with just a use may need to be kept,
- // because it may be copying a block from the stack to the heap.
- if (!IsRetainBlockOptimizable(Inst))
- break;
- // FALLTHROUGH
- case IC_Retain:
- case IC_RetainRV: {
- Arg = GetObjCArg(Inst);
-
- PtrState &S = MyStates.getPtrBottomUpState(Arg);
- S.SetKnownPositiveRefCount();
-
- switch (S.GetSeq()) {
- case S_Stop:
- case S_Release:
- case S_MovableRelease:
- case S_Use:
- S.RRI.ReverseInsertPts.clear();
- // FALL THROUGH
- case S_CanRelease:
- // Don't do retain+release tracking for IC_RetainRV, because it's
- // better to let it remain as the first instruction after a call.
- if (Class != IC_RetainRV) {
- S.RRI.IsRetainBlock = Class == IC_RetainBlock;
- Retains[Inst] = S.RRI;
- }
- S.ClearSequenceProgress();
- break;
- case S_None:
- break;
- case S_Retain:
- llvm_unreachable("bottom-up pointer in retain state!");
- }
- return NestingDetected;
- }
- case IC_AutoreleasepoolPop:
- // Conservatively, clear MyStates for all known pointers.
- MyStates.clearBottomUpPointers();
- return NestingDetected;
- case IC_AutoreleasepoolPush:
- case IC_None:
- // These are irrelevant.
- return NestingDetected;
- default:
- break;
- }
-
- // Consider any other possible effects of this instruction on each
- // pointer being tracked.
- for (BBState::ptr_iterator MI = MyStates.bottom_up_ptr_begin(),
- ME = MyStates.bottom_up_ptr_end(); MI != ME; ++MI) {
- const Value *Ptr = MI->first;
- if (Ptr == Arg)
- continue; // Handled above.
- PtrState &S = MI->second;
- Sequence Seq = S.GetSeq();
-
- // Check for possible releases.
- if (CanAlterRefCount(Inst, Ptr, PA, Class)) {
- S.ClearRefCount();
- switch (Seq) {
- case S_Use:
- S.SetSeq(S_CanRelease);
- continue;
- case S_CanRelease:
- case S_Release:
- case S_MovableRelease:
- case S_Stop:
- case S_None:
- break;
- case S_Retain:
- llvm_unreachable("bottom-up pointer in retain state!");
- }
- }
-
- // Check for possible direct uses.
- switch (Seq) {
- case S_Release:
- case S_MovableRelease:
- if (CanUse(Inst, Ptr, PA, Class)) {
- assert(S.RRI.ReverseInsertPts.empty());
- // If this is an invoke instruction, we're scanning it as part of
- // one of its successor blocks, since we can't insert code after it
- // in its own block, and we don't want to split critical edges.
- if (isa<InvokeInst>(Inst))
- S.RRI.ReverseInsertPts.insert(BB->getFirstInsertionPt());
- else
- S.RRI.ReverseInsertPts.insert(llvm::next(BasicBlock::iterator(Inst)));
- S.SetSeq(S_Use);
- } else if (Seq == S_Release &&
- (Class == IC_User || Class == IC_CallOrUser)) {
- // Non-movable releases depend on any possible objc pointer use.
- S.SetSeq(S_Stop);
- assert(S.RRI.ReverseInsertPts.empty());
- // As above; handle invoke specially.
- if (isa<InvokeInst>(Inst))
- S.RRI.ReverseInsertPts.insert(BB->getFirstInsertionPt());
- else
- S.RRI.ReverseInsertPts.insert(llvm::next(BasicBlock::iterator(Inst)));
- }
- break;
- case S_Stop:
- if (CanUse(Inst, Ptr, PA, Class))
- S.SetSeq(S_Use);
- break;
- case S_CanRelease:
- case S_Use:
- case S_None:
- break;
- case S_Retain:
- llvm_unreachable("bottom-up pointer in retain state!");
- }
- }
-
- return NestingDetected;
-}
-
-bool
-ObjCARCOpt::VisitBottomUp(BasicBlock *BB,
- DenseMap<const BasicBlock *, BBState> &BBStates,
- MapVector<Value *, RRInfo> &Retains) {
- bool NestingDetected = false;
- BBState &MyStates = BBStates[BB];
-
- // Merge the states from each successor to compute the initial state
- // for the current block.
- BBState::edge_iterator SI(MyStates.succ_begin()),
- SE(MyStates.succ_end());
- if (SI != SE) {
- const BasicBlock *Succ = *SI;
- DenseMap<const BasicBlock *, BBState>::iterator I = BBStates.find(Succ);
- assert(I != BBStates.end());
- MyStates.InitFromSucc(I->second);
- ++SI;
- for (; SI != SE; ++SI) {
- Succ = *SI;
- I = BBStates.find(Succ);
- assert(I != BBStates.end());
- MyStates.MergeSucc(I->second);
- }
- }
-
- // Visit all the instructions, bottom-up.
- for (BasicBlock::iterator I = BB->end(), E = BB->begin(); I != E; --I) {
- Instruction *Inst = llvm::prior(I);
-
- // Invoke instructions are visited as part of their successors (below).
- if (isa<InvokeInst>(Inst))
- continue;
-
- DEBUG(dbgs() << "ObjCARCOpt::VisitButtonUp: Visiting " << *Inst << "\n");
-
- NestingDetected |= VisitInstructionBottomUp(Inst, BB, Retains, MyStates);
- }
-
- // If there's a predecessor with an invoke, visit the invoke as if it were
- // part of this block, since we can't insert code after an invoke in its own
- // block, and we don't want to split critical edges.
- for (BBState::edge_iterator PI(MyStates.pred_begin()),
- PE(MyStates.pred_end()); PI != PE; ++PI) {
- BasicBlock *Pred = *PI;
- if (InvokeInst *II = dyn_cast<InvokeInst>(&Pred->back()))
- NestingDetected |= VisitInstructionBottomUp(II, BB, Retains, MyStates);
- }
-
- return NestingDetected;
-}
-
-bool
-ObjCARCOpt::VisitInstructionTopDown(Instruction *Inst,
- DenseMap<Value *, RRInfo> &Releases,
- BBState &MyStates) {
- bool NestingDetected = false;
- InstructionClass Class = GetInstructionClass(Inst);
- const Value *Arg = 0;
-
- switch (Class) {
- case IC_RetainBlock:
- // An objc_retainBlock call with just a use may need to be kept,
- // because it may be copying a block from the stack to the heap.
- if (!IsRetainBlockOptimizable(Inst))
- break;
- // FALLTHROUGH
- case IC_Retain:
- case IC_RetainRV: {
- Arg = GetObjCArg(Inst);
-
- PtrState &S = MyStates.getPtrTopDownState(Arg);
-
- // Don't do retain+release tracking for IC_RetainRV, because it's
- // better to let it remain as the first instruction after a call.
- if (Class != IC_RetainRV) {
- // If we see two retains in a row on the same pointer. If so, make
- // a note, and we'll cicle back to revisit it after we've
- // hopefully eliminated the second retain, which may allow us to
- // eliminate the first retain too.
- // Theoretically we could implement removal of nested retain+release
- // pairs by making PtrState hold a stack of states, but this is
- // simple and avoids adding overhead for the non-nested case.
- if (S.GetSeq() == S_Retain)
- NestingDetected = true;
-
- S.ResetSequenceProgress(S_Retain);
- S.RRI.IsRetainBlock = Class == IC_RetainBlock;
- S.RRI.KnownSafe = S.IsKnownIncremented();
- S.RRI.Calls.insert(Inst);
- }
-
- S.SetKnownPositiveRefCount();
-
- // A retain can be a potential use; procede to the generic checking
- // code below.
- break;
- }
- case IC_Release: {
- Arg = GetObjCArg(Inst);
-
- PtrState &S = MyStates.getPtrTopDownState(Arg);
- S.ClearRefCount();
-
- switch (S.GetSeq()) {
- case S_Retain:
- case S_CanRelease:
- S.RRI.ReverseInsertPts.clear();
- // FALL THROUGH
- case S_Use:
- S.RRI.ReleaseMetadata = Inst->getMetadata(ImpreciseReleaseMDKind);
- S.RRI.IsTailCallRelease = cast<CallInst>(Inst)->isTailCall();
- Releases[Inst] = S.RRI;
- S.ClearSequenceProgress();
- break;
- case S_None:
- break;
- case S_Stop:
- case S_Release:
- case S_MovableRelease:
- llvm_unreachable("top-down pointer in release state!");
- }
- break;
- }
- case IC_AutoreleasepoolPop:
- // Conservatively, clear MyStates for all known pointers.
