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dnl x86-64 mpn_div_qr_2n_pi1
dnl -- Divide an mpn number by a normalized 2-limb number,
dnl using a single-limb inverse.
dnl Copyright 2007, 2008, 2010-2012 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 c/l
C INPUT PARAMETERS
define(`qp', `%rdi')
define(`rp', `%rsi')
define(`up_param', `%rdx')
define(`un', `%rcx')
define(`d1', `%r8')
define(`d0', `%r9')
define(`di_param', `8(%rsp)')
define(`di', `%r10')
define(`up', `%r11')
define(`u2', `%rbx')
define(`u1', `%r12')
define(`t1', `%r13')
define(`t0', `%r14')
define(`md1', `%r15')
C TODO
C * Store qh in the same stack slot as di_param, instead of pushing
C it. (we could put it in register %rbp, but then we would need to
C save and restore that instead, which doesn't seem like a win).
ABI_SUPPORT(DOS64)
ABI_SUPPORT(STD64)
ASM_START()
TEXT
ALIGN(16)
PROLOGUE(mpn_div_qr_2n_pi1)
FUNC_ENTRY(4)
IFDOS(` mov 56(%rsp), %r8 ')
IFDOS(` mov 64(%rsp), %r9 ')
IFDOS(`define(`di_param', `72(%rsp)')')
mov di_param, di
mov up_param, up
push %r15
push %r14
push %r13
push %r12
push %rbx
mov -16(up, un, 8), u1
mov -8(up, un, 8), u2
mov u1, t0
mov u2, t1
sub d0, t0
sbb d1, t1
cmovnc t0, u1
cmovnc t1, u2
C push qh which is !carry
sbb %rax, %rax
inc %rax
push %rax
lea -2(un), un
mov d1, md1
neg md1
jmp L(next)
ALIGN(16)
L(loop):
C udiv_qr_3by2 (q,u2,u1,u2,u1,n0, d1,d0,di)
C Based on the optimized divrem_2.asm code.
mov di, %rax
mul u2
mov u1, t0
add %rax, t0 C q0 in t0
adc u2, %rdx
mov %rdx, t1 C q in t1
imul md1, %rdx
mov d0, %rax
lea (%rdx, u1), u2
mul t1
mov (up, un, 8), u1
sub d0, u1
sbb d1, u2
sub %rax, u1
sbb %rdx, u2
xor R32(%rax), R32(%rax)
xor R32(%rdx), R32(%rdx)
cmp t0, u2
cmovnc d0, %rax
cmovnc d1, %rdx
adc $0, t1
nop
add %rax, u1
adc %rdx, u2
cmp d1, u2
jae L(fix)
L(bck):
mov t1, (qp, un, 8)
L(next):
sub $1, un
jnc L(loop)
L(end):
mov u2, 8(rp)
mov u1, (rp)
C qh on stack
pop %rax
pop %rbx
pop %r12
pop %r13
pop %r14
pop %r15
FUNC_EXIT()
ret
L(fix): C Unlikely update. u2 >= d1
seta %dl
cmp d0, u1
setae %al
orb %dl, %al C "orb" form to placate Sun tools
je L(bck)
inc t1
sub d0, u1
sbb d1, u2
jmp L(bck)
EPILOGUE()
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