[LiveRangeEdit] Handle instructions with no defs correctly.

Summary:
The code in LiveRangeEdit::eliminateDeadDef() that computes isOrigDef
doesn't handle instructions in which operand 0 is not a def (e.g. KILL)
correctly.  Add a check that operand 0 is a def before doing the rest of
the isOrigDef computation.

Reviewers: qcolombet, MatzeB, wmi

Subscribers: mcrosier, llvm-commits

Differential Revision: https://reviews.llvm.org/D27174

llvm-svn: 288189

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/CodeGen/LiveRangeEdit.cpp b/llvm/lib/CodeGen/LiveRangeEdit.cpp
index 264e7f713b9..88fed6212d1 100644
--- a/llvm/lib/CodeGen/LiveRangeEdit.cpp
+++ b/llvm/lib/CodeGen/LiveRangeEdit.cpp
@@ -272,7 +272,8 @@ void LiveRangeEdit::eliminateDeadDef(MachineInstr *MI, ToShrinkSet &ToShrink,
   bool ReadsPhysRegs = false;
   bool isOrigDef = false;
   unsigned Dest;
-  if (VRM && MI->getOperand(0).isReg()) {
+  if (VRM && MI->getOperand(0).isReg() && MI->getOperand(0).isDef()) {
+    assert(MI->getDesc().getNumDefs() == 1);
     Dest = MI->getOperand(0).getReg();
     unsigned Original = VRM->getOriginal(Dest);
     LiveInterval &OrigLI = LIS.getInterval(Original);