759 lines
14 KiB
NASM
759 lines
14 KiB
NASM
dnl Intel Pentium-II mpn_divrem_1 -- mpn by limb division.
|
|
|
|
dnl Copyright 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
|
|
dnl
|
|
dnl This file is part of the GNU MP Library.
|
|
dnl
|
|
dnl The GNU MP Library is free software; you can redistribute it and/or
|
|
dnl modify it under the terms of the GNU Lesser General Public License as
|
|
dnl published by the Free Software Foundation; either version 2.1 of the
|
|
dnl License, or (at your option) any later version.
|
|
dnl
|
|
dnl The GNU MP Library is distributed in the hope that it will be useful,
|
|
dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
dnl Lesser General Public License for more details.
|
|
dnl
|
|
dnl You should have received a copy of the GNU Lesser General Public
|
|
dnl License along with the GNU MP Library; see the file COPYING.LIB. If
|
|
dnl not, write to the Free Software Foundation, Inc., 51 Franklin Street,
|
|
dnl Fifth Floor, Boston, MA 02110-1301, USA.
|
|
|
|
include(`../config.m4')
|
|
|
|
|
|
C P6MMX: 25.0 cycles/limb integer part, 17.5 cycles/limb fraction part.
|
|
|
|
|
|
C mp_limb_t mpn_divrem_1 (mp_ptr dst, mp_size_t xsize,
|
|
C mp_srcptr src, mp_size_t size,
|
|
C mp_limb_t divisor);
|
|
C mp_limb_t mpn_divrem_1c (mp_ptr dst, mp_size_t xsize,
|
|
C mp_srcptr src, mp_size_t size,
|
|
C mp_limb_t divisor, mp_limb_t carry);
|
|
C mp_limb_t mpn_preinv_divrem_1 (mp_ptr dst, mp_size_t xsize,
|
|
C mp_srcptr src, mp_size_t size,
|
|
C mp_limb_t divisor, mp_limb_t inverse,
|
|
C unsigned shift);
|
|
C
|
|
C This code is a lightly reworked version of mpn/x86/k7/mmx/divrem_1.asm,
|
|
C see that file for some comments. It's possible what's here can be improved.
|
|
|
|
|
|
dnl MUL_THRESHOLD is the value of xsize+size at which the multiply by
|
|
dnl inverse method is used, rather than plain "divl"s. Minimum value 1.
|
|
dnl
|
|
dnl The different speeds of the integer and fraction parts means that using
|
|
dnl xsize+size isn't quite right. The threshold wants to be a bit higher
|
|
dnl for the integer part and a bit lower for the fraction part. (Or what's
|
|
dnl really wanted is to speed up the integer part!)
|
|
dnl
|
|
dnl The threshold is set to make the integer part right. At 4 limbs the
|
|
dnl div and mul are about the same there, but on the fractional part the
|
|
dnl mul is much faster.
|
|
|
|
deflit(MUL_THRESHOLD, 4)
|
|
|
|
|
|
defframe(PARAM_PREINV_SHIFT, 28) dnl mpn_preinv_divrem_1
|
|
defframe(PARAM_PREINV_INVERSE, 24) dnl mpn_preinv_divrem_1
|
|
defframe(PARAM_CARRY, 24) dnl mpn_divrem_1c
|
|
defframe(PARAM_DIVISOR,20)
|
|
defframe(PARAM_SIZE, 16)
|
|
defframe(PARAM_SRC, 12)
|
|
defframe(PARAM_XSIZE, 8)
|
|
defframe(PARAM_DST, 4)
|
|
|
|
defframe(SAVE_EBX, -4)
|
|
defframe(SAVE_ESI, -8)
|
|
defframe(SAVE_EDI, -12)
|
|
defframe(SAVE_EBP, -16)
|
|
|
|
defframe(VAR_NORM, -20)
|
|
defframe(VAR_INVERSE, -24)
|
|
defframe(VAR_SRC, -28)
|
|
defframe(VAR_DST, -32)
|
|
defframe(VAR_DST_STOP,-36)
|
|
|
|
deflit(STACK_SPACE, 36)
|
|
|
|
TEXT
|
|
ALIGN(16)
|
|
|
|
PROLOGUE(mpn_preinv_divrem_1)
|
|
deflit(`FRAME',0)
|
|
movl PARAM_XSIZE, %ecx
|
|
subl $STACK_SPACE, %esp FRAME_subl_esp(STACK_SPACE)
|
|
|
|
movl %esi, SAVE_ESI
|
|
movl PARAM_SRC, %esi
|
|
|
|
movl %ebx, SAVE_EBX
|
|
movl PARAM_SIZE, %ebx
|
|
|
|
movl %ebp, SAVE_EBP
|
|
movl PARAM_DIVISOR, %ebp
|
|
|
|
movl %edi, SAVE_EDI
|
|
movl PARAM_DST, %edx
|
|
|
|
movl -4(%esi,%ebx,4), %eax C src high limb
|
|
xorl %edi, %edi C initial carry (if can't skip a div)
|
|
|
|
C
|
|
|
|
leal 8(%edx,%ecx,4), %edx C &dst[xsize+2]
|
|
xor %ecx, %ecx
|
|
|
|
movl %edx, VAR_DST_STOP C &dst[xsize+2]
|
|
cmpl %ebp, %eax C high cmp divisor
|
|
|
|
cmovc( %eax, %edi) C high is carry if high<divisor
|
|
|
|
cmovnc( %eax, %ecx) C 0 if skip div, src high if not
|
|
C (the latter in case src==dst)
|
|
|
|
movl %ecx, -12(%edx,%ebx,4) C dst high limb
|
|
|
|
sbbl $0, %ebx C skip one division if high<divisor
|
|
movl PARAM_PREINV_SHIFT, %ecx
|
|
|
|
leal -8(%edx,%ebx,4), %edx C &dst[xsize+size]
|
|
movl $32, %eax
|
|
|
|
movl %edx, VAR_DST C &dst[xsize+size]
|
|
|
|
shll %cl, %ebp C d normalized
|
|
subl %ecx, %eax
|
|
movl %ecx, VAR_NORM
|
|
|
|
movd %eax, %mm7 C rshift
|
|
movl PARAM_PREINV_INVERSE, %eax
|
|
jmp L(start_preinv)
|
|
|
|
EPILOGUE()
|
|
|
|
|
|
|
|
ALIGN(16)
|
|
|
|
PROLOGUE(mpn_divrem_1c)
|
|
deflit(`FRAME',0)
|
|
movl PARAM_CARRY, %edx
|
|
|
|
movl PARAM_SIZE, %ecx
|
|
subl $STACK_SPACE, %esp
|
|
deflit(`FRAME',STACK_SPACE)
|
|
|
|
movl %ebx, SAVE_EBX
|
|
movl PARAM_XSIZE, %ebx
|
|
|
|
movl %edi, SAVE_EDI
|
|
movl PARAM_DST, %edi
|
|
|
|
movl %ebp, SAVE_EBP
|
|
movl PARAM_DIVISOR, %ebp
|
|
|
|
movl %esi, SAVE_ESI
|
|
movl PARAM_SRC, %esi
|
|
|
|
leal -4(%edi,%ebx,4), %edi
|
|
jmp L(start_1c)
|
|
|
|
EPILOGUE()
|
|
|
|
|
|
C offset 0x31, close enough to aligned
|
|
PROLOGUE(mpn_divrem_1)
|
|
deflit(`FRAME',0)
|
|
|
|
movl PARAM_SIZE, %ecx
|
|
movl $0, %edx C initial carry (if can't skip a div)
|
|
subl $STACK_SPACE, %esp
|
|
deflit(`FRAME',STACK_SPACE)
|
|
|
|
movl %ebp, SAVE_EBP
|
|
movl PARAM_DIVISOR, %ebp
|
|
|
|
movl %ebx, SAVE_EBX
|
|
movl PARAM_XSIZE, %ebx
|
|
|
|
movl %esi, SAVE_ESI
|
|
movl PARAM_SRC, %esi
|
|
orl %ecx, %ecx C size
|
|
|
|
movl %edi, SAVE_EDI
|
|
movl PARAM_DST, %edi
|
|
|
|
leal -4(%edi,%ebx,4), %edi C &dst[xsize-1]
|
|
jz L(no_skip_div) C if size==0
|
|
|
|
movl -4(%esi,%ecx,4), %eax C src high limb
|
|
xorl %esi, %esi
|
|
cmpl %ebp, %eax C high cmp divisor
|
|
|
|
cmovc( %eax, %edx) C high is carry if high<divisor
|
|
|
|
cmovnc( %eax, %esi) C 0 if skip div, src high if not
|
|
C (the latter in case src==dst)
|
|
|
|
movl %esi, (%edi,%ecx,4) C dst high limb
|
|
|
|
sbbl $0, %ecx C size-1 if high<divisor
|
|
movl PARAM_SRC, %esi C reload
|
|
L(no_skip_div):
|
|
|
|
|
|
L(start_1c):
|
|
C eax
|
|
C ebx xsize
|
|
C ecx size
|
|
C edx carry
|
|
C esi src
|
|
C edi &dst[xsize-1]
|
|
C ebp divisor
|
|
|
|
leal (%ebx,%ecx), %eax C size+xsize
|
|
cmpl $MUL_THRESHOLD, %eax
|
|
jae L(mul_by_inverse)
|
|
|
|
orl %ecx, %ecx
|
|
jz L(divide_no_integer)
|
|
|
|
L(divide_integer):
|
|
C eax scratch (quotient)
|
|
C ebx xsize
|
|
C ecx counter
|
|
C edx scratch (remainder)
|
|
C esi src
|
|
C edi &dst[xsize-1]
|
|
C ebp divisor
|
|
|
|
movl -4(%esi,%ecx,4), %eax
|
|
|
|
divl %ebp
|
|
|
|
movl %eax, (%edi,%ecx,4)
|
|
decl %ecx
|
|
jnz L(divide_integer)
|
|
|
|
|
|
L(divide_no_integer):
|
|
movl PARAM_DST, %edi
|
|
orl %ebx, %ebx
|
|
jnz L(divide_fraction)
|
|
|
|
L(divide_done):
|
|
movl SAVE_ESI, %esi
|
|
|
|
movl SAVE_EDI, %edi
|
|
|
|
movl SAVE_EBX, %ebx
|
|
movl %edx, %eax
|
|
|
|
movl SAVE_EBP, %ebp
|
|
addl $STACK_SPACE, %esp
|
|
|
|
ret
|
|
|
|
|
|
L(divide_fraction):
|
|
C eax scratch (quotient)
|
|
C ebx counter
|
|
C ecx
|
|
C edx scratch (remainder)
|
|
C esi
|
|
C edi dst
|
|
C ebp divisor
|
|
|
|
movl $0, %eax
|
|
|
|
divl %ebp
|
|
|
|
movl %eax, -4(%edi,%ebx,4)
|
|
decl %ebx
|
|
jnz L(divide_fraction)
|
|
|
|
jmp L(divide_done)
|
|
|
|
|
|
|
|
C -----------------------------------------------------------------------------
|
|
|
|
L(mul_by_inverse):
|
|
C eax
|
|
C ebx xsize
|
|
C ecx size
|
|
C edx carry
|
|
C esi src
|
|
C edi &dst[xsize-1]
|
|
C ebp divisor
|
|
|
|
leal 12(%edi), %ebx C &dst[xsize+2], loop dst stop
|
|
|
|
movl %ebx, VAR_DST_STOP
|
|
leal 4(%edi,%ecx,4), %edi C &dst[xsize+size]
|
|
|
|
movl %edi, VAR_DST
|
|
movl %ecx, %ebx C size
|
|
|
|
bsrl %ebp, %ecx C 31-l
|
|
movl %edx, %edi C carry
|
|
|
|
leal 1(%ecx), %eax C 32-l
|
|
xorl $31, %ecx C l
|
|
|
|
movl %ecx, VAR_NORM
|
|
movl $-1, %edx
|
|
|
|
shll %cl, %ebp C d normalized
|
|
movd %eax, %mm7
|
|
|
|
movl $-1, %eax
|
|
subl %ebp, %edx C (b-d)-1 giving edx:eax = b*(b-d)-1
|
|
|
|
divl %ebp C floor (b*(b-d)-1) / d
|
|
|
|
L(start_preinv):
|
|
C eax inverse
|
|
C ebx size
|
|
C ecx shift
|
|
C edx
|
|
C esi src
|
|
C edi carry
|
|
C ebp divisor
|
|
C
|
|
C mm7 rshift
|
|
|
|
movl %eax, VAR_INVERSE
|
|
orl %ebx, %ebx C size
|
|
leal -12(%esi,%ebx,4), %eax C &src[size-3]
|
|
|
|
movl %eax, VAR_SRC
|
|
jz L(start_zero)
|
|
|
|
movl 8(%eax), %esi C src high limb
|
|
cmpl $1, %ebx
|
|
jz L(start_one)
|
|
|
|
L(start_two_or_more):
|
|
movl 4(%eax), %edx C src second highest limb
|
|
|
|
shldl( %cl, %esi, %edi) C n2 = carry,high << l
|
|
|
|
shldl( %cl, %edx, %esi) C n10 = high,second << l
|
|
|
|
cmpl $2, %ebx
|
|
je L(integer_two_left)
|
|
jmp L(integer_top)
|
|
|
|
|
|
L(start_one):
|
|
shldl( %cl, %esi, %edi) C n2 = carry,high << l
|
|
|
|
shll %cl, %esi C n10 = high << l
|
|
jmp L(integer_one_left)
|
|
|
|
|
|
L(start_zero):
|
|
C Can be here with xsize==0 if mpn_preinv_divrem_1 had size==1 and
|
|
C skipped a division.
|
|
|
|
shll %cl, %edi C n2 = carry << l
|
|
movl %edi, %eax C return value for zero_done
|
|
cmpl $0, PARAM_XSIZE
|
|
|
|
je L(zero_done)
|
|
jmp L(fraction_some)
|
|
|
|
|
|
|
|
C -----------------------------------------------------------------------------
|
|
C
|
|
C This loop runs at about 25 cycles, which is probably sub-optimal, and
|
|
C certainly more than the dependent chain would suggest. A better loop, or
|
|
C a better rough analysis of what's possible, would be welcomed.
|
|
C
|
|
C In the current implementation, the following successively dependent
|
|
C micro-ops seem to exist.
|
|
C
|
|
C uops
|
|
C n2+n1 1 (addl)
|
|
C mul 5
|
|
C q1+1 3 (addl/adcl)
|
|
C mul 5
|
|
C sub 3 (subl/sbbl)
|
|
C addback 2 (cmov)
|
|
C ---
|
|
C 19
|
|
C
|
|
C Lack of registers hinders explicit scheduling and it might be that the
|
|
C normal out of order execution isn't able to hide enough under the mul
|
|
C latencies.
|
|
C
|
|
C Using sarl/negl to pick out n1 for the n2+n1 stage is a touch faster than
|
|
C cmov (and takes one uop off the dependent chain). A sarl/andl/addl
|
|
C combination was tried for the addback (despite the fact it would lengthen
|
|
C the dependent chain) but found to be no faster.
|
|
|
|
|
|
ALIGN(16)
|
|
L(integer_top):
|
|
C eax scratch
|
|
C ebx scratch (nadj, q1)
|
|
C ecx scratch (src, dst)
|
|
C edx scratch
|
|
C esi n10
|
|
C edi n2
|
|
C ebp d
|
|
C
|
|
C mm0 scratch (src qword)
|
|
C mm7 rshift for normalization
|
|
|
|
movl %esi, %eax
|
|
movl %ebp, %ebx
|
|
|
|
sarl $31, %eax C -n1
|
|
movl VAR_SRC, %ecx
|
|
|
|
andl %eax, %ebx C -n1 & d
|
|
negl %eax C n1
|
|
|
|
addl %esi, %ebx C nadj = n10 + (-n1 & d), ignoring overflow
|
|
addl %edi, %eax C n2+n1
|
|
movq (%ecx), %mm0 C next src limb and the one below it
|
|
|
|
mull VAR_INVERSE C m*(n2+n1)
|
|
|
|
subl $4, %ecx
|
|
|
|
movl %ecx, VAR_SRC
|
|
|
|
C
|
|
|
|
C
|
|
|
|
addl %ebx, %eax C m*(n2+n1) + nadj, low giving carry flag
|
|
movl %ebp, %eax C d
|
|
leal 1(%edi), %ebx C n2+1
|
|
|
|
adcl %edx, %ebx C 1 + high(n2<<32 + m*(n2+n1) + nadj) = q1+1
|
|
jz L(q1_ff)
|
|
|
|
mull %ebx C (q1+1)*d
|
|
|
|
movl VAR_DST, %ecx
|
|
psrlq %mm7, %mm0
|
|
|
|
C
|
|
|
|
C
|
|
|
|
C
|
|
|
|
subl %eax, %esi
|
|
movl VAR_DST_STOP, %eax
|
|
|
|
sbbl %edx, %edi C n - (q1+1)*d
|
|
movl %esi, %edi C remainder -> n2
|
|
leal (%ebp,%esi), %edx
|
|
|
|
cmovc( %edx, %edi) C n - q1*d if underflow from using q1+1
|
|
movd %mm0, %esi
|
|
|
|
sbbl $0, %ebx C q
|
|
subl $4, %ecx
|
|
|
|
movl %ebx, (%ecx)
|
|
cmpl %eax, %ecx
|
|
|
|
movl %ecx, VAR_DST
|
|
jne L(integer_top)
|
|
|
|
|
|
L(integer_loop_done):
|
|
|
|
|
|
C -----------------------------------------------------------------------------
|
|
C
|
|
C Here, and in integer_one_left below, an sbbl $0 is used rather than a jz
|
|
C q1_ff special case. This make the code a bit smaller and simpler, and
|
|
C costs only 2 cycles (each).
