If call result is in ST0 and it is not being passed to the caller's
caller, then it is not safe to optimize the call into a sibcall since
the call result has to be popped off the x87 stack.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@99032 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Target/X86/X86ISelLowering.cpp b/lib/Target/X86/X86ISelLowering.cpp
index 7d2140b..704f9c6 100644
--- a/lib/Target/X86/X86ISelLowering.cpp
+++ b/lib/Target/X86/X86ISelLowering.cpp
@@ -2310,6 +2310,28 @@
if (isCalleeStructRet || isCallerStructRet)
return false;
+ // If the call result is in ST0 / ST1, it needs to be popped off the x87 stack.
+ // Therefore if it's not used by the call it is not safe to optimize this into
+ // a sibcall.
+ bool Unused = false;
+ for (unsigned i = 0, e = Ins.size(); i != e; ++i) {
+ if (!Ins[i].Used) {
+ Unused = true;
+ break;
+ }
+ }
+ if (Unused) {
+ SmallVector<CCValAssign, 16> RVLocs;
+ CCState CCInfo(CalleeCC, false, getTargetMachine(),
+ RVLocs, *DAG.getContext());
+ CCInfo.AnalyzeCallResult(Ins, RetCC_X86);
+ for (unsigned i = 0; i != RVLocs.size(); ++i) {
+ CCValAssign &VA = RVLocs[i];
+ if (VA.getLocReg() == X86::ST0 || VA.getLocReg() == X86::ST1)
+ return false;
+ }
+ }
+
// If the callee takes no arguments then go on to check the results of the
// call.
if (!Outs.empty()) {