dnl Intel Pentium mpn_modexact_1_odd -- exact division style remainder.
dnl Copyright 2000-2002, 2014 Free Software Foundation, Inc.
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 modify
dnl it under the terms of either:
dnl
dnl * the GNU Lesser General Public License as published by the Free
dnl Software Foundation; either version 3 of the License, or (at your
dnl option) any later version.
dnl
dnl or
dnl
dnl * the GNU General Public License as published by the Free Software
dnl Foundation; either version 2 of the License, or (at your option) any
dnl later version.
dnl
dnl or both in parallel, as here.
dnl
dnl The GNU MP Library is distributed in the hope that it will be useful, but
dnl WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
dnl or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
dnl for more details.
dnl
dnl You should have received copies of the GNU General Public License and the
dnl GNU Lesser General Public License along with the GNU MP Library. If not,
dnl see https://www.gnu.org/licenses/.
include(`../config.m4')
C P5: 23.0 cycles/limb
C mp_limb_t mpn_modexact_1_odd (mp_srcptr src, mp_size_t size,
C mp_limb_t divisor);
C mp_limb_t mpn_modexact_1c_odd (mp_srcptr src, mp_size_t size,
C mp_limb_t divisor, mp_limb_t carry);
C
C There seems no way to pair up the two lone instructions in the main loop.
C
C The special case for size==1 saves about 20 cycles (non-PIC), making it
C the same as mpn_mod_1, and in fact making modexact faster than mod_1 at
C all sizes.
C
C Alternatives:
C
C Using mmx for the multiplies might be possible, with pmullw and pmulhw
C having just 3 cycle latencies, but carry bit handling would probably be
C complicated.
defframe(PARAM_CARRY, 16)
defframe(PARAM_DIVISOR,12)
defframe(PARAM_SIZE, 8)
defframe(PARAM_SRC, 4)
dnl re-using parameter space
define(VAR_INVERSE,`PARAM_SIZE')
TEXT
ALIGN(16)
PROLOGUE(mpn_modexact_1c_odd)
deflit(`FRAME',0)
movl PARAM_DIVISOR, %eax
movl PARAM_CARRY, %edx
jmp L(start_1c)
EPILOGUE()
ALIGN(16)
PROLOGUE(mpn_modexact_1_odd)
deflit(`FRAME',0)
movl PARAM_DIVISOR, %eax
xorl %edx, %edx C carry
L(start_1c):
ifdef(`PIC',`
ifdef(`DARWIN',`
shrl %eax C d/2
LEA( binvert_limb_table, %ecx)
pushl %ebx FRAME_pushl()
movl PARAM_SIZE, %ebx
andl $127, %eax
subl $2, %ebx
movb (%eax,%ecx), %cl
jc L(one_limb)
',`
call L(here) FRAME_pushl()
L(here):
shrl %eax C d/2
movl (%esp), %ecx C eip
addl $_GLOBAL_OFFSET_TABLE_+[.-L(here)], %ecx
movl %ebx, (%esp) C push ebx
andl $127, %eax
movl PARAM_SIZE, %ebx
movl binvert_limb_table@GOT(%ecx), %ecx
subl $2, %ebx
movb (%eax,%ecx), %cl C inv 8 bits
jc L(one_limb)
')
',`
dnl non-PIC
shrl %eax C d/2
pushl %ebx FRAME_pushl()
movl PARAM_SIZE, %ebx
andl $127, %eax
subl $2, %ebx
jc L(one_limb)
movb binvert_limb_table(%eax), %cl C inv 8 bits
')
movl %ecx, %eax
addl %ecx, %ecx C 2*inv
imull %eax, %eax C inv*inv
imull PARAM_DIVISOR, %eax C inv*inv*d
subl %eax, %ecx C inv = 2*inv - inv*inv*d
movl %ecx, %eax
addl %ecx, %ecx C 2*inv
imull %eax, %eax C inv*inv
imull PARAM_DIVISOR, %eax C inv*inv*d
subl %eax, %ecx C inv = 2*inv - inv*inv*d
pushl %esi FRAME_pushl()
ASSERT(e,` C d*inv == 1 mod 2^GMP_LIMB_BITS
movl %ecx, %eax
imull PARAM_DIVISOR, %eax
cmpl $1, %eax')
movl PARAM_SRC, %esi
movl %ecx, VAR_INVERSE
movl (%esi), %eax C src[0]
leal 4(%esi,%ebx,4), %esi C &src[size-1]
xorl $-1, %ebx C -(size-1)
ASSERT(nz)
jmp L(entry)
C The use of VAR_INVERSE means only a store is needed for that value, rather
C than a push and pop of say %edi.
ALIGN(16)
L(top):
C eax scratch, low product
C ebx counter, limbs, negative
C ecx carry bit
C edx scratch, high product
C esi &src[size-1]
C edi
C ebp
mull PARAM_DIVISOR C h:dummy = q*d
movl (%esi,%ebx,4), %eax C src[i]
subl %ecx, %edx C h -= -c
L(entry):
subl %edx, %eax C s = src[i] - h
sbbl %ecx, %ecx C new -c (0 or -1)
imull VAR_INVERSE, %eax C q = s*i
incl %ebx
jnz L(top)
mull PARAM_DIVISOR
movl (%esi), %eax C src high
subl %ecx, %edx C h -= -c
cmpl PARAM_DIVISOR, %eax
jbe L(skip_last)
deflit(FRAME_LAST,FRAME)
subl %edx, %eax C s = src[i] - h
popl %esi FRAME_popl()
sbbl %ecx, %ecx C c (0 or -1)
popl %ebx FRAME_popl()
imull VAR_INVERSE, %eax C q = s*i
mull PARAM_DIVISOR C h:dummy = q*d
movl %edx, %eax
subl %ecx, %eax
ret
C When high<divisor can skip last step.
L(skip_last):
deflit(`FRAME',FRAME_LAST)
C eax src high
C ebx
C ecx
C edx r
C esi
subl %eax, %edx C r-s
popl %esi FRAME_popl()
sbbl %eax, %eax C -1 if underflow
movl PARAM_DIVISOR, %ebx
andl %ebx, %eax C divisor if underflow
popl %ebx FRAME_popl()
addl %edx, %eax C addback if underflow
ret
C Special case for size==1 using a division for r = c-a mod d.
C Could look for a-c<d and save a division sometimes, but that doesn't seem
C worth bothering about.
L(one_limb):
deflit(`FRAME',4)
C eax
C ebx size-2 (==-1)
C ecx
C edx carry
C esi src end
C edi
C ebp
movl %edx, %eax
movl PARAM_SRC, %edx
movl PARAM_DIVISOR, %ecx
popl %ebx FRAME_popl()
subl (%edx), %eax C c-a
sbbl %edx, %edx
decl %ecx C d-1
andl %ecx, %edx C b*d+c-a if c<a, or c-a if c>=a
divl PARAM_DIVISOR
movl %edx, %eax
ret
EPILOGUE()
ASM_END()