ARM: Fix CMP_SWAP expansion

Clean up after my misguided attempt in r304267 to "fix" CMP_SWAP
returning an uninitialized status value.

- I was always using tMOVi8 to zero the status register which cannot
  encode higher register numbers and llvm would silently miscompile)

- Nobody was ever looking at that status value outside the expansion.
  ARMDAGToDAGISel::SelectCMP_SWAP() the only place creating CMP_SWAP
  instructions was not mapping anything to it. (The cmpxchg status value
  from llvm IR is lowered to a manual comparison after the CMP_SWAP)

So this:
- Renames the register from "status" to "temp" it make it obvious that
  it isn't used outside the expansion.
- Remove the zeroing status/temp register.
- Keep the live-in list improvements from r304267

Fixes http://llvm.org/PR34056

llvm-svn: 310534

1 files changed, 3 insertions, 6 deletions

diff --git a/llvm/test/CodeGen/ARM/cmpxchg-O0.ll b/llvm/test/CodeGen/ARM/cmpxchg-O0.ll
index a3be72112c7..f8ad2bbbbe0 100644
--- a/llvm/test/CodeGen/ARM/cmpxchg-O0.ll
+++ b/llvm/test/CodeGen/ARM/cmpxchg-O0.ll
@@ -10,11 +10,10 @@ define { i8, i1 } @test_cmpxchg_8(i8* %addr, i8 %desired, i8 %new) nounwind {
 ; CHECK:     dmb ish
 ; CHECK:     uxtb [[DESIRED:r[0-9]+]], [[DESIRED]]
 ; CHECK: [[RETRY:.LBB[0-9]+_[0-9]+]]:
-; CHECK:     mov{{s?}} [[STATUS:r[0-9]+]], #0
 ; CHECK:     ldrexb [[OLD:r[0-9]+]], [r0]
 ; CHECK:     cmp [[OLD]], [[DESIRED]]
 ; CHECK:     bne [[DONE:.LBB[0-9]+_[0-9]+]]
-; CHECK:     strexb [[STATUS]], r2, [r0]
+; CHECK:     strexb [[STATUS:r[0-9]+]], r2, [r0]
 ; CHECK:     cmp{{(\.w)?}} [[STATUS]], #0
 ; CHECK:     bne [[RETRY]]
 ; CHECK: [[DONE]]:
@@ -30,11 +29,10 @@ define { i16, i1 } @test_cmpxchg_16(i16* %addr, i16 %desired, i16 %new) nounwind
 ; CHECK:     dmb ish
 ; CHECK:     uxth [[DESIRED:r[0-9]+]], [[DESIRED]]
 ; CHECK: [[RETRY:.LBB[0-9]+_[0-9]+]]:
-; CHECK:     mov{{s?}} [[STATUS:r[0-9]+]], #0
 ; CHECK:     ldrexh [[OLD:r[0-9]+]], [r0]
 ; CHECK:     cmp [[OLD]], [[DESIRED]]
 ; CHECK:     bne [[DONE:.LBB[0-9]+_[0-9]+]]
-; CHECK:     strexh [[STATUS]], r2, [r0]
+; CHECK:     strexh [[STATUS:r[0-9]+]], r2, [r0]
 ; CHECK:     cmp{{(\.w)?}} [[STATUS]], #0
 ; CHECK:     bne [[RETRY]]
 ; CHECK: [[DONE]]:
@@ -50,11 +48,10 @@ define { i32, i1 } @test_cmpxchg_32(i32* %addr, i32 %desired, i32 %new) nounwind
 ; CHECK:     dmb ish
 ; CHECK-NOT:     uxt
 ; CHECK: [[RETRY:.LBB[0-9]+_[0-9]+]]:
-; CHECK:     mov{{s?}} [[STATUS:r[0-9]+]], #0
 ; CHECK:     ldrex [[OLD:r[0-9]+]], [r0]
 ; CHECK:     cmp [[OLD]], [[DESIRED]]
 ; CHECK:     bne [[DONE:.LBB[0-9]+_[0-9]+]]
-; CHECK:     strex [[STATUS]], r2, [r0]
+; CHECK:     strex [[STATUS:r[0-9]+]], r2, [r0]
 ; CHECK:     cmp{{(\.w)?}} [[STATUS]], #0
 ; CHECK:     bne [[RETRY]]
 ; CHECK: [[DONE]]: