[X86] Transform setcc + movzbl into xorl + setcc

xorl + setcc is generally the preferred sequence due to the partial register
stall setcc + movzbl suffers from. As a bonus, it also encodes one byte smaller.

This fixes PR28146.

Differential Revision: http://reviews.llvm.org/D21774

llvm-svn: 274692

1 files changed, 2 insertions, 1 deletions

diff --git a/llvm/lib/Target/X86/X86TargetMachine.cpp b/llvm/lib/Target/X86/X86TargetMachine.cpp
index 8dd4c66..f9d2d0a 100644
--- a/llvm/lib/Target/X86/X86TargetMachine.cpp
+++ b/llvm/lib/Target/X86/X86TargetMachine.cpp
@@ -285,7 +285,6 @@ bool X86PassConfig::addInstSelector() {
     addPass(createCleanupLocalDynamicTLSPass());
 
   addPass(createX86GlobalBaseRegPass());
-
   return false;
 }
 
@@ -305,6 +304,8 @@ bool X86PassConfig::addPreISel() {
 }
 
 void X86PassConfig::addPreRegAlloc() {
+  addPass(createX86FixupSetCC());
+
   if (getOptLevel() != CodeGenOpt::None)
     addPass(createX86OptimizeLEAs());