// important that the hash function be high quality. The equality comparison
// iterates through each instruction in each basic block.
//
-// When a match is found, the functions are folded. We can only fold two
-// functions when we know that the definition of one of them is not
-// overridable.
+// When a match is found the functions are folded. If both functions are
+// overridable, we move the functionality into a new internal function and
+// leave two overridable thunks to it.
//
//===----------------------------------------------------------------------===//
//
// Future work:
//
-// * fold vector<T*>::push_back and vector<S*>::push_back.
-//
-// These two functions have different types, but in a way that doesn't matter
-// to us. As long as we never see an S or T itself, using S* and S** is the
-// same as using a T* and T**.
-//
// * virtual functions.
//
// Many functions have their address taken by the virtual function table for
// the object they belong to. However, as long as it's only used for a lookup
-// and call, this is irrelevant, and we'd like to fold such implementations.
+// and call, this is irrelevant, and we'd like to fold such functions.
+//
+// * switch from n^2 pair-wise comparisons to an n-way comparison for each
+// bucket.
+//
+// * be smarter about bitcasts.
+//
+// In order to fold functions, we will sometimes add either bitcast instructions
+// or bitcast constant expressions. Unfortunately, this can confound further
+// analysis since the two functions differ where one has a bitcast and the
+// other doesn't. We should learn to look through bitcasts.
//
//===----------------------------------------------------------------------===//
-#define DEBUG_TYPE "mergefunc"
#include "llvm/Transforms/IPO.h"
-#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/FoldingSet.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallSet.h"
#include "llvm/ADT/Statistic.h"
-#include "llvm/Constants.h"
-#include "llvm/InlineAsm.h"
-#include "llvm/Instructions.h"
-#include "llvm/LLVMContext.h"
-#include "llvm/Module.h"
+#include "llvm/IR/CallSite.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/InlineAsm.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/LLVMContext.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/Operator.h"
+#include "llvm/IR/ValueHandle.h"
#include "llvm/Pass.h"
-#include "llvm/Support/CallSite.h"
-#include "llvm/Support/Compiler.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
-#include <map>
#include <vector>
using namespace llvm;
-STATISTIC(NumFunctionsMerged, "Number of functions merged");
-
-namespace {
- struct VISIBILITY_HIDDEN MergeFunctions : public ModulePass {
- static char ID; // Pass identification, replacement for typeid
- MergeFunctions() : ModulePass((intptr_t)&ID) {}
-
- bool runOnModule(Module &M);
- };
-}
-
-char MergeFunctions::ID = 0;
-static RegisterPass<MergeFunctions>
-X("mergefunc", "Merge Functions");
+#define DEBUG_TYPE "mergefunc"
-ModulePass *llvm::createMergeFunctionsPass() {
- return new MergeFunctions();
+STATISTIC(NumFunctionsMerged, "Number of functions merged");
+STATISTIC(NumThunksWritten, "Number of thunks generated");
+STATISTIC(NumAliasesWritten, "Number of aliases generated");
+STATISTIC(NumDoubleWeak, "Number of new functions created");
+
+/// Returns the type id for a type to be hashed. We turn pointer types into
+/// integers here because the actual compare logic below considers pointers and
+/// integers of the same size as equal.
+static Type::TypeID getTypeIDForHash(Type *Ty) {
+ if (Ty->isPointerTy())
+ return Type::IntegerTyID;
+ return Ty->getTypeID();
}
-// ===----------------------------------------------------------------------===
-// Comparison of functions
-// ===----------------------------------------------------------------------===
-
-static unsigned long hash(const Function *F) {
- const FunctionType *FTy = F->getFunctionType();
+/// Creates a hash-code for the function which is the same for any two
+/// functions that will compare equal, without looking at the instructions
+/// inside the function.
+static unsigned profileFunction(const Function *F) {
+ FunctionType *FTy = F->getFunctionType();
FoldingSetNodeID ID;
ID.AddInteger(F->size());
ID.AddInteger(F->getCallingConv());
ID.AddBoolean(F->hasGC());
ID.AddBoolean(FTy->isVarArg());
- ID.AddInteger(FTy->getReturnType()->getTypeID());
+ ID.AddInteger(getTypeIDForHash(FTy->getReturnType()));
for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i)
- ID.AddInteger(FTy->getParamType(i)->getTypeID());
+ ID.AddInteger(getTypeIDForHash(FTy->getParamType(i)));
return ID.ComputeHash();
}
-/// IgnoreBitcasts - given a bitcast, returns the first non-bitcast found by
-/// walking the chain of cast operands. Otherwise, returns the argument.
-static Value* IgnoreBitcasts(Value *V) {
- while (BitCastInst *BC = dyn_cast<BitCastInst>(V))
- V = BC->getOperand(0);
+namespace {
+
+/// ComparableFunction - A struct that pairs together functions with a
+/// DataLayout so that we can keep them together as elements in the DenseSet.
+class ComparableFunction {
+public:
+ static const ComparableFunction EmptyKey;
+ static const ComparableFunction TombstoneKey;
+ static DataLayout * const LookupOnly;
+
+ ComparableFunction(Function *Func, const DataLayout *DL)
+ : Func(Func), Hash(profileFunction(Func)), DL(DL) {}
+
+ Function *getFunc() const { return Func; }
+ unsigned getHash() const { return Hash; }
+ const DataLayout *getDataLayout() const { return DL; }
+
+ // Drops AssertingVH reference to the function. Outside of debug mode, this
+ // does nothing.
+ void release() {
+ assert(Func &&
+ "Attempted to release function twice, or release empty/tombstone!");
+ Func = NULL;
+ }
+
+private:
+ explicit ComparableFunction(unsigned Hash)
+ : Func(NULL), Hash(Hash), DL(NULL) {}
+
+ AssertingVH<Function> Func;
+ unsigned Hash;
+ const DataLayout *DL;
+};
+
+const ComparableFunction ComparableFunction::EmptyKey = ComparableFunction(0);
+const ComparableFunction ComparableFunction::TombstoneKey =
+ ComparableFunction(1);
+DataLayout *const ComparableFunction::LookupOnly = (DataLayout*)(-1);
- return V;
}
-/// isEquivalentType - any two pointers are equivalent. Otherwise, standard
-/// type equivalence rules apply.
-static bool isEquivalentType(const Type *Ty1, const Type *Ty2) {
- if (Ty1 == Ty2)
- return true;
- if (Ty1->getTypeID() != Ty2->getTypeID())
- return false;
+namespace llvm {
+ template <>
+ struct DenseMapInfo<ComparableFunction> {
+ static ComparableFunction getEmptyKey() {
+ return ComparableFunction::EmptyKey;
+ }
+ static ComparableFunction getTombstoneKey() {
+ return ComparableFunction::TombstoneKey;
+ }
+ static unsigned getHashValue(const ComparableFunction &CF) {
+ return CF.getHash();
+ }
+ static bool isEqual(const ComparableFunction &LHS,
+ const ComparableFunction &RHS);
+ };
+}
+
+namespace {
+
+/// FunctionComparator - Compares two functions to determine whether or not
+/// they will generate machine code with the same behaviour. DataLayout is
+/// used if available. The comparator always fails conservatively (erring on the
+/// side of claiming that two functions are different).
