On Sat, Mar 19, 2011 at 01:43:26AM +0100, thus spake Christian Lamparter:
> I gave it a try and It worked?!
>
> [54670.551750] ieee80211 phy14: FW: a:0x4537 b:0x2c a/b:0x192 (0x192 = 402).
>
> (It was nothing else than just define "a" and "b" (as global variables) and
> add the INFO("a:0x%x b:0x%x a/b:0x%x", a, b, a/b);)
I suppose in your case the values are known at compile time and the compiler
does the calculation statically. If you define the global variables as
volatile, then the optimization is forbidden and you should get the bogus
results.
BTW, I used udivsi3_i4i.S from the Linux kernel, modified it as you indicated.
Please find my version attached.
Ignacy
--
To err is human, to purr feline.
/* Copyright (C) 1994, 1995, 1997, 1998, 1999, 2000, 2001, 2002, 2003,
2004, 2005, 2006
Free Software Foundation, Inc.
This file is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by the
Free Software Foundation; either version 2, or (at your option) any
later version.
In addition to the permissions in the GNU General Public License, the
Free Software Foundation gives you unlimited permission to link the
compiled version of this file into combinations with other programs,
and to distribute those combinations without any restriction coming
from the use of this file. (The General Public License restrictions
do apply in other respects; for example, they cover modification of
the file, and distribution when not linked into a combine
executable.)
This file is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; see the file COPYING. If not, write to
the Free Software Foundation, 51 Franklin Street, Fifth Floor,
Boston, MA 02110-1301, USA. */
!! libgcc routines for the Renesas / SuperH SH CPUs.
!! Contributed by Steve Chamberlain.
!! sac@xxxxxxxxxx
!! ashiftrt_r4_x, ___ashrsi3, ___ashlsi3, ___lshrsi3 routines
!! recoded in assembly by Toshiyasu Morita
!! tm@xxxxxxxxxx
/* SH2 optimizations for ___ashrsi3, ___ashlsi3, ___lshrsi3 and
ELF local label prefixes by J"orn Rennecke
amylaar@xxxxxxxxxx */
/* This code used shld, thus is not suitable for SH1 / SH2. */
/* Signed / unsigned division without use of FPU, optimized for SH4.
Uses a lookup table for divisors in the range -128 .. +128, and
div1 with case distinction for larger divisors in three more ranges.
The code is lumped together with the table to allow the use of mova. */
#ifdef CONFIG_CPU_LITTLE_ENDIAN
#define L_LSB 0
#define L_LSWMSB 1
#define L_MSWLSB 2
#else
#define L_LSB 3
#define L_LSWMSB 2
#define L_MSWLSB 1
#endif
.balign 4
.global ___udivsi3_i4i
.global ___udivsi3_i4
.set ___udivsi3_i4, ___udivsi3_i4i
.type ___udivsi3_i4i, @function
___udivsi3_i4i:
mov.w c128_w, r1
div0u
mov r4,r0
shlr8 r0
cmp/hi r1,r5
extu.w r5,r1
bf udiv_le128
cmp/eq r5,r1
bf udiv_ge64k
shlr r0
mov r5,r1
shll16 r5
mov.l r4,@-r15
