[llvm] r371047 - [X86] X86InstrInfo::optimizeCompareInstr - fix potential null dereference.

[Simon Pilgrim via llvm-commits]

Author: rksimon
Date: Thu Sep  5 03:18:24 2019
New Revision: 371047

URL: http://llvm.org/viewvc/llvm-project?rev=371047&view=rev
Log:
[X86] X86InstrInfo::optimizeCompareInstr - fix potential null dereference. 

Fixes clang static-analyzer warning.

Technically the MachineInstr *Sub might still be null if we're comparing zero (IsCmpZero == true), although this probably won't happen as SrcReg2 is probably == 0.

Modified:
    llvm/trunk/lib/Target/X86/X86InstrInfo.cpp

Modified: llvm/trunk/lib/Target/X86/X86InstrInfo.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Target/X86/X86InstrInfo.cpp?rev=371047&r1=371046&r2=371047&view=diff
==============================================================================
--- llvm/trunk/lib/Target/X86/X86InstrInfo.cpp (original)
+++ llvm/trunk/lib/Target/X86/X86InstrInfo.cpp Thu Sep  5 03:18:24 2019
@@ -3616,8 +3616,9 @@ bool X86InstrInfo::optimizeCompareInstr(
   if (!IsCmpZero && !Sub)
     return false;
 
-  bool IsSwapped = (SrcReg2 != 0 && Sub->getOperand(1).getReg() == SrcReg2 &&
-                    Sub->getOperand(2).getReg() == SrcReg);
+  bool IsSwapped =
+      (SrcReg2 != 0 && Sub && Sub->getOperand(1).getReg() == SrcReg2 &&
+       Sub->getOperand(2).getReg() == SrcReg);
 
   // Scan forward from the instruction after CmpInstr for uses of EFLAGS.
   // It is safe to remove CmpInstr if EFLAGS is redefined or killed.