dnl  AMD K6 mpn_rshift -- mpn right shift.

dnl  Copyright 1999, 2000, 2002 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 K6: 3.0 cycles/limb

C mp_limb_t mpn_rshift (mp_ptr dst, mp_srcptr src, mp_size_t size,

C                       unsigned shift);

C

C The loop runs at 3 cycles/limb, limited by decoding and by having 3 mmx

C instructions.  This is despite every second fetch being unaligned.

defframe(PARAM_SHIFT,16)

defframe(PARAM_SIZE, 12)

defframe(PARAM_SRC,  8)

defframe(PARAM_DST,  4)

deflit(`FRAME',0)

	TEXT

	ALIGN(32)

PROLOGUE(mpn_rshift)

deflit(`FRAME',0)

	C The 1 limb case can be done without the push %ebx, but it's then

	C still the same speed.  The push is left as a free helping hand for

	C the two_or_more code.

	movl	PARAM_SIZE, %eax

	pushl	%ebx			FRAME_pushl()

	movl	PARAM_SRC, %ebx

	decl	%eax

	movl	PARAM_SHIFT, %ecx

	jnz	L(two_or_more)

	movl	(%ebx), %edx		C src limb

	movl	PARAM_DST, %ebx

	shrdl(	%cl, %edx, %eax)	C return value

	shrl	%cl, %edx

	movl	%edx, (%ebx)		C dst limb

	popl	%ebx

	ret

	ALIGN(16)	C avoid offset 0x1f

L(two_or_more):

	C eax	size-1

	C ebx	src

	C ecx	shift

	C edx

	movl	(%ebx), %edx	C src low limb

	negl	%ecx

	addl	$32, %ecx	C 32-shift

	movd	PARAM_SHIFT, %mm6

	shll	%cl, %edx	C retval

	movl	PARAM_DST, %ecx

	leal	(%ebx,%eax,4), %ebx

	leal	-4(%ecx,%eax,4), %ecx

	negl	%eax

L(simple):

	C eax	counter (negative)

	C ebx	&src[size-1]

	C ecx	&dst[size-1]

	C edx	retval

	C

	C mm0	scratch

	C mm6	shift

Zdisp(	movq,	0,(%ebx,%eax,4), %mm0)

	incl	%eax

	psrlq	%mm6, %mm0

Zdisp(	movd,	%mm0, 0,(%ecx,%eax,4))

	jnz	L(simple)

	movq	%mm0, (%ecx)

	movl	%edx, %eax

	popl	%ebx

	emms

	ret

EPILOGUE()