Add the Optimize Compares pass (disabled by default).

This pass tries to remove comparison instructions when possible. For instance,
if you have this code:

   sub r1, 1
   cmp r1, 0
   bz  L1

and "sub" either sets the same flag as the "cmp" instruction or could be
converted to set the same flag, then we can eliminate the "cmp" instruction all
together. This is a important for ARM where the ALU instructions could set the
CPSR flag, but need a special suffix ('s') to do so.

llvm-svn: 110423

1 files changed, 1 insertions, 0 deletions

diff --git a/llvm/lib/CodeGen/LLVMTargetMachine.cpp b/llvm/lib/CodeGen/LLVMTargetMachine.cpp
index 36c837d59fe..5b2d40b5857 100644
--- a/llvm/lib/CodeGen/LLVMTargetMachine.cpp
+++ b/llvm/lib/CodeGen/LLVMTargetMachine.cpp
@@ -354,6 +354,7 @@ bool LLVMTargetMachine::addCommonCodeGenPasses(PassManagerBase &PM,
     printAndVerify(PM, "After codegen DCE pass");
 
     PM.add(createOptimizeExtsPass());
+    PM.add(createOptimizeCmpsPass());
     if (!DisableMachineLICM)
       PM.add(createMachineLICMPass());
     PM.add(createMachineCSEPass());