+class FunctionComparator {
+public:
+ FunctionComparator(const DataLayout *DL, const Function *F1,
+ const Function *F2)
+ : F1(F1), F2(F2), DL(DL) {}
+
+ /// Test whether the two functions have equivalent behaviour.
+ bool compare();
+
+private:
+ /// Test whether two basic blocks have equivalent behaviour.
+ bool compare(const BasicBlock *BB1, const BasicBlock *BB2);
+
+ /// Assign or look up previously assigned numbers for the two values, and
+ /// return whether the numbers are equal. Numbers are assigned in the order
+ /// visited.
+ bool enumerate(const Value *V1, const Value *V2);
+
+ /// Compare two Instructions for equivalence, similar to
+ /// Instruction::isSameOperationAs but with modifications to the type
+ /// comparison.
+ bool isEquivalentOperation(const Instruction *I1,
+ const Instruction *I2) const;
+
+ /// Compare two GEPs for equivalent pointer arithmetic.
+ bool isEquivalentGEP(const GEPOperator *GEP1, const GEPOperator *GEP2);
+ bool isEquivalentGEP(const GetElementPtrInst *GEP1,
+ const GetElementPtrInst *GEP2) {
+ return isEquivalentGEP(cast<GEPOperator>(GEP1), cast<GEPOperator>(GEP2));
+ }
+
+ /// cmpType - compares two types,
+ /// defines total ordering among the types set.
+ ///
+ /// Return values:
+ /// 0 if types are equal,
+ /// -1 if Left is less than Right,
+ /// +1 if Left is greater than Right.
+ ///
+ /// Description:
+ /// Comparison is broken onto stages. Like in lexicographical comparison
+ /// stage coming first has higher priority.
+ /// On each explanation stage keep in mind total ordering properties.
+ ///
+ /// 0. Before comparison we coerce pointer types of 0 address space to
+ /// integer.
+ /// We also don't bother with same type at left and right, so
+ /// just return 0 in this case.
+ ///
+ /// 1. If types are of different kind (different type IDs).
+ /// Return result of type IDs comparison, treating them as numbers.
+ /// 2. If types are vectors or integers, compare Type* values as numbers.
+ /// 3. Types has same ID, so check whether they belongs to the next group:
+ /// * Void
+ /// * Float
+ /// * Double
+ /// * X86_FP80
+ /// * FP128
+ /// * PPC_FP128
+ /// * Label
+ /// * Metadata
+ /// If so - return 0, yes - we can treat these types as equal only because
+ /// their IDs are same.
+ /// 4. If Left and Right are pointers, return result of address space
+ /// comparison (numbers comparison). We can treat pointer types of same
+ /// address space as equal.
+ /// 5. If types are complex.
+ /// Then both Left and Right are to be expanded and their element types will
+ /// be checked with the same way. If we get Res != 0 on some stage, return it.
+ /// Otherwise return 0.
+ /// 6. For all other cases put llvm_unreachable.
+ int cmpType(Type *TyL, Type *TyR) const;
+
+ bool isEquivalentType(Type *Ty1, Type *Ty2) const {
+ return cmpType(Ty1, Ty2) == 0;
+ }
+
+ int cmpNumbers(uint64_t L, uint64_t R) const;
+
+ // The two functions undergoing comparison.
+ const Function *F1, *F2;
+
+ const DataLayout *DL;
+
+ DenseMap<const Value *, const Value *> id_map;
+ DenseSet<const Value *> seen_values;
+};
+
+}
+
+int FunctionComparator::cmpNumbers(uint64_t L, uint64_t R) const {
+ if (L < R) return -1;
+ if (L > R) return 1;
+ return 0;
+}
+
+/// cmpType - compares two types,
+/// defines total ordering among the types set.
+/// See method declaration comments for more details.
+int FunctionComparator::cmpType(Type *TyL, Type *TyR) const {
+
+ PointerType *PTyL = dyn_cast<PointerType>(TyL);
+ PointerType *PTyR = dyn_cast<PointerType>(TyR);
+
+ if (DL) {
+ if (PTyL && PTyL->getAddressSpace() == 0) TyL = DL->getIntPtrType(TyL);
+ if (PTyR && PTyR->getAddressSpace() == 0) TyR = DL->getIntPtrType(TyR);
+ }
+
+ if (TyL == TyR)
+ return 0;
+
+ if (int Res = cmpNumbers(TyL->getTypeID(), TyR->getTypeID()))
+ return Res;
+
+ switch (TyL->getTypeID()) {
+ default:
+ llvm_unreachable("Unknown type!");
+ // Fall through in Release mode.
+ case Type::IntegerTyID:
+ case Type::VectorTyID:
+ // TyL == TyR would have returned true earlier.
+ return cmpNumbers((uint64_t)TyL, (uint64_t)TyR);
- switch(Ty1->getTypeID()) {
case Type::VoidTyID:
case Type::FloatTyID:
case Type::DoubleTyID:
case Type::PPC_FP128TyID:
case Type::LabelTyID:
case Type::MetadataTyID:
- return true;
-
- case Type::IntegerTyID:
- case Type::OpaqueTyID:
- // Ty1 == Ty2 would have returned true earlier.
