From 63fd408a61ae9b94e8d8a986832f526f7cdbfa84 Mon Sep 17 00:00:00 2001 From: Manman Ren Date: Wed, 20 Mar 2013 16:59:38 +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. Updated from r177211. rdar://12818789 git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@177541 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/CodeGen/CodeGenFunction.cpp | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'lib/CodeGen/CodeGenFunction.cpp') diff --git a/lib/CodeGen/CodeGenFunction.cpp b/lib/CodeGen/CodeGenFunction.cpp index 27ef65fa94..bd244355f0 100644 --- a/lib/CodeGen/CodeGenFunction.cpp +++ b/lib/CodeGen/CodeGenFunction.cpp @@ -564,6 +564,10 @@ void CodeGenFunction::GenerateCode(GlobalDecl GD, llvm::Function *Fn, SourceRange BodyRange; if (Stmt *Body = FD->getBody()) BodyRange = Body->getSourceRange(); + // CalleeWithThisReturn keeps track of the last callee inside this function + // that returns 'this'. Before starting the function, we set it to null. + CalleeWithThisReturn = 0; + // Emit the standard function prologue. StartFunction(GD, ResTy, Fn, FnInfo, Args, BodyRange.getBegin()); @@ -615,6 +619,9 @@ void CodeGenFunction::GenerateCode(GlobalDecl GD, llvm::Function *Fn, // Emit the standard function epilogue. FinishFunction(BodyRange.getEnd()); + // CalleeWithThisReturn keeps track of the last callee inside this function + // that returns 'this'. After finishing the function, we set it to null. + CalleeWithThisReturn = 0; // If we haven't marked the function nothrow through other means, do // a quick pass now to see if we can. -- cgit v1.2.3-18-g5258