From 58dd990c112ada1d37813f95fe4a929dee46a476 Mon Sep 17 00:00:00 2001 From: Manman Ren Date: Sat, 16 Mar 2013 00:11:09 +0000 Subject: Exploit this-return of a callsite in a this-return function. For constructors/desctructors that return 'this', if there exists a callsite that returns 'this' and is immediately before the return instruction, make sure we are using the return value from the callsite. We don't need to keep 'this' alive through the callsite. It also enables optimizations in the backend, such as tail call optimization. rdar://12818789 llvm-svn: 177211 --- clang/lib/CodeGen/CGClass.cpp | 17 +++++++++++++---- 1 file changed, 13 insertions(+), 4 deletions(-) (limited to 'clang/lib/CodeGen/CGClass.cpp') diff --git a/clang/lib/CodeGen/CGClass.cpp b/clang/lib/CodeGen/CGClass.cpp index 287d164cb99..2ececb03651 100644 --- a/clang/lib/CodeGen/CGClass.cpp +++ b/clang/lib/CodeGen/CGClass.cpp @@ -1666,8 +1666,11 @@ CodeGenFunction::EmitCXXConstructorCall(const CXXConstructorDecl *D, } // Non-trivial constructors are handled in an ABI-specific manner. - CGM.getCXXABI().EmitConstructorCall(*this, D, Type, ForVirtualBase, - Delegating, This, ArgBeg, ArgEnd); + llvm::Value *Callee = CGM.getCXXABI().EmitConstructorCall(*this, D, Type, + ForVirtualBase, Delegating, This, ArgBeg, ArgEnd); + if (CGM.getCXXABI().HasThisReturn(CurGD) && + CGM.getCXXABI().HasThisReturn(GlobalDecl(D, Type))) + CalleeWithThisReturn = Callee; } void @@ -1756,9 +1759,12 @@ CodeGenFunction::EmitDelegateCXXConstructorCall(const CXXConstructorDecl *Ctor, EmitDelegateCallArg(DelegateArgs, param); } + llvm::Value *Callee = CGM.GetAddrOfCXXConstructor(Ctor, CtorType); EmitCall(CGM.getTypes().arrangeCXXConstructorDeclaration(Ctor, CtorType), - CGM.GetAddrOfCXXConstructor(Ctor, CtorType), - ReturnValueSlot(), DelegateArgs, Ctor); + Callee, ReturnValueSlot(), DelegateArgs, Ctor); + if (CGM.getCXXABI().HasThisReturn(CurGD) && + CGM.getCXXABI().HasThisReturn(GlobalDecl(Ctor, CtorType))) + CalleeWithThisReturn = Callee; } namespace { @@ -1825,6 +1831,9 @@ void CodeGenFunction::EmitCXXDestructorCall(const CXXDestructorDecl *DD, EmitCXXMemberCall(DD, SourceLocation(), Callee, ReturnValueSlot(), This, VTT, getContext().getPointerType(getContext().VoidPtrTy), 0, 0); + if (CGM.getCXXABI().HasThisReturn(CurGD) && + CGM.getCXXABI().HasThisReturn(GlobalDecl(DD, Type))) + CalleeWithThisReturn = Callee; } namespace { -- cgit v1.2.3