dnl  AMD64 mpn_gcd_1 -- mpn by 1 gcd.

dnl  Based on the K7 gcd_1.asm, by Kevin Ryde.  Rehacked for AMD64 by Torbjorn

dnl  Granlund.

dnl  Copyright 2000-2002, 2005, 2009, 2011, 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	     cycles/bit (approx)

C AMD K8,K9	 5.21                 (4.95)

C AMD K10	 5.15                 (5.00)

C AMD bd1	 5.42                 (5.14)

C AMD bobcat	 6.71                 (6.56)

C Intel P4	13.5                 (12.75)

C Intel core2	 6.20                 (6.16)

C Intel NHM	 6.49                 (6.25)

C Intel SBR	 7.75                 (7.57)

C Intel atom	 8.77                 (8.54)

C VIA nano	 6.60                 (6.20)

C Numbers measured with: speed -CD -s16-64 -t48 mpn_gcd_1

C ctz_table[n] is the number of trailing zeros on n, or MAXSHIFT if n==0.

deflit(MAXSHIFT, 7)

deflit(MASK, eval((m4_lshift(1,MAXSHIFT))-1))

DEF_OBJECT(ctz_table,64)

	.byte	MAXSHIFT

forloop(i,1,MASK,

`	.byte	m4_count_trailing_zeros(i)

')

END_OBJECT(ctz_table)

C Threshold of when to call bmod when U is one limb.  Should be about

C (time_in_cycles(bmod_1,1) + call_overhead) / (cycles/bit).

define(`BMOD_THRES_LOG2', 8)

C INPUT PARAMETERS

define(`up',    `%rdi')

define(`n',     `%rsi')

define(`v0',    `%rdx')

ABI_SUPPORT(DOS64)

ABI_SUPPORT(STD64)

IFDOS(`define(`STACK_ALLOC', 40)')

IFSTD(`define(`STACK_ALLOC', 8)')

ASM_START()

	TEXT

	ALIGN(16)

PROLOGUE(mpn_gcd_1)

	FUNC_ENTRY(3)

	mov	(up), %rax		C U low limb

	mov	$-1, R32(%rcx)

	or	v0, %rax		C x | y

L(twos):

	inc	R32(%rcx)

	shr	%rax

	jnc	L(twos)

	shr	R8(%rcx), v0

	push	%rcx			C common twos

L(divide_strip_y):

	shr	v0

	jnc	L(divide_strip_y)

	adc	v0, v0

	cmp	$1, n

	jnz	L(reduce_nby1)

C Both U and V are single limbs, reduce with bmod if u0 >> v0.

	mov	(up), %r8

	mov	%r8, %rax

	shr	$BMOD_THRES_LOG2, %r8

	cmp	%r8, v0

	ja	L(noreduce)

	push	v0

	sub	$STACK_ALLOC, %rsp	C maintain ABI required rsp alignment

L(bmod):

IFDOS(`	mov	%rdx, %r8	')

IFDOS(`	mov	%rsi, %rdx	')

IFDOS(`	mov	%rdi, %rcx	')

	ASSERT(nz, `test $15, %rsp')

	CALL(	mpn_modexact_1_odd)

L(reduced):

	add	$STACK_ALLOC, %rsp

	pop	%rdx

L(noreduce):

	LEA(	ctz_table, %rsi)

	test	%rax, %rax

	mov	%rax, %rcx

	jnz	L(mid)

	jmp	L(end)

L(reduce_nby1):

	push	v0

	sub	$STACK_ALLOC, %rsp	C maintain ABI required rsp alignment

	cmp	$BMOD_1_TO_MOD_1_THRESHOLD, n

	jl	L(bmod)

IFDOS(`	mov	%rdx, %r8	')

IFDOS(`	mov	%rsi, %rdx	')

IFDOS(`	mov	%rdi, %rcx	')

	ASSERT(nz, `test $15, %rsp')

	CALL(	mpn_mod_1)

	jmp	L(reduced)

	ALIGN(16)			C               K8    BC    P4    NHM   SBR

L(top):	cmovc	%rcx, %rax		C if x-y < 0	0

	cmovc	%rdi, %rdx		C use x,y-x	0

L(mid):	and	$MASK, R32(%rcx)	C		0

	movzbl	(%rsi,%rcx), R32(%rcx)	C		1

	jz	L(shift_alot)		C		1

	shr	R8(%rcx), %rax		C		3

	mov	%rax, %rdi		C		4

	mov	%rdx, %rcx		C		3

	sub	%rax, %rcx		C		4

	sub	%rdx, %rax		C		4

	jnz	L(top)			C		5

L(end):	pop	%rcx

	mov	%rdx, %rax

	shl	R8(%rcx), %rax

	FUNC_EXIT()

	ret

L(shift_alot):

	shr	$MAXSHIFT, %rax

	mov	%rax, %rcx

	jmp	L(mid)

EPILOGUE()

CF_PROT