Make the peephole optimizer clear kill flags on a vreg if it's about to add new

uses of the vreg, since the old kills may no longer be valid.  This was causing
-verify-machineinstrs to complain about uses after kills, and could potentially
have been causing subtle register allocation issues, but I haven't come across a
test case yet.

llvm-svn: 151425

1 files changed, 4 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/PeepholeOptimizer.cpp b/llvm/lib/CodeGen/PeepholeOptimizer.cpp
index 203f2bffb7b..9c5c029000c 100644
--- a/llvm/lib/CodeGen/PeepholeOptimizer.cpp
+++ b/llvm/lib/CodeGen/PeepholeOptimizer.cpp
@@ -237,6 +237,10 @@ OptimizeExtInstr(MachineInstr *MI, MachineBasicBlock *MBB,
       if (PHIBBs.count(UseMBB))
         continue;
 
+      // About to add uses of DstReg, clear DstReg's kill flags.
+      if (!Changed)
+        MRI->clearKillFlags(DstReg);
+
       unsigned NewVR = MRI->createVirtualRegister(RC);
       BuildMI(*UseMBB, UseMI, UseMI->getDebugLoc(),
               TII->get(TargetOpcode::COPY), NewVR)