- MyStates.clearTopDownPointers();
- return NestingDetected;
- case IC_AutoreleasepoolPush:
- case IC_None:
- // These are irrelevant.
- return NestingDetected;
- default:
- break;
- }
-
- // Consider any other possible effects of this instruction on each
- // pointer being tracked.
- for (BBState::ptr_iterator MI = MyStates.top_down_ptr_begin(),
- ME = MyStates.top_down_ptr_end(); MI != ME; ++MI) {
- const Value *Ptr = MI->first;
- if (Ptr == Arg)
- continue; // Handled above.
- PtrState &S = MI->second;
- Sequence Seq = S.GetSeq();
-
- // Check for possible releases.
- if (CanAlterRefCount(Inst, Ptr, PA, Class)) {
- S.ClearRefCount();
- switch (Seq) {
- case S_Retain:
- S.SetSeq(S_CanRelease);
- assert(S.RRI.ReverseInsertPts.empty());
- S.RRI.ReverseInsertPts.insert(Inst);
-
- // One call can't cause a transition from S_Retain to S_CanRelease
- // and S_CanRelease to S_Use. If we've made the first transition,
- // we're done.
- continue;
- case S_Use:
- case S_CanRelease:
- case S_None:
- break;
- case S_Stop:
- case S_Release:
- case S_MovableRelease:
- llvm_unreachable("top-down pointer in release state!");
- }
- }
-
- // Check for possible direct uses.
- switch (Seq) {
- case S_CanRelease:
- if (CanUse(Inst, Ptr, PA, Class))
- S.SetSeq(S_Use);
- break;
- case S_Retain:
- case S_Use:
- case S_None:
- break;
- case S_Stop:
- case S_Release:
- case S_MovableRelease:
- llvm_unreachable("top-down pointer in release state!");
- }
- }
-
- return NestingDetected;
-}
-
-bool
-ObjCARCOpt::VisitTopDown(BasicBlock *BB,
- DenseMap<const BasicBlock *, BBState> &BBStates,
- DenseMap<Value *, RRInfo> &Releases) {
- bool NestingDetected = false;
- BBState &MyStates = BBStates[BB];
-
- // Merge the states from each predecessor to compute the initial state
- // for the current block.
- BBState::edge_iterator PI(MyStates.pred_begin()),
- PE(MyStates.pred_end());
- if (PI != PE) {
- const BasicBlock *Pred = *PI;
- DenseMap<const BasicBlock *, BBState>::iterator I = BBStates.find(Pred);
- assert(I != BBStates.end());
- MyStates.InitFromPred(I->second);
- ++PI;
- for (; PI != PE; ++PI) {
- Pred = *PI;
- I = BBStates.find(Pred);
- assert(I != BBStates.end());
- MyStates.MergePred(I->second);
- }
- }
-
- // Visit all the instructions, top-down.
- for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
- Instruction *Inst = I;
-
- DEBUG(dbgs() << "ObjCARCOpt::VisitTopDown: Visiting " << *Inst << "\n");
-
- NestingDetected |= VisitInstructionTopDown(Inst, Releases, MyStates);
- }
-
- CheckForCFGHazards(BB, BBStates, MyStates);
- return NestingDetected;
-}
-
-static void
-ComputePostOrders(Function &F,
- SmallVectorImpl<BasicBlock *> &PostOrder,
- SmallVectorImpl<BasicBlock *> &ReverseCFGPostOrder,
- unsigned NoObjCARCExceptionsMDKind,
- DenseMap<const BasicBlock *, BBState> &BBStates) {
- /// The visited set, for doing DFS walks.
- SmallPtrSet<BasicBlock *, 16> Visited;
-
- // Do DFS, computing the PostOrder.
- SmallPtrSet<BasicBlock *, 16> OnStack;
- SmallVector<std::pair<BasicBlock *, succ_iterator>, 16> SuccStack;
-
- // Functions always have exactly one entry block, and we don't have
- // any other block that we treat like an entry block.
- BasicBlock *EntryBB = &F.getEntryBlock();
- BBState &MyStates = BBStates[EntryBB];
- MyStates.SetAsEntry();
- TerminatorInst *EntryTI = cast<TerminatorInst>(&EntryBB->back());
- SuccStack.push_back(std::make_pair(EntryBB, succ_iterator(EntryTI)));
- Visited.insert(EntryBB);
- OnStack.insert(EntryBB);
- do {
- dfs_next_succ:
- BasicBlock *CurrBB = SuccStack.back().first;
- TerminatorInst *TI = cast<TerminatorInst>(&CurrBB->back());
- succ_iterator SE(TI, false);
-
- while (SuccStack.back().second != SE) {
- BasicBlock *SuccBB = *SuccStack.back().second++;
- if (Visited.insert(SuccBB)) {
- TerminatorInst *TI = cast<TerminatorInst>(&SuccBB->back());
- SuccStack.push_back(std::make_pair(SuccBB, succ_iterator(TI)));
- BBStates[CurrBB].addSucc(SuccBB);
- BBState &SuccStates = BBStates[SuccBB];
- SuccStates.addPred(CurrBB);
- OnStack.insert(SuccBB);
- goto dfs_next_succ;
- }
-
- if (!OnStack.count(SuccBB)) {
- BBStates[CurrBB].addSucc(SuccBB);
- BBStates[SuccBB].addPred(CurrBB);
- }
- }
- OnStack.erase(CurrBB);
- PostOrder.push_back(CurrBB);
- SuccStack.pop_back();
- } while (!SuccStack.empty());
-
- Visited.clear();
-
- // Do reverse-CFG DFS, computing the reverse-CFG PostOrder.
- // Functions may have many exits, and there also blocks which we treat
- // as exits due to ignored edges.
- SmallVector<std::pair<BasicBlock *, BBState::edge_iterator>, 16> PredStack;
- for (Function::iterator I = F.begin(), E = F.end(); I != E; ++I) {
- BasicBlock *ExitBB = I;
- BBState &MyStates = BBStates[ExitBB];
- if (!MyStates.isExit())
- continue;
-
- MyStates.SetAsExit();
-
- PredStack.push_back(std::make_pair(ExitBB, MyStates.pred_begin()));
- Visited.insert(ExitBB);
- while (!PredStack.empty()) {
- reverse_dfs_next_succ:
- BBState::edge_iterator PE = BBStates[PredStack.back().first].pred_end();
- while (PredStack.back().second != PE) {
- BasicBlock *BB = *PredStack.back().second++;
- if (Visited.insert(BB)) {
- PredStack.push_back(std::make_pair(BB, BBStates[BB].pred_begin()));
- goto reverse_dfs_next_succ;
- }
- }
- ReverseCFGPostOrder.push_back(PredStack.pop_back_val().first);
- }
- }
-}
-
-// Visit the function both top-down and bottom-up.
-bool
-ObjCARCOpt::Visit(Function &F,
- DenseMap<const BasicBlock *, BBState> &BBStates,
- MapVector<Value *, RRInfo> &Retains,
- DenseMap<Value *, RRInfo> &Releases) {
-
- // Use reverse-postorder traversals, because we magically know that loops
- // will be well behaved, i.e. they won't repeatedly call retain on a single
- // pointer without doing a release. We can't use the ReversePostOrderTraversal
- // class here because we want the reverse-CFG postorder to consider each
- // function exit point, and we want to ignore selected cycle edges.
- SmallVector<BasicBlock *, 16> PostOrder;
- SmallVector<BasicBlock *, 16> ReverseCFGPostOrder;
- ComputePostOrders(F, PostOrder, ReverseCFGPostOrder,
- NoObjCARCExceptionsMDKind,
- BBStates);
-
- // Use reverse-postorder on the reverse CFG for bottom-up.
- bool BottomUpNestingDetected = false;
- for (SmallVectorImpl<BasicBlock *>::const_reverse_iterator I =
- ReverseCFGPostOrder.rbegin(), E = ReverseCFGPostOrder.rend();
- I != E; ++I)
- BottomUpNestingDetected |= VisitBottomUp(*I, BBStates, Retains);
-
- // Use reverse-postorder for top-down.
- bool TopDownNestingDetected = false;
- for (SmallVectorImpl<BasicBlock *>::const_reverse_iterator I =
- PostOrder.rbegin(), E = PostOrder.rend();
- I != E; ++I)
- TopDownNestingDetected |= VisitTopDown(*I, BBStates, Releases);
-
- return TopDownNestingDetected && BottomUpNestingDetected;
-}
-
-/// Move the calls in RetainsToMove and ReleasesToMove.
