292 lines
5.4 KiB
NASM
292 lines
5.4 KiB
NASM
dnl AMD K6 mpn_divexact_1 -- mpn by limb exact division.
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dnl Copyright 2000, 2001, 2002 Free Software Foundation, Inc.
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dnl
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dnl This file is part of the GNU MP Library.
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dnl
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dnl The GNU MP Library is free software; you can redistribute it and/or
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dnl modify it under the terms of the GNU Lesser General Public License as
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dnl published by the Free Software Foundation; either version 2.1 of the
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dnl License, or (at your option) any later version.
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dnl
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dnl The GNU MP Library is distributed in the hope that it will be useful,
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dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
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dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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dnl Lesser General Public License for more details.
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dnl
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dnl You should have received a copy of the GNU Lesser General Public
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dnl License along with the GNU MP Library; see the file COPYING.LIB. If
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dnl not, write to the Free Software Foundation, Inc., 51 Franklin Street,
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dnl Fifth Floor, Boston, MA 02110-1301, USA.
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include(`../config.m4')
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C divisor
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C odd even
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C K6: 10.0 12.0 cycles/limb
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C K6-2: 10.0 11.5
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C void mpn_divexact_1 (mp_ptr dst, mp_srcptr src, mp_size_t size,
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C mp_limb_t divisor);
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C
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C A simple divl is used for size==1. This is about 10 cycles faster for an
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C odd divisor or 20 cycles for an even divisor.
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C
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C The loops are quite sensitive to code alignment, speeds should be
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C rechecked (odd and even divisor, pic and non-pic) if contemplating
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C changing anything.
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defframe(PARAM_DIVISOR,16)
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defframe(PARAM_SIZE, 12)
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defframe(PARAM_SRC, 8)
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defframe(PARAM_DST, 4)
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dnl re-use parameter space
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define(VAR_INVERSE,`PARAM_DST')
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TEXT
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ALIGN(32)
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PROLOGUE(mpn_divexact_1)
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deflit(`FRAME',0)
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movl PARAM_SIZE, %ecx
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movl PARAM_SRC, %eax
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xorl %edx, %edx
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cmpl $1, %ecx
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jnz L(two_or_more)
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movl (%eax), %eax
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divl PARAM_DIVISOR
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movl PARAM_DST, %ecx
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movl %eax, (%ecx)
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ret
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L(two_or_more):
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movl PARAM_DIVISOR, %eax
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pushl %ebx FRAME_pushl()
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movl PARAM_SRC, %ebx
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pushl %ebp FRAME_pushl()
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L(strip_twos):
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shrl %eax
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incl %edx C will get shift+1
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jnc L(strip_twos)
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pushl %esi FRAME_pushl()
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leal 1(%eax,%eax), %esi C d without twos
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andl $127, %eax C d/2, 7 bits
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ifdef(`PIC',`
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call L(movl_eip_ebp)
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addl $_GLOBAL_OFFSET_TABLE_, %ebp
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C
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movl modlimb_invert_table@GOT(%ebp), %ebp
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C
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Zdisp( movzbl, 0,(%eax,%ebp), %eax)
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',`
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dnl non-PIC
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movzbl modlimb_invert_table(%eax), %eax C inv 8 bits
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')
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pushl %edi FRAME_pushl()
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leal (%eax,%eax), %ebp C 2*inv
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imull %eax, %eax C inv*inv
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movl PARAM_DST, %edi
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imull %esi, %eax C inv*inv*d
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subl %eax, %ebp C inv = 2*inv - inv*inv*d
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leal (%ebp,%ebp), %eax C 2*inv
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imull %ebp, %ebp C inv*inv
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movl %esi, PARAM_DIVISOR C d without twos
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leal (%ebx,%ecx,4), %ebx C src end
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imull %esi, %ebp C inv*inv*d
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leal (%edi,%ecx,4), %edi C dst end
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negl %ecx C -size
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subl %ebp, %eax C inv = 2*inv - inv*inv*d
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subl $1, %edx C shift amount, and clear carry
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ASSERT(e,` C expect d*inv == 1 mod 2^BITS_PER_MP_LIMB
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pushl %eax FRAME_pushl()
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imull PARAM_DIVISOR, %eax
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cmpl $1, %eax
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popl %eax FRAME_popl()')
