180 lines
3.9 KiB
NASM
180 lines
3.9 KiB
NASM
dnl AMD K6 mpn_modexact_1_odd -- exact division style remainder.
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dnl Copyright 2000, 2001, 2002, 2003 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 K6: 10.0 cycles/limb
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C mp_limb_t mpn_modexact_1_odd (mp_srcptr src, mp_size_t size,
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C mp_limb_t divisor);
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C mp_limb_t mpn_modexact_1c_odd (mp_srcptr src, mp_size_t size,
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C mp_limb_t divisor, mp_limb_t carry);
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C
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C A special case for high<divisor at the end measured only about 4 cycles
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C faster, and so isn't used.
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C
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C A special case for size==1 using a divl rather than the inverse measured
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C only about 5 cycles faster, and so isn't used. When size==1 and
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C high<divisor it can skip a division and be a full 24 cycles faster, but
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C this isn't an important case.
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defframe(PARAM_CARRY, 16)
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defframe(PARAM_DIVISOR,12)
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defframe(PARAM_SIZE, 8)
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defframe(PARAM_SRC, 4)
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TEXT
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ALIGN(32)
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PROLOGUE(mpn_modexact_1c_odd)
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deflit(`FRAME',0)
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movl PARAM_DIVISOR, %ecx
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pushl %esi FRAME_pushl()
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movl PARAM_CARRY, %edx
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jmp L(start_1c)
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ifdef(`PIC',`
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L(movl_eip_edi):
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movl (%esp), %edi
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ret_internal
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')
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EPILOGUE()
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ALIGN(16)
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PROLOGUE(mpn_modexact_1_odd)
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deflit(`FRAME',0)
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movl PARAM_DIVISOR, %ecx
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pushl %esi FRAME_pushl()
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xorl %edx, %edx
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L(start_1c):
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pushl %edi FRAME_pushl()
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shrl %ecx C d/2
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movl PARAM_DIVISOR, %esi
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andl $127, %ecx C d/2, 7 bits
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pushl %ebp FRAME_pushl()
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ifdef(`PIC',`
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call L(movl_eip_edi)
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addl $_GLOBAL_OFFSET_TABLE_, %edi
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C
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movl modlimb_invert_table@GOT(%edi), %edi
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C
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Zdisp( movzbl, 0,(%ecx,%edi), %edi) C inv 8 bits
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',`
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dnl non-PIC
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movzbl modlimb_invert_table(%ecx), %edi C inv 8 bits
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')
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leal (%edi,%edi), %ecx C 2*inv
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imull %edi, %edi C inv*inv
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movl PARAM_SRC, %eax
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movl PARAM_SIZE, %ebp
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imull %esi, %edi C inv*inv*d
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pushl %ebx FRAME_pushl()
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leal (%eax,%ebp,4), %ebx C src end
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subl %edi, %ecx C inv = 2*inv - inv*inv*d
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leal (%ecx,%ecx), %edi C 2*inv
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imull %ecx, %ecx C inv*inv
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movl (%eax), %eax C src low limb
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negl %ebp C -size
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imull %esi, %ecx C inv*inv*d
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subl %ecx, %edi C inv = 2*inv - inv*inv*d
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ASSERT(e,` C d*inv == 1 mod 2^BITS_PER_MP_LIMB
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pushl %eax
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movl %esi, %eax
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imull %edi, %eax
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cmpl $1, %eax
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popl %eax')
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jmp L(entry)
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C Rotating the mul to the top of the loop saves 1 cycle, presumably by
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C hiding the loop control under the imul latency.
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C
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C The run time is 10 cycles, but decoding is only 9 (and the dependent chain
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C only 8). It's not clear how to get down to 9 cycles.
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C
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C The xor and rcl to handle the carry bit could be an sbb instead, with the
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C the carry bit add becoming a sub, but that doesn't save anything.
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L(top):
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C eax (low product)
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C ebx src end
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C ecx carry bit, 0 or 1
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C edx (high product, being carry limb)
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C esi divisor
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C edi inverse
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C ebp counter, limbs, negative
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mull %esi
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movl (%ebx,%ebp,4), %eax
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addl %ecx, %edx C apply carry bit to carry limb
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L(entry):
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xorl %ecx, %ecx
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subl %edx, %eax C apply carry limb
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rcll %ecx
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imull %edi, %eax
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incl %ebp
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jnz L(top)
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popl %ebx
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popl %ebp
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mull %esi
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popl %edi
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popl %esi
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leal (%ecx,%edx), %eax
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ret
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EPILOGUE()
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