[PATCH] D21774: [X86] Transform setcc + movzbl into xorl + setcc

[Elena Demikhovsky via llvm-commits]

delena added inline comments.

================
Comment at: lib/Target/X86/X86FixupSetCC.cpp:119
@@ +118,3 @@
+        MachineInstr *FlagsDefMI = findFlagsImpDef(
+            MI.getParent(), MachineBasicBlock::reverse_iterator(&MI));
+        if (!FlagsDefMI)
----------------
When you go backward, you should ensure that MI.getOperand(0).getReg() is not used between setcc and FlagsDefMI, including the second one.

for example:

   test %eax, %eax
   setcc %al

you can kill %eax before the "test".



http://reviews.llvm.org/D21774