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dnl x86 mpn_invert_limb
dnl Contributed to the GNU project by Niels Möller
dnl Copyright 2009, 2011 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 3 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 License
dnl along with the GNU MP Library. If not, see http://www.gnu.org/licenses/.
include(`../config.m4')
C cycles (approx) div
C P5 ?
C P6 model 0-8,10-12 ?
C P6 model 9 (Banias) ?
C P6 model 13 (Dothan) ?
C P4 model 0 (Willamette) ?
C P4 model 1 (?) ?
C P4 model 2 (Northwood) ?
C P4 model 3 (Prescott) ?
C P4 model 4 (Nocona) ?
C AMD K6 ?
C AMD K7 41 53
C AMD K8 ?
C TODO
C * These c/l numbers are for a non-PIC build. Consider falling back to using
C the 'div' instruction for PIC builds.
C * Perhaps use this file--or at least the algorithm--for more machines than k7.
C Register usage:
C Input D in %edi
C Current approximation is in %eax and/or %ecx
C %ebx and %edx are temporaries
C %esi and %ebp are unused
defframe(PARAM_DIVISOR,4)
ASM_START()
C Make approx_tab global to work around Apple relocation bug.
ifdef(`DARWIN',`
deflit(`approx_tab', MPN(invert_limb_tab))
GLOBL approx_tab')
TEXT
ALIGN(16)
PROLOGUE(mpn_invert_limb)
deflit(`FRAME', 0)
mov PARAM_DIVISOR, %eax
C Avoid push/pop on k7.
sub $8, %esp FRAME_subl_esp(8)
mov %ebx, (%esp)
mov %edi, 4(%esp)
mov %eax, %edi
shr $22, %eax
ifdef(`PIC',`
LEA( approx_tab, %ebx)
movzwl -1024(%ebx, %eax, 2), %eax
',`
movzwl -1024+approx_tab(%eax, %eax), %eax C %eax = v0
')
C v1 = (v0 << 4) - ((v0*v0*d_21) >> 32) - 1
mov %eax, %ecx
imul %eax, %eax
mov %edi, %ebx
shr $11, %ebx
inc %ebx
mul %ebx
mov %edi, %ebx C Prepare
shr %ebx
sbb %eax, %eax
sub %eax, %ebx C %ebx = d_31, %eax = mask
shl $4, %ecx
dec %ecx
sub %edx, %ecx C %ecx = v1
C v_2 = (v1 << 15) + ((v1 *(2^48 - v1 * d31 + (v1 >> 1) & mask)) >> 33)
imul %ecx, %ebx
and %ecx, %eax
shr %eax
sub %ebx, %eax
mul %ecx
mov %edi, %eax C Prepare for next mul
shl $15, %ecx
shr %edx
add %edx, %ecx C %ecx = v2
mul %ecx
add %edi, %eax
mov %ecx, %eax
adc %edi, %edx
sub %edx, %eax C %eax = v3
mov (%esp), %ebx
mov 4(%esp), %edi
add $8, %esp
ret
EPILOGUE()
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END_OBJECT(approx_tab)
|
