From: Bill Wendling <isanbard@gmail.com>
Date: Tue, 27 Oct 2009 22:34:43 +0000 (+0000)
Subject: Add a note.
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=1ff2c485e240e00e7d84f1dd53ee7a111d25f5d3;p=oota-llvm.git

Add a note.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85329 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt
index 046d35ce5b6..5967fd55c09 100644
--- a/lib/Target/X86/README.txt
+++ b/lib/Target/X86/README.txt
@@ -1952,3 +1952,26 @@ fact these instructions are identical to the non-lock versions. We need a way to
 add target specific information to target nodes and have this information
 carried over to machine instructions. Asm printer (or JIT) can use this
 information to add the "lock" prefix.
+
+//===---------------------------------------------------------------------===//
+
+int func(int a, int b) { if (a & 0x80) b |= 0x80; else b &= 0x80; return b; }
+
+Current:
+
+        movb    %sil, %al
+        andb    $-128, %sil
+        orb     $-128, %al
+        testb   %dil, %dil
+        js      LBB1_2
+        movb    %sil, %al
+LBB1_2:
+        movsbl  %al, %eax
+
+Better:
+        movl    %esi, %eax
+        orl     $-128, %eax
+        andl    $-128, %esi
+        testb   %dil, %dil
+        cmovns  %esi, %eax
+        movsbl  %al,%eax