512 lines
10 KiB
NASM
512 lines
10 KiB
NASM
dnl AMD K7 mpn_mod_1 -- mpn by limb remainder.
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dnl Copyright 1999, 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 K7: 17.0 cycles/limb.
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C mp_limb_t mpn_mod_1 (mp_srcptr src, mp_size_t size, mp_limb_t divisor);
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C mp_limb_t mpn_mod_1c (mp_srcptr src, mp_size_t size, mp_limb_t divisor,
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C mp_limb_t carry);
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C mp_limb_t mpn_preinv_mod_1 (mp_srcptr src, mp_size_t size, mp_limb_t divisor,
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C mp_limb_t inverse);
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C
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C The code here is the same as mpn_divrem_1, but with the quotient
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C discarded. See mpn/x86/k7/mmx/divrem_1.c for some comments.
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dnl MUL_THRESHOLD is the size at which the multiply by inverse method is
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dnl used, rather than plain "divl"s. Minimum value 2.
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dnl
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dnl The inverse takes about 50 cycles to calculate, but after that the
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dnl multiply is 17 c/l versus division at 41 c/l.
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dnl
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dnl Using mul or div is about the same speed at 3 limbs, so the threshold
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dnl is set to 4 to get the smaller div code used at 3.
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deflit(MUL_THRESHOLD, 4)
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defframe(PARAM_INVERSE,16) dnl mpn_preinv_mod_1
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defframe(PARAM_CARRY, 16) dnl mpn_mod_1c
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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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defframe(SAVE_EBX, -4)
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defframe(SAVE_ESI, -8)
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defframe(SAVE_EDI, -12)
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defframe(SAVE_EBP, -16)
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defframe(VAR_NORM, -20)
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defframe(VAR_INVERSE, -24)
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defframe(VAR_SRC_STOP,-28)
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deflit(STACK_SPACE, 28)
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TEXT
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ALIGN(32)
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PROLOGUE(mpn_preinv_mod_1)
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deflit(`FRAME',0)
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movl PARAM_SRC, %ecx
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movl PARAM_SIZE, %eax
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subl $STACK_SPACE, %esp FRAME_subl_esp(STACK_SPACE)
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movl %ebp, SAVE_EBP
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movl PARAM_DIVISOR, %ebp
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movl %edi, SAVE_EDI
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movl PARAM_INVERSE, %edx
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movl %esi, SAVE_ESI
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movl -4(%ecx,%eax,4), %edi C src high limb
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leal -16(%ecx,%eax,4), %ecx C &src[size-4]
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movl %ebx, SAVE_EBX
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movl PARAM_INVERSE, %edx
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movl $0, VAR_NORM C l==0
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movl %edi, %esi
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subl %ebp, %edi C high-divisor
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cmovc( %esi, %edi) C restore if underflow
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decl %eax
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jz L(done_edi) C size==1, high-divisor only
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movl 8(%ecx), %esi C src second high limb
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movl %edx, VAR_INVERSE
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movl $32, %ebx C 32-l
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decl %eax
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jz L(inverse_one_left) C size==2, one divide
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movd %ebx, %mm7 C 32-l
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decl %eax
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jz L(inverse_two_left) C size==3, two divides
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jmp L(inverse_top) C size>=4
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L(done_edi):
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movl SAVE_ESI, %esi
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movl SAVE_EBP, %ebp
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movl %edi, %eax
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movl SAVE_EDI, %edi
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addl $STACK_SPACE, %esp
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ret
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EPILOGUE()
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ALIGN(32)
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PROLOGUE(mpn_mod_1c)
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deflit(`FRAME',0)
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movl PARAM_CARRY, %edx
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movl PARAM_SIZE, %ecx
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subl $STACK_SPACE, %esp
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deflit(`FRAME',STACK_SPACE)
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movl %ebp, SAVE_EBP
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movl PARAM_DIVISOR, %ebp
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movl %esi, SAVE_ESI
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movl PARAM_SRC, %esi
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jmp L(start_1c)
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EPILOGUE()
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ALIGN(32)
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PROLOGUE(mpn_mod_1)
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deflit(`FRAME',0)
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movl PARAM_SIZE, %ecx
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movl $0, %edx C initial carry (if can't skip a div)
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subl $STACK_SPACE, %esp
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deflit(`FRAME',STACK_SPACE)
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movl %esi, SAVE_ESI
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movl PARAM_SRC, %esi
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movl %ebp, SAVE_EBP
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movl PARAM_DIVISOR, %ebp
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orl %ecx, %ecx
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jz L(divide_done)
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movl -4(%esi,%ecx,4), %eax C src high limb
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cmpl %ebp, %eax C carry flag if high<divisor
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cmovc( %eax, %edx) C src high limb as initial carry
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sbbl $0, %ecx C size-1 to skip one div
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jz L(divide_done)
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ALIGN(16)
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L(start_1c):
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C eax
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C ebx
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C ecx size
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C edx carry
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C esi src
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C edi
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C ebp divisor
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cmpl $MUL_THRESHOLD, %ecx
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jae L(mul_by_inverse)
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C With a MUL_THRESHOLD of 4, this "loop" only ever does 1 to 3 iterations,
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C but it's already fast and compact, and there's nothing to gain by
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C expanding it out.
