Annotation of OpenXM_contrib/gmp/mpn/x86/pentium4/sse2/diveby3.asm, Revision 1.1
1.1 ! ohara 1: dnl Intel Pentium-4 mpn_divexact_by3 -- mpn exact division by 3.
! 2:
! 3: dnl Copyright 2001, 2002 Free Software Foundation, Inc.
! 4: dnl
! 5: dnl This file is part of the GNU MP Library.
! 6: dnl
! 7: dnl The GNU MP Library is free software; you can redistribute it and/or
! 8: dnl modify it under the terms of the GNU Library General Public License as
! 9: dnl published by the Free Software Foundation; either version 2 of the
! 10: dnl License, or (at your option) any later version.
! 11: dnl
! 12: dnl The GNU MP Library is distributed in the hope that it will be useful,
! 13: dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
! 14: dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
! 15: dnl Library General Public License for more details.
! 16: dnl
! 17: dnl You should have received a copy of the GNU Library General Public
! 18: dnl License along with the GNU MP Library; see the file COPYING.LIB. If
! 19: dnl not, write to the Free Software Foundation, Inc., 59 Temple Place -
! 20: dnl Suite 330, Boston, MA 02111-1307, USA.
! 21:
! 22: include(`../config.m4')
! 23:
! 24:
! 25: C P4: 18.0 cycles/limb
! 26:
! 27:
! 28: C mp_limb_t mpn_divexact_by3c (mp_ptr dst, mp_srcptr src, mp_size_t size,
! 29: C mp_limb_t carry);
! 30: C
! 31: C The dependent chain in the loop is as follows, and this is what the code
! 32: C measures.
! 33: C
! 34: C psubq (src-cbit) - climb 2
! 35: C pmuludq s*inverse 8
! 36: C pand mask q 2
! 37: C psllq 2*q 2
! 38: C paddq q+2*q 2
! 39: C psrlq high(3*q) 2
! 40: C --
! 41: C 18
! 42: C
! 43: C Perhaps the s*inverse can be taken off the dependent chain as described in
! 44: C mpn/generic/diveby3.c, with a modified 3*q calculation that can give
! 45: C high(3*q)*inv too.
! 46:
! 47:
! 48: defframe(PARAM_CARRY,16)
! 49: defframe(PARAM_SIZE, 12)
! 50: defframe(PARAM_SRC, 8)
! 51: defframe(PARAM_DST, 4)
! 52:
! 53: RODATA
! 54: C multiplicative inverse of 3, modulo 2^32
! 55: ALIGN(4)
! 56: L(inverse):
! 57: .long 0xAAAAAAAB
! 58:
! 59: TEXT
! 60: ALIGN(16)
! 61:
! 62: PROLOGUE(mpn_divexact_by3c)
! 63: deflit(`FRAME',0)
! 64:
! 65: movl PARAM_SRC, %eax
! 66: pxor %mm0, %mm0
! 67:
! 68: movd PARAM_CARRY, %mm1
! 69: pcmpeqd %mm6, %mm6
! 70:
! 71: movd L(inverse), %mm7
! 72:
! 73: movl PARAM_DST, %edx
! 74: psrlq $32, %mm6 C 0x00000000FFFFFFFF
! 75:
! 76: movl PARAM_SIZE, %ecx
! 77:
! 78: L(top):
! 79: C eax src, incrementing
! 80: C ebx
! 81: C ecx counter, limbs, decrementing
! 82: C edx dst, incrementing
! 83: C
! 84: C mm0 carry bit
! 85: C mm1 carry limb
! 86: C mm6 0x00000000FFFFFFFF
! 87: C mm7 inverse
! 88:
! 89: movd (%eax), %mm2
! 90: addl $4, %eax
! 91:
! 92: psubq %mm0, %mm2 C src - cbit
! 93:
! 94: psubq %mm1, %mm2 C src - cbit - climb
! 95: movq %mm2, %mm0
! 96: psrlq $63, %mm0 C new cbit
! 97:
! 98: pmuludq %mm7, %mm2 C s*inverse
! 99: movd %mm2, (%edx) C q
! 100: addl $4, %edx
! 101:
! 102: movq %mm6, %mm1
! 103:
! 104: pand %mm2, %mm1
! 105:
! 106: pand %mm6, %mm2
! 107:
! 108: psllq $1, %mm1
! 109:
! 110: C
! 111:
! 112: paddq %mm2, %mm1
! 113:
! 114: C
! 115:
! 116: psrlq $32, %mm1
! 117:
! 118: subl $1, %ecx
! 119: jnz L(top)
! 120:
! 121:
! 122: paddd %mm1, %mm0
! 123: movd %mm0, %eax
! 124: emms
! 125: ret
! 126:
! 127: EPILOGUE()
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