mod_34lsub1.asm
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上传日期:2022-08-06
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- dnl AMD K6 mpn_mod_34lsub1 -- mpn remainder modulo 2**24-1.
- dnl Copyright 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 3 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 License
- dnl along with the GNU MP Library. If not, see http://www.gnu.org/licenses/.
- include(`../config.m4')
- C K6: 2.66 cycles/limb
- C mp_limb_t mpn_mod_34lsub1 (mp_srcptr src, mp_size_t size)
- C
- C An attempt was made to use a loop like
- C
- C L(top):
- C adcl (%edx), %eax
- C adcl 4(%edx), %ebx
- C adcl 8(%edx), %esi
- C leal 12(%edx), %edx
- C loop L(top)
- C
- C with %ecx starting from floor(size/3), but it still measured 2.66 c/l.
- C The form used instead can save about 6 cycles by not dividing by 3.
- C
- C In the code used, putting the "leal"s at the top of the loop is necessary
- C for the claimed speed, anywhere else costs an extra cycle per loop.
- C Perhaps a tight loop like this needs short decode instructions at the
- C branch target, which would explain the leal/loop form above taking 8
- C cycles instead of 7 too.
- defframe(PARAM_SIZE, 8)
- defframe(PARAM_SRC, 4)
- dnl re-use parameter space
- define(SAVE_EBX, `PARAM_SIZE')
- define(SAVE_ESI, `PARAM_SRC')
- TEXT
- ALIGN(16)
- PROLOGUE(mpn_mod_34lsub1)
- deflit(`FRAME',0)
- movl PARAM_SIZE, %eax
- movl PARAM_SRC, %edx
- subl $2, %eax
- ja L(three_or_more)
- Zdisp( movl, 0,(%edx), %eax) C avoid code cache line boundary
- jne L(one)
- movl %eax, %ecx
- movl 4(%edx), %edx
- shrl $24, %eax C src[0] high
- andl $0x00FFFFFF, %ecx C src[0] low
- addl %ecx, %eax
- movl %edx, %ecx
- shll $8, %edx
- andl $0x00FFFF00, %edx C src[1] high
- shrl $16, %ecx C src[1] low
- addl %ecx, %eax
- addl %edx, %eax
- L(one):
- ret
- L(three_or_more):
- C eax size-2
- C ebx
- C ecx
- C edx src
- movl %ebx, SAVE_EBX
- xorl %ebx, %ebx
- movl %esi, SAVE_ESI
- pushl %edi FRAME_pushl()
- xorl %esi, %esi
- xorl %edi, %edi C and clear carry flag
- L(top):
- C eax counter, limbs
- C ebx acc 0mod3
- C ecx
- C edx src, incrementing
- C esi acc 1mod3
- C edi acc 2mod3
- C ebp
- leal -2(%eax), %eax
- leal 12(%edx), %edx
- adcl -12(%edx), %ebx
- adcl -8(%edx), %esi
- adcl -4(%edx), %edi
- decl %eax
- jg L(top)
- C ecx is -3, -2 or -1 representing 0, 1 or 2 more limbs, respectively
- movb $0, %cl
- incl %eax
- js L(combine) C 0 more
- Zdisp( adcl, 0,(%edx), %ebx) C avoid code cache line crossings
- movb $8, %cl
- decl %eax
- js L(combine) C 1 more
- adcl 4(%edx), %esi
- movb $16, %cl
- L(combine):
- sbbl %edx, %edx
- shll %cl, %edx C carry
- movl %ebx, %eax C 0mod3
- shrl $24, %eax C 0mod3 high
- andl $0x00FFFFFF, %ebx C 0mod3 low
- subl %edx, %eax C apply carry
- movl %esi, %ecx C 1mod3
- shrl $16, %esi C 1mod3 high
- addl %ebx, %eax C apply 0mod3 low
- andl $0x0000FFFF, %ecx
- addl %esi, %eax C apply 1mod3 high
- shll $8, %ecx C 1mod3 low
- movl %edi, %edx C 2mod3
- shrl $8, %edx C 2mod3 high
- addl %ecx, %eax C apply 1mod3 low
- addl %edx, %eax C apply 2mod3 high
- andl $0x000000FF, %edi
- shll $16, %edi C 2mod3 low
- movl SAVE_EBX, %ebx
- addl %edi, %eax C apply 2mod3 low
- movl SAVE_ESI, %esi
- popl %edi
- ret
- EPILOGUE()