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movl %eax, VAR_INVERSE
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jnz L(even)
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movl (%ebx,%ecx,4), %esi C src low limb
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jmp L(odd_entry)
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ALIGN(16)
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nop C code alignment
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L(odd_top):
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C eax scratch
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C ebx src end
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C ecx counter, limbs, negative
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C edx inverse
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C esi next limb, adjusted for carry
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C edi dst end
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C ebp carry bit, 0 or -1
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imull %edx, %esi
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movl PARAM_DIVISOR, %eax
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movl %esi, -4(%edi,%ecx,4)
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mull %esi C carry limb in edx
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subl %ebp, %edx C apply carry bit
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movl (%ebx,%ecx,4), %esi
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L(odd_entry):
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subl %edx, %esi C apply carry limb
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movl VAR_INVERSE, %edx
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sbbl %ebp, %ebp C 0 or -1
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incl %ecx
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jnz L(odd_top)
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imull %edx, %esi
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movl %esi, -4(%edi,%ecx,4)
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popl %edi
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popl %esi
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popl %ebp
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popl %ebx
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ret
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ifdef(`PIC',`
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L(movl_eip_ebp):
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movl (%esp), %ebp
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ret_internal
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ALIGN(8)
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nop C code alignment, necessary for claimed speed
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nop
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',`
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C non-PIC code alignment already ok at 0x9a
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')
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L(even):
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C eax
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C ebx src end
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C ecx -size
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C edx twos
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C esi
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C edi dst end
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C ebp
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xorl %ebp, %ebp
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Zdisp( movq, 0,(%ebx,%ecx,4), %mm0) C src[0,1]
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movd %edx, %mm7
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movl VAR_INVERSE, %edx
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addl $2, %ecx
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psrlq %mm7, %mm0
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movd %mm0, %esi
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jz L(even_two) C if only two limbs
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C Out-of-order execution is good enough to hide the load/rshift/movd
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C latency. Having imul at the top of the loop gives 11.5 c/l instead of 12,
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C on K6-2. In fact there's only 11 of decode, but nothing running at 11 has
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C been found. Maybe the fact every second movq is unaligned costs the extra
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C 0.5.
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L(even_top):
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C eax scratch
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C ebx src end
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C ecx counter, limbs, negative
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C edx inverse
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C esi next limb, adjusted for carry
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C edi dst end
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C ebp carry bit, 0 or -1
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C
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C mm0 scratch, source limbs
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C mm7 twos
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imull %edx, %esi
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movl %esi, -8(%edi,%ecx,4)
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movl PARAM_DIVISOR, %eax
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mull %esi C carry limb in edx
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movq -4(%ebx,%ecx,4), %mm0
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psrlq %mm7, %mm0
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movd %mm0, %esi
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subl %ebp, %edx C apply carry bit
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subl %edx, %esi C apply carry limb
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movl VAR_INVERSE, %edx
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sbbl %ebp, %ebp C 0 or -1
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incl %ecx
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jnz L(even_top)
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L(even_two):
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movd -4(%ebx), %mm0 C src high limb
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psrlq %mm7, %mm0
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imull %edx, %esi
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movl %esi, -8(%edi)
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movl PARAM_DIVISOR, %eax
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mull %esi C carry limb in edx
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movd %mm0, %esi
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subl %ebp, %edx C apply carry bit
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movl VAR_INVERSE, %eax
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subl %edx, %esi C apply carry limb
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imull %eax, %esi
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movl %esi, -4(%edi)
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popl %edi
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popl %esi
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popl %ebp
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popl %ebx
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emms
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ret
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EPILOGUE()
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