[SystemZ] Fix fall-out from r314428

The expensive-checks build bot found a problem with the r314428 commit:
if CC is live after a ATOMIC_CMP_SWAPW instruction, it needs to be
marked as live-in to the block after the loop the pseudo gets expanded
to.  This actually fixes a code-gen bug as well, since if the CC isn't
live, the CR and JLH are merged to a CRJLH which doesn't actually set
the condition code any more.

llvm-svn: 314465

1 files changed, 6 insertions, 0 deletions

diff --git a/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp b/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
index be7c5e430fc..d49d7316e68 100644
--- a/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZISelLowering.cpp
@@ -6027,6 +6027,12 @@ SystemZTargetLowering::emitAtomicCmpSwapW(MachineInstr &MI,
   MBB->addSuccessor(LoopMBB);
   MBB->addSuccessor(DoneMBB);
 
+  // If the CC def wasn't dead in the ATOMIC_CMP_SWAPW, mark CC as live-in
+  // to the block after the loop.  At this point, CC may have been defined
+  // either by the CR in LoopMBB or by the CS in SetMBB.
+  if (!MI.registerDefIsDead(SystemZ::CC))
+    DoneMBB->addLiveIn(SystemZ::CC);
+
   MI.eraseFromParent();
   return DoneMBB;
 }