From 1361796dd081f5d6c6be4981e7563c5e46799aa4 Mon Sep 17 00:00:00 2001
From: Evan Cheng <evan.cheng@apple.com>
Date: Fri, 30 Apr 2010 01:12:32 +0000
Subject: [PATCH] Another sibcall bug. If caller and callee calling conventions
 differ, then it's only safe to do a tail call if the results are returned in
 the same way.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@102683 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Target/X86/X86ISelLowering.cpp | 38 +++++++++++++++++++++++++++---
 test/CodeGen/X86/sibcall.ll        | 18 ++++++++++++++
 2 files changed, 53 insertions(+), 3 deletions(-)

diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 4c0c5f6d432..cdbe1ad9f2e 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -2326,9 +2326,11 @@ X86TargetLowering::IsEligibleForTailCallOptimization(SDValue Callee,
   // If -tailcallopt is specified, make fastcc functions tail-callable.
   const MachineFunction &MF = DAG.getMachineFunction();
   const Function *CallerF = DAG.getMachineFunction().getFunction();
+  CallingConv::ID CallerCC = CallerF->getCallingConv();
+  bool CCMatch = CallerCC == CalleeCC;
+
   if (GuaranteedTailCallOpt) {
-    if (IsTailCallConvention(CalleeCC) &&
-        CallerF->getCallingConv() == CalleeCC)
+    if (IsTailCallConvention(CalleeCC) && CCMatch)
       return true;
     return false;
   }
@@ -2366,13 +2368,43 @@ X86TargetLowering::IsEligibleForTailCallOptimization(SDValue Callee,
     CCState CCInfo(CalleeCC, false, getTargetMachine(),
                    RVLocs, *DAG.getContext());
     CCInfo.AnalyzeCallResult(Ins, RetCC_X86);
-    for (unsigned i = 0; i != RVLocs.size(); ++i) {
+    for (unsigned i = 0, e = RVLocs.size(); i != e; ++i) {
       CCValAssign &VA = RVLocs[i];
       if (VA.getLocReg() == X86::ST0 || VA.getLocReg() == X86::ST1)
         return false;
     }
   }
 
+  // If the calling conventions do not match, then we'd better make sure the
+  // results are returned in the same way as what the caller expects.
+  if (!CCMatch) {
+    SmallVector<CCValAssign, 16> RVLocs1;
+    CCState CCInfo1(CalleeCC, false, getTargetMachine(),
+                    RVLocs1, *DAG.getContext());
+    CCInfo1.AnalyzeCallResult(Ins, RetCC_X86);
+
+    SmallVector<CCValAssign, 16> RVLocs2;
+    CCState CCInfo2(CallerCC, false, getTargetMachine(),
+                    RVLocs2, *DAG.getContext());
+    CCInfo2.AnalyzeCallResult(Ins, RetCC_X86);
+
+    if (RVLocs1.size() != RVLocs2.size())
+      return false;
+    for (unsigned i = 0, e = RVLocs1.size(); i != e; ++i) {
+      if (RVLocs1[i].isRegLoc() != RVLocs2[i].isRegLoc())
+        return false;
+      if (RVLocs1[i].getLocInfo() != RVLocs2[i].getLocInfo())
+        return false;
+      if (RVLocs1[i].isRegLoc()) {
+        if (RVLocs1[i].getLocReg() != RVLocs2[i].getLocReg())
+          return false;
+      } else {
+        if (RVLocs1[i].getLocMemOffset() != RVLocs2[i].getLocMemOffset())
+          return false;
+      }
+    }
+  }
+
   // If the callee takes no arguments then go on to check the results of the
   // call.
   if (!Outs.empty()) {
diff --git a/test/CodeGen/X86/sibcall.ll b/test/CodeGen/X86/sibcall.ll
index 8e52a7cbfe7..ff581ae2b5e 100644
--- a/test/CodeGen/X86/sibcall.ll
+++ b/test/CodeGen/X86/sibcall.ll
@@ -313,3 +313,21 @@ entry:
 }
 
 declare void @foo()
+
+; If caller / callee calling convention mismatch then check if the return
+; values are returned in the same registers.
+; rdar://7874780
+
+define double @t20(double %x) nounwind {
+entry:
+; 32: t20:
+; 32: call {{_?}}foo20
+; 32: fldl (%esp)
+
+; 64: t20:
+; 64: jmp {{_?}}foo20
+  %0 = tail call fastcc double @foo20(double %x) nounwind
+  ret double %0
+}
+
+declare fastcc double @foo20(double) nounwind