-void ObjCARCOpt::MoveCalls(Value *Arg,
- RRInfo &RetainsToMove,
- RRInfo &ReleasesToMove,
- MapVector<Value *, RRInfo> &Retains,
- DenseMap<Value *, RRInfo> &Releases,
- SmallVectorImpl<Instruction *> &DeadInsts,
- Module *M) {
- Type *ArgTy = Arg->getType();
- Type *ParamTy = PointerType::getUnqual(Type::getInt8Ty(ArgTy->getContext()));
-
- // Insert the new retain and release calls.
- for (SmallPtrSet<Instruction *, 2>::const_iterator
- PI = ReleasesToMove.ReverseInsertPts.begin(),
- PE = ReleasesToMove.ReverseInsertPts.end(); PI != PE; ++PI) {
- Instruction *InsertPt = *PI;
- Value *MyArg = ArgTy == ParamTy ? Arg :
- new BitCastInst(Arg, ParamTy, "", InsertPt);
- CallInst *Call =
- CallInst::Create(RetainsToMove.IsRetainBlock ?
- getRetainBlockCallee(M) : getRetainCallee(M),
- MyArg, "", InsertPt);
- Call->setDoesNotThrow();
- if (RetainsToMove.IsRetainBlock)
- Call->setMetadata(CopyOnEscapeMDKind,
- MDNode::get(M->getContext(), ArrayRef<Value *>()));
- else
- Call->setTailCall();
-
- DEBUG(dbgs() << "ObjCARCOpt::MoveCalls: Inserting new Release: " << *Call
- << "\n"
- " At insertion point: " << *InsertPt
- << "\n");
- }
- for (SmallPtrSet<Instruction *, 2>::const_iterator
- PI = RetainsToMove.ReverseInsertPts.begin(),
- PE = RetainsToMove.ReverseInsertPts.end(); PI != PE; ++PI) {
- Instruction *InsertPt = *PI;
- Value *MyArg = ArgTy == ParamTy ? Arg :
- new BitCastInst(Arg, ParamTy, "", InsertPt);
- CallInst *Call = CallInst::Create(getReleaseCallee(M), MyArg,
- "", InsertPt);
- // Attach a clang.imprecise_release metadata tag, if appropriate.
- if (MDNode *M = ReleasesToMove.ReleaseMetadata)
- Call->setMetadata(ImpreciseReleaseMDKind, M);
- Call->setDoesNotThrow();
- if (ReleasesToMove.IsTailCallRelease)
- Call->setTailCall();
-
- DEBUG(dbgs() << "ObjCARCOpt::MoveCalls: Inserting new Retain: " << *Call
- << "\n"
- " At insertion point: " << *InsertPt
- << "\n");
- }
-
- // Delete the original retain and release calls.
- for (SmallPtrSet<Instruction *, 2>::const_iterator
- AI = RetainsToMove.Calls.begin(),
- AE = RetainsToMove.Calls.end(); AI != AE; ++AI) {
- Instruction *OrigRetain = *AI;
- Retains.blot(OrigRetain);
- DeadInsts.push_back(OrigRetain);
- DEBUG(dbgs() << "ObjCARCOpt::MoveCalls: Deleting retain: " << *OrigRetain <<
- "\n");
- }
- for (SmallPtrSet<Instruction *, 2>::const_iterator
- AI = ReleasesToMove.Calls.begin(),
- AE = ReleasesToMove.Calls.end(); AI != AE; ++AI) {
- Instruction *OrigRelease = *AI;
- Releases.erase(OrigRelease);
- DeadInsts.push_back(OrigRelease);
- DEBUG(dbgs() << "ObjCARCOpt::MoveCalls: Deleting release: " << *OrigRelease
- << "\n");
- }
-}
-
-bool
-ObjCARCOpt::ConnectTDBUTraversals(DenseMap<const BasicBlock *, BBState>
- &BBStates,
- MapVector<Value *, RRInfo> &Retains,
- DenseMap<Value *, RRInfo> &Releases,
- Module *M,
- SmallVector<Instruction *, 4> &NewRetains,
- SmallVector<Instruction *, 4> &NewReleases,
- SmallVector<Instruction *, 8> &DeadInsts,
- RRInfo &RetainsToMove,
- RRInfo &ReleasesToMove,
- Value *Arg,
- bool KnownSafe,
- bool &AnyPairsCompletelyEliminated) {
- // If a pair happens in a region where it is known that the reference count
- // is already incremented, we can similarly ignore possible decrements.
- bool KnownSafeTD = true, KnownSafeBU = true;
-
- // Connect the dots between the top-down-collected RetainsToMove and
- // bottom-up-collected ReleasesToMove to form sets of related calls.
- // This is an iterative process so that we connect multiple releases
- // to multiple retains if needed.
- unsigned OldDelta = 0;
- unsigned NewDelta = 0;
- unsigned OldCount = 0;
- unsigned NewCount = 0;
- bool FirstRelease = true;
- bool FirstRetain = true;
- for (;;) {
- for (SmallVectorImpl<Instruction *>::const_iterator
- NI = NewRetains.begin(), NE = NewRetains.end(); NI != NE; ++NI) {
- Instruction *NewRetain = *NI;
- MapVector<Value *, RRInfo>::const_iterator It = Retains.find(NewRetain);
- assert(It != Retains.end());
- const RRInfo &NewRetainRRI = It->second;
- KnownSafeTD &= NewRetainRRI.KnownSafe;
- for (SmallPtrSet<Instruction *, 2>::const_iterator
- LI = NewRetainRRI.Calls.begin(),
- LE = NewRetainRRI.Calls.end(); LI != LE; ++LI) {
- Instruction *NewRetainRelease = *LI;
- DenseMap<Value *, RRInfo>::const_iterator Jt =
- Releases.find(NewRetainRelease);
- if (Jt == Releases.end())
- return false;
- const RRInfo &NewRetainReleaseRRI = Jt->second;
- assert(NewRetainReleaseRRI.Calls.count(NewRetain));
- if (ReleasesToMove.Calls.insert(NewRetainRelease)) {
- OldDelta -=
- BBStates[NewRetainRelease->getParent()].GetAllPathCount();
-
- // Merge the ReleaseMetadata and IsTailCallRelease values.
- if (FirstRelease) {
- ReleasesToMove.ReleaseMetadata =
- NewRetainReleaseRRI.ReleaseMetadata;
- ReleasesToMove.IsTailCallRelease =
- NewRetainReleaseRRI.IsTailCallRelease;
- FirstRelease = false;
- } else {
- if (ReleasesToMove.ReleaseMetadata !=
- NewRetainReleaseRRI.ReleaseMetadata)
- ReleasesToMove.ReleaseMetadata = 0;
- if (ReleasesToMove.IsTailCallRelease !=
- NewRetainReleaseRRI.IsTailCallRelease)
- ReleasesToMove.IsTailCallRelease = false;
- }
-
- // Collect the optimal insertion points.
- if (!KnownSafe)
- for (SmallPtrSet<Instruction *, 2>::const_iterator
- RI = NewRetainReleaseRRI.ReverseInsertPts.begin(),
- RE = NewRetainReleaseRRI.ReverseInsertPts.end();
- RI != RE; ++RI) {
- Instruction *RIP = *RI;
- if (ReleasesToMove.ReverseInsertPts.insert(RIP))
- NewDelta -= BBStates[RIP->getParent()].GetAllPathCount();
- }
- NewReleases.push_back(NewRetainRelease);
- }
- }
- }
- NewRetains.clear();
- if (NewReleases.empty()) break;
-
- // Back the other way.
- for (SmallVectorImpl<Instruction *>::const_iterator
- NI = NewReleases.begin(), NE = NewReleases.end(); NI != NE; ++NI) {
- Instruction *NewRelease = *NI;
- DenseMap<Value *, RRInfo>::const_iterator It =
- Releases.find(NewRelease);
- assert(It != Releases.end());
- const RRInfo &NewReleaseRRI = It->second;
- KnownSafeBU &= NewReleaseRRI.KnownSafe;
- for (SmallPtrSet<Instruction *, 2>::const_iterator
- LI = NewReleaseRRI.Calls.begin(),
- LE = NewReleaseRRI.Calls.end(); LI != LE; ++LI) {
- Instruction *NewReleaseRetain = *LI;
- MapVector<Value *, RRInfo>::const_iterator Jt =
- Retains.find(NewReleaseRetain);
- if (Jt == Retains.end())
- return false;
- const RRInfo &NewReleaseRetainRRI = Jt->second;
- assert(NewReleaseRetainRRI.Calls.count(NewRelease));
- if (RetainsToMove.Calls.insert(NewReleaseRetain)) {
- unsigned PathCount =
- BBStates[NewReleaseRetain->getParent()].GetAllPathCount();
- OldDelta += PathCount;
- OldCount += PathCount;
-
- // Merge the IsRetainBlock values.
