[llvm] r350896 - [MachineCombiner][NFC] Prevent dereferencing past-the-end object in an MRI container

[Gerolf Hoflehner via llvm-commits]

Author: ghoflehner
Date: Thu Jan 10 13:53:13 2019
New Revision: 350896

URL: http://llvm.org/viewvc/llvm-project?rev=350896&view=rev
Log:
[MachineCombiner][NFC] Prevent dereferencing past-the-end object in an MRI container

Modified:
    llvm/trunk/lib/CodeGen/MachineCombiner.cpp

Modified: llvm/trunk/lib/CodeGen/MachineCombiner.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/MachineCombiner.cpp?rev=350896&r1=350895&r2=350896&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/MachineCombiner.cpp (original)
+++ llvm/trunk/lib/CodeGen/MachineCombiner.cpp Thu Jan 10 13:53:13 2019
@@ -231,6 +231,8 @@ unsigned MachineCombiner::getLatency(Mac
     // 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)) {