|
|
|
|
L(integer_two_left):
|
|
C eax scratch
|
|
C ebx scratch (nadj, q1)
|
|
C ecx scratch (src, dst)
|
|
C edx scratch
|
|
C esi n10
|
|
C edi n2
|
|
C ebp divisor
|
|
C
|
|
C mm7 rshift
|
|
|
|
|
|
movl %esi, %eax
|
|
movl %ebp, %ebx
|
|
|
|
sarl $31, %eax C -n1
|
|
movl PARAM_SRC, %ecx
|
|
|
|
andl %eax, %ebx C -n1 & d
|
|
negl %eax C n1
|
|
|
|
addl %esi, %ebx C nadj = n10 + (-n1 & d), ignoring overflow
|
|
addl %edi, %eax C n2+n1
|
|
|
|
mull VAR_INVERSE C m*(n2+n1)
|
|
|
|
movd (%ecx), %mm0 C src low limb
|
|
|
|
movl VAR_DST_STOP, %ecx
|
|
|
|
C
|
|
|
|
C
|
|
|
|
addl %ebx, %eax C m*(n2+n1) + nadj, low giving carry flag
|
|
leal 1(%edi), %ebx C n2+1
|
|
movl %ebp, %eax C d
|
|
|
|
adcl %edx, %ebx C 1 + high(n2<<32 + m*(n2+n1) + nadj) = q1+1
|
|
|
|
sbbl $0, %ebx
|
|
|
|
mull %ebx C (q1+1)*d
|
|
|
|
psllq $32, %mm0
|
|
|
|
psrlq %mm7, %mm0
|
|
|
|
C
|
|
|
|
C
|
|
|
|
subl %eax, %esi
|
|
|
|
sbbl %edx, %edi C n - (q1+1)*d
|
|
movl %esi, %edi C remainder -> n2
|
|
leal (%ebp,%esi), %edx
|
|
|
|
cmovc( %edx, %edi) C n - q1*d if underflow from using q1+1
|
|
movd %mm0, %esi
|
|
|
|
sbbl $0, %ebx C q
|
|
|
|
movl %ebx, -4(%ecx)
|
|
|
|
|
|
C -----------------------------------------------------------------------------
|
|
L(integer_one_left):
|
|
C eax scratch
|
|
C ebx scratch (nadj, q1)
|
|
C ecx scratch (dst)
|
|
C edx scratch
|
|
C esi n10
|
|
C edi n2
|
|
C ebp divisor
|
|
C
|
|
C mm7 rshift
|
|
|
|
|
|
movl %esi, %eax
|
|
movl %ebp, %ebx
|
|
|
|
sarl $31, %eax C -n1
|
|
movl VAR_DST_STOP, %ecx
|
|
|
|
andl %eax, %ebx C -n1 & d
|
|
negl %eax C n1
|
|
|
|
addl %esi, %ebx C nadj = n10 + (-n1 & d), ignoring overflow
|
|
addl %edi, %eax C n2+n1
|
|
|
|
mull VAR_INVERSE C m*(n2+n1)
|
|
|
|
C
|
|
|
|
C
|
|
|
|
C
|
|
|
|
addl %ebx, %eax C m*(n2+n1) + nadj, low giving carry flag
|
|
leal 1(%edi), %ebx C n2+1
|
|
movl %ebp, %eax C d
|
|
|
|
C
|
|
|
|
adcl %edx, %ebx C 1 + high(n2<<32 + m*(n2+n1) + nadj) = q1+1
|
|
|
|
sbbl $0, %ebx C q1 if q1+1 overflowed
|
|
|
|
mull %ebx
|
|
|
|
C
|
|
|
|
C
|
|
|
|
C
|
|
|
|
C
|
|
|
|
subl %eax, %esi
|
|
movl PARAM_XSIZE, %eax
|
|
|
|
sbbl %edx, %edi C n - (q1+1)*d
|
|
movl %esi, %edi C remainder -> n2
|
|
leal (%ebp,%esi), %edx
|
|
|
|
cmovc( %edx, %edi) C n - q1*d if underflow from using q1+1
|
|
|
|
sbbl $0, %ebx C q
|
|
|
|
movl %ebx, -8(%ecx)
|
|
subl $8, %ecx
|
|
|
|
|
|
|
|
orl %eax, %eax C xsize
|
|
jnz L(fraction_some)
|
|
|
|
movl %edi, %eax
|
|
L(fraction_done):
|
|
movl VAR_NORM, %ecx
