MachineScheduler: Ignore COPYs with undef/dead op in CopyConstrain mutation.

There is no problem with the code today, but the fix will avoid a crash
in test/CodeGen/AMDGPU/subreg-coalescer-undef-use.ll once the
DetectDeadLanes pass is added.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@265351 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/MachineScheduler.cpp b/lib/CodeGen/MachineScheduler.cpp
index 18933a9..9a7cae6 100644 (file)
--- a/lib/CodeGen/MachineScheduler.cpp
+++ b/lib/CodeGen/MachineScheduler.cpp
@@ -1580,12 +1580,14 @@ void CopyConstrain::constrainLocalCopy(SUnit *CopySU, ScheduleDAGMILive *DAG) {
   MachineInstr *Copy = CopySU->getInstr();
 
   // Check for pure vreg copies.
-  unsigned SrcReg = Copy->getOperand(1).getReg();
-  if (!TargetRegisterInfo::isVirtualRegister(SrcReg))
+  const MachineOperand &SrcOp = Copy->getOperand(1);
+  unsigned SrcReg = SrcOp.getReg();
+  if (!TargetRegisterInfo::isVirtualRegister(SrcReg) || !SrcOp.readsReg())
     return;
 
-  unsigned DstReg = Copy->getOperand(0).getReg();
-  if (!TargetRegisterInfo::isVirtualRegister(DstReg))
+  const MachineOperand &DstOp = Copy->getOperand(0);
+  unsigned DstReg = DstOp.getReg();
+  if (!TargetRegisterInfo::isVirtualRegister(DstReg) || DstOp.isDead())
     return;
 
   // Check if either the dest or source is local. If it's live across a back