- return false;
-
- default:
- llvm_unreachable("Unknown type!");
- return false;
+ return 0;
case Type::PointerTyID: {
- const PointerType *PTy1 = cast<PointerType>(Ty1);
- const PointerType *PTy2 = cast<PointerType>(Ty2);
- return PTy1->getAddressSpace() == PTy2->getAddressSpace();
+ assert(PTyL && PTyR && "Both types must be pointers here.");
+ return cmpNumbers(PTyL->getAddressSpace(), PTyR->getAddressSpace());
}
case Type::StructTyID: {
- const StructType *STy1 = cast<StructType>(Ty1);
- const StructType *STy2 = cast<StructType>(Ty2);
- if (STy1->getNumElements() != STy2->getNumElements())
- return false;
-
- if (STy1->isPacked() != STy2->isPacked())
- return false;
-
- for (unsigned i = 0, e = STy1->getNumElements(); i != e; ++i) {
- if (!isEquivalentType(STy1->getElementType(i), STy2->getElementType(i)))
- return false;
+ StructType *STyL = cast<StructType>(TyL);
+ StructType *STyR = cast<StructType>(TyR);
+ if (STyL->getNumElements() != STyR->getNumElements())
+ return cmpNumbers(STyL->getNumElements(), STyR->getNumElements());
+
+ if (STyL->isPacked() != STyR->isPacked())
+ return cmpNumbers(STyL->isPacked(), STyR->isPacked());
+
+ for (unsigned i = 0, e = STyL->getNumElements(); i != e; ++i) {
+ if (int Res = cmpType(STyL->getElementType(i),
+ STyR->getElementType(i)))
+ return Res;
}
- return true;
+ return 0;
}
case Type::FunctionTyID: {
- const FunctionType *FTy1 = cast<FunctionType>(Ty1);
- const FunctionType *FTy2 = cast<FunctionType>(Ty2);
- if (FTy1->getNumParams() != FTy2->getNumParams() ||
- FTy1->isVarArg() != FTy2->isVarArg())
- return false;
+ FunctionType *FTyL = cast<FunctionType>(TyL);
+ FunctionType *FTyR = cast<FunctionType>(TyR);
+ if (FTyL->getNumParams() != FTyR->getNumParams())
+ return cmpNumbers(FTyL->getNumParams(), FTyR->getNumParams());
- if (!isEquivalentType(FTy1->getReturnType(), FTy2->getReturnType()))
- return false;
+ if (FTyL->isVarArg() != FTyR->isVarArg())
+ return cmpNumbers(FTyL->isVarArg(), FTyR->isVarArg());
- for (unsigned i = 0, e = FTy1->getNumParams(); i != e; ++i) {
- if (!isEquivalentType(FTy1->getParamType(i), FTy2->getParamType(i)))
- return false;
+ if (int Res = cmpType(FTyL->getReturnType(), FTyR->getReturnType()))
+ return Res;
+
+ for (unsigned i = 0, e = FTyL->getNumParams(); i != e; ++i) {
+ if (int Res = cmpType(FTyL->getParamType(i), FTyR->getParamType(i)))
+ return Res;
}
- return true;
+ return 0;
}
- case Type::ArrayTyID:
- case Type::VectorTyID: {
- const SequentialType *STy1 = cast<SequentialType>(Ty1);
- const SequentialType *STy2 = cast<SequentialType>(Ty2);
- return isEquivalentType(STy1->getElementType(), STy2->getElementType());
+ case Type::ArrayTyID: {
+ ArrayType *ATyL = cast<ArrayType>(TyL);
+ ArrayType *ATyR = cast<ArrayType>(TyR);
+ if (ATyL->getNumElements() != ATyR->getNumElements())
+ return cmpNumbers(ATyL->getNumElements(), ATyR->getNumElements());
+ return cmpType(ATyL->getElementType(), ATyR->getElementType());
}
}
}
-/// isEquivalentOperation - determine whether the two operations are the same
-/// except that pointer-to-A and pointer-to-B are equivalent. This should be
-/// kept in sync with Instruction::isSameOperationAs.
-static bool
-isEquivalentOperation(const Instruction *I1, const Instruction *I2) {
+// Determine whether the two operations are the same except that pointer-to-A
+// and pointer-to-B are equivalent. This should be kept in sync with
+// Instruction::isSameOperationAs.
+bool FunctionComparator::isEquivalentOperation(const Instruction *I1,
+ const Instruction *I2) const {
+ // Differences from Instruction::isSameOperationAs:
+ // * replace type comparison with calls to isEquivalentType.
+ // * we test for I->hasSameSubclassOptionalData (nuw/nsw/tail) at the top
+ // * because of the above, we don't test for the tail bit on calls later on
if (I1->getOpcode() != I2->getOpcode() ||
I1->getNumOperands() != I2->getNumOperands() ||
- !isEquivalentType(I1->getType(), I2->getType()))
+ !isEquivalentType(I1->getType(), I2->getType()) ||
+ !I1->hasSameSubclassOptionalData(I2))
return false;
// We have two instructions of identical opcode and #operands. Check to see
// Check special state that is a part of some instructions.
if (const LoadInst *LI = dyn_cast<LoadInst>(I1))
return LI->isVolatile() == cast<LoadInst>(I2)->isVolatile() &&
- LI->getAlignment() == cast<LoadInst>(I2)->getAlignment();
+ LI->getAlignment() == cast<LoadInst>(I2)->getAlignment() &&
+ LI->getOrdering() == cast<LoadInst>(I2)->getOrdering() &&
+ LI->getSynchScope() == cast<LoadInst>(I2)->getSynchScope();
if (const StoreInst *SI = dyn_cast<StoreInst>(I1))
return SI->isVolatile() == cast<StoreInst>(I2)->isVolatile() &&
- SI->getAlignment() == cast<StoreInst>(I2)->getAlignment();
+ SI->getAlignment() == cast<StoreInst>(I2)->getAlignment() &&
+ SI->getOrdering() == cast<StoreInst>(I2)->getOrdering() &&
+ SI->getSynchScope() == cast<StoreInst>(I2)->getSynchScope();
if (const CmpInst *CI = dyn_cast<CmpInst>(I1))
return CI->getPredicate() == cast<CmpInst>(I2)->getPredicate();
if (const CallInst *CI = dyn_cast<CallInst>(I1))
- return CI->isTailCall() == cast<CallInst>(I2)->isTailCall() &&
- CI->getCallingConv() == cast<CallInst>(I2)->getCallingConv() &&
- CI->getAttributes().getRawPointer() ==
- cast<CallInst>(I2)->getAttributes().getRawPointer();
+ return CI->getCallingConv() == cast<CallInst>(I2)->getCallingConv() &&
+ CI->getAttributes() == cast<CallInst>(I2)->getAttributes();
if (const InvokeInst *CI = dyn_cast<InvokeInst>(I1))
return CI->getCallingConv() == cast<InvokeInst>(I2)->getCallingConv() &&
- CI->getAttributes().getRawPointer() ==
- cast<InvokeInst>(I2)->getAttributes().getRawPointer();
- if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(I1)) {
- if (IVI->getNumIndices() != cast<InsertValueInst>(I2)->getNumIndices())
- return false;
- for (unsigned i = 0, e = IVI->getNumIndices(); i != e; ++i)
- if (IVI->idx_begin()[i] != cast<InsertValueInst>(I2)->idx_begin()[i])
- return false;
- return true;
- }
- if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(I1)) {
- if (EVI->getNumIndices() != cast<ExtractValueInst>(I2)->getNumIndices())
- return false;
- for (unsigned i = 0, e = EVI->getNumIndices(); i != e; ++i)
- if (EVI->idx_begin()[i] != cast<ExtractValueInst>(I2)->idx_begin()[i])
- return false;
- return true;
- }
+ CI->getAttributes() == cast<InvokeInst>(I2)->getAttributes();
+ if (const InsertValueInst *IVI = dyn_cast<InsertValueInst>(I1))
+ return IVI->getIndices() == cast<InsertValueInst>(I2)->getIndices();
+ if (const ExtractValueInst *EVI = dyn_cast<ExtractValueInst>(I1))
+ return EVI->getIndices() == cast<ExtractValueInst>(I2)->getIndices();
+ if (const FenceInst *FI = dyn_cast<FenceInst>(I1))
+ return FI->getOrdering() == cast<FenceInst>(I2)->getOrdering() &&
+ FI->getSynchScope() == cast<FenceInst>(I2)->getSynchScope();
+ if (const AtomicCmpXchgInst *CXI = dyn_cast<AtomicCmpXchgInst>(I1))
+ return CXI->isVolatile() == cast<AtomicCmpXchgInst>(I2)->isVolatile() &&
+ CXI->getSuccessOrdering() ==
+ cast<AtomicCmpXchgInst>(I2)->getSuccessOrdering() &&
+ CXI->getFailureOrdering() ==
+ cast<AtomicCmpXchgInst>(I2)->getFailureOrdering() &&
+ CXI->getSynchScope() == cast<AtomicCmpXchgInst>(I2)->getSynchScope();
+ if (const AtomicRMWInst *RMWI = dyn_cast<AtomicRMWInst>(I1))
+ return RMWI->getOperation() == cast<AtomicRMWInst>(I2)->getOperation() &&
+ RMWI->isVolatile() == cast<AtomicRMWInst>(I2)->isVolatile() &&
+ RMWI->getOrdering() == cast<AtomicRMWInst>(I2)->getOrdering() &&
+ RMWI->getSynchScope() == cast<AtomicRMWInst>(I2)->getSynchScope();
return true;
}
-static bool compare(const Value *V, const Value *U) {
- assert(!isa<BasicBlock>(V) && !isa<BasicBlock>(U) &&
- "Must not compare basic blocks.");
+// Determine whether two GEP operations perform the same underlying arithmetic.
