diff options
Diffstat (limited to 'lib/CodeGen/CGCall.cpp')
-rw-r--r-- | lib/CodeGen/CGCall.cpp | 25 |
1 files changed, 25 insertions, 0 deletions
diff --git a/lib/CodeGen/CGCall.cpp b/lib/CodeGen/CGCall.cpp index 9e97bce6c3..9318973e64 100644 --- a/lib/CodeGen/CGCall.cpp +++ b/lib/CodeGen/CGCall.cpp @@ -1614,6 +1614,18 @@ static llvm::StoreInst *findDominatingStoreToReturnValue(CodeGenFunction &CGF) { return store; } +/// Check whether 'this' argument of a callsite matches 'this' of the caller. +static bool checkThisPointer(llvm::Value *ThisArg, llvm::Value *This) { + if (ThisArg == This) + return true; + // Check whether ThisArg is a bitcast of This. + llvm::BitCastInst *Bitcast; + if ((Bitcast = dyn_cast<llvm::BitCastInst>(ThisArg)) && + Bitcast->getOperand(0) == This) + return true; + return false; +} + void CodeGenFunction::EmitFunctionEpilog(const CGFunctionInfo &FI) { // Functions with no result always return void. if (ReturnValue == 0) { @@ -1705,6 +1717,19 @@ void CodeGenFunction::EmitFunctionEpilog(const CGFunctionInfo &FI) { llvm_unreachable("Invalid ABI kind for return argument"); } + // If this function returns 'this', the last instruction is a CallInst + // that returns 'this', and 'this' argument of the CallInst points to + // the same object as CXXThisValue, use the return value from the CallInst. + // We will not need to keep 'this' alive through the callsite. It also enables + // optimizations in the backend, such as tail call optimization. + if (CalleeWithThisReturn && CGM.getCXXABI().HasThisReturn(CurGD)) { + llvm::BasicBlock *IP = Builder.GetInsertBlock(); + llvm::CallInst *Callsite; + if (!IP->empty() && (Callsite = dyn_cast<llvm::CallInst>(&IP->back())) && + Callsite->getCalledFunction() == CalleeWithThisReturn && + checkThisPointer(Callsite->getOperand(0), CXXThisValue)) + RV = Builder.CreateBitCast(Callsite, RetAI.getCoerceToType()); + } llvm::Instruction *Ret = RV ? Builder.CreateRet(RV) : Builder.CreateRetVoid(); if (!RetDbgLoc.isUnknown()) Ret->setDebugLoc(RetDbgLoc); |