- if (FirstRetain) {
- RetainsToMove.IsRetainBlock = NewReleaseRetainRRI.IsRetainBlock;
- FirstRetain = false;
- } else if (ReleasesToMove.IsRetainBlock !=
- NewReleaseRetainRRI.IsRetainBlock)
- // It's not possible to merge the sequences if one uses
- // objc_retain and the other uses objc_retainBlock.
- return false;
-
- // Collect the optimal insertion points.
- if (!KnownSafe)
- for (SmallPtrSet<Instruction *, 2>::const_iterator
- RI = NewReleaseRetainRRI.ReverseInsertPts.begin(),
- RE = NewReleaseRetainRRI.ReverseInsertPts.end();
- RI != RE; ++RI) {
- Instruction *RIP = *RI;
- if (RetainsToMove.ReverseInsertPts.insert(RIP)) {
- PathCount = BBStates[RIP->getParent()].GetAllPathCount();
- NewDelta += PathCount;
- NewCount += PathCount;
- }
- }
- NewRetains.push_back(NewReleaseRetain);
- }
- }
- }
- NewReleases.clear();
- if (NewRetains.empty()) break;
- }
-
- // If the pointer is known incremented or nested, we can safely delete the
- // pair regardless of what's between them.
- if (KnownSafeTD || KnownSafeBU) {
- RetainsToMove.ReverseInsertPts.clear();
- ReleasesToMove.ReverseInsertPts.clear();
- NewCount = 0;
- } else {
- // Determine whether the new insertion points we computed preserve the
- // balance of retain and release calls through the program.
- // TODO: If the fully aggressive solution isn't valid, try to find a
- // less aggressive solution which is.
- if (NewDelta != 0)
- return false;
- }
-
- // Determine whether the original call points are balanced in the retain and
- // release calls through the program. If not, conservatively don't touch
- // them.
- // TODO: It's theoretically possible to do code motion in this case, as
- // long as the existing imbalances are maintained.
- if (OldDelta != 0)
- return false;
-
- Changed = true;
- assert(OldCount != 0 && "Unreachable code?");
- NumRRs += OldCount - NewCount;
- // Set to true if we completely removed any RR pairs.
- AnyPairsCompletelyEliminated = NewCount == 0;
-
- // We can move calls!
- return true;
-}
-
-/// Identify pairings between the retains and releases, and delete and/or move
-/// them.
-bool
-ObjCARCOpt::PerformCodePlacement(DenseMap<const BasicBlock *, BBState>
- &BBStates,
- MapVector<Value *, RRInfo> &Retains,
- DenseMap<Value *, RRInfo> &Releases,
- Module *M) {
- bool AnyPairsCompletelyEliminated = false;
- RRInfo RetainsToMove;
- RRInfo ReleasesToMove;
- SmallVector<Instruction *, 4> NewRetains;
- SmallVector<Instruction *, 4> NewReleases;
- SmallVector<Instruction *, 8> DeadInsts;
-
- // Visit each retain.
- for (MapVector<Value *, RRInfo>::const_iterator I = Retains.begin(),
- E = Retains.end(); I != E; ++I) {
- Value *V = I->first;
- if (!V) continue; // blotted
-
- Instruction *Retain = cast<Instruction>(V);
-
- DEBUG(dbgs() << "ObjCARCOpt::PerformCodePlacement: Visiting: " << *Retain
- << "\n");
-
- Value *Arg = GetObjCArg(Retain);
-
- // If the object being released is in static or stack storage, we know it's
- // not being managed by ObjC reference counting, so we can delete pairs
- // regardless of what possible decrements or uses lie between them.
- bool KnownSafe = isa<Constant>(Arg) || isa<AllocaInst>(Arg);
-
- // A constant pointer can't be pointing to an object on the heap. It may
- // be reference-counted, but it won't be deleted.
- if (const LoadInst *LI = dyn_cast<LoadInst>(Arg))
- if (const GlobalVariable *GV =
- dyn_cast<GlobalVariable>(
- StripPointerCastsAndObjCCalls(LI->getPointerOperand())))
- if (GV->isConstant())
- KnownSafe = true;
-
- // Connect the dots between the top-down-collected RetainsToMove and
- // bottom-up-collected ReleasesToMove to form sets of related calls.
- NewRetains.push_back(Retain);
- bool PerformMoveCalls =
- ConnectTDBUTraversals(BBStates, Retains, Releases, M, NewRetains,
- NewReleases, DeadInsts, RetainsToMove,
- ReleasesToMove, Arg, KnownSafe,
- AnyPairsCompletelyEliminated);
-
- if (PerformMoveCalls) {
- // Ok, everything checks out and we're all set. Let's move/delete some
- // code!
- MoveCalls(Arg, RetainsToMove, ReleasesToMove,
- Retains, Releases, DeadInsts, M);
- }
-
- // Clean up state for next retain.
- NewReleases.clear();
- NewRetains.clear();
- RetainsToMove.clear();
- ReleasesToMove.clear();
- }
-
- // Now that we're done moving everything, we can delete the newly dead
- // instructions, as we no longer need them as insert points.
- while (!DeadInsts.empty())
- EraseInstruction(DeadInsts.pop_back_val());
-
- return AnyPairsCompletelyEliminated;
-}
-
-/// Weak pointer optimizations.
-void ObjCARCOpt::OptimizeWeakCalls(Function &F) {
- // First, do memdep-style RLE and S2L optimizations. We can't use memdep
- // itself because it uses AliasAnalysis and we need to do provenance
- // queries instead.
- for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
- Instruction *Inst = &*I++;
-
- DEBUG(dbgs() << "ObjCARCOpt::OptimizeWeakCalls: Visiting: " << *Inst <<
- "\n");
-
- InstructionClass Class = GetBasicInstructionClass(Inst);
- if (Class != IC_LoadWeak && Class != IC_LoadWeakRetained)
- continue;
-
- // Delete objc_loadWeak calls with no users.
- if (Class == IC_LoadWeak && Inst->use_empty()) {
- Inst->eraseFromParent();
- continue;
- }
-
- // TODO: For now, just look for an earlier available version of this value
- // within the same block. Theoretically, we could do memdep-style non-local
- // analysis too, but that would want caching. A better approach would be to
- // use the technique that EarlyCSE uses.
- inst_iterator Current = llvm::prior(I);
- BasicBlock *CurrentBB = Current.getBasicBlockIterator();
- for (BasicBlock::iterator B = CurrentBB->begin(),
- J = Current.getInstructionIterator();
- J != B; --J) {
- Instruction *EarlierInst = &*llvm::prior(J);
- InstructionClass EarlierClass = GetInstructionClass(EarlierInst);
- switch (EarlierClass) {
- case IC_LoadWeak:
- case IC_LoadWeakRetained: {
- // If this is loading from the same pointer, replace this load's value
- // with that one.
- CallInst *Call = cast<CallInst>(Inst);
- CallInst *EarlierCall = cast<CallInst>(EarlierInst);
- Value *Arg = Call->getArgOperand(0);
- Value *EarlierArg = EarlierCall->getArgOperand(0);
- switch (PA.getAA()->alias(Arg, EarlierArg)) {
- case AliasAnalysis::MustAlias:
- Changed = true;
- // If the load has a builtin retain, insert a plain retain for it.
- if (Class == IC_LoadWeakRetained) {
- CallInst *CI =
- CallInst::Create(getRetainCallee(F.getParent()), EarlierCall,
- "", Call);
- CI->setTailCall();
- }
- // Zap the fully redundant load.
- Call->replaceAllUsesWith(EarlierCall);
- Call->eraseFromParent();
- goto clobbered;
- case AliasAnalysis::MayAlias:
- case AliasAnalysis::PartialAlias:
- goto clobbered;
- case AliasAnalysis::NoAlias:
- break;
- }
- break;
- }
- case IC_StoreWeak:
- case IC_InitWeak: {
- // If this is storing to the same pointer and has the same size etc.