+bool FunctionComparator::isEquivalentGEP(const GEPOperator *GEP1,
+ const GEPOperator *GEP2) {
+ unsigned AS = GEP1->getPointerAddressSpace();
+ if (AS != GEP2->getPointerAddressSpace())
+ return false;
- assert(isEquivalentType(V->getType(), U->getType()) &&
- "Two of the same operation have operands of different type.");
+ if (DL) {
+ // When we have target data, we can reduce the GEP down to the value in bytes
+ // added to the address.
+ unsigned BitWidth = DL ? DL->getPointerSizeInBits(AS) : 1;
+ APInt Offset1(BitWidth, 0), Offset2(BitWidth, 0);
+ if (GEP1->accumulateConstantOffset(*DL, Offset1) &&
+ GEP2->accumulateConstantOffset(*DL, Offset2)) {
+ return Offset1 == Offset2;
+ }
+ }
- // TODO: If the constant is an expression of F, we should accept that it's
- // equal to the same expression in terms of G.
- if (isa<Constant>(V))
- return V == U;
+ if (GEP1->getPointerOperand()->getType() !=
+ GEP2->getPointerOperand()->getType())
+ return false;
- // The caller has ensured that ValueMap[V] != U. Since Arguments are
- // pre-loaded into the ValueMap, and Instructions are added as we go, we know
- // that this can only be a mis-match.
- if (isa<Instruction>(V) || isa<Argument>(V))
+ if (GEP1->getNumOperands() != GEP2->getNumOperands())
return false;
- if (isa<InlineAsm>(V) && isa<InlineAsm>(U)) {
- const InlineAsm *IAF = cast<InlineAsm>(V);
- const InlineAsm *IAG = cast<InlineAsm>(U);
- return IAF->getAsmString() == IAG->getAsmString() &&
- IAF->getConstraintString() == IAG->getConstraintString();
+ for (unsigned i = 0, e = GEP1->getNumOperands(); i != e; ++i) {
+ if (!enumerate(GEP1->getOperand(i), GEP2->getOperand(i)))
+ return false;
}
- return false;
+ return true;
}
-static bool equals(const BasicBlock *BB1, const BasicBlock *BB2,
- DenseMap<const Value *, const Value *> &ValueMap,
- DenseMap<const Value *, const Value *> &SpeculationMap) {
- // Speculatively add it anyways. If it's false, we'll notice a difference
- // later, and this won't matter.
- ValueMap[BB1] = BB2;
-
- BasicBlock::const_iterator FI = BB1->begin(), FE = BB1->end();
- BasicBlock::const_iterator GI = BB2->begin(), GE = BB2->end();
+// Compare two values used by the two functions under pair-wise comparison. If
+// this is the first time the values are seen, they're added to the mapping so
+// that we will detect mismatches on next use.
+bool FunctionComparator::enumerate(const Value *V1, const Value *V2) {
+ // Check for function @f1 referring to itself and function @f2 referring to
+ // itself, or referring to each other, or both referring to either of them.
+ // They're all equivalent if the two functions are otherwise equivalent.
+ if (V1 == F1 && V2 == F2)
+ return true;
+ if (V1 == F2 && V2 == F1)
+ return true;
- do {
- if (isa<BitCastInst>(FI)) {
- ++FI;
- continue;
- }
- if (isa<BitCastInst>(GI)) {
- ++GI;
- continue;
- }
+ if (const Constant *C1 = dyn_cast<Constant>(V1)) {
+ if (V1 == V2) return true;
+ const Constant *C2 = dyn_cast<Constant>(V2);
+ if (!C2) return false;
+ // TODO: constant expressions with GEP or references to F1 or F2.
+ if (C1->isNullValue() && C2->isNullValue() &&
+ isEquivalentType(C1->getType(), C2->getType()))
+ return true;
+ // Try bitcasting C2 to C1's type. If the bitcast is legal and returns C1
+ // then they must have equal bit patterns.
+ return C1->getType()->canLosslesslyBitCastTo(C2->getType()) &&
+ C1 == ConstantExpr::getBitCast(const_cast<Constant*>(C2), C1->getType());
+ }
- if (!isEquivalentOperation(FI, GI))
- return false;
+ if (isa<InlineAsm>(V1) || isa<InlineAsm>(V2))
+ return V1 == V2;
- if (isa<GetElementPtrInst>(FI)) {
- const GetElementPtrInst *GEPF = cast<GetElementPtrInst>(FI);
- const GetElementPtrInst *GEPG = cast<GetElementPtrInst>(GI);
- if (GEPF->hasAllZeroIndices() && GEPG->hasAllZeroIndices()) {
- // It's effectively a bitcast.
- ++FI, ++GI;
- continue;
- }
+ // Check that V1 maps to V2. If we find a value that V1 maps to then we simply
+ // check whether it's equal to V2. When there is no mapping then we need to
+ // ensure that V2 isn't already equivalent to something else. For this
+ // purpose, we track the V2 values in a set.
- // TODO: we only really care about the elements before the index
- if (FI->getOperand(0)->getType() != GI->getOperand(0)->getType())
- return false;
- }
+ const Value *&map_elem = id_map[V1];
+ if (map_elem)
+ return map_elem == V2;
+ if (!seen_values.insert(V2).second)
+ return false;
+ map_elem = V2;
+ return true;
+}
- if (ValueMap[FI] == GI) {
- ++FI, ++GI;
- continue;
- }
+// Test whether two basic blocks have equivalent behaviour.
