Fix PR16508.

[oota-llvm.git] / lib / CodeGen / RegisterCoalescer.cpp

diff --git a/lib/CodeGen/RegisterCoalescer.cpp b/lib/CodeGen/RegisterCoalescer.cpp
index 3cede9f4907758e7b8e54a354d41bd9295fae5e4..70a2462880e93df1906757bb881d37f4290234c2 100644 (file)
--- a/lib/CodeGen/RegisterCoalescer.cpp
+++ b/lib/CodeGen/RegisterCoalescer.cpp
@@ -2072,6 +2072,9 @@ static bool isLocalCopy(MachineInstr *Copy, const LiveIntervals *LIS) {
   if (!Copy->isCopy())
     return false;
 
+  if (Copy->getOperand(1).isUndef())
+    return false;
+
   unsigned SrcReg = Copy->getOperand(1).getReg();
   unsigned DstReg = Copy->getOperand(0).getReg();
   if (TargetRegisterInfo::isPhysicalRegister(SrcReg)
@@ -2117,8 +2120,8 @@ RegisterCoalescer::copyCoalesceInMBB(MachineBasicBlock *MBB) {
     // are not inherently easier to resolve, but slightly preferable until we
     // have local live range splitting. In particular this is required by
     // cmp+jmp macro fusion.
-    for (MachineBasicBlock::reverse_iterator
-           MII = MBB->rbegin(), E = MBB->rend(); MII != E; ++MII) {
+    for (MachineBasicBlock::iterator MII = MBB->begin(), E = MBB->end();
+         MII != E; ++MII) {
       if (!MII->isCopyLike())
         continue;
       if (isLocalCopy(&(*MII), LIS))