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dnl AMD64 mpn_divexact_1 -- mpn by limb exact division.
dnl Copyright 2001, 2002, 2004, 2005, 2006 Free Software Foundation, Inc.
dnl This file is part of the GNU MP Library.
dnl The GNU MP Library is free software; you can redistribute it and/or modify
dnl it under the terms of the GNU Lesser General Public License as published
dnl by the Free Software Foundation; either version 3 of the License, or (at
dnl your option) any later version.
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 Lesser General Public
dnl License for more details.
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/limb
C K8,K9: 10
C K10: 10
C P4: 33
C P6-15 (Core2):13.25
C P6-28 (Atom): 42
C A quick adoption of the 32-bit K7 code.
C INPUT PARAMETERS
C rp rdi
C up rsi
C n rdx
C divisor rcx
ASM_START()
TEXT
ALIGN(16)
PROLOGUE(mpn_divexact_1)
pushq %rbx
movq %rcx, %rax
movl $0, %ecx C shift count
movq %rdx, %r8
btl $0, %eax
jnc L(evn) C skip bsfq unless divisor is even
L(odd): movq %rax, %rbx
shrl %eax
andl $127, %eax C d/2, 7 bits
ifdef(`PIC',`
movq binvert_limb_table@GOTPCREL(%rip), %rdx
',`
movabsq $binvert_limb_table, %rdx
')
movzbl (%rax,%rdx), %eax C inv 8 bits
movq %rbx, %r11 C d without twos
leal (%rax,%rax), %edx C 2*inv
imull %eax, %eax C inv*inv
imull %ebx, %eax C inv*inv*d
subl %eax, %edx C inv = 2*inv - inv*inv*d, 16 bits
leal (%rdx,%rdx), %eax C 2*inv
imull %edx, %edx C inv*inv
imull %ebx, %edx C inv*inv*d
subl %edx, %eax C inv = 2*inv - inv*inv*d, 32 bits
leaq (%rax,%rax), %rdx C 2*inv
imulq %rax, %rax C inv*inv
imulq %rbx, %rax C inv*inv*d
subq %rax, %rdx C inv = 2*inv - inv*inv*d, 64 bits
leaq (%rsi,%r8,8), %rsi C up end
leaq -8(%rdi,%r8,8), %rdi C rp end
negq %r8 C -n
movq %rdx, %r10 C final inverse
movq (%rsi,%r8,8), %rax C up[0]
incq %r8
jz L(one)
movq (%rsi,%r8,8), %rdx C up[1]
shrdq %cl, %rdx, %rax
xorl %ebx, %ebx
jmp L(entry)
L(evn): bsfq %rax, %rcx
shrq %cl, %rax
jmp L(odd)
ALIGN(8)
L(top):
C rax q
C rbx carry bit, 0 or 1
C rcx shift
C rdx
C rsi up end
C rdi rp end
C r8 counter, limbs, negative
mulq %r11 C carry limb in rdx
movq -8(%rsi,%r8,8), %rax
movq (%rsi,%r8,8), %r9
shrdq %cl, %r9, %rax
nop
subq %rbx, %rax C apply carry bit
setc %bl
subq %rdx, %rax C apply carry limb
adcq $0, %rbx
L(entry):
imulq %r10, %rax
movq %rax, (%rdi,%r8,8)
incq %r8
jnz L(top)
mulq %r11 C carry limb in rdx
movq -8(%rsi), %rax C up high limb
shrq %cl, %rax
subq %rbx, %rax C apply carry bit
subq %rdx, %rax C apply carry limb
imulq %r10, %rax
movq %rax, (%rdi)
popq %rbx
ret
L(one):
shrq %cl, %rax
imulq %r10, %rax
movq %rax, (%rdi)
popq %rbx
ret
EPILOGUE()
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