[llvm] r278355 - Hexagon: Avoid dereferencing end() in HexagonCopyToCombine::findPairable

[Duncan P. N. Exon Smith via llvm-commits]

Author: dexonsmith
Date: Thu Aug 11 11:40:03 2016
New Revision: 278355

URL: http://llvm.org/viewvc/llvm-project?rev=278355&view=rev
Log:
Hexagon: Avoid dereferencing end() in HexagonCopyToCombine::findPairable

Check for end() before skipping through debug values.  This avoids
dereferencing end() when the instruction is the final one in the basic
block.  (It still assumes that a debug value will not be the final
instruction in the basic block.  No tests seemed to violate that.)

Many Hexagon tests trigger this, but they happen to magically pass right
now.  I found this because WIP patches for PR26753 convert them into
crashes.

Modified:
    llvm/trunk/lib/Target/Hexagon/HexagonCopyToCombine.cpp

Modified: llvm/trunk/lib/Target/Hexagon/HexagonCopyToCombine.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/Hexagon/HexagonCopyToCombine.cpp?rev=278355&r1=278354&r2=278355&view=diff
==============================================================================
--- llvm/trunk/lib/Target/Hexagon/HexagonCopyToCombine.cpp (original)
+++ llvm/trunk/lib/Target/Hexagon/HexagonCopyToCombine.cpp Thu Aug 11 11:40:03 2016
@@ -505,8 +505,9 @@ MachineInstr *HexagonCopyToCombine::find
                                                  bool AllowC64) {
   MachineBasicBlock::iterator I2 = std::next(MachineBasicBlock::iterator(I1));
 
-  while (I2->isDebugValue())
-    ++I2;
+  if (I2 != I1.getParent()->end())
+    while (I2->isDebugValue())
+      ++I2;
 
   unsigned I1DestReg = I1.getOperand(0).getReg();