From 8a4f9390d0dddc2198f82b7f6bc01cc8abda11ba Mon Sep 17 00:00:00 2001
From: Tanya Lattner <tonic@nondot.org>
Date: Tue, 23 Mar 2010 17:06:56 +0000
Subject: [PATCH] Merge 98561 from mainline. Avoid sibcall optimization if
 either caller or callee is using sret semantics.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/branches/release_27@99290 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/X86/X86ISelLowering.cpp | 13 ++++++++++---
 lib/Target/X86/X86ISelLowering.h   |  2 ++
 2 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index f75df6c8f8f..9c40a7007fe 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -1477,7 +1477,6 @@ X86TargetLowering::LowerFormalArguments(SDValue Chain,
                                         DebugLoc dl,
                                         SelectionDAG &DAG,
                                         SmallVectorImpl<SDValue> &InVals) {
-
   MachineFunction &MF = DAG.getMachineFunction();
   X86MachineFunctionInfo *FuncInfo = MF.getInfo<X86MachineFunctionInfo>();
 
@@ -1779,7 +1778,8 @@ X86TargetLowering::LowerCall(SDValue Chain, SDValue Callee,
 
   if (isTailCall) {
     // Check if it's really possible to do a tail call.
-    isTailCall = IsEligibleForTailCallOptimization(Callee, CallConv, isVarArg,
+    isTailCall = IsEligibleForTailCallOptimization(Callee, CallConv,
+                    isVarArg, IsStructRet, MF.getFunction()->hasStructRetAttr(),
                                                    Outs, Ins, DAG);
 
     // Sibcalls are automatically detected tailcalls which do not require
@@ -2297,6 +2297,8 @@ bool
 X86TargetLowering::IsEligibleForTailCallOptimization(SDValue Callee,
                                                      CallingConv::ID CalleeCC,
                                                      bool isVarArg,
+                                                     bool isCalleeStructRet,
+                                                     bool isCallerStructRet,
                                     const SmallVectorImpl<ISD::OutputArg> &Outs,
                                     const SmallVectorImpl<ISD::InputArg> &Ins,
                                                      SelectionDAG& DAG) const {
@@ -2316,10 +2318,15 @@ X86TargetLowering::IsEligibleForTailCallOptimization(SDValue Callee,
   // Look for obvious safe cases to perform tail call optimization that does not
   // requite ABI changes. This is what gcc calls sibcall.
 
-  // Do not tail call optimize vararg calls for now.
+  // Do not sibcall optimize vararg calls for now.
   if (isVarArg)
     return false;
 
+  // Also avoid sibcall optimization if either caller or callee uses struct
+  // return semantics.
+  if (isCalleeStructRet || isCallerStructRet)
+    return false;
+
   // If the callee takes no arguments then go on to check the results of the
   // call.
   if (!Outs.empty()) {
diff --git a/lib/Target/X86/X86ISelLowering.h b/lib/Target/X86/X86ISelLowering.h
index 4c12fcc32fd..59369754049 100644
--- a/lib/Target/X86/X86ISelLowering.h
+++ b/lib/Target/X86/X86ISelLowering.h
@@ -637,6 +637,8 @@ namespace llvm {
     bool IsEligibleForTailCallOptimization(SDValue Callee,
                                            CallingConv::ID CalleeCC,
                                            bool isVarArg,
+                                           bool isCalleeStructRet,
+                                           bool isCallerStructRet,
                                     const SmallVectorImpl<ISD::OutputArg> &Outs,
                                     const SmallVectorImpl<ISD::InputArg> &Ins,
                                            SelectionDAG& DAG) const;