dnl  x86 mpn_gcd_1 optimised for AMD K7.

dnl  Contributed to the GNU project by by Kevin Ryde.  Rehacked by Torbjorn

dnl  Granlund.

dnl  Copyright 2000-2002, 2005, 2009, 2011, 2012, 2014, 2015 Free Software

dnl  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 K7	 5.31

C AMD K8,K9	 5.33

C AMD K10	 5.30

C AMD bd1	 ?

C AMD bobcat	 7.02

C Intel P4-2	10.1

C Intel P4-3/4	10.0

C Intel P6/13	 5.88

C Intel core2	 6.26

C Intel NHM	 6.83

C Intel SBR	 8.50

C Intel atom	 8.90

C VIA nano	 ?

C Numbers measured with: speed -CD -s16-32 -t16 mpn_gcd_1

C TODO

C  * Tune overhead, this takes 2-3 cycles more than old code when v0 is tiny.

C  * Stream things better through registers, avoiding some copying.

C  * For ELF, avoid putting GOT base in both ebx and esi.  Needs special

C    LEA/LEAL or else discrete code here.

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

deflit(MAXSHIFT, 6)

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(`DIV_THRES_LOG2', 7)

define(`up',    `%edi')

define(`n',     `%esi')

define(`v0',    `%edx')

ASM_START()

	TEXT

	ALIGN(16)

PROLOGUE(mpn_gcd_1)

	push	%edi

	push	%esi

	mov	12(%esp), up

	mov	16(%esp), n

	mov	20(%esp), v0

	mov	(up), %eax		C U low limb

	or	v0, %eax		C x | y

	mov	$-1, %ecx

L(twos):

	inc	%ecx

	shr	%eax

	jnc	L(twos)

	shr	%cl, v0

	mov	%ecx, %eax		C common twos

L(divide_strip_y):

	shr	v0

	jnc	L(divide_strip_y)

	adc	v0, v0

	push	%eax

	push	v0

	cmp	$1, n

	jnz	L(reduce_nby1)

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

	mov	(up), %ecx

	mov	%ecx, %eax

	shr	$DIV_THRES_LOG2, %ecx

	cmp	%ecx, v0

	ja	L(reduced)

	mov	v0, %esi

	xor	%edx, %edx

	div	%esi

	mov	%edx, %eax

	jmp	L(reduced)

L(reduce_nby1):

ifdef(`PIC_WITH_EBX',`dnl

	push	%ebx

	add	$-4, %esp

	call	L(movl_eip_ebx)

	add	$_GLOBAL_OFFSET_TABLE_, %ebx

')

	push	v0			C param 3

	push	n			C param 2

	push	up			C param 1

	cmp	$BMOD_1_TO_MOD_1_THRESHOLD, n

	jl	L(bmod)

	CALL(	mpn_mod_1)

	jmp	L(called)

L(bmod):

	CALL(	mpn_modexact_1_odd)

L(called):

ifdef(`PIC_WITH_EBX',`dnl

	add	$16, %esp	C deallocate params

	pop	%ebx

',`

	add	$12, %esp		C deallocate params

')

L(reduced):

	pop	%edx

	LEAL(	ctz_table, %esi)

	test	%eax, %eax

	mov	%eax, %ecx

	jnz	L(mid)

	jmp	L(end)

	ALIGN(16)			C               K8    BC    P4    NHM   SBR

L(top):	cmovc(	%ecx, %eax)		C if x-y < 0	0

	cmovc(	%edi, %edx)		C use x,y-x	0

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

	movzbl	(%esi,%ecx), %ecx	C		1

	jz	L(shift_alot)		C		1

	shr	%cl, %eax		C		3

	mov	%eax, %edi		C		4

	mov	%edx, %ecx		C		3

	sub	%eax, %ecx		C		4

	sub	%edx, %eax		C		4

	jnz	L(top)			C		5

L(end):	pop	%ecx

	mov	%edx, %eax

	shl	%cl, %eax

	pop	%esi

	pop	%edi

	ret

L(shift_alot):

	shr	$MAXSHIFT, %eax

	mov	%eax, %ecx

	jmp	L(mid)

ifdef(`PIC_WITH_EBX',`dnl

L(movl_eip_ebx):

	mov	(%esp), %ebx

	ret

')

EPILOGUE()

ASM_END()