div1 r5,r0
mov.l r1,@-r15
div1 r5,r0
div1 r5,r0
bra udiv_25
div1 r5,r0
div_le128:
mova div_table_ix,r0
bra div_le128_2
mov.b @(r0,r5),r1
udiv_le128:
mov.l r4,@-r15
mova div_table_ix,r0
mov.b @(r0,r5),r1
mov.l r5,@-r15
div_le128_2:
mova div_table_inv,r0
mov.l @(r0,r1),r1
mov r5,r0
tst #0xfe,r0
mova div_table_clz,r0
dmulu.l r1,r4
mov.b @(r0,r5),r1
bt/s div_by_1
mov r4,r0
mov.l @r15+,r5
sts mach,r0
/* clrt */
addc r4,r0
mov.l @r15+,r4
rotcr r0
rts
shld r1,r0
div_by_1_neg:
neg r4,r0
div_by_1:
mov.l @r15+,r5
rts
mov.l @r15+,r4
div_ge64k:
bt/s div_r8
div0u
shll8 r5
bra div_ge64k_2
div1 r5,r0
udiv_ge64k:
cmp/hi r0,r5
mov r5,r1
bt udiv_r8
shll8 r5
mov.l r4,@-r15
div1 r5,r0
mov.l r1,@-r15
div_ge64k_2:
div1 r5,r0
mov.l zero_l,r1
.rept 4
div1 r5,r0
.endr
mov.l r1,@-r15
div1 r5,r0
mov.w m256_w,r1
div1 r5,r0
mov.b r0,@(L_LSWMSB,r15)
xor r4,r0
and r1,r0
bra div_ge64k_end
xor r4,r0
div_r8:
shll16 r4
bra div_r8_2
shll8 r4
udiv_r8:
mov.l r4,@-r15
shll16 r4
clrt
shll8 r4
mov.l r5,@-r15
div_r8_2:
rotcl r4
mov r0,r1
div1 r5,r1
mov r4,r0
rotcl r0
mov r5,r4
div1 r5,r1
.rept 5
rotcl r0; div1 r5,r1
.endr
rotcl r0
mov.l @r15+,r5
div1 r4,r1
mov.l @r15+,r4
rts
rotcl r0
.global ___sdivsi3_i4i
.global ___sdivsi3_i4
.global ___sdivsi3
.set ___sdivsi3_i4, ___sdivsi3_i4i
.set ___sdivsi3, ___sdivsi3_i4i
.type ___sdivsi3_i4i, @function
/* This is link-compatible with a __sdivsi3 call,
but we effectively clobber only r1. */
___sdivsi3_i4i:
mov.l r4,@-r15
cmp/pz r5
mov.w c128_w, r1
bt/s pos_divisor
cmp/pz r4
mov.l r5,@-r15
neg r5,r5
bt/s neg_result
cmp/hi r1,r5
neg r4,r4
pos_result:
extu.w r5,r0
bf div_le128
cmp/eq r5,r0
mov r4,r0
shlr8 r0
bf/s div_ge64k
cmp/hi r0,r5
div0u
shll16 r5
div1 r5,r0
div1 r5,r0
div1 r5,r0
udiv_25:
mov.l zero_l,r1
div1 r5,r0
div1 r5,r0
mov.l r1,@-r15
.rept 3
div1 r5,r0
.endr
mov.b r0,@(L_MSWLSB,r15)
xtrct r4,r0
swap.w r0,r0
.rept 8
div1 r5,r0
.endr
mov.b r0,@(L_LSWMSB,r15)
div_ge64k_end:
.rept 8
div1 r5,r0
.endr
mov.l @r15+,r4 ! zero-extension and swap using LS unit.
extu.b r0,r0
mov.l @r15+,r5
or r4,r0
mov.l @r15+,r4
rts
rotcl r0
div_le128_neg:
tst #0xfe,r0
mova div_table_ix,r0
mov.b @(r0,r5),r1
mova div_table_inv,r0
bt/s div_by_1_neg
mov.l @(r0,r1),r1
mova div_table_clz,r0
dmulu.l r1,r4
mov.b @(r0,r5),r1
mov.l @r15+,r5
sts mach,r0
/* clrt */
addc r4,r0
mov.l @r15+,r4
rotcr r0
shld r1,r0
rts
neg r0,r0
pos_divisor:
mov.l r5,@-r15
bt/s pos_result
cmp/hi r1,r5
neg r4,r4
neg_result:
extu.w r5,r0
bf div_le128_neg
cmp/eq r5,r0
mov r4,r0
shlr8 r0
bf/s div_ge64k_neg
cmp/hi r0,r5
div0u
mov.l zero_l,r1
shll16 r5
div1 r5,r0
mov.l r1,@-r15
.rept 7
div1 r5,r0
.endr
mov.b r0,@(L_MSWLSB,r15)
xtrct r4,r0
swap.w r0,r0
.rept 8
div1 r5,r0
.endr
mov.b r0,@(L_LSWMSB,r15)
div_ge64k_neg_end:
.rept 8
div1 r5,r0
.endr
mov.l @r15+,r4 ! zero-extension and swap using LS unit.