+bool FunctionComparator::compare(const BasicBlock *BB1, const BasicBlock *BB2) {
+ BasicBlock::const_iterator F1I = BB1->begin(), F1E = BB1->end();
+ BasicBlock::const_iterator F2I = BB2->begin(), F2E = BB2->end();
- if (ValueMap[FI] != NULL)
+ do {
+ if (!enumerate(F1I, F2I))
return false;
- for (unsigned i = 0, e = FI->getNumOperands(); i != e; ++i) {
- Value *OpF = IgnoreBitcasts(FI->getOperand(i));
- Value *OpG = IgnoreBitcasts(GI->getOperand(i));
-
- if (ValueMap[OpF] == OpG)
- continue;
+ if (const GetElementPtrInst *GEP1 = dyn_cast<GetElementPtrInst>(F1I)) {
+ const GetElementPtrInst *GEP2 = dyn_cast<GetElementPtrInst>(F2I);
+ if (!GEP2)
+ return false;
- if (ValueMap[OpF] != NULL)
+ if (!enumerate(GEP1->getPointerOperand(), GEP2->getPointerOperand()))
return false;
- if (OpF->getValueID() != OpG->getValueID() ||
- !isEquivalentType(OpF->getType(), OpG->getType()))
+ if (!isEquivalentGEP(GEP1, GEP2))
+ return false;
+ } else {
+ if (!isEquivalentOperation(F1I, F2I))
return false;
- if (isa<PHINode>(FI)) {
- if (SpeculationMap[OpF] == NULL)
- SpeculationMap[OpF] = OpG;
- else if (SpeculationMap[OpF] != OpG)
- return false;
- continue;
- } else if (isa<BasicBlock>(OpF)) {
- assert(isa<TerminatorInst>(FI) &&
- "BasicBlock referenced by non-Terminator non-PHI");
- // This call changes the ValueMap, hence we can't use
- // Value *& = ValueMap[...]
- if (!equals(cast<BasicBlock>(OpF), cast<BasicBlock>(OpG), ValueMap,
- SpeculationMap))
+ assert(F1I->getNumOperands() == F2I->getNumOperands());
+ for (unsigned i = 0, e = F1I->getNumOperands(); i != e; ++i) {
+ Value *OpF1 = F1I->getOperand(i);
+ Value *OpF2 = F2I->getOperand(i);
+
+ if (!enumerate(OpF1, OpF2))
return false;
- } else {
- if (!compare(OpF, OpG))
+
+ if (OpF1->getValueID() != OpF2->getValueID() ||
+ !isEquivalentType(OpF1->getType(), OpF2->getType()))
return false;
}
-
- ValueMap[OpF] = OpG;
}
- ValueMap[FI] = GI;
- ++FI, ++GI;
- } while (FI != FE && GI != GE);
+ ++F1I, ++F2I;
+ } while (F1I != F1E && F2I != F2E);
- return FI == FE && GI == GE;
+ return F1I == F1E && F2I == F2E;
}
-static bool equals(const Function *F, const Function *G) {
+// Test whether the two functions have equivalent behaviour.
+bool FunctionComparator::compare() {
// We need to recheck everything, but check the things that weren't included
// in the hash first.
- if (F->getAttributes() != G->getAttributes())
+ if (F1->getAttributes() != F2->getAttributes())
return false;
- if (F->hasGC() != G->hasGC())
+ if (F1->hasGC() != F2->hasGC())
return false;
- if (F->hasGC() && F->getGC() != G->getGC())
+ if (F1->hasGC() && F1->getGC() != F2->getGC())
return false;
- if (F->hasSection() != G->hasSection())
+ if (F1->hasSection() != F2->hasSection())
return false;
- if (F->hasSection() && F->getSection() != G->getSection())
+ if (F1->hasSection() && F1->getSection() != F2->getSection())
return false;
- if (F->isVarArg() != G->isVarArg())
+ if (F1->isVarArg() != F2->isVarArg())
return false;
// TODO: if it's internal and only used in direct calls, we could handle this
// case too.
- if (F->getCallingConv() != G->getCallingConv())
+ if (F1->getCallingConv() != F2->getCallingConv())
return false;
- if (!isEquivalentType(F->getFunctionType(), G->getFunctionType()))
+ if (!isEquivalentType(F1->getFunctionType(), F2->getFunctionType()))
return false;
- DenseMap<const Value *, const Value *> ValueMap;
- DenseMap<const Value *, const Value *> SpeculationMap;
- ValueMap[F] = G;
+ assert(F1->arg_size() == F2->arg_size() &&
+ "Identically typed functions have different numbers of args!");
- assert(F->arg_size() == G->arg_size() &&
- "Identical functions have a different number of args.");
+ // Visit the arguments so that they get enumerated in the order they're
+ // passed in.
+ for (Function::const_arg_iterator f1i = F1->arg_begin(),
+ f2i = F2->arg_begin(), f1e = F1->arg_end(); f1i != f1e; ++f1i, ++f2i) {
+ if (!enumerate(f1i, f2i))
+ llvm_unreachable("Arguments repeat!");
+ }
- for (Function::const_arg_iterator fi = F->arg_begin(), gi = G->arg_begin(),
- fe = F->arg_end(); fi != fe; ++fi, ++gi)
- ValueMap[fi] = gi;
+ // We do a CFG-ordered walk since the actual ordering of the blocks in the
+ // linked list is immaterial. Our walk starts at the entry block for both
+ // functions, then takes each block from each terminator in order. As an
+ // artifact, this also means that unreachable blocks are ignored.
+ SmallVector<const BasicBlock *, 8> F1BBs, F2BBs;
+ SmallSet<const BasicBlock *, 128> VisitedBBs; // in terms of F1.
- if (!equals(&F->getEntryBlock(), &G->getEntryBlock(), ValueMap,
- SpeculationMap))
- return false;
+ F1BBs.push_back(&F1->getEntryBlock());
+ F2BBs.push_back(&F2->getEntryBlock());
- for (DenseMap<const Value *, const Value *>::iterator
- I = SpeculationMap.begin(), E = SpeculationMap.end(); I != E; ++I) {
- if (ValueMap[I->first] != I->second)
+ VisitedBBs.insert(F1BBs[0]);
+ while (!F1BBs.empty()) {
+ const BasicBlock *F1BB = F1BBs.pop_back_val();
+ const BasicBlock *F2BB = F2BBs.pop_back_val();
+
+ if (!enumerate(F1BB, F2BB) || !compare(F1BB, F2BB))
return false;
- }
+ const TerminatorInst *F1TI = F1BB->getTerminator();
+ const TerminatorInst *F2TI = F2BB->getTerminator();
+
+ assert(F1TI->getNumSuccessors() == F2TI->getNumSuccessors());
+ for (unsigned i = 0, e = F1TI->getNumSuccessors(); i != e; ++i) {
+ if (!VisitedBBs.insert(F1TI->getSuccessor(i)))
+ continue;
+
+ F1BBs.push_back(F1TI->getSuccessor(i));
+ F2BBs.push_back(F2TI->getSuccessor(i));
+ }
+ }
return true;
}
-// ===----------------------------------------------------------------------===
-// Folding of functions
-// ===----------------------------------------------------------------------===
-
-// Cases:
-// * F is external strong, G is external strong:
-// turn G into a thunk to F (1)
-// * F is external strong, G is external weak:
-// turn G into a thunk to F (1)
-// * F is external weak, G is external weak:
-// unfoldable
-// * F is external strong, G is internal:
-// address of G taken:
-// turn G into a thunk to F (1)
-// address of G not taken:
-// make G an alias to F (2)
-// * F is internal, G is external weak
-// address of F is taken:
-// turn G into a thunk to F (1)
-// address of F is not taken:
-// make G an alias of F (2)
-// * F is internal, G is internal:
-// address of F and G are taken:
-// turn G into a thunk to F (1)
-// address of G is not taken:
-// make G an alias to F (2)
-//
-// alias requires linkage == (external,local,weak) fallback to creating a thunk
-// external means 'externally visible' linkage != (internal,private)
-// internal means linkage == (internal,private)
-// weak means linkage mayBeOverridable
-// being external implies that the address is taken
-//
-// 1. turn G into a thunk to F
-// 2. make G an alias to F
+namespace {
+
+/// MergeFunctions finds functions which will generate identical machine code,
+/// by considering all pointer types to be equivalent. Once identified,
+/// MergeFunctions will fold them by replacing a call to one to a call to a
+/// bitcast of the other.
