From 91c5346d91973a1d3458a20f8c6b0e899b732e38 Mon Sep 17 00:00:00 2001
From: Manman Ren <mren@apple.com>
Date: Thu, 31 May 2012 17:20:29 +0000
Subject: X86: replace SUB with CMP if possible

This patch will optimize the following
        movq    %rdi, %rax
        subq    %rsi, %rax
        cmovsq  %rsi, %rdi
        movq    %rdi, %rax
to
        cmpq    %rsi, %rdi
        cmovsq  %rsi, %rdi
        movq    %rdi, %rax

Perform this optimization if the actual result of SUB is not used.

rdar: 11540023


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@157755 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/CodeGen/PeepholeOptimizer.cpp | 1 +
 1 file changed, 1 insertion(+)

(limited to 'lib/CodeGen/PeepholeOptimizer.cpp')

diff --git a/lib/CodeGen/PeepholeOptimizer.cpp b/lib/CodeGen/PeepholeOptimizer.cpp
index 81cf9011d1..d7d112f1d9 100644
--- a/lib/CodeGen/PeepholeOptimizer.cpp
+++ b/lib/CodeGen/PeepholeOptimizer.cpp
@@ -472,6 +472,7 @@ bool PeepholeOptimizer::runOnMachineFunction(MachineFunction &MF) {
         if (SeenMoveImm)
           Changed |= foldImmediate(MI, MBB, ImmDefRegs, ImmDefMIs);
       }
+      Changed |= TII->OptimizeSubInstr(MI, MRI);
 
       First = false;
       PMII = MII;
-- 
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