From: Chris Lattner <sabre@nondot.org>
Date: Fri, 6 Oct 2006 17:39:34 +0000 (+0000)
Subject: ugly codegen
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=6e1f1fdd359666f3f8cf8996c12f9efbf6d0f2dd;p=oota-llvm.git

ugly codegen


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@30769 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/Target/X86/README.txt b/lib/Target/X86/README.txt
index 9f22bab55d2..3ee32cce055 100644
--- a/lib/Target/X86/README.txt
+++ b/lib/Target/X86/README.txt
@@ -711,4 +711,26 @@ bool %test(ulong %x) {
 
 into x.h == 0
 
+//===---------------------------------------------------------------------===//
+
+We currently compile sign_extend_inreg into two shifts:
+
+long foo(long X) {
+  return (long)(signed char)X;
+}
+
+becomes:
+
+_foo:
+        movl 4(%esp), %eax
+        shll $24, %eax
+        sarl $24, %eax
+        ret
 
+This could be:
+
+_foo:
+        movsbl  4(%esp),%eax
+        ret
+
+//===---------------------------------------------------------------------===//