+///
+class MergeFunctions : public ModulePass {
+public:
+ static char ID;
+ MergeFunctions()
+ : ModulePass(ID), HasGlobalAliases(false) {
+ initializeMergeFunctionsPass(*PassRegistry::getPassRegistry());
+ }
+
+ bool runOnModule(Module &M) override;
+
+private:
+ typedef DenseSet<ComparableFunction> FnSetType;
+
+ /// A work queue of functions that may have been modified and should be
+ /// analyzed again.
+ std::vector<WeakVH> Deferred;
+
+ /// Insert a ComparableFunction into the FnSet, or merge it away if it's
+ /// equal to one that's already present.
+ bool insert(ComparableFunction &NewF);
+
+ /// Remove a Function from the FnSet and queue it up for a second sweep of
+ /// analysis.
+ void remove(Function *F);
+
+ /// Find the functions that use this Value and remove them from FnSet and
+ /// queue the functions.
+ void removeUsers(Value *V);
+
+ /// Replace all direct calls of Old with calls of New. Will bitcast New if
+ /// necessary to make types match.
+ void replaceDirectCallers(Function *Old, Function *New);
-enum LinkageCategory {
- ExternalStrong,
- ExternalWeak,
- Internal
+ /// Merge two equivalent functions. Upon completion, G may be deleted, or may
+ /// be converted into a thunk. In either case, it should never be visited
+ /// again.
+ void mergeTwoFunctions(Function *F, Function *G);
+
+ /// Replace G with a thunk or an alias to F. Deletes G.
+ void writeThunkOrAlias(Function *F, Function *G);
+
+ /// Replace G with a simple tail call to bitcast(F). Also replace direct uses
+ /// of G with bitcast(F). Deletes G.
+ void writeThunk(Function *F, Function *G);
+
+ /// Replace G with an alias to F. Deletes G.
+ void writeAlias(Function *F, Function *G);
+
+ /// The set of all distinct functions. Use the insert() and remove() methods
+ /// to modify it.
+ FnSetType FnSet;
+
+ /// DataLayout for more accurate GEP comparisons. May be NULL.
+ const DataLayout *DL;
+
+ /// Whether or not the target supports global aliases.
+ bool HasGlobalAliases;
};
-static LinkageCategory categorize(const Function *F) {
- switch (F->getLinkage()) {
- case GlobalValue::InternalLinkage:
- case GlobalValue::PrivateLinkage:
- case GlobalValue::LinkerPrivateLinkage:
- return Internal;
-
- case GlobalValue::WeakAnyLinkage:
- case GlobalValue::WeakODRLinkage:
- case GlobalValue::ExternalWeakLinkage:
- return ExternalWeak;
-
- case GlobalValue::ExternalLinkage:
- case GlobalValue::AvailableExternallyLinkage:
- case GlobalValue::LinkOnceAnyLinkage:
- case GlobalValue::LinkOnceODRLinkage:
- case GlobalValue::AppendingLinkage:
- case GlobalValue::DLLImportLinkage:
- case GlobalValue::DLLExportLinkage:
- case GlobalValue::GhostLinkage:
- case GlobalValue::CommonLinkage:
- return ExternalStrong;
+} // end anonymous namespace
+
+char MergeFunctions::ID = 0;
+INITIALIZE_PASS(MergeFunctions, "mergefunc", "Merge Functions", false, false)
+
+ModulePass *llvm::createMergeFunctionsPass() {
+ return new MergeFunctions();
+}
+
+bool MergeFunctions::runOnModule(Module &M) {
+ bool Changed = false;
+ DataLayoutPass *DLP = getAnalysisIfAvailable<DataLayoutPass>();
+ DL = DLP ? &DLP->getDataLayout() : 0;
+
+ for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
+ if (!I->isDeclaration() && !I->hasAvailableExternallyLinkage())
+ Deferred.push_back(WeakVH(I));
+ }
+ FnSet.resize(Deferred.size());
+
+ do {
+ std::vector<WeakVH> Worklist;
+ Deferred.swap(Worklist);
+
+ DEBUG(dbgs() << "size of module: " << M.size() << '\n');
+ DEBUG(dbgs() << "size of worklist: " << Worklist.size() << '\n');
+
+ // Insert only strong functions and merge them. Strong function merging
+ // always deletes one of them.
+ for (std::vector<WeakVH>::iterator I = Worklist.begin(),
+ E = Worklist.end(); I != E; ++I) {
+ if (!*I) continue;
+ Function *F = cast<Function>(*I);
+ if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage() &&
+ !F->mayBeOverridden()) {
+ ComparableFunction CF = ComparableFunction(F, DL);
+ Changed |= insert(CF);
+ }
+ }
+
+ // Insert only weak functions and merge them. By doing these second we
+ // create thunks to the strong function when possible. When two weak
+ // functions are identical, we create a new strong function with two weak
+ // weak thunks to it which are identical but not mergable.
+ for (std::vector<WeakVH>::iterator I = Worklist.begin(),
+ E = Worklist.end(); I != E; ++I) {
+ if (!*I) continue;
+ Function *F = cast<Function>(*I);
+ if (!F->isDeclaration() && !F->hasAvailableExternallyLinkage() &&
+ F->mayBeOverridden()) {
+ ComparableFunction CF = ComparableFunction(F, DL);
+ Changed |= insert(CF);
+ }
+ }
+ DEBUG(dbgs() << "size of FnSet: " << FnSet.size() << '\n');
+ } while (!Deferred.empty());
+
+ FnSet.clear();
+
+ return Changed;
+}
+
+bool DenseMapInfo<ComparableFunction>::isEqual(const ComparableFunction &LHS,
+ const ComparableFunction &RHS) {
+ if (LHS.getFunc() == RHS.getFunc() &&
+ LHS.getHash() == RHS.getHash())
+ return true;
+ if (!LHS.getFunc() || !RHS.getFunc())
+ return false;
+
+ // One of these is a special "underlying pointer comparison only" object.