- // replace this load's value with the stored value.
- CallInst *Call = cast<CallInst>(Inst);
- CallInst *EarlierCall = cast<CallInst>(EarlierInst);
- Value *Arg = Call->getArgOperand(0);
- Value *EarlierArg = EarlierCall->getArgOperand(0);
- switch (PA.getAA()->alias(Arg, EarlierArg)) {
- case AliasAnalysis::MustAlias:
- Changed = true;
- // If the load has a builtin retain, insert a plain retain for it.
- if (Class == IC_LoadWeakRetained) {
- CallInst *CI =
- CallInst::Create(getRetainCallee(F.getParent()), EarlierCall,
- "", Call);
- CI->setTailCall();
- }
- // Zap the fully redundant load.
- Call->replaceAllUsesWith(EarlierCall->getArgOperand(1));
- Call->eraseFromParent();
- goto clobbered;
- case AliasAnalysis::MayAlias:
- case AliasAnalysis::PartialAlias:
- goto clobbered;
- case AliasAnalysis::NoAlias:
- break;
- }
- break;
- }
- case IC_MoveWeak:
- case IC_CopyWeak:
- // TOOD: Grab the copied value.
- goto clobbered;
- case IC_AutoreleasepoolPush:
- case IC_None:
- case IC_User:
- // Weak pointers are only modified through the weak entry points
- // (and arbitrary calls, which could call the weak entry points).
- break;
- default:
- // Anything else could modify the weak pointer.
- goto clobbered;
- }
- }
- clobbered:;
- }
-
- // Then, for each destroyWeak with an alloca operand, check to see if
- // the alloca and all its users can be zapped.
- for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
- Instruction *Inst = &*I++;
- InstructionClass Class = GetBasicInstructionClass(Inst);
- if (Class != IC_DestroyWeak)
- continue;
-
- CallInst *Call = cast<CallInst>(Inst);
- Value *Arg = Call->getArgOperand(0);
- if (AllocaInst *Alloca = dyn_cast<AllocaInst>(Arg)) {
- for (Value::use_iterator UI = Alloca->use_begin(),
- UE = Alloca->use_end(); UI != UE; ++UI) {
- const Instruction *UserInst = cast<Instruction>(*UI);
- switch (GetBasicInstructionClass(UserInst)) {
- case IC_InitWeak:
- case IC_StoreWeak:
- case IC_DestroyWeak:
- continue;
- default:
- goto done;
- }
- }
- Changed = true;
- for (Value::use_iterator UI = Alloca->use_begin(),
- UE = Alloca->use_end(); UI != UE; ) {
- CallInst *UserInst = cast<CallInst>(*UI++);
- switch (GetBasicInstructionClass(UserInst)) {
- case IC_InitWeak:
- case IC_StoreWeak:
- // These functions return their second argument.
- UserInst->replaceAllUsesWith(UserInst->getArgOperand(1));
- break;
- case IC_DestroyWeak:
- // No return value.
- break;
- default:
- llvm_unreachable("alloca really is used!");
- }
- UserInst->eraseFromParent();
- }
- Alloca->eraseFromParent();
- done:;
- }
- }
-
- DEBUG(dbgs() << "ObjCARCOpt::OptimizeWeakCalls: Finished List.\n\n");
-
-}
-
-/// Identify program paths which execute sequences of retains and releases which
-/// can be eliminated.
-bool ObjCARCOpt::OptimizeSequences(Function &F) {
- /// Releases, Retains - These are used to store the results of the main flow
- /// analysis. These use Value* as the key instead of Instruction* so that the
- /// map stays valid when we get around to rewriting code and calls get
- /// replaced by arguments.
- DenseMap<Value *, RRInfo> Releases;
- MapVector<Value *, RRInfo> Retains;
-
- /// This is used during the traversal of the function to track the
- /// states for each identified object at each block.
- DenseMap<const BasicBlock *, BBState> BBStates;
-
- // Analyze the CFG of the function, and all instructions.
- bool NestingDetected = Visit(F, BBStates, Retains, Releases);
-
- // Transform.
- return PerformCodePlacement(BBStates, Retains, Releases, F.getParent()) &&
- NestingDetected;
-}
-
-/// Look for this pattern:
-/// \code
-/// %call = call i8* @something(...)
-/// %2 = call i8* @objc_retain(i8* %call)
-/// %3 = call i8* @objc_autorelease(i8* %2)
-/// ret i8* %3
-/// \endcode
-/// And delete the retain and autorelease.
-///
-/// Otherwise if it's just this:
-/// \code
-/// %3 = call i8* @objc_autorelease(i8* %2)
-/// ret i8* %3
-/// \endcode
-/// convert the autorelease to autoreleaseRV.
-void ObjCARCOpt::OptimizeReturns(Function &F) {
- if (!F.getReturnType()->isPointerTy())
- return;
-
- SmallPtrSet<Instruction *, 4> DependingInstructions;
- SmallPtrSet<const BasicBlock *, 4> Visited;
- for (Function::iterator FI = F.begin(), FE = F.end(); FI != FE; ++FI) {
- BasicBlock *BB = FI;
- ReturnInst *Ret = dyn_cast<ReturnInst>(&BB->back());
-
- DEBUG(dbgs() << "ObjCARCOpt::OptimizeReturns: Visiting: " << *Ret << "\n");
-
- if (!Ret) continue;
-
- const Value *Arg = StripPointerCastsAndObjCCalls(Ret->getOperand(0));
- FindDependencies(NeedsPositiveRetainCount, Arg,
- BB, Ret, DependingInstructions, Visited, PA);
- if (DependingInstructions.size() != 1)
- goto next_block;
-
- {
- CallInst *Autorelease =
- dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
- if (!Autorelease)
- goto next_block;
- InstructionClass AutoreleaseClass = GetBasicInstructionClass(Autorelease);
- if (!IsAutorelease(AutoreleaseClass))
- goto next_block;
- if (GetObjCArg(Autorelease) != Arg)
- goto next_block;
-
- DependingInstructions.clear();
- Visited.clear();
-
- // Check that there is nothing that can affect the reference
- // count between the autorelease and the retain.
- FindDependencies(CanChangeRetainCount, Arg,
- BB, Autorelease, DependingInstructions, Visited, PA);
- if (DependingInstructions.size() != 1)
- goto next_block;
-
- {
- CallInst *Retain =
- dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
-
- // Check that we found a retain with the same argument.
- if (!Retain ||
- !IsRetain(GetBasicInstructionClass(Retain)) ||
- GetObjCArg(Retain) != Arg)
- goto next_block;
-
- DependingInstructions.clear();
- Visited.clear();
-
- // Convert the autorelease to an autoreleaseRV, since it's
- // returning the value.
- if (AutoreleaseClass == IC_Autorelease) {
- DEBUG(dbgs() << "ObjCARCOpt::OptimizeReturns: Converting autorelease "
- "=> autoreleaseRV since it's returning a value.\n"
- " In: " << *Autorelease
- << "\n");
- Autorelease->setCalledFunction(getAutoreleaseRVCallee(F.getParent()));
- DEBUG(dbgs() << " Out: " << *Autorelease
- << "\n");
- Autorelease->setTailCall(); // Always tail call autoreleaseRV.
- AutoreleaseClass = IC_AutoreleaseRV;
- }
-
- // Check that there is nothing that can affect the reference
- // count between the retain and the call.
- // Note that Retain need not be in BB.
- FindDependencies(CanChangeRetainCount, Arg, Retain->getParent(), Retain,
- DependingInstructions, Visited, PA);
- if (DependingInstructions.size() != 1)
- goto next_block;
-
- {
- CallInst *Call =
- dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
-
- // Check that the pointer is the return value of the call.
- if (!Call || Arg != Call)
- goto next_block;
-
- // Check that the call is a regular call.
- InstructionClass Class = GetBasicInstructionClass(Call);
- if (Class != IC_CallOrUser && Class != IC_Call)
- goto next_block;
-
- // If so, we can zap the retain and autorelease.
- Changed = true;
- ++NumRets;
- DEBUG(dbgs() << "ObjCARCOpt::OptimizeReturns: Erasing: " << *Retain
- << "\n Erasing: "
- << *Autorelease << "\n");
- EraseInstruction(Retain);
- EraseInstruction(Autorelease);
- }
- }
- }
-
- next_block:
- DependingInstructions.clear();
- Visited.clear();
- }
-
- DEBUG(dbgs() << "ObjCARCOpt::OptimizeReturns: Finished List.\n\n");
-
-}
-
-bool ObjCARCOpt::doInitialization(Module &M) {
- if (!EnableARCOpts)
- return false;
-
- // If nothing in the Module uses ARC, don't do anything.
