[PowerPC] Don't mark the return-address slot as immutable

It is tempting to mark the fixed stack slot used to store the return address as
immutable when lowering @llvm.returnaddress(i32 0). Unfortunately, within the
function, it is not completely immutable: it is written during the function
prologue. When using post-RA instruction scheduling, the prologue instructions
are available for scheduling, and we're not free to interchange the order of a
particular store in the prologue with loads from that stack location.

Fixes PR21976.

llvm-svn: 224761

1 files changed, 1 insertions, 1 deletions

diff --git a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
index 18384627ced..06cf9af80b6 100644
--- a/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
+++ b/llvm/lib/Target/PowerPC/PPCISelLowering.cpp
@@ -5164,7 +5164,7 @@ PPCTargetLowering::getReturnAddrFrameIndex(SelectionDAG & DAG) const {
     // Find out what the fix offset of the frame pointer save area.
     int LROffset = PPCFrameLowering::getReturnSaveOffset(isPPC64, isDarwinABI);
     // Allocate the frame index for frame pointer save area.
-    RASI = MF.getFrameInfo()->CreateFixedObject(isPPC64? 8 : 4, LROffset, true);
+    RASI = MF.getFrameInfo()->CreateFixedObject(isPPC64? 8 : 4, LROffset, false);
     // Save the result.
     FI->setReturnAddrSaveIndex(RASI);
   }