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C
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C Using PARAM_DIVISOR in the divl is a couple of cycles faster than %ebp.
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orl %ecx, %ecx
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jz L(divide_done)
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L(divide_top):
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C eax scratch (quotient)
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C ebx
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C ecx counter, limbs, decrementing
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C edx scratch (remainder)
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C esi src
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C edi
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C ebp
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movl -4(%esi,%ecx,4), %eax
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divl PARAM_DIVISOR
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decl %ecx
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jnz L(divide_top)
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L(divide_done):
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movl SAVE_ESI, %esi
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movl SAVE_EBP, %ebp
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addl $STACK_SPACE, %esp
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movl %edx, %eax
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ret
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C -----------------------------------------------------------------------------
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L(mul_by_inverse):
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C eax
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C ebx
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C ecx size
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C edx carry
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C esi src
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C edi
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C ebp divisor
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bsrl %ebp, %eax C 31-l
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movl %ebx, SAVE_EBX
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movl %ecx, %ebx C size
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movl %edi, SAVE_EDI
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movl $31, %ecx
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movl %edx, %edi C carry
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movl $-1, %edx
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C
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xorl %eax, %ecx C l
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incl %eax C 32-l
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shll %cl, %ebp C d normalized
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movl %ecx, VAR_NORM
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movd %eax, %mm7 C 32-l
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movl $-1, %eax
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subl %ebp, %edx C (b-d)-1 so edx:eax = b*(b-d)-1
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divl %ebp C floor (b*(b-d)-1) / d
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C
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movl %eax, VAR_INVERSE
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leal -12(%esi,%ebx,4), %eax C &src[size-3]
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movl 8(%eax), %esi C src high limb
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movl 4(%eax), %edx C src second highest limb
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shldl( %cl, %esi, %edi) C n2 = carry,high << l
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shldl( %cl, %edx, %esi) C n10 = high,second << l
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movl %eax, %ecx C &src[size-3]
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ifelse(MUL_THRESHOLD,2,`
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cmpl $2, %ebx
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je L(inverse_two_left)
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')
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C The dependent chain here is the same as in mpn_divrem_1, but a few
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C instructions are saved by not needing to store the quotient limbs.
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C Unfortunately this doesn't get the code down to the theoretical 16 c/l.
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C
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C There's four dummy instructions in the loop, all of which are necessary
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C for the claimed 17 c/l. It's a 1 to 3 cycle slowdown if any are removed,
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C or changed from load to store or vice versa. They're not completely
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C random, since they correspond to what mpn_divrem_1 has, but there's no
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C obvious reason why they're necessary. Presumably they induce something
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C good in the out of order execution, perhaps through some load/store
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C ordering and/or decoding effects.
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C
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C The q1==0xFFFFFFFF case is handled here the same as in mpn_divrem_1. On
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C on special data that comes out as q1==0xFFFFFFFF always, the loop runs at
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C about 13.5 c/l.
