[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.

llvm-svn: 371047

diff --git a/llvm/lib/Target/X86/X86InstrInfo.cpp b/llvm/lib/Target/X86/X86InstrInfo.cpp
index d597ec9..bf7dcb2 100644 (file)
--- a/llvm/lib/Target/X86/X86InstrInfo.cpp
+++ b/llvm/lib/Target/X86/X86InstrInfo.cpp
@@ -3616,8 +3616,9 @@ bool X86InstrInfo::optimizeCompareInstr(MachineInstr &CmpInstr, unsigned SrcReg,
   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.