mpir/mpn/x86_64/submul_1.as

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; AMD64 mpn_submul_1 -- Multiply a limb vector with a limb and subtract the
; result from a second limb vector.
;
; Copyright 2004 Free Software Foundation, Inc.
;
; This file is part of the GNU MP Library.
;
; The GNU MP Library is free software; you can redistribute it and/or modify
; it under the terms of the GNU Lesser General Public License as published
; by the Free Software Foundation; either version 2.1 of the License, or (at
; your option) any later version.
;
; The GNU MP Library is distributed in the hope that it will be useful, but
; WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
; or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
; License for more details.
;
; You should have received a copy of the GNU Lesser General Public License
; along with the GNU MP Library; see the file COPYING.LIB. If not, write
; to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
; Boston, MA 02110-1301, USA.
;
; cycles/limb
; Hammer: 4.7
;
;
; INPUT PARAMETERS
; rp rdi
; up rsi
; n rdx
; vl rcx
%include '../yasm_mac.inc'
BITS 64
GLOBAL_FUNC mpn_submul_1
mov r11, rdx
lea rsi, [rsi+r11*8]
lea rdi, [rdi+r11*8]
neg r11
xor r8d, r8d
align 8 ; minimal alignment for claimed speed
loop1:
mov rax, [rsi+r11*8]
mov r10, [rdi+r11*8] ; load limb from rp
mul rcx ; multiply
sub r10, r8 ; subtract any previous high limb (stored in r8)
mov r8d, 0 ; clear r8 again
adc r8d, r8d ; put any borrow from this iteration in r8
sub r10, rax ; subtract low limb of product
adc r8, rdx ; add high limb and any borrow to r8 for next iteration
mov [rdi+r11*8], r10 ; store low limb
inc r11
jne loop1
mov rax, r8
ret