gcc/gmp/mpn/x86_64/sublsh1_n.asm

dnl  AMD64 mpn_sublsh1_n -- rp[] = up[] - (vp[] << 1)

dnl  Copyright 2003, 2005, 2006, 2007 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:	 2.2
C K10:		 2.2
C P4:		12.75
C P6-15:	 3.45


C Sometimes speed degenerates, supposedly related to that some operand
C alignments cause cache conflicts.

C The speed is limited by decoding/issue bandwidth.  There are 26 instructions
C in the loop, which corresponds to 26/3/4 = 2.167 c/l.

C INPUT PARAMETERS
define(`rp',`%rdi')
define(`up',`%rsi')
define(`vp',`%rdx')
define(`n', `%rcx')

ASM_START()
	TEXT
	ALIGN(16)
PROLOGUE(mpn_sublsh1_n)
	push	%rbx
	push	%rbp

	mov	(vp), %r8
	mov	R32(n), R32(%rax)
	lea	(rp,n,8), rp
	lea	(up,n,8), up
	lea	(vp,n,8), vp
	neg	n
	xor	R32(%rbp), R32(%rbp)
	and	$3, R32(%rax)
	je	L(b00)
	cmp	$2, R32(%rax)
	jc	L(b01)
	je	L(b10)

L(b11):	add	%r8, %r8
	mov	8(vp,n,8), %r9
	adc	%r9, %r9
	mov	16(vp,n,8), %r10
	adc	%r10, %r10
	sbb	R32(%rax), R32(%rax)	C save scy
	mov	(up,n,8), %rbp
	mov	8(up,n,8), %rbx
	sub	%r8, %rbp
	sbb	%r9, %rbx
	mov	%rbp, (rp,n,8)
	mov	%rbx, 8(rp,n,8)
	mov	16(up,n,8), %rbp
	sbb	%r10, %rbp
	mov	%rbp, 16(rp,n,8)
	sbb	R32(%rbp), R32(%rbp)	C save acy
	add	$3, n
	jmp	L(ent)

L(b10):	add	%r8, %r8
	mov	8(vp,n,8), %r9
	adc	%r9, %r9
	sbb	R32(%rax), R32(%rax)	C save scy
	mov	(up,n,8), %rbp
	mov	8(up,n,8), %rbx
	sub	%r8, %rbp
	sbb	%r9, %rbx
	mov	%rbp, (rp,n,8)
	mov	%rbx, 8(rp,n,8)
	sbb	R32(%rbp), R32(%rbp)	C save acy
	add	$2, n
	jmp	L(ent)

L(b01):	add	%r8, %r8
	sbb	R32(%rax), R32(%rax)	C save scy
	mov	(up,n,8), %rbp
	sub	%r8, %rbp
	mov	%rbp, (rp,n,8)
	sbb	R32(%rbp), R32(%rbp)	C save acy
	inc	n
L(ent):	jns	L(end)

	ALIGN(16)
L(oop):	add	R32(%rax), R32(%rax)	C restore scy

	mov	(vp,n,8), %r8
L(b00):	adc	%r8, %r8
	mov	8(vp,n,8), %r9
	adc	%r9, %r9
	mov	16(vp,n,8), %r10
	adc	%r10, %r10
	mov	24(vp,n,8), %r11
	adc	%r11, %r11

	sbb	R32(%rax), R32(%rax)	C save scy
	add	R32(%rbp), R32(%rbp)	C restore acy

	mov	(up,n,8), %rbp
	mov	8(up,n,8), %rbx
	sbb	%r8, %rbp
	sbb	%r9, %rbx
	mov	%rbp, (rp,n,8)
	mov	%rbx, 8(rp,n,8)
	mov	16(up,n,8), %rbp
	mov	24(up,n,8), %rbx
	sbb	%r10, %rbp
	sbb	%r11, %rbx
	mov	%rbp, 16(rp,n,8)
	mov	%rbx, 24(rp,n,8)

	sbb	R32(%rbp), R32(%rbp)	C save acy
	add	$4, n
	js	L(oop)

L(end):	add	R32(%rbp), R32(%rax)
	neg	R32(%rax)

	pop	%rbp
	pop	%rbx
	ret
EPILOGUE()