SplitKit: Fix subreg copy related problems

Fix two problems related to r298025:
- SplitKit would create duplicate VNIs in some cases leading to crashs
  when hoisting copies.
- VirtRegMap could fail expanding copies at the beginning of a basic
  block.

This fixes http://llvm.org/PR32353

llvm-svn: 298448

1 files changed, 3 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/VirtRegMap.cpp b/llvm/lib/CodeGen/VirtRegMap.cpp
index 06a97fd6d4d..c8946010e9d 100644
--- a/llvm/lib/CodeGen/VirtRegMap.cpp
+++ b/llvm/lib/CodeGen/VirtRegMap.cpp
@@ -383,8 +383,10 @@ void VirtRegRewriter::expandCopyBundle(MachineInstr &MI) const {
 
   if (MI.isBundledWithPred() && !MI.isBundledWithSucc()) {
     // Only do this when the complete bundle is made out of COPYs.
+    MachineBasicBlock &MBB = *MI.getParent();
     for (MachineBasicBlock::reverse_instr_iterator I =
-         std::next(MI.getReverseIterator()); I->isBundledWithSucc(); ++I) {
+         std::next(MI.getReverseIterator()), E = MBB.instr_rend();
+         I != E && I->isBundledWithSucc(); ++I) {
       if (!I->isCopy())
         return;
     }