[llvm] r224761 - [PowerPC] Don't mark the return-address slot as immutable

[Hal Finkel]

Author: hfinkel
Date: Tue Dec 23 03:45:06 2014
New Revision: 224761

URL: http://llvm.org/viewvc/llvm-project?rev=224761&view=rev
Log:
[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.

Added:
    llvm/trunk/test/CodeGen/PowerPC/retaddr2.ll
Modified:
    llvm/trunk/lib/Target/PowerPC/PPCISelLowering.cpp

Modified: llvm/trunk/lib/Target/PowerPC/PPCISelLowering.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/PowerPC/PPCISelLowering.cpp?rev=224761&r1=224760&r2=224761&view=diff
==============================================================================
--- llvm/trunk/lib/Target/PowerPC/PPCISelLowering.cpp (original)
+++ llvm/trunk/lib/Target/PowerPC/PPCISelLowering.cpp Tue Dec 23 03:45:06 2014
@@ -5164,7 +5164,7 @@ PPCTargetLowering::getReturnAddrFrameInd
     // 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);
   }

Added: llvm/trunk/test/CodeGen/PowerPC/retaddr2.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/PowerPC/retaddr2.ll?rev=224761&view=auto
==============================================================================
--- llvm/trunk/test/CodeGen/PowerPC/retaddr2.ll (added)
+++ llvm/trunk/test/CodeGen/PowerPC/retaddr2.ll Tue Dec 23 03:45:06 2014
@@ -0,0 +1,25 @@
+; RUN: llc -mcpu=pwr7 < %s | FileCheck %s
+target datalayout = "E-m:e-i64:64-n32:64"
+target triple = "powerpc64-unknown-linux-gnu"
+
+; Function Attrs: nounwind readnone
+define i8* @test1() #0 {
+entry:
+  %0 = tail call i8* @llvm.returnaddress(i32 0)
+  ret i8* %0
+}
+
+; CHECK-LABEL: @test1
+; CHECK: mflr 0
+; CHECK: std 0, 16(1)
+; FIXME: These next two lines don't both need to load the same value.
+; CHECK-DAG: ld 3, 16(1)
+; CHECK-DAG: ld 0, 16(1)
+; CHECK: mtlr 0
+; CHECK: blr
+
+; Function Attrs: nounwind readnone
+declare i8* @llvm.returnaddress(i32) #0
+
+attributes #0 = { nounwind readnone }
+