dive_1.asm
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上传日期:2022-08-06
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- dnl AMD K6 mpn_divexact_1 -- mpn by limb exact division.
- dnl Copyright 2000, 2001, 2002, 2007 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 divisor
- C odd even
- C K6: 10.0 12.0 cycles/limb
- C K6-2: 10.0 11.5
- C void mpn_divexact_1 (mp_ptr dst, mp_srcptr src, mp_size_t size,
- C mp_limb_t divisor);
- C
- C A simple divl is used for size==1. This is about 10 cycles faster for an
- C odd divisor or 20 cycles for an even divisor.
- C
- C The loops are quite sensitive to code alignment, speeds should be
- C rechecked (odd and even divisor, pic and non-pic) if contemplating
- C changing anything.
- defframe(PARAM_DIVISOR,16)
- defframe(PARAM_SIZE, 12)
- defframe(PARAM_SRC, 8)
- defframe(PARAM_DST, 4)
- dnl re-use parameter space
- define(VAR_INVERSE,`PARAM_DST')
- TEXT
- ALIGN(32)
- PROLOGUE(mpn_divexact_1)
- deflit(`FRAME',0)
- movl PARAM_SIZE, %ecx
- movl PARAM_SRC, %eax
- xorl %edx, %edx
- cmpl $1, %ecx
- jnz L(two_or_more)
- movl (%eax), %eax
- divl PARAM_DIVISOR
- movl PARAM_DST, %ecx
- movl %eax, (%ecx)
- ret
- L(two_or_more):
- movl PARAM_DIVISOR, %eax
- pushl %ebx FRAME_pushl()
- movl PARAM_SRC, %ebx
- pushl %ebp FRAME_pushl()
- L(strip_twos):
- shrl %eax
- incl %edx C will get shift+1
- jnc L(strip_twos)
- pushl %esi FRAME_pushl()
- leal 1(%eax,%eax), %esi C d without twos
- andl $127, %eax C d/2, 7 bits
- ifdef(`PIC',`
- LEA( binvert_limb_table, %ebp)
- Zdisp( movzbl, 0,(%eax,%ebp), %eax)
- ',`
- movzbl binvert_limb_table(%eax), %eax C inv 8 bits
- ')
- pushl %edi FRAME_pushl()
- leal (%eax,%eax), %ebp C 2*inv
- imull %eax, %eax C inv*inv
- movl PARAM_DST, %edi
- imull %esi, %eax C inv*inv*d
- subl %eax, %ebp C inv = 2*inv - inv*inv*d
- leal (%ebp,%ebp), %eax C 2*inv
- imull %ebp, %ebp C inv*inv
- movl %esi, PARAM_DIVISOR C d without twos
- leal (%ebx,%ecx,4), %ebx C src end
- imull %esi, %ebp C inv*inv*d
- leal (%edi,%ecx,4), %edi C dst end
- negl %ecx C -size
- subl %ebp, %eax C inv = 2*inv - inv*inv*d
- subl $1, %edx C shift amount, and clear carry
- ASSERT(e,` C expect d*inv == 1 mod 2^GMP_LIMB_BITS
- pushl %eax FRAME_pushl()
- imull PARAM_DIVISOR, %eax
- cmpl $1, %eax
- popl %eax FRAME_popl()')
- movl %eax, VAR_INVERSE
- jnz L(even)
- movl (%ebx,%ecx,4), %esi C src low limb
- jmp L(odd_entry)
- ALIGN(16)
- nop C code alignment
- L(odd_top):
- C eax scratch
- C ebx src end
- C ecx counter, limbs, negative
- C edx inverse
- C esi next limb, adjusted for carry
- C edi dst end
- C ebp carry bit, 0 or -1
- imull %edx, %esi
- movl PARAM_DIVISOR, %eax
- movl %esi, -4(%edi,%ecx,4)
- mull %esi C carry limb in edx
- subl %ebp, %edx C apply carry bit
- movl (%ebx,%ecx,4), %esi
- L(odd_entry):
- subl %edx, %esi C apply carry limb
- movl VAR_INVERSE, %edx
- sbbl %ebp, %ebp C 0 or -1
- incl %ecx
- jnz L(odd_top)
- imull %edx, %esi
- movl %esi, -4(%edi,%ecx,4)
- popl %edi
- popl %esi
- popl %ebp
- popl %ebx
- ret
- L(even):
- C eax
- C ebx src end
- C ecx -size
- C edx twos
- C esi
- C edi dst end
- C ebp
- xorl %ebp, %ebp
- Zdisp( movq, 0,(%ebx,%ecx,4), %mm0) C src[0,1]
- movd %edx, %mm7
- movl VAR_INVERSE, %edx
- addl $2, %ecx
- psrlq %mm7, %mm0
- movd %mm0, %esi
- jz L(even_two) C if only two limbs
- C Out-of-order execution is good enough to hide the load/rshift/movd
- C latency. Having imul at the top of the loop gives 11.5 c/l instead of 12,
- C on K6-2. In fact there's only 11 of decode, but nothing running at 11 has
- C been found. Maybe the fact every second movq is unaligned costs the extra
- C 0.5.
- L(even_top):
- C eax scratch
- C ebx src end
- C ecx counter, limbs, negative
- C edx inverse
- C esi next limb, adjusted for carry
- C edi dst end
- C ebp carry bit, 0 or -1
- C
- C mm0 scratch, source limbs
- C mm7 twos
- imull %edx, %esi
- movl %esi, -8(%edi,%ecx,4)
- movl PARAM_DIVISOR, %eax
- mull %esi C carry limb in edx
- movq -4(%ebx,%ecx,4), %mm0
- psrlq %mm7, %mm0
- movd %mm0, %esi
- subl %ebp, %edx C apply carry bit
- subl %edx, %esi C apply carry limb
- movl VAR_INVERSE, %edx
- sbbl %ebp, %ebp C 0 or -1
- incl %ecx
- jnz L(even_top)
- L(even_two):
- movd -4(%ebx), %mm0 C src high limb
- psrlq %mm7, %mm0
- imull %edx, %esi
- movl %esi, -8(%edi)
- movl PARAM_DIVISOR, %eax
- mull %esi C carry limb in edx
- movd %mm0, %esi
- subl %ebp, %edx C apply carry bit
- movl VAR_INVERSE, %eax
- subl %edx, %esi C apply carry limb
- imull %eax, %esi
- movl %esi, -4(%edi)
- popl %edi
- popl %esi
- popl %ebp
- popl %ebx
- emms_or_femms
- ret
- EPILOGUE()