From: Lang Hames <lhames@gmail.com>
Date: Sat, 25 Feb 2012 02:01:00 +0000 (+0000)
Subject: Make the peephole optimizer clear kill flags on a vreg if it's about to add new
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=c69cbd0a7431b047dbc4a9758e81bf122926ba0a;p=oota-llvm.git

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.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151425 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/CodeGen/PeepholeOptimizer.cpp b/lib/CodeGen/PeepholeOptimizer.cpp
index 203f2bffb7b..9c5c029000c 100644
--- a/lib/CodeGen/PeepholeOptimizer.cpp
+++ b/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)