178 lines
3.5 KiB
NASM
178 lines
3.5 KiB
NASM
dnl Intel Pentium-4 mpn_modexact_1_odd -- mpn by limb exact remainder.
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dnl Copyright 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 P4: 19.0 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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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(16)
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PROLOGUE(mpn_modexact_1c_odd)
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deflit(`FRAME',0)
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movd PARAM_CARRY, %mm1
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jmp L(start_1c)
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ifdef(`PIC',`
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L(movl_eip_edx):
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movl (%esp), %edx
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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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pxor %mm1, %mm1 C carry limb
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L(start_1c):
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movl PARAM_DIVISOR, %eax
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movd PARAM_DIVISOR, %mm7
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shrl %eax
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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_edx)
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addl $_GLOBAL_OFFSET_TABLE_, %edx
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movl modlimb_invert_table@GOT(%edx), %edx
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C
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movzbl (%eax,%edx), %eax C inv 8 bits
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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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C
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movd %eax, %mm6 C inv
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movd %eax, %mm0 C inv
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pmuludq %mm6, %mm6 C inv*inv
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C
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pmuludq %mm7, %mm6 C inv*inv*d
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paddd %mm0, %mm0 C 2*inv
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C
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psubd %mm6, %mm0 C inv = 2*inv - inv*inv*d
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pxor %mm6, %mm6
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paddd %mm0, %mm6
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pmuludq %mm0, %mm0 C inv*inv
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C
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pmuludq %mm7, %mm0 C inv*inv*d
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paddd %mm6, %mm6 C 2*inv
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movl PARAM_SRC, %eax
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movl PARAM_SIZE, %ecx
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C
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psubd %mm0, %mm6 C inv = 2*inv - inv*inv*d
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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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movd %mm6, %eax
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imul PARAM_DIVISOR, %eax
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cmpl $1, %eax
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popl %eax FRAME_popl()')
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pxor %mm0, %mm0 C carry bit
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C The dependent chain here is as follows.
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C
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C latency
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C psubq s = (src-cbit) - climb 2
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C pmuludq q = s*inverse 8
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C pmuludq prod = q*divisor 8
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C psrlq climb = high(prod) 2
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C --
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C 20
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C
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C Yet the loop measures 19.0 c/l, so obviously there's something gained
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C there over a straight reading of the chip documentation.
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L(top):
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C eax src, incrementing
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C ebx
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C ecx counter, limbs
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C edx
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C
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C mm0 carry bit
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C mm1 carry limb
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C mm6 inverse
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C mm7 divisor
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movd (%eax), %mm2
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addl $4, %eax
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psubq %mm0, %mm2 C src - cbit
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psubq %mm1, %mm2 C src - cbit - climb
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movq %mm2, %mm0
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psrlq $63, %mm0 C new cbit
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pmuludq %mm6, %mm2 C s*inverse
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movq %mm7, %mm1
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pmuludq %mm2, %mm1 C q*divisor
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psrlq $32, %mm1 C new climb
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subl $1, %ecx
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jnz L(top)
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L(done):
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paddq %mm1, %mm0
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movd %mm0, %eax
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emms
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ret
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EPILOGUE()
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