From ca66ec5eec6f7407d4bdbb1e091a9ccde66a5194 Mon Sep 17 00:00:00 2001
From: "H. Peter Anvin" <hpa@zytor.com>
Date: Thu, 17 Jul 2008 14:22:10 -0700
Subject: smartalign: adjust the alignment threshold

Apparently the current recommendation is for a smaller threshold when
using the "generic"-style alignment macros (short jumps are cheaper on
newer CPUs.)

Also change the alignment threshold definition to reflect the maximum
number of padding instead of when to start using jumps.
---
 macros/smartalign.mac | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

(limited to 'macros')

diff --git a/macros/smartalign.mac b/macros/smartalign.mac
index 6ff294ae..12850867 100644
--- a/macros/smartalign.mac
+++ b/macros/smartalign.mac
@@ -4,8 +4,9 @@
 USE: smartalign
 
 %imacro alignmode 1-2.nolist
-  %define __ALIGN_JMP_THRESHOLD__ 17
   %ifidni %1,nop
+    %define __ALIGN_JMP_THRESHOLD__ 16
+
     %define __ALIGN_16BIT_1B__ 0x90
     %define __ALIGN_16BIT_2B__ 0x90,0x90
     %define __ALIGN_16BIT_3B__ 0x90,0x90,0x90
@@ -33,6 +34,8 @@ USE: smartalign
     %define __ALIGN_64BIT_7B__ 0x90,0x90,0x90,0x90,0x90,0x90,0x90
     %define __ALIGN_64BIT_8B__ 0x90,0x90,0x90,0x90,0x90,0x90,0x90,0x90
   %elifidni %1,generic
+    %define __ALIGN_JMP_THRESHOLD__ 8
+
     %define __ALIGN_16BIT_1B__ 0x90
     %define __ALIGN_16BIT_2B__ 0x89,0xf6
     %define __ALIGN_16BIT_3B__ 0x8d,0x74,0x00
@@ -60,6 +63,8 @@ USE: smartalign
     %define __ALIGN_64BIT_7B__ 0x66,0x66,0x66,0x90,0x66,0x66,0x90
     %define __ALIGN_64BIT_8B__ 0x66,0x66,0x66,0x90,0x66,0x66,0x66,0x90
   %elifidni %1,k8
+    %define __ALIGN_JMP_THRESHOLD__ 16
+
     %define __ALIGN_16BIT_1B__ 0x90
     %define __ALIGN_16BIT_2B__ 0x66,0x90
     %define __ALIGN_16BIT_3B__ 0x66,0x66,0x90
@@ -87,6 +92,8 @@ USE: smartalign
     %define __ALIGN_64BIT_7B__ 0x66,0x66,0x66,0x90,0x66,0x66,0x90
     %define __ALIGN_64BIT_8B__ 0x66,0x66,0x66,0x90,0x66,0x66,0x66,0x90
   %elifidni %1,k7
+    %define __ALIGN_JMP_THRESHOLD__ 16
+
     %define __ALIGN_16BIT_1B__ 0x90
     %define __ALIGN_16BIT_2B__ 0x66,0x90
     %define __ALIGN_16BIT_3B__ 0x66,0x66,0x90
@@ -114,6 +121,8 @@ USE: smartalign
     %define __ALIGN_64BIT_7B__ 0x66,0x66,0x66,0x90,0x66,0x66,0x90
     %define __ALIGN_64BIT_8B__ 0x66,0x66,0x66,0x90,0x66,0x66,0x66,0x90
   %elifidni %1,p6
+    %define __ALIGN_JMP_THRESHOLD__ 16
+
     %define __ALIGN_16BIT_1B__ 0x90
     %define __ALIGN_16BIT_2B__ 0x66,0x90
     %define __ALIGN_16BIT_3B__ 0x0f,0x1f,0x00
@@ -156,7 +165,7 @@ USE: smartalign
   %else
     %push
     %assign %$pad ($$-$) % %1
-    %if %$pad >= __ALIGN_JMP_THRESHOLD__
+    %if %$pad > __ALIGN_JMP_THRESHOLD__
       jmp %%end
       ; We can't re-use %$pad here as $ will have changed!
       times ($$-$) % %1 db 90h
-- 
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