- Run = ModuleHasARC(M);
- if (!Run)
- return false;
-
- // Identify the imprecise release metadata kind.
- ImpreciseReleaseMDKind =
- M.getContext().getMDKindID("clang.imprecise_release");
- CopyOnEscapeMDKind =
- M.getContext().getMDKindID("clang.arc.copy_on_escape");
- NoObjCARCExceptionsMDKind =
- M.getContext().getMDKindID("clang.arc.no_objc_arc_exceptions");
-
- // Intuitively, objc_retain and others are nocapture, however in practice
- // they are not, because they return their argument value. And objc_release
- // calls finalizers which can have arbitrary side effects.
-
- // These are initialized lazily.
- RetainRVCallee = 0;
- AutoreleaseRVCallee = 0;
- ReleaseCallee = 0;
- RetainCallee = 0;
- RetainBlockCallee = 0;
- AutoreleaseCallee = 0;
-
- return false;
-}
-
-bool ObjCARCOpt::runOnFunction(Function &F) {
- if (!EnableARCOpts)
- return false;
-
- // If nothing in the Module uses ARC, don't do anything.
- if (!Run)
- return false;
-
- Changed = false;
-
- DEBUG(dbgs() << "ObjCARCOpt: Visiting Function: " << F.getName() << "\n");
-
- PA.setAA(&getAnalysis<AliasAnalysis>());
-
- // This pass performs several distinct transformations. As a compile-time aid
- // when compiling code that isn't ObjC, skip these if the relevant ObjC
- // library functions aren't declared.
-
- // Preliminary optimizations. This also computs UsedInThisFunction.
- OptimizeIndividualCalls(F);
-
- // Optimizations for weak pointers.
- if (UsedInThisFunction & ((1 << IC_LoadWeak) |
- (1 << IC_LoadWeakRetained) |
- (1 << IC_StoreWeak) |
- (1 << IC_InitWeak) |
- (1 << IC_CopyWeak) |
- (1 << IC_MoveWeak) |
- (1 << IC_DestroyWeak)))
- OptimizeWeakCalls(F);
-
- // Optimizations for retain+release pairs.
- if (UsedInThisFunction & ((1 << IC_Retain) |
- (1 << IC_RetainRV) |
- (1 << IC_RetainBlock)))
- if (UsedInThisFunction & (1 << IC_Release))
- // Run OptimizeSequences until it either stops making changes or
- // no retain+release pair nesting is detected.
- while (OptimizeSequences(F)) {}
-
- // Optimizations if objc_autorelease is used.
- if (UsedInThisFunction & ((1 << IC_Autorelease) |
- (1 << IC_AutoreleaseRV)))
- OptimizeReturns(F);
-
- DEBUG(dbgs() << "\n");
-
- return Changed;
-}
-
-void ObjCARCOpt::releaseMemory() {
- PA.clear();
-}
-
-/// @}
-///
-/// \defgroup ARCContract ARC Contraction.
-/// @{
-
-// TODO: ObjCARCContract could insert PHI nodes when uses aren't
-// dominated by single calls.
-
-#include "llvm/Analysis/Dominators.h"
-#include "llvm/IR/InlineAsm.h"
-#include "llvm/IR/Operator.h"
-
-STATISTIC(NumStoreStrongs, "Number objc_storeStrong calls formed");
-
-namespace {
- /// \brief Late ARC optimizations
- ///
- /// These change the IR in a way that makes it difficult to be analyzed by
- /// ObjCARCOpt, so it's run late.
- class ObjCARCContract : public FunctionPass {
- bool Changed;
- AliasAnalysis *AA;
- DominatorTree *DT;
- ProvenanceAnalysis PA;
-
- /// A flag indicating whether this optimization pass should run.
- bool Run;
-
- /// Declarations for ObjC runtime functions, for use in creating calls to
- /// them. These are initialized lazily to avoid cluttering up the Module
- /// with unused declarations.
-
- /// Declaration for objc_storeStrong().
- Constant *StoreStrongCallee;
- /// Declaration for objc_retainAutorelease().
- Constant *RetainAutoreleaseCallee;
- /// Declaration for objc_retainAutoreleaseReturnValue().
- Constant *RetainAutoreleaseRVCallee;
-
- /// The inline asm string to insert between calls and RetainRV calls to make
- /// the optimization work on targets which need it.
- const MDString *RetainRVMarker;
-
- /// The set of inserted objc_storeStrong calls. If at the end of walking the
- /// function we have found no alloca instructions, these calls can be marked
- /// "tail".
- SmallPtrSet<CallInst *, 8> StoreStrongCalls;
-
- Constant *getStoreStrongCallee(Module *M);
- Constant *getRetainAutoreleaseCallee(Module *M);
- Constant *getRetainAutoreleaseRVCallee(Module *M);
-
- bool ContractAutorelease(Function &F, Instruction *Autorelease,
- InstructionClass Class,
- SmallPtrSet<Instruction *, 4>
- &DependingInstructions,
- SmallPtrSet<const BasicBlock *, 4>
- &Visited);
-
- void ContractRelease(Instruction *Release,
- inst_iterator &Iter);
-
- virtual void getAnalysisUsage(AnalysisUsage &AU) const;
- virtual bool doInitialization(Module &M);
- virtual bool runOnFunction(Function &F);
-
- public:
- static char ID;
- ObjCARCContract() : FunctionPass(ID) {
- initializeObjCARCContractPass(*PassRegistry::getPassRegistry());
- }
- };
-}
-
-char ObjCARCContract::ID = 0;
-INITIALIZE_PASS_BEGIN(ObjCARCContract,
- "objc-arc-contract", "ObjC ARC contraction", false, false)
-INITIALIZE_AG_DEPENDENCY(AliasAnalysis)
-INITIALIZE_PASS_DEPENDENCY(DominatorTree)
-INITIALIZE_PASS_END(ObjCARCContract,
- "objc-arc-contract", "ObjC ARC contraction", false, false)
-
-Pass *llvm::createObjCARCContractPass() {
- return new ObjCARCContract();
-}
-
-void ObjCARCContract::getAnalysisUsage(AnalysisUsage &AU) const {
- AU.addRequired<AliasAnalysis>();
- AU.addRequired<DominatorTree>();
- AU.setPreservesCFG();
-}
-
-Constant *ObjCARCContract::getStoreStrongCallee(Module *M) {
- if (!StoreStrongCallee) {
- LLVMContext &C = M->getContext();
- Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
- Type *I8XX = PointerType::getUnqual(I8X);
- Type *Params[] = { I8XX, I8X };
-
- AttributeSet Attr = AttributeSet()
- .addAttribute(M->getContext(), AttributeSet::FunctionIndex,
- Attribute::NoUnwind)
- .addAttribute(M->getContext(), 1, Attribute::NoCapture);
-
- StoreStrongCallee =
- M->getOrInsertFunction(
- "objc_storeStrong",
- FunctionType::get(Type::getVoidTy(C), Params, /*isVarArg=*/false),
- Attr);
- }
- return StoreStrongCallee;
-}
-
-Constant *ObjCARCContract::getRetainAutoreleaseCallee(Module *M) {
- if (!RetainAutoreleaseCallee) {
- LLVMContext &C = M->getContext();
- Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
- Type *Params[] = { I8X };
- FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
- AttributeSet Attribute =
- AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
- Attribute::NoUnwind);
- RetainAutoreleaseCallee =
- M->getOrInsertFunction("objc_retainAutorelease", FTy, Attribute);
- }
- return RetainAutoreleaseCallee;
-}
-
-Constant *ObjCARCContract::getRetainAutoreleaseRVCallee(Module *M) {
- if (!RetainAutoreleaseRVCallee) {
- LLVMContext &C = M->getContext();
- Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
- Type *Params[] = { I8X };
- FunctionType *FTy = FunctionType::get(I8X, Params, /*isVarArg=*/false);
- AttributeSet Attribute =
- AttributeSet().addAttribute(M->getContext(), AttributeSet::FunctionIndex,
- Attribute::NoUnwind);
- RetainAutoreleaseRVCallee =
- M->getOrInsertFunction("objc_retainAutoreleaseReturnValue", FTy,
- Attribute);
- }
- return RetainAutoreleaseRVCallee;
-}
-
-/// Merge an autorelease with a retain into a fused call.
