Avoid unnecessary stack realignment in musttail thunks with SSE2 enabled

The X86 musttail implementation finds register parameters to forward by
running the calling convention algorithm until a non-register location
is returned. However, assigning a vector memory location has the side
effect of increasing the function's stack alignment. We shouldn't
increase the stack alignment when we are only looking for register
parameters, so this change conditionalizes it.

llvm-svn: 258442

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/CallingConvLower.cpp b/llvm/lib/CodeGen/CallingConvLower.cpp
index bdd5b5552c0..2a8a9e793ab 100644
--- a/llvm/lib/CodeGen/CallingConvLower.cpp
+++ b/llvm/lib/CodeGen/CallingConvLower.cpp
@@ -51,7 +51,7 @@ void CCState::HandleByVal(unsigned ValNo, MVT ValVT,
     Size = MinSize;
   if (MinAlign > (int)Align)
     Align = MinAlign;
-  MF.getFrameInfo()->ensureMaxAlignment(Align);
+  ensureMaxAlignment(Align);
   MF.getSubtarget().getTargetLowering()->HandleByVal(this, Size, Align);
   Size = unsigned(alignTo(Size, MinAlign));
   unsigned Offset = AllocateStack(Size, Align);
@@ -236,6 +236,7 @@ void CCState::analyzeMustTailForwardedRegisters(
   // variadic functions, so we need to assume we're not variadic so that we get
   // all the registers that might be used in a non-variadic call.
   SaveAndRestore<bool> SavedVarArg(IsVarArg, false);
+  SaveAndRestore<bool> SavedMustTail(AnalyzingMustTailForwardedRegs, true);
 
   for (MVT RegVT : RegParmTypes) {
     SmallVector<MCPhysReg, 8> RemainingRegs;