From ab24aaeca303abadd987c2a4ab3a56efe755c37c Mon Sep 17 00:00:00 2001
From: Kirill Smelkov <kirr@navytux.spb.ru>
Date: Fri, 16 Nov 2012 00:04:56 +0400
Subject: [PATCH] i386: We can change 'lea 0(%ebp),r'  to  'mov %ebp,r'

Because that mov is 1 byte shorter, look:

    int *func()
    {
        return __builtin_frame_address(0);
    }

before patch:

00000000 <func>:
   0:   55                      push   %ebp
   1:   89 e5                   mov    %esp,%ebp
   3:   81 ec 00 00 00 00       sub    $0x0,%esp
   9:   8d 45 00                lea    0x0(%ebp),%eax   // <- here
   c:   e9 00 00 00 00          jmp    11 <func+0x11>
  11:   c9                      leave
  12:   c3                      ret

after patch:

00000000 <func>:
   0:   55                      push   %ebp
   1:   89 e5                   mov    %esp,%ebp
   3:   81 ec 00 00 00 00       sub    $0x0,%esp
   9:   89 e8                   mov    %ebp,%eax        // <- here
   b:   e9 00 00 00 00          jmp    10 <func+0x10>
  10:   c9                      leave
  11:   c3                      ret
---
 i386-gen.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/i386-gen.c b/i386-gen.c
index 66355598..c3f03c78 100644
--- a/i386-gen.c
+++ b/i386-gen.c
@@ -260,8 +260,13 @@ ST_FUNC void load(int r, SValue *sv)
             o(0xb8 + r); /* mov $xx, r */
             gen_addr32(fr, sv->sym, fc);
         } else if (v == VT_LOCAL) {
-            o(0x8d); /* lea xxx(%ebp), r */
-            gen_modrm(r, VT_LOCAL, sv->sym, fc);
+            if (fc) {
+                o(0x8d); /* lea xxx(%ebp), r */
+                gen_modrm(r, VT_LOCAL, sv->sym, fc);
+            } else {
+                o(0x89);
+                o(0xe8 + r); /* mov %ebp, r */
+            }
         } else if (v == VT_CMP) {
             oad(0xb8 + r, 0); /* mov $0, r */
             o(0x0f); /* setxx %br */
-- 
2.11.4.GIT