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smartalign: adjust the alignment threshold

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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.
This commit is contained in:
H. Peter Anvin 2008-07-17 14:22:10 -07:00
parent 1ac41d34ba
commit ca66ec5eec
1 changed files with 11 additions and 2 deletions
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13
macros/smartalign.mac
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@ -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