mpir/mpn/x86_64w/k8/half.asm

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; GLOBAL_FUNC(half)
; Copyright 2009 Jason Moxham
;
; Windows Conversion Copyright 2008 Brian Gladman
;
; This file is part of the MPIR Library.
; The MPIR 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 MPIR 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 MPIR 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.
;
; mp_limb_t mpn_half(mp_ptr, mp_size_t)
; rdi rsi
; rcx rdx
%include "yasm_mac.inc"
CPU Athlon64
BITS 64
LEAF_PROC mpn_half
mov rax, rdx
lea rcx, [rcx+rdx*8-8]
shr rdx, 2
and eax, 3
jz .1
shr qword [rcx], 1
lea rcx, [rcx-8]
dec rax
jz .1
rcr qword [rcx], 1
lea rcx, [rcx-8]
dec rax
jz .1
rcr qword [rcx], 1
lea rcx, [rcx-8]
dec rax
.1: sbb r8, r8
cmp rdx, 0
jz .3
add r8, r8
xalign 16
.2: rcr qword [rcx], 1
nop
rcr qword [rcx-8], 1
rcr qword [rcx-16], 1
rcr qword [rcx-24], 1
nop
dec rdx
lea rcx, [rcx-32]
jnz .2
sbb r8, r8
.3: sub rax, r8
shl rax, 63
ret
end