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dnl AMD64 mpn_gcd_1 -- mpn by 1 gcd.
dnl Based on the K7 gcd_1.asm, by Kevin Ryde. Rehacked for AMD64 by Torbjorn
dnl Granlund.
dnl Copyright 2000-2002, 2005, 2009, 2011, 2012 Free Software Foundation, Inc.
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 modify
dnl it under the terms of either:
dnl
dnl * the GNU Lesser General Public License as published by the Free
dnl Software Foundation; either version 3 of the License, or (at your
dnl option) any later version.
dnl
dnl or
dnl
dnl * the GNU General Public License as published by the Free Software
dnl Foundation; either version 2 of the License, or (at your option) any
dnl later version.
dnl
dnl or both in parallel, as here.
dnl
dnl The GNU MP Library is distributed in the hope that it will be useful, but
dnl WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
dnl or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
dnl for more details.
dnl
dnl You should have received copies of the GNU General Public License and the
dnl GNU Lesser General Public License along with the GNU MP Library. If not,
dnl see https://www.gnu.org/licenses/.
include(`../config.m4')
C cycles/bit (approx)
C AMD K8,K9 5.21 (4.95)
C AMD K10 5.15 (5.00)
C AMD bd1 5.42 (5.14)
C AMD bobcat 6.71 (6.56)
C Intel P4 13.5 (12.75)
C Intel core2 6.20 (6.16)
C Intel NHM 6.49 (6.25)
C Intel SBR 7.75 (7.57)
C Intel atom 8.77 (8.54)
C VIA nano 6.60 (6.20)
C Numbers measured with: speed -CD -s16-64 -t48 mpn_gcd_1
C ctz_table[n] is the number of trailing zeros on n, or MAXSHIFT if n==0.
deflit(MAXSHIFT, 7)
deflit(MASK, eval((m4_lshift(1,MAXSHIFT))-1))
DEF_OBJECT(ctz_table,64)
.byte MAXSHIFT
forloop(i,1,MASK,
` .byte m4_count_trailing_zeros(i)
')
END_OBJECT(ctz_table)
C Threshold of when to call bmod when U is one limb. Should be about
C (time_in_cycles(bmod_1,1) + call_overhead) / (cycles/bit).
define(`BMOD_THRES_LOG2', 8)
C INPUT PARAMETERS
define(`up', `%rdi')
define(`n', `%rsi')
define(`v0', `%rdx')
ABI_SUPPORT(DOS64)
ABI_SUPPORT(STD64)
IFDOS(`define(`STACK_ALLOC', 40)')
IFSTD(`define(`STACK_ALLOC', 8)')
ASM_START()
TEXT
ALIGN(16)
PROLOGUE(mpn_gcd_1)
FUNC_ENTRY(3)
mov (up), %rax C U low limb
mov $-1, R32(%rcx)
or v0, %rax C x | y
L(twos):
inc R32(%rcx)
shr %rax
jnc L(twos)
shr R8(%rcx), v0
push %rcx C common twos
L(divide_strip_y):
shr v0
jnc L(divide_strip_y)
adc v0, v0
cmp $1, n
jnz L(reduce_nby1)
C Both U and V are single limbs, reduce with bmod if u0 >> v0.
mov (up), %r8
mov %r8, %rax
shr $BMOD_THRES_LOG2, %r8
cmp %r8, v0
ja L(noreduce)
push v0
sub $STACK_ALLOC, %rsp C maintain ABI required rsp alignment
L(bmod):
IFDOS(` mov %rdx, %r8 ')
IFDOS(` mov %rsi, %rdx ')
IFDOS(` mov %rdi, %rcx ')
CALL( mpn_modexact_1_odd)
L(reduced):
add $STACK_ALLOC, %rsp
pop %rdx
L(noreduce):
LEA( ctz_table, %rsi)
test %rax, %rax
mov %rax, %rcx
jnz L(mid)
jmp L(end)
L(reduce_nby1):
push v0
sub $STACK_ALLOC, %rsp C maintain ABI required rsp alignment
cmp $BMOD_1_TO_MOD_1_THRESHOLD, n
jl L(bmod)
IFDOS(` mov %rdx, %r8 ')
IFDOS(` mov %rsi, %rdx ')
IFDOS(` mov %rdi, %rcx ')
CALL( mpn_mod_1)
jmp L(reduced)
ALIGN(16) C K8 BC P4 NHM SBR
L(top): cmovc %rcx, %rax C if x-y < 0 0
cmovc %rdi, %rdx C use x,y-x 0
L(mid): and $MASK, R32(%rcx) C 0
movzbl (%rsi,%rcx), R32(%rcx) C 1
jz L(shift_alot) C 1
shr R8(%rcx), %rax C 3
mov %rax, %rdi C 4
mov %rdx, %rcx C 3
sub %rax, %rcx C 4
sub %rdx, %rax C 4
jnz L(top) C 5
L(end): pop %rcx
mov %rdx, %rax
shl R8(%rcx), %rax
FUNC_EXIT()
ret
L(shift_alot):
shr $MAXSHIFT, %rax
mov %rax, %rcx
jmp L(mid)
EPILOGUE()
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