[objc-arc] Apply the RV optimization to retains next to calls in ObjCARCContract...

[oota-llvm.git] / lib / Transforms / ObjCARC / ObjCARCContract.cpp

diff --git a/lib/Transforms/ObjCARC/ObjCARCContract.cpp b/lib/Transforms/ObjCARC/ObjCARCContract.cpp
index 7d1768ab9270338b3484389b6232c7ed4a9a5b61..c43f4f4a4431b23a3ca831d91d62ac60959e78f1 100644 (file)
--- a/lib/Transforms/ObjCARC/ObjCARCContract.cpp
+++ b/lib/Transforms/ObjCARC/ObjCARCContract.cpp
@@ -1,4 +1,4 @@
-//===- ObjCARCOpts.cpp - ObjC ARC Optimization ----------------------------===//
+//===- ObjCARCContract.cpp - ObjC ARC Optimization ------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
@@ -11,6 +11,9 @@
 /// Reference Counting and is a system for managing reference counts for objects
 /// in Objective C.
 ///
+/// This specific file mainly deals with ``contracting'' multiple lower level
+/// operations into singular higher level operations through pattern matching.
+///
 /// WARNING: This file knows about certain library functions. It recognizes them
 /// by name, and hardwires knowledge of their semantics.
 ///
@@ -63,6 +66,8 @@ namespace {
     Constant *RetainAutoreleaseCallee;
     /// Declaration for objc_retainAutoreleaseReturnValue().
     Constant *RetainAutoreleaseRVCallee;
+    /// Declaration for objc_retainAutoreleasedReturnValue().
+    Constant *RetainRVCallee;
 
     /// The inline asm string to insert between calls and RetainRV calls to make
     /// the optimization work on targets which need it.
@@ -74,9 +79,12 @@ namespace {
     SmallPtrSet<CallInst *, 8> StoreStrongCalls;
 
     Constant *getStoreStrongCallee(Module *M);
+    Constant *getRetainRVCallee(Module *M);
     Constant *getRetainAutoreleaseCallee(Module *M);
     Constant *getRetainAutoreleaseRVCallee(Module *M);
 
+    bool OptimizeRetainCall(Function &F, Instruction *Retain);
+
     bool ContractAutorelease(Function &F, Instruction *Autorelease,
                              InstructionClass Class,
                              SmallPtrSet<Instruction *, 4>
@@ -169,6 +177,57 @@ Constant *ObjCARCContract::getRetainAutoreleaseRVCallee(Module *M) {
   return RetainAutoreleaseRVCallee;
 }
 
+Constant *ObjCARCContract::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;
+}
+
+/// Turn objc_retain into objc_retainAutoreleasedReturnValue if the operand is a
+/// return value. We do this late so we do not disrupt the dataflow analysis in
+/// ObjCARCOpt.
+bool
+ObjCARCContract::OptimizeRetainCall(Function &F, Instruction *Retain) {
+  ImmutableCallSite CS(GetObjCArg(Retain));
+  const Instruction *Call = CS.getInstruction();
+  if (!Call)
+    return false;
+  if (Call->getParent() != Retain->getParent())
+    return false;
+
+  // Check that the call is next to the retain.
+  BasicBlock::const_iterator I = Call;
+  ++I;
+  while (IsNoopInstruction(I)) ++I;
+  if (&*I != Retain)
+    return false;
+
+  // Turn it to an objc_retainAutoreleasedReturnValue.
+  Changed = true;
+  ++NumPeeps;
+
+  DEBUG(dbgs() << "Transforming objc_retain => "
+                  "objc_retainAutoreleasedReturnValue since the operand is a "
+                  "return value.\nOld: "<< *Retain << "\n");
+
+  // We do not have to worry about tail calls/does not throw since
+  // retain/retainRV have the same properties.
+  cast<CallInst>(Retain)->setCalledFunction(getRetainRVCallee(F.getParent()));
+
+  DEBUG(dbgs() << "New: " << *Retain << "\n");
+  return true;
+}
+
 /// Merge an autorelease with a retain into a fused call.
 bool
 ObjCARCContract::ContractAutorelease(Function &F, Instruction *Autorelease,
@@ -326,6 +385,7 @@ bool ObjCARCContract::doInitialization(Module &M) {
   StoreStrongCallee = 0;
   RetainAutoreleaseCallee = 0;
   RetainAutoreleaseRVCallee = 0;
+  RetainRVCallee = 0;
 
   // Initialize RetainRVMarker.
   RetainRVMarker = 0;
@@ -377,7 +437,6 @@ bool ObjCARCContract::runOnFunction(Function &F) {
     // objc_retainBlock does not necessarily return its argument.
     InstructionClass Class = GetBasicInstructionClass(Inst);
     switch (Class) {
-    case IC_Retain:
     case IC_FusedRetainAutorelease:
     case IC_FusedRetainAutoreleaseRV:
       break;
@@ -386,6 +445,13 @@ bool ObjCARCContract::runOnFunction(Function &F) {
       if (ContractAutorelease(F, Inst, Class, DependingInstructions, Visited))
         continue;
       break;
+    case IC_Retain:
+      // Attempt to convert retains to retainrvs if they are next to function
+      // calls.
+      if (!OptimizeRetainCall(F, Inst))
+        break;
+      // If we succeed in our optimization, fall through.
+      // FALLTHROUGH
     case IC_RetainRV: {
       // If we're compiling for a target which needs a special inline-asm
       // marker to do the retainAutoreleasedReturnValue optimization,
@@ -407,7 +473,7 @@ bool ObjCARCContract::runOnFunction(Function &F) {
           break;
         }
         --BBI;
-      } while (isNoopInstruction(BBI));
+      } while (IsNoopInstruction(BBI));
 
       if (&*BBI == GetObjCArg(Inst)) {
         DEBUG(dbgs() << "ObjCARCContract: Adding inline asm marker for "
@@ -426,7 +492,7 @@ bool ObjCARCContract::runOnFunction(Function &F) {
     case IC_InitWeak: {
       // objc_initWeak(p, null) => *p = null
       CallInst *CI = cast<CallInst>(Inst);
-      if (isNullOrUndef(CI->getArgOperand(1))) {
+      if (IsNullOrUndef(CI->getArgOperand(1))) {
         Value *Null =
           ConstantPointerNull::get(cast<PointerType>(CI->getType()));
         Changed = true;
@@ -450,6 +516,10 @@ bool ObjCARCContract::runOnFunction(Function &F) {
       if (isa<AllocaInst>(Inst))
         TailOkForStoreStrongs = false;
       continue;
+    case IC_IntrinsicUser:
+      // Remove calls to @clang.arc.use(...).
+      Inst->eraseFromParent();
+      continue;
     default:
       continue;
     }