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dnl AMD64 mpn_gcd_22. Assumes useless bsf, useless shrd, no tzcnt, no shlx.
dnl We actually use tzcnt here, when table cannot count bits, as tzcnt always
dnl works for our use, and helps a lot for certain CPUs.
dnl Copyright 2019 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
C AMD K8,K9 8.9
C AMD K10 8.8
C AMD bd1 9.7
C AMD bd2 7.8
C AMD bd3 ?
C AMD bd4 7.4
C AMD bt1 9.2
C AMD bt2 9.1
C AMD zn1 7.5
C AMD zn2 7.5
C Intel P4 ?
C Intel CNR 10.5
C Intel PNR 10.5
C Intel NHM 9.7
C Intel WSM 9.7
C Intel SBR 10.7
C Intel IBR ?
C Intel HWL 9.5
C Intel BWL 8.7
C Intel SKL 8.6
C Intel atom 18.9
C Intel SLM 14.0
C Intel GLM 9.8
C Intel GLM+ 8.8
C VIA nano ?
C ctz_table[n] is the number of trailing zeros on n, or MAXSHIFT if n==0.
deflit(MAXSHIFT, 8)
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)
define(`u1', `%rdi')
define(`u0', `%rsi')
define(`v1', `%rdx')
define(`v0_param', `%rcx')
define(`v0', `%rax')
define(`cnt', `%rcx')
define(`s0', `%r8')
define(`s1', `%r9')
define(`t0', `%rcx')
define(`t1', `%r11')
dnl ABI_SUPPORT(DOS64) C returns mp_double_limb_t in memory
ABI_SUPPORT(STD64)
ASM_START()
TEXT
ALIGN(64)
PROLOGUE(mpn_gcd_22)
FUNC_ENTRY(4)
mov v0_param, v0
LEA( ctz_table, %r10)
ALIGN(16)
L(top): mov v0, t0
sub u0, t0
jz L(lowz) C jump when low limb result = 0
mov v1, t1
sbb u1, t1
mov u0, s0
mov u1, s1
sub v0, u0
sbb v1, u1
L(bck): cmovc t0, u0 C u = |u - v|
cmovc t1, u1 C u = |u - v|
cmovc s0, v0 C v = min(u,v)
cmovc s1, v1 C v = min(u,v)
and $MASK, R32(t0)
movzbl (%r10,t0), R32(cnt)
jz L(count_better)
C Rightshift (u1,,u0) into (u1,,u0)
L(shr): shr R8(cnt), u0
mov u1, t1
shr R8(cnt), u1
neg cnt
shl R8(cnt), t1
or t1, u0
test v1, v1
jnz L(top)
test u1, u1
jnz L(top)
L(gcd_11):
mov v0, %rdi
C mov u0, %rsi
TCALL( mpn_gcd_11)
L(count_better):
rep;bsf u0, cnt C tzcnt!
jmp L(shr)
L(lowz):C We come here when v0 - u0 = 0
C 1. If v1 - u1 = 0, then gcd is u = v.
C 2. Else compute gcd_21({v1,v0}, |u1-v1|)
mov v1, t0
sub u1, t0
je L(end)
xor t1, t1
mov u0, s0
mov u1, s1
mov u1, u0
xor u1, u1
sub v1, u0
jmp L(bck)
L(end): C mov v0, %rax
C mov v1, %rdx
FUNC_EXIT()
ret
EPILOGUE()
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