+ if (LHS.getDataLayout() == ComparableFunction::LookupOnly ||
+ RHS.getDataLayout() == ComparableFunction::LookupOnly)
+ return false;
+
+ assert(LHS.getDataLayout() == RHS.getDataLayout() &&
+ "Comparing functions for different targets");
+
+ return FunctionComparator(LHS.getDataLayout(), LHS.getFunc(),
+ RHS.getFunc()).compare();
+}
+
+// Replace direct callers of Old with New.
+void MergeFunctions::replaceDirectCallers(Function *Old, Function *New) {
+ Constant *BitcastNew = ConstantExpr::getBitCast(New, Old->getType());
+ for (auto UI = Old->use_begin(), UE = Old->use_end(); UI != UE;) {
+ Use *U = &*UI;
+ ++UI;
+ CallSite CS(U->getUser());
+ if (CS && CS.isCallee(U)) {
+ remove(CS.getInstruction()->getParent()->getParent());
+ U->set(BitcastNew);
+ }
+ }
+}
+
+// Replace G with an alias to F if possible, or else a thunk to F. Deletes G.
+void MergeFunctions::writeThunkOrAlias(Function *F, Function *G) {
+ if (HasGlobalAliases && G->hasUnnamedAddr()) {
+ if (G->hasExternalLinkage() || G->hasLocalLinkage() ||
+ G->hasWeakLinkage()) {
+ writeAlias(F, G);
+ return;
+ }
}
- llvm_unreachable("Unknown LinkageType.");
- return ExternalWeak;
+ writeThunk(F, G);
+}
+
+// Helper for writeThunk,
+// Selects proper bitcast operation,
+// but a bit simpler then CastInst::getCastOpcode.
+static Value* createCast(IRBuilder<false> &Builder, Value *V, Type *DestTy) {
+ Type *SrcTy = V->getType();
+ if (SrcTy->isIntegerTy() && DestTy->isPointerTy())
+ return Builder.CreateIntToPtr(V, DestTy);
+ else if (SrcTy->isPointerTy() && DestTy->isIntegerTy())
+ return Builder.CreatePtrToInt(V, DestTy);
+ else
+ return Builder.CreateBitCast(V, DestTy);
}
-static void ThunkGToF(Function *F, Function *G) {
+// Replace G with a simple tail call to bitcast(F). Also replace direct uses
+// of G with bitcast(F). Deletes G.
+void MergeFunctions::writeThunk(Function *F, Function *G) {
+ if (!G->mayBeOverridden()) {
+ // Redirect direct callers of G to F.
+ replaceDirectCallers(G, F);
+ }
+
+ // If G was internal then we may have replaced all uses of G with F. If so,
+ // stop here and delete G. There's no need for a thunk.
+ if (G->hasLocalLinkage() && G->use_empty()) {
+ G->eraseFromParent();
+ return;
+ }
+
Function *NewG = Function::Create(G->getFunctionType(), G->getLinkage(), "",
G->getParent());
- BasicBlock *BB = BasicBlock::Create("", NewG);
+ BasicBlock *BB = BasicBlock::Create(F->getContext(), "", NewG);
+ IRBuilder<false> Builder(BB);
- std::vector<Value *> Args;
+ SmallVector<Value *, 16> Args;
unsigned i = 0;
- const FunctionType *FFTy = F->getFunctionType();
+ FunctionType *FFTy = F->getFunctionType();
for (Function::arg_iterator AI = NewG->arg_begin(), AE = NewG->arg_end();
AI != AE; ++AI) {
- if (FFTy->getParamType(i) == AI->getType())
- Args.push_back(AI);
- else {
- Value *BCI = new BitCastInst(AI, FFTy->getParamType(i), "", BB);
- Args.push_back(BCI);
- }
+ Args.push_back(createCast(Builder, (Value*)AI, FFTy->getParamType(i)));
++i;
}
- CallInst *CI = CallInst::Create(F, Args.begin(), Args.end(), "", BB);
+ CallInst *CI = Builder.CreateCall(F, Args);
CI->setTailCall();
CI->setCallingConv(F->getCallingConv());
- if (NewG->getReturnType() == Type::VoidTy) {
- ReturnInst::Create(BB);
- } else if (CI->getType() != NewG->getReturnType()) {
- Value *BCI = new BitCastInst(CI, NewG->getReturnType(), "", BB);
- ReturnInst::Create(BCI, BB);
+ if (NewG->getReturnType()->isVoidTy()) {
+ Builder.CreateRetVoid();
} else {
- ReturnInst::Create(CI, BB);
+ Builder.CreateRet(createCast(Builder, CI, NewG->getReturnType()));
}
NewG->copyAttributesFrom(G);
NewG->takeName(G);
+ removeUsers(G);
G->replaceAllUsesWith(NewG);
G->eraseFromParent();
- // TODO: look at direct callers to G and make them all direct callers to F.
+ DEBUG(dbgs() << "writeThunk: " << NewG->getName() << '\n');
+ ++NumThunksWritten;
}
-static void AliasGToF(Function *F, Function *G) {
- if (!G->hasExternalLinkage() && !G->hasLocalLinkage() && !G->hasWeakLinkage())
- return ThunkGToF(F, G);
-
- GlobalAlias *GA = new GlobalAlias(
- G->getType(), G->getLinkage(), "",
- F->getContext().getConstantExprBitCast(F, G->getType()), G->getParent());
+// Replace G with an alias to F and delete G.
+void MergeFunctions::writeAlias(Function *F, Function *G) {
+ Constant *BitcastF = ConstantExpr::getBitCast(F, G->getType());
+ GlobalAlias *GA = new GlobalAlias(G->getType(), G->getLinkage(), "",
+ BitcastF, G->getParent());
F->setAlignment(std::max(F->getAlignment(), G->getAlignment()));
GA->takeName(G);
GA->setVisibility(G->getVisibility());
+ removeUsers(G);
G->replaceAllUsesWith(GA);
G->eraseFromParent();
-}
-
-static bool fold(std::vector<Function *> &FnVec, unsigned i, unsigned j) {
- Function *F = FnVec[i];
- Function *G = FnVec[j];
-
- LinkageCategory catF = categorize(F);
- LinkageCategory catG = categorize(G);
-
- if (catF == ExternalWeak || (catF == Internal && catG == ExternalStrong)) {
- std::swap(FnVec[i], FnVec[j]);
- std::swap(F, G);
- std::swap(catF, catG);
- }
- switch (catF) {
- case ExternalStrong:
- switch (catG) {
- case ExternalStrong:
- case ExternalWeak:
- ThunkGToF(F, G);
- break;
- case Internal:
- if (G->hasAddressTaken())
- ThunkGToF(F, G);
- else
- AliasGToF(F, G);
- break;
- }
- break;
+ DEBUG(dbgs() << "writeAlias: " << GA->getName() << '\n');
+ ++NumAliasesWritten;
+}
- case ExternalWeak: {
- assert(catG == ExternalWeak);
+// Merge two equivalent functions. Upon completion, Function G is deleted.