extu.b r0,r1
mov.l @r15+,r5
or r4,r1
div_r8_neg_end:
mov.l @r15+,r4
rotcl r1
rts
neg r1,r0
div_ge64k_neg:
bt/s div_r8_neg
div0u
shll8 r5
mov.l zero_l,r1
.rept 6
div1 r5,r0
.endr
mov.l r1,@-r15
div1 r5,r0
mov.w m256_w,r1
div1 r5,r0
mov.b r0,@(L_LSWMSB,r15)
xor r4,r0
and r1,r0
bra div_ge64k_neg_end
xor r4,r0
c128_w:
.word 128
div_r8_neg:
clrt
shll16 r4
mov r4,r1
shll8 r1
mov r5,r4
.rept 7
rotcl r1; div1 r5,r0
.endr
mov.l @r15+,r5
rotcl r1
bra div_r8_neg_end
div1 r4,r0
m256_w:
.word 0xff00
/* This table has been generated by divtab-sh4.c. */
.balign 4
div_table_clz:
.byte 0
.byte 1
.byte 0
.byte -1
.byte -1
.byte -2
.byte -2
.byte -2
.byte -2
.byte -3
.byte -3
.byte -3
.byte -3
.byte -3
.byte -3
.byte -3
.byte -3
.byte -4
.byte -4
.byte -4
.byte -4
.byte -4
.byte -4
.byte -4
.byte -4
.byte -4
.byte -4
.byte -4
.byte -4
.byte -4
.byte -4
.byte -4
.byte -4
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -5
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
.byte -6
/* Lookup table translating positive divisor to index into table of
normalized inverse. N.B. the '0' entry is also the last entry of the
previous table, and causes an unaligned access for division by zero. */
div_table_ix:
.byte -6
.byte -128
.byte -128
.byte 0
.byte -128
.byte -64
.byte 0
.byte 64
.byte -128
.byte -96
.byte -64
.byte -32
.byte 0
.byte 32
.byte 64
.byte 96
.byte -128
.byte -112
.byte -96
.byte -80
.byte -64
.byte -48
.byte -32
.byte -16
.byte 0
.byte 16
.byte 32
.byte 48
.byte 64
.byte 80
.byte 96
.byte 112
.byte -128
.byte -120
.byte -112
.byte -104
.byte -96
.byte -88
.byte -80
.byte -72
.byte -64
.byte -56
.byte -48
.byte -40
.byte -32
.byte -24
.byte -16
.byte -8
.byte 0
.byte 8
.byte 16
.byte 24
.byte 32
.byte 40
.byte 48
.byte 56
.byte 64
.byte 72
.byte 80
.byte 88
.byte 96
.byte 104
.byte 112
.byte 120
.byte -128
.byte -124
.byte -120
.byte -116
.byte -112
.byte -108
.byte -104
.byte -100
.byte -96
.byte -92
.byte -88
.byte -84
.byte -80
.byte -76
.byte -72
.byte -68
.byte -64
.byte -60
.byte -56
.byte -52
.byte -48
.byte -44
.byte -40
.byte -36
.byte -32
.byte -28
.byte -24
.byte -20
.byte -16
.byte -12
.byte -8
.byte -4
.byte 0
.byte 4
.byte 8
.byte 12
.byte 16
.byte 20
.byte 24
.byte 28
.byte 32
.byte 36
.byte 40
.byte 44
.byte 48
.byte 52
.byte 56
.byte 60
.byte 64
.byte 68
.byte 72
.byte 76
.byte 80
.byte 84
.byte 88
.byte 92
.byte 96
.byte 100
.byte 104
.byte 108
.byte 112
.byte 116
.byte 120
.byte 124
.byte -128
/* 1/64 .. 1/127, normalized. There is an implicit leading 1 in bit 32. */
.balign 4
zero_l:
.long 0x0
.long 0xF81F81F9
.long 0xF07C1F08
.long 0xE9131AC0
.long 0xE1E1E1E2
.long 0xDAE6076C
.long 0xD41D41D5
.long 0xCD856891
.long 0xC71C71C8
.long 0xC0E07039
.long 0xBACF914D
.long 0xB4E81B4F
.long 0xAF286BCB
.long 0xA98EF607
.long 0xA41A41A5
.long 0x9EC8E952
.long 0x9999999A
.long 0x948B0FCE
.long 0x8F9C18FA
.long 0x8ACB90F7
.long 0x86186187
.long 0x81818182
.long 0x7D05F418
.long 0x78A4C818
.long 0x745D1746
.long 0x702E05C1
.long 0x6C16C16D
.long 0x68168169
.long 0x642C8591
.long 0x60581606
.long 0x5C9882BA
.long 0x58ED2309
div_table_inv:
.long 0x55555556
.long 0x51D07EAF
.long 0x4E5E0A73
.long 0x4AFD6A06
.long 0x47AE147B
.long 0x446F8657
.long 0x41414142
.long 0x3E22CBCF
.long 0x3B13B13C
.long 0x38138139
.long 0x3521CFB3
.long 0x323E34A3
.long 0x2F684BDB
.long 0x2C9FB4D9
.long 0x29E4129F
.long 0x27350B89
.long 0x24924925
.long 0x21FB7813
.long 0x1F7047DD
.long 0x1CF06ADB
.long 0x1A7B9612
.long 0x18118119
.long 0x15B1E5F8
.long 0x135C8114
.long 0x11111112
.long 0xECF56BF
.long 0xC9714FC
.long 0xA6810A7
.long 0x8421085
.long 0x624DD30
.long 0x4104105
.long 0x2040811
/* maximum error: 0.987342 scaled: 0.921875*/
