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dnl Intel Pentium-4 mpn_modexact_1_odd -- mpn by limb exact remainder.
dnl Copyright 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 2.1 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
dnl License along with the GNU MP Library; see the file COPYING.LIB. If
dnl not, write to the Free Software Foundation, Inc., 51 Franklin Street,
dnl Fifth Floor, Boston, MA 02110-1301, USA.
include(`../config.m4')
C P4: 19.0 cycles/limb
C mp_limb_t mpn_modexact_1_odd (mp_srcptr src, mp_size_t size,
C mp_limb_t divisor);
C mp_limb_t mpn_modexact_1c_odd (mp_srcptr src, mp_size_t size,
C mp_limb_t divisor, mp_limb_t carry);
C
defframe(PARAM_CARRY, 16)
defframe(PARAM_DIVISOR,12)
defframe(PARAM_SIZE, 8)
defframe(PARAM_SRC, 4)
TEXT
ALIGN(16)
PROLOGUE(mpn_modexact_1c_odd)
deflit(`FRAME',0)
movd PARAM_CARRY, %mm1
jmp L(start_1c)
ifdef(`PIC',`
L(movl_eip_edx):
movl (%esp), %edx
ret_internal
')
EPILOGUE()
ALIGN(16)
PROLOGUE(mpn_modexact_1_odd)
deflit(`FRAME',0)
pxor %mm1, %mm1 C carry limb
L(start_1c):
movl PARAM_DIVISOR, %eax
movd PARAM_DIVISOR, %mm7
shrl %eax
andl $127, %eax C d/2, 7 bits
ifdef(`PIC',`
call L(movl_eip_edx)
addl $_GLOBAL_OFFSET_TABLE_, %edx
movl modlimb_invert_table@GOT(%edx), %edx
C
movzbl (%eax,%edx), %eax C inv 8 bits
',`
dnl non-PIC
movzbl modlimb_invert_table(%eax), %eax C inv 8 bits
')
C
movd %eax, %mm6 C inv
movd %eax, %mm0 C inv
pmuludq %mm6, %mm6 C inv*inv
C
pmuludq %mm7, %mm6 C inv*inv*d
paddd %mm0, %mm0 C 2*inv
C
psubd %mm6, %mm0 C inv = 2*inv - inv*inv*d
pxor %mm6, %mm6
paddd %mm0, %mm6
pmuludq %mm0, %mm0 C inv*inv
C
pmuludq %mm7, %mm0 C inv*inv*d
paddd %mm6, %mm6 C 2*inv
movl PARAM_SRC, %eax
movl PARAM_SIZE, %ecx
C
psubd %mm0, %mm6 C inv = 2*inv - inv*inv*d
ASSERT(e,` C expect d*inv == 1 mod 2^BITS_PER_MP_LIMB
pushl %eax FRAME_pushl()
movd %mm6, %eax
imul PARAM_DIVISOR, %eax
cmpl $1, %eax
popl %eax FRAME_popl()')
pxor %mm0, %mm0 C carry bit
C The dependent chain here is as follows.
C
C latency
C psubq s = (src-cbit) - climb 2
C pmuludq q = s*inverse 8
C pmuludq prod = q*divisor 8
C psrlq climb = high(prod) 2
C --
C 20
C
C Yet the loop measures 19.0 c/l, so obviously there's something gained
C there over a straight reading of the chip documentation.
L(top):
C eax src, incrementing
C ebx
C ecx counter, limbs
C edx
C
C mm0 carry bit
C mm1 carry limb
C mm6 inverse
C mm7 divisor
movd (%eax), %mm2
addl $4, %eax
psubq %mm0, %mm2 C src - cbit
psubq %mm1, %mm2 C src - cbit - climb
movq %mm2, %mm0
psrlq $63, %mm0 C new cbit
pmuludq %mm6, %mm2 C s*inverse
movq %mm7, %mm1
pmuludq %mm2, %mm1 C q*divisor
psrlq $32, %mm1 C new climb
subl $1, %ecx
jnz L(top)
L(done):
paddq %mm1, %mm0
movd %mm0, %eax
emms
ret
EPILOGUE()
|