|
|
L(zero_done):
|
|
movl SAVE_EBP, %ebp
|
|
|
|
movl SAVE_EDI, %edi
|
|
|
|
movl SAVE_ESI, %esi
|
|
|
|
movl SAVE_EBX, %ebx
|
|
addl $STACK_SPACE, %esp
|
|
|
|
shrl %cl, %eax
|
|
emms
|
|
|
|
ret
|
|
|
|
|
|
C -----------------------------------------------------------------------------
|
|
C
|
|
C Special case for q1=0xFFFFFFFF, giving q=0xFFFFFFFF meaning the low dword
|
|
C of q*d is simply -d and the remainder n-q*d = n10+d
|
|
|
|
L(q1_ff):
|
|
C eax (divisor)
|
|
C ebx (q1+1 == 0)
|
|
C ecx
|
|
C edx
|
|
C esi n10
|
|
C edi n2
|
|
C ebp divisor
|
|
|
|
movl VAR_DST, %ecx
|
|
movl VAR_DST_STOP, %edx
|
|
subl $4, %ecx
|
|
|
|
movl %ecx, VAR_DST
|
|
psrlq %mm7, %mm0
|
|
leal (%ebp,%esi), %edi C n-q*d remainder -> next n2
|
|
|
|
movl $-1, (%ecx)
|
|
movd %mm0, %esi C next n10
|
|
|
|
cmpl %ecx, %edx
|
|
jne L(integer_top)
|
|
|
|
jmp L(integer_loop_done)
|
|
|
|
|
|
|
|
C -----------------------------------------------------------------------------
|
|
C
|
|
C In the current implementation, the following successively dependent
|
|
C micro-ops seem to exist.
|
|
C
|
|
C uops
|
|
C mul 5
|
|
C q1+1 1 (addl)
|
|
C mul 5
|
|
C sub 3 (negl/sbbl)
|
|
C addback 2 (cmov)
|
|
C ---
|
|
C 16
|
|
C
|
|
C The loop in fact runs at about 17.5 cycles. Using a sarl/andl/addl for
|
|
C the addback was found to be a touch slower.
|
|
|
|
|
|
ALIGN(16)
|
|
L(fraction_some):
|
|
C eax
|
|
C ebx
|
|
C ecx
|
|
C edx
|
|
C esi
|
|
C edi carry
|
|
C ebp divisor
|
|
|
|
movl PARAM_DST, %esi
|
|
movl VAR_DST_STOP, %ecx C &dst[xsize+2]
|
|
movl %edi, %eax
|
|
|
|
subl $8, %ecx C &dst[xsize]
|
|
|
|
|
|
ALIGN(16)
|
|
L(fraction_top):
|
|
C eax n2, then scratch
|
|
C ebx scratch (nadj, q1)
|
|
C ecx dst, decrementing
|
|
C edx scratch
|
|
C esi dst stop point
|
|
C edi n2
|
|
C ebp divisor
|
|
|
|
mull VAR_INVERSE C m*n2
|
|
|
|
movl %ebp, %eax C d
|
|
subl $4, %ecx C dst
|
|
leal 1(%edi), %ebx
|
|
|
|
C
|
|
|
|
C
|
|
|
|
C
|
|
|
|
addl %edx, %ebx C 1 + high(n2<<32 + m*n2) = q1+1
|
|
|
|
mull %ebx C (q1+1)*d
|
|
|
|
C
|
|
|
|
C
|
|
|
|
C
|
|
|
|
C
|
|
|
|
negl %eax C low of n - (q1+1)*d
|
|
|
|
sbbl %edx, %edi C high of n - (q1+1)*d, caring only about carry
|
|
leal (%ebp,%eax), %edx
|
|
|
|
cmovc( %edx, %eax) C n - q1*d if underflow from using q1+1
|
|
|
|
sbbl $0, %ebx C q
|
|
movl %eax, %edi C remainder->n2
|
|
cmpl %esi, %ecx
|
|
|
|
movl %ebx, (%ecx) C previous q
|
|
jne L(fraction_top)
|
|
|
|
|
|
jmp L(fraction_done)
|
|
|
|
EPILOGUE()
|