-bool
-ObjCARCContract::ContractAutorelease(Function &F, Instruction *Autorelease,
- InstructionClass Class,
- SmallPtrSet<Instruction *, 4>
- &DependingInstructions,
- SmallPtrSet<const BasicBlock *, 4>
- &Visited) {
- const Value *Arg = GetObjCArg(Autorelease);
-
- // Check that there are no instructions between the retain and the autorelease
- // (such as an autorelease_pop) which may change the count.
- CallInst *Retain = 0;
- if (Class == IC_AutoreleaseRV)
- FindDependencies(RetainAutoreleaseRVDep, Arg,
- Autorelease->getParent(), Autorelease,
- DependingInstructions, Visited, PA);
- else
- FindDependencies(RetainAutoreleaseDep, Arg,
- Autorelease->getParent(), Autorelease,
- DependingInstructions, Visited, PA);
-
- Visited.clear();
- if (DependingInstructions.size() != 1) {
- DependingInstructions.clear();
- return false;
- }
-
- Retain = dyn_cast_or_null<CallInst>(*DependingInstructions.begin());
- DependingInstructions.clear();
-
- if (!Retain ||
- GetBasicInstructionClass(Retain) != IC_Retain ||
- GetObjCArg(Retain) != Arg)
- return false;
-
- Changed = true;
- ++NumPeeps;
-
- DEBUG(dbgs() << "ObjCARCContract::ContractAutorelease: Fusing "
- "retain/autorelease. Erasing: " << *Autorelease << "\n"
- " Old Retain: "
- << *Retain << "\n");
-
- if (Class == IC_AutoreleaseRV)
- Retain->setCalledFunction(getRetainAutoreleaseRVCallee(F.getParent()));
- else
- Retain->setCalledFunction(getRetainAutoreleaseCallee(F.getParent()));
-
- DEBUG(dbgs() << " New Retain: "
- << *Retain << "\n");
-
- EraseInstruction(Autorelease);
- return true;
-}
-
-/// Attempt to merge an objc_release with a store, load, and objc_retain to form
-/// an objc_storeStrong. This can be a little tricky because the instructions
-/// don't always appear in order, and there may be unrelated intervening
-/// instructions.
-void ObjCARCContract::ContractRelease(Instruction *Release,
- inst_iterator &Iter) {
- LoadInst *Load = dyn_cast<LoadInst>(GetObjCArg(Release));
- if (!Load || !Load->isSimple()) return;
-
- // For now, require everything to be in one basic block.
- BasicBlock *BB = Release->getParent();
- if (Load->getParent() != BB) return;
-
- // Walk down to find the store and the release, which may be in either order.
- BasicBlock::iterator I = Load, End = BB->end();
- ++I;
- AliasAnalysis::Location Loc = AA->getLocation(Load);
- StoreInst *Store = 0;
- bool SawRelease = false;
- for (; !Store || !SawRelease; ++I) {
- if (I == End)
- return;
-
- Instruction *Inst = I;
- if (Inst == Release) {
- SawRelease = true;
- continue;
- }
-
- InstructionClass Class = GetBasicInstructionClass(Inst);
-
- // Unrelated retains are harmless.
- if (IsRetain(Class))
- continue;
-
- if (Store) {
- // The store is the point where we're going to put the objc_storeStrong,
- // so make sure there are no uses after it.
- if (CanUse(Inst, Load, PA, Class))
- return;
- } else if (AA->getModRefInfo(Inst, Loc) & AliasAnalysis::Mod) {
- // We are moving the load down to the store, so check for anything
- // else which writes to the memory between the load and the store.
- Store = dyn_cast<StoreInst>(Inst);
- if (!Store || !Store->isSimple()) return;
- if (Store->getPointerOperand() != Loc.Ptr) return;
- }
- }
-
- Value *New = StripPointerCastsAndObjCCalls(Store->getValueOperand());
-
- // Walk up to find the retain.
- I = Store;
- BasicBlock::iterator Begin = BB->begin();
- while (I != Begin && GetBasicInstructionClass(I) != IC_Retain)
- --I;
- Instruction *Retain = I;
- if (GetBasicInstructionClass(Retain) != IC_Retain) return;
- if (GetObjCArg(Retain) != New) return;
-
- Changed = true;
- ++NumStoreStrongs;
-
- LLVMContext &C = Release->getContext();
- Type *I8X = PointerType::getUnqual(Type::getInt8Ty(C));
- Type *I8XX = PointerType::getUnqual(I8X);
-
- Value *Args[] = { Load->getPointerOperand(), New };
- if (Args[0]->getType() != I8XX)
- Args[0] = new BitCastInst(Args[0], I8XX, "", Store);
- if (Args[1]->getType() != I8X)
- Args[1] = new BitCastInst(Args[1], I8X, "", Store);
- CallInst *StoreStrong =
- CallInst::Create(getStoreStrongCallee(BB->getParent()->getParent()),
- Args, "", Store);
- StoreStrong->setDoesNotThrow();
- StoreStrong->setDebugLoc(Store->getDebugLoc());
-
- // We can't set the tail flag yet, because we haven't yet determined
- // whether there are any escaping allocas. Remember this call, so that
- // we can set the tail flag once we know it's safe.
- StoreStrongCalls.insert(StoreStrong);
-
- if (&*Iter == Store) ++Iter;
- Store->eraseFromParent();
- Release->eraseFromParent();
- EraseInstruction(Retain);
- if (Load->use_empty())
- Load->eraseFromParent();
-}
-
-bool ObjCARCContract::doInitialization(Module &M) {
- // If nothing in the Module uses ARC, don't do anything.
- Run = ModuleHasARC(M);
- if (!Run)
- return false;
-
- // These are initialized lazily.
- StoreStrongCallee = 0;
- RetainAutoreleaseCallee = 0;
- RetainAutoreleaseRVCallee = 0;
-
- // Initialize RetainRVMarker.
- RetainRVMarker = 0;
- if (NamedMDNode *NMD =
- M.getNamedMetadata("clang.arc.retainAutoreleasedReturnValueMarker"))
- if (NMD->getNumOperands() == 1) {
- const MDNode *N = NMD->getOperand(0);
- if (N->getNumOperands() == 1)
- if (const MDString *S = dyn_cast<MDString>(N->getOperand(0)))
- RetainRVMarker = S;
- }
-
- return false;
-}
-
-bool ObjCARCContract::runOnFunction(Function &F) {
- if (!EnableARCOpts)
- return false;
-
- // If nothing in the Module uses ARC, don't do anything.
- if (!Run)
- return false;
-
- Changed = false;
- AA = &getAnalysis<AliasAnalysis>();
- DT = &getAnalysis<DominatorTree>();
-
- PA.setAA(&getAnalysis<AliasAnalysis>());
-
- // Track whether it's ok to mark objc_storeStrong calls with the "tail"
- // keyword. Be conservative if the function has variadic arguments.
- // It seems that functions which "return twice" are also unsafe for the
- // "tail" argument, because they are setjmp, which could need to
- // return to an earlier stack state.
- bool TailOkForStoreStrongs = !F.isVarArg() &&
- !F.callsFunctionThatReturnsTwice();
-
- // For ObjC library calls which return their argument, replace uses of the
- // argument with uses of the call return value, if it dominates the use. This
- // reduces register pressure.
- SmallPtrSet<Instruction *, 4> DependingInstructions;
- SmallPtrSet<const BasicBlock *, 4> Visited;
- for (inst_iterator I = inst_begin(&F), E = inst_end(&F); I != E; ) {
- Instruction *Inst = &*I++;
-
- DEBUG(dbgs() << "ObjCARCContract: Visiting: " << *Inst << "\n");
-
- // Only these library routines return their argument. In particular,
- // objc_retainBlock does not necessarily return its argument.
- InstructionClass Class = GetBasicInstructionClass(Inst);
- switch (Class) {
- case IC_Retain:
- case IC_FusedRetainAutorelease:
- case IC_FusedRetainAutoreleaseRV:
- break;
- case IC_Autorelease:
- case IC_AutoreleaseRV:
- if (ContractAutorelease(F, Inst, Class, DependingInstructions, Visited))
- continue;
- break;
- case IC_RetainRV: {
- // If we're compiling for a target which needs a special inline-asm
- // marker to do the retainAutoreleasedReturnValue optimization,
- // insert it now.
- if (!RetainRVMarker)
- break;
- BasicBlock::iterator BBI = Inst;
- BasicBlock *InstParent = Inst->getParent();
-
- // Step up to see if the call immediately precedes the RetainRV call.
