commit d4c0cd07641681de6ed12164aa7a4495ab4b18e5
author Stephen Lin <stephenwlin@gmail.com> Tue Jun 18 17:00:49 2013 +0000
committer Stephen Lin <stephenwlin@gmail.com> Tue Jun 18 17:00:49 2013 +0000
tree e2bc6e9ebbd9dd2314d84a3302a1b803c7c17faa
parent 52fdc568e9412f0afe401fb36eac93814846650a

CodeGen: Have 'this'-returning constructors and destructors to take advantage of the new backend 'returned' attribute.

The backend will now use the generic 'returned' attribute to form tail calls where possible, as well as avoid save-restores of 'this' in some cases (specifically the cases that matter for the ARM C++ ABI).

This patch also reverts a prior front-end only partial implementation of these optimizations, since it's no longer required.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@184205 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/CodeGenFunction.cpp

diff --git a/lib/CodeGen/CodeGenFunction.cpp b/lib/CodeGen/CodeGenFunction.cpp
index 297fc65..e8469e6 100644
--- a/lib/CodeGen/CodeGenFunction.cpp
+++ b/lib/CodeGen/CodeGenFunction.cpp
@@ -42,8 +42,7 @@
     AutoreleaseResult(false), BlockInfo(0), BlockPointer(0),
     LambdaThisCaptureField(0), NormalCleanupDest(0), NextCleanupDestIndex(1),
     FirstBlockInfo(0), EHResumeBlock(0), ExceptionSlot(0), EHSelectorSlot(0),
-    DebugInfo(0), DisableDebugInfo(false), CalleeWithThisReturn(0),
-    DidCallStackSave(false),
+    DebugInfo(0), DisableDebugInfo(false), DidCallStackSave(false),
     IndirectBranch(0), SwitchInsn(0), CaseRangeBlock(0), UnreachableBlock(0),
     NumReturnExprs(0), NumSimpleReturnExprs(0),
     CXXABIThisDecl(0), CXXABIThisValue(0), CXXThisValue(0),
@@ -662,8 +661,12 @@
   QualType ResTy = FD->getResultType();
 
   CurGD = GD;
-  if (isa<CXXMethodDecl>(FD) && cast<CXXMethodDecl>(FD)->isInstance())
+  const CXXMethodDecl *MD;
+  if ((MD = dyn_cast<CXXMethodDecl>(FD)) && MD->isInstance()) {
+    if (CGM.getCXXABI().HasThisReturn(GD))
+      ResTy = MD->getThisType(getContext());
     CGM.getCXXABI().BuildInstanceFunctionParams(*this, ResTy, Args);
+  }
 
   for (unsigned i = 0, e = FD->getNumParams(); i != e; ++i)
     Args.push_back(FD->getParamDecl(i));
@@ -672,10 +675,6 @@
   if (Stmt *Body = FD->getBody()) BodyRange = Body->getSourceRange();
   CurEHLocation = BodyRange.getEnd();
 
-  // 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());
 
@@ -727,9 +726,6 @@
 
   // 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.