Commit 2db982c4 authored by Tanya Lattner's avatar Tanya Lattner
Browse files

Merge 99032 from mainline. 

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.

llvm-svn: 99293
parent 650437f2

llvm/lib/Target/X86/X86ISelLowering.cpp

+22 −0
Original line number Diff line number Diff line
@@ -2327,6 +2327,28 @@ X86TargetLowering::IsEligibleForTailCallOptimization(SDValue Callee, 
  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()) {