[MachineCombiner][NFC] Prevent dereferencing past-the-end object in an MRI container

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@350896 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/CodeGen/MachineCombiner.cpp b/lib/CodeGen/MachineCombiner.cpp
index 0c6efff7bb40ea8ada12b4944895c92235e23301..f51b482e20e33f5302a9c924ca6f44e76f83a280 100644 (file)
--- a/lib/CodeGen/MachineCombiner.cpp
+++ b/lib/CodeGen/MachineCombiner.cpp
@@ -231,6 +231,8 @@ unsigned MachineCombiner::getLatency(MachineInstr *Root, MachineInstr *NewRoot,
     // Get the first instruction that uses MO
     MachineRegisterInfo::reg_iterator RI = MRI->reg_begin(MO.getReg());
     RI++;
+    if (RI == MRI->reg_end())
+      continue;
     MachineInstr *UseMO = RI->getParent();
     unsigned LatencyOp = 0;
     if (UseMO && BlockTrace.isDepInTrace(*Root, *UseMO)) {