- // If it's an invoke, we have to cross a block boundary. And we have
- // to carefully dodge no-op instructions.
- do {
- if (&*BBI == InstParent->begin()) {
- BasicBlock *Pred = InstParent->getSinglePredecessor();
- if (!Pred)
- goto decline_rv_optimization;
- BBI = Pred->getTerminator();
- break;
- }
- --BBI;
- } while (isNoopInstruction(BBI));
-
- if (&*BBI == GetObjCArg(Inst)) {
- DEBUG(dbgs() << "ObjCARCContract: Adding inline asm marker for "
- "retainAutoreleasedReturnValue optimization.\n");
- Changed = true;
- InlineAsm *IA =
- InlineAsm::get(FunctionType::get(Type::getVoidTy(Inst->getContext()),
- /*isVarArg=*/false),
- RetainRVMarker->getString(),
- /*Constraints=*/"", /*hasSideEffects=*/true);
- CallInst::Create(IA, "", Inst);
- }
- decline_rv_optimization:
- break;
- }
- case IC_InitWeak: {
- // objc_initWeak(p, null) => *p = null
- CallInst *CI = cast<CallInst>(Inst);
- if (isNullOrUndef(CI->getArgOperand(1))) {
- Value *Null =
- ConstantPointerNull::get(cast<PointerType>(CI->getType()));
- Changed = true;
- new StoreInst(Null, CI->getArgOperand(0), CI);
-
- DEBUG(dbgs() << "OBJCARCContract: Old = " << *CI << "\n"
- << " New = " << *Null << "\n");
-
- CI->replaceAllUsesWith(Null);
- CI->eraseFromParent();
- }
- continue;
- }
- case IC_Release:
- ContractRelease(Inst, I);
- continue;
- case IC_User:
- // Be conservative if the function has any alloca instructions.
- // Technically we only care about escaping alloca instructions,
- // but this is sufficient to handle some interesting cases.
- if (isa<AllocaInst>(Inst))
- TailOkForStoreStrongs = false;
- continue;
- default:
- continue;
- }
-
- DEBUG(dbgs() << "ObjCARCContract: Finished List.\n\n");
-
- // Don't use GetObjCArg because we don't want to look through bitcasts
- // and such; to do the replacement, the argument must have type i8*.
- const Value *Arg = cast<CallInst>(Inst)->getArgOperand(0);
- for (;;) {
- // If we're compiling bugpointed code, don't get in trouble.
- if (!isa<Instruction>(Arg) && !isa<Argument>(Arg))
- break;
- // Look through the uses of the pointer.
- for (Value::const_use_iterator UI = Arg->use_begin(), UE = Arg->use_end();
- UI != UE; ) {
- Use &U = UI.getUse();
- unsigned OperandNo = UI.getOperandNo();
- ++UI; // Increment UI now, because we may unlink its element.
-
- // If the call's return value dominates a use of the call's argument
- // value, rewrite the use to use the return value. We check for
- // reachability here because an unreachable call is considered to
- // trivially dominate itself, which would lead us to rewriting its
- // argument in terms of its return value, which would lead to
- // infinite loops in GetObjCArg.
- if (DT->isReachableFromEntry(U) && DT->dominates(Inst, U)) {
- Changed = true;
- Instruction *Replacement = Inst;
- Type *UseTy = U.get()->getType();
- if (PHINode *PHI = dyn_cast<PHINode>(U.getUser())) {
- // For PHI nodes, insert the bitcast in the predecessor block.
- unsigned ValNo = PHINode::getIncomingValueNumForOperand(OperandNo);
- BasicBlock *BB = PHI->getIncomingBlock(ValNo);
- if (Replacement->getType() != UseTy)
- Replacement = new BitCastInst(Replacement, UseTy, "",
- &BB->back());
- // While we're here, rewrite all edges for this PHI, rather
- // than just one use at a time, to minimize the number of
- // bitcasts we emit.
- for (unsigned i = 0, e = PHI->getNumIncomingValues(); i != e; ++i)
- if (PHI->getIncomingBlock(i) == BB) {
- // Keep the UI iterator valid.
- if (&PHI->getOperandUse(
- PHINode::getOperandNumForIncomingValue(i)) ==
- &UI.getUse())
- ++UI;
- PHI->setIncomingValue(i, Replacement);
- }
- } else {
- if (Replacement->getType() != UseTy)
- Replacement = new BitCastInst(Replacement, UseTy, "",
- cast<Instruction>(U.getUser()));
- U.set(Replacement);
- }
- }
- }
-
- // If Arg is a no-op casted pointer, strip one level of casts and iterate.
- if (const BitCastInst *BI = dyn_cast<BitCastInst>(Arg))
- Arg = BI->getOperand(0);
- else if (isa<GEPOperator>(Arg) &&
- cast<GEPOperator>(Arg)->hasAllZeroIndices())
- Arg = cast<GEPOperator>(Arg)->getPointerOperand();
- else if (isa<GlobalAlias>(Arg) &&
- !cast<GlobalAlias>(Arg)->mayBeOverridden())
- Arg = cast<GlobalAlias>(Arg)->getAliasee();
- else
- break;
- }
- }
-
- // If this function has no escaping allocas or suspicious vararg usage,
- // objc_storeStrong calls can be marked with the "tail" keyword.
- if (TailOkForStoreStrongs)
- for (SmallPtrSet<CallInst *, 8>::iterator I = StoreStrongCalls.begin(),
- E = StoreStrongCalls.end(); I != E; ++I)
- (*I)->setTailCall();
- StoreStrongCalls.clear();
-
- return Changed;
-}
-
-/// @}
-///
initializeLowerAtomicPass(Registry);
initializeLowerExpectIntrinsicPass(Registry);
initializeMemCpyOptPass(Registry);
- initializeObjCARCAliasAnalysisPass(Registry);
- initializeObjCARCAPElimPass(Registry);
- initializeObjCARCExpandPass(Registry);
- initializeObjCARCContractPass(Registry);
- initializeObjCARCOptPass(Registry);
initializeReassociatePass(Registry);
initializeRegToMemPass(Registry);
initializeSCCPPass(Registry);
set(LLVM_LINK_COMPONENTS asmparser instrumentation scalaropts ipo
- linker bitreader bitwriter vectorize)
+ linker bitreader bitwriter vectorize objcarcopts)
add_llvm_tool(bugpoint
BugDriver.cpp
type = Tool
name = bugpoint
parent = Tools
-required_libraries = AsmParser BitReader BitWriter IPO Instrumentation Linker Scalar
+required_libraries = AsmParser BitReader BitWriter IPO Instrumentation Linker Scalar ObjCARC
LEVEL := ../..
TOOLNAME := bugpoint
LINK_COMPONENTS := asmparser instrumentation scalaropts ipo linker bitreader \
- bitwriter vectorize
+ bitwriter vectorize objcarcopts
include $(LEVEL)/Makefile.common
PassRegistry &Registry = *PassRegistry::getPassRegistry();
initializeCore(Registry);
initializeScalarOpts(Registry);
+ initializeObjCARCOpts(Registry);
initializeVectorization(Registry);
initializeIPO(Registry);
initializeAnalysis(Registry);
-set(LLVM_LINK_COMPONENTS ${LLVM_TARGETS_TO_BUILD} bitreader asmparser bitwriter instrumentation scalaropts ipo vectorize)
+set(LLVM_LINK_COMPONENTS ${LLVM_TARGETS_TO_BUILD} bitreader asmparser bitwriter instrumentation scalaropts objcarcopts ipo vectorize)
add_llvm_tool(opt
AnalysisWrappers.cpp
type = Tool
name = opt
parent = Tools
-required_libraries = AsmParser BitReader BitWriter IPO Instrumentation Scalar all-targets
+required_libraries = AsmParser BitReader BitWriter IPO Instrumentation Scalar ObjCARC all-targets
LEVEL := ../..
TOOLNAME := opt
-LINK_COMPONENTS := bitreader bitwriter asmparser instrumentation scalaropts ipo vectorize all-targets
+LINK_COMPONENTS := bitreader bitwriter asmparser instrumentation scalaropts objcarcopts ipo vectorize all-targets
include $(LEVEL)/Makefile.common
PassRegistry &Registry = *PassRegistry::getPassRegistry();
initializeCore(Registry);
initializeScalarOpts(Registry);
+ initializeObjCARCOpts(Registry);
initializeVectorization(Registry);
initializeIPO(Registry);
initializeAnalysis(Registry);
projects / oota-llvm.git / commitdiff