+void MergeFunctions::mergeTwoFunctions(Function *F, Function *G) {
+ if (F->mayBeOverridden()) {
+ assert(G->mayBeOverridden());
+ if (HasGlobalAliases) {
// Make them both thunks to the same internal function.
- F->setAlignment(std::max(F->getAlignment(), G->getAlignment()));
Function *H = Function::Create(F->getFunctionType(), F->getLinkage(), "",
F->getParent());
H->copyAttributesFrom(F);
H->takeName(F);
+ removeUsers(F);
F->replaceAllUsesWith(H);
- ThunkGToF(F, G);
- ThunkGToF(F, H);
-
- F->setLinkage(GlobalValue::InternalLinkage);
- } break;
-
- case Internal:
- switch (catG) {
- case ExternalStrong:
- llvm_unreachable(0);
- // fall-through
- case ExternalWeak:
- if (F->hasAddressTaken())
- ThunkGToF(F, G);
- else
- AliasGToF(F, G);
- break;
- case Internal: {
- bool addrTakenF = F->hasAddressTaken();
- bool addrTakenG = G->hasAddressTaken();
- if (!addrTakenF && addrTakenG) {
- std::swap(FnVec[i], FnVec[j]);
- std::swap(F, G);
- std::swap(addrTakenF, addrTakenG);
- }
-
- if (addrTakenF && addrTakenG) {
- ThunkGToF(F, G);
- } else {
- assert(!addrTakenG);
- AliasGToF(F, G);
- }
- } break;
- }
- break;
+ unsigned MaxAlignment = std::max(G->getAlignment(), H->getAlignment());
+
+ writeAlias(F, G);
+ writeAlias(F, H);
+
+ F->setAlignment(MaxAlignment);
+ F->setLinkage(GlobalValue::PrivateLinkage);
+ } else {
+ // We can't merge them. Instead, pick one and update all direct callers
+ // to call it and hope that we improve the instruction cache hit rate.
+ replaceDirectCallers(G, F);
+ }
+
+ ++NumDoubleWeak;
+ } else {
+ writeThunkOrAlias(F, G);
}
++NumFunctionsMerged;
- return true;
}
-// ===----------------------------------------------------------------------===
-// Pass definition
-// ===----------------------------------------------------------------------===
+// Insert a ComparableFunction into the FnSet, or merge it away if equal to one
+// that was already inserted.
+bool MergeFunctions::insert(ComparableFunction &NewF) {
+ std::pair<FnSetType::iterator, bool> Result = FnSet.insert(NewF);
+ if (Result.second) {
+ DEBUG(dbgs() << "Inserting as unique: " << NewF.getFunc()->getName() << '\n');
+ return false;
+ }
-bool MergeFunctions::runOnModule(Module &M) {
- bool Changed = false;
+ const ComparableFunction &OldF = *Result.first;
- std::map<unsigned long, std::vector<Function *> > FnMap;
+ // Don't merge tiny functions, since it can just end up making the function
+ // larger.
+ // FIXME: Should still merge them if they are unnamed_addr and produce an
+ // alias.
+ if (NewF.getFunc()->size() == 1) {
+ if (NewF.getFunc()->front().size() <= 2) {
+ DEBUG(dbgs() << NewF.getFunc()->getName()
+ << " is to small to bother merging\n");
+ return false;
+ }
+ }
- for (Module::iterator F = M.begin(), E = M.end(); F != E; ++F) {
- if (F->isDeclaration() || F->isIntrinsic())
- continue;
+ // Never thunk a strong function to a weak function.
+ assert(!OldF.getFunc()->mayBeOverridden() ||
+ NewF.getFunc()->mayBeOverridden());
- FnMap[hash(F)].push_back(F);
- }
+ DEBUG(dbgs() << " " << OldF.getFunc()->getName() << " == "
+ << NewF.getFunc()->getName() << '\n');
- // TODO: instead of running in a loop, we could also fold functions in
- // callgraph order. Constructing the CFG probably isn't cheaper than just
- // running in a loop, unless it happened to already be available.
+ Function *DeleteF = NewF.getFunc();
+ NewF.release();
+ mergeTwoFunctions(OldF.getFunc(), DeleteF);
+ return true;
+}
- bool LocalChanged;
- do {
- LocalChanged = false;
- DOUT << "size: " << FnMap.size() << "\n";
- for (std::map<unsigned long, std::vector<Function *> >::iterator
- I = FnMap.begin(), E = FnMap.end(); I != E; ++I) {
- std::vector<Function *> &FnVec = I->second;
- DOUT << "hash (" << I->first << "): " << FnVec.size() << "\n";
-
- for (int i = 0, e = FnVec.size(); i != e; ++i) {
- for (int j = i + 1; j != e; ++j) {
- bool isEqual = equals(FnVec[i], FnVec[j]);
-
- DEBUG(errs() << " " << FnVec[i]->getName()
- << (isEqual ? " == " : " != ")
- << FnVec[j]->getName() << "\n");
-
- if (isEqual) {
- if (fold(FnVec, i, j)) {
- LocalChanged = true;
- FnVec.erase(FnVec.begin() + j);
- --j, --e;
- }
- }
- }
- }
+// Remove a function from FnSet. If it was already in FnSet, add it to Deferred
+// so that we'll look at it in the next round.
+void MergeFunctions::remove(Function *F) {
+ // We need to make sure we remove F, not a function "equal" to F per the
+ // function equality comparator.
+ //
+ // The special "lookup only" ComparableFunction bypasses the expensive
+ // function comparison in favour of a pointer comparison on the underlying
+ // Function*'s.
+ ComparableFunction CF = ComparableFunction(F, ComparableFunction::LookupOnly);
+ if (FnSet.erase(CF)) {
+ DEBUG(dbgs() << "Removed " << F->getName() << " from set and deferred it.\n");
+ Deferred.push_back(F);
+ }
+}
+// For each instruction used by the value, remove() the function that contains
+// the instruction. This should happen right before a call to RAUW.
+void MergeFunctions::removeUsers(Value *V) {
+ std::vector<Value *> Worklist;
+ Worklist.push_back(V);
+ while (!Worklist.empty()) {
+ Value *V = Worklist.back();
+ Worklist.pop_back();
+
+ for (User *U : V->users()) {
+ if (Instruction *I = dyn_cast<Instruction>(U)) {
+ remove(I->getParent()->getParent());
+ } else if (isa<GlobalValue>(U)) {
+ // do nothing
+ } else if (Constant *C = dyn_cast<Constant>(U)) {
+ for (User *UU : C->users())
+ Worklist.push_back(UU);
+ }
}
- Changed |= LocalChanged;
- } while (LocalChanged);
-
- return Changed;
+ }
}
projects / oota-llvm.git / blobdiff