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ALIGN(32)
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L(inverse_top):
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C eax scratch
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C ebx scratch (nadj, q1)
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C ecx src pointer, decrementing
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C edx scratch
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C esi n10
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C edi n2
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C ebp divisor
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C
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C mm0 scratch (src qword)
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C mm7 rshift for normalization
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cmpl $0x80000000, %esi C n1 as 0=c, 1=nc
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movl %edi, %eax C n2
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movl PARAM_SIZE, %ebx C dummy
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leal (%ebp,%esi), %ebx
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cmovc( %esi, %ebx) C nadj = n10 + (-n1 & d), ignoring overflow
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sbbl $-1, %eax C n2+n1
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mull VAR_INVERSE C m*(n2+n1)
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movq (%ecx), %mm0 C next src limb and the one below it
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subl $4, %ecx
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movl %ecx, PARAM_SIZE C dummy
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C
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addl %ebx, %eax C m*(n2+n1) + nadj, low giving carry flag
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leal 1(%edi), %ebx C n2+1
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movl %ebp, %eax C d
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C
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adcl %edx, %ebx C 1 + high(n2<<32 + m*(n2+n1) + nadj) = q1+1
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jz L(q1_ff)
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nop C dummy
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mull %ebx C (q1+1)*d
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psrlq %mm7, %mm0
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leal (%ecx), %ecx C dummy
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C
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C
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subl %eax, %esi C low n - (q1+1)*d
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movl PARAM_SRC, %eax
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C
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sbbl %edx, %edi C high n - (q1+1)*d, 0 or -1
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movl %esi, %edi C remainder -> n2
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leal (%ebp,%esi), %edx
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movd %mm0, %esi
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cmovc( %edx, %edi) C n - q1*d if underflow from using q1+1
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cmpl %eax, %ecx
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jae L(inverse_top)
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L(inverse_loop_done):
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C -----------------------------------------------------------------------------
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L(inverse_two_left):
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C eax scratch
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C ebx scratch (nadj, q1)
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C ecx &src[-1]
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C edx scratch
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C esi n10
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C edi n2
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C ebp divisor
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C
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C mm0 scratch (src dword)
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C mm7 rshift
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cmpl $0x80000000, %esi C n1 as 0=c, 1=nc
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movl %edi, %eax C n2
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leal (%ebp,%esi), %ebx
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cmovc( %esi, %ebx) C nadj = n10 + (-n1 & d), ignoring overflow
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sbbl $-1, %eax C n2+n1
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mull VAR_INVERSE C m*(n2+n1)
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movd 4(%ecx), %mm0 C src low limb
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C
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C
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addl %ebx, %eax C m*(n2+n1) + nadj, low giving carry flag
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leal 1(%edi), %ebx C n2+1
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movl %ebp, %eax C d
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adcl %edx, %ebx C 1 + high(n2<<32 + m*(n2+n1) + nadj) = q1+1
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sbbl $0, %ebx
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mull %ebx C (q1+1)*d
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psllq $32, %mm0
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psrlq %mm7, %mm0
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C
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subl %eax, %esi
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C
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sbbl %edx, %edi C n - (q1+1)*d
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movl %esi, %edi C remainder -> n2
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leal (%ebp,%esi), %edx
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movd %mm0, %esi
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cmovc( %edx, %edi) C n - q1*d if underflow from using q1+1
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L(inverse_one_left):
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C eax scratch
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C ebx scratch (nadj, q1)
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C ecx
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C edx scratch
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C esi n10
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C edi n2
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C ebp divisor
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C
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C mm0 src limb, shifted
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C mm7 rshift
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cmpl $0x80000000, %esi C n1 as 0=c, 1=nc
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movl %edi, %eax C n2
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leal (%ebp,%esi), %ebx
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cmovc( %esi, %ebx) C nadj = n10 + (-n1 & d), ignoring overflow
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sbbl $-1, %eax C n2+n1
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mull VAR_INVERSE C m*(n2+n1)
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movl VAR_NORM, %ecx C for final denorm
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C
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C
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addl %ebx, %eax C m*(n2+n1) + nadj, low giving carry flag
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leal 1(%edi), %ebx C n2+1
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movl %ebp, %eax C d
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C
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adcl %edx, %ebx C 1 + high(n2<<32 + m*(n2+n1) + nadj) = q1+1
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sbbl $0, %ebx
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mull %ebx C (q1+1)*d
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movl SAVE_EBX, %ebx
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C
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C
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subl %eax, %esi
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movl %esi, %eax C remainder
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movl SAVE_ESI, %esi
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sbbl %edx, %edi C n - (q1+1)*d
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leal (%ebp,%eax), %edx
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movl SAVE_EBP, %ebp
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cmovc( %edx, %eax) C n - q1*d if underflow from using q1+1
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movl SAVE_EDI, %edi
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shrl %cl, %eax C denorm remainder
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addl $STACK_SPACE, %esp
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emms
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ret
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C -----------------------------------------------------------------------------
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C
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C Special case for q1=0xFFFFFFFF, giving q=0xFFFFFFFF meaning the low dword
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C of q*d is simply -d and the remainder n-q*d = n10+d
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L(q1_ff):
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C eax (divisor)
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C ebx (q1+1 == 0)
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C ecx src pointer
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C edx
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C esi n10
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C edi (n2)
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C ebp divisor
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movl PARAM_SRC, %edx
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leal (%ebp,%esi), %edi C n-q*d remainder -> next n2
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psrlq %mm7, %mm0
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movd %mm0, %esi C next n10
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cmpl %edx, %ecx
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jae L(inverse_top)
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jmp L(inverse_loop_done)
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EPILOGUE()
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