mpir/mpn/x86/p6/modexact_1c_odd.asm

dnl  Intel P6 mpn_modexact_1_odd -- exact division style remainder.

dnl  Copyright 2000, 2001, 2002 Free Software Foundation, Inc.
dnl
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
dnl  modify it under the terms of the GNU Lesser General Public License as
dnl  published by the Free Software Foundation; either version 2.1 of the
dnl  License, or (at your option) any later version.
dnl
dnl  The GNU MP Library is distributed in the hope that it will be useful,
dnl  but WITHOUT ANY WARRANTY; without even the implied warranty of
dnl  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
dnl  Lesser General Public License for more details.
dnl
dnl  You should have received a copy of the GNU Lesser General Public
dnl  License along with the GNU MP Library; see the file COPYING.LIB.  If
dnl  not, write to the Free Software Foundation, Inc., 51 Franklin Street,
dnl  Fifth Floor, Boston, MA 02110-1301, USA.

include(`../config.m4')


C P6: 10.0 cycles/limb


C mp_limb_t mpn_modexact_1_odd (mp_srcptr src, mp_size_t size,
C                               mp_limb_t divisor);
C mp_limb_t mpn_modexact_1c_odd (mp_srcptr src, mp_size_t size,
C                                mp_limb_t divisor, mp_limb_t carry);
C
C It's not worth skipping a step at the end when high<divisor since the main
C loop is only 10 cycles.

defframe(PARAM_CARRY,  16)
defframe(PARAM_DIVISOR,12)
defframe(PARAM_SIZE,   8)
defframe(PARAM_SRC,    4)

dnl  Not enough room under modexact_1 to make these re-use the parameter
dnl  space, unfortunately.
defframe(SAVE_EBX,     -4)
defframe(SAVE_ESI,     -8)
defframe(SAVE_EDI,    -12)
deflit(STACK_SPACE, 12)

	TEXT

	ALIGN(16)
PROLOGUE(mpn_modexact_1c_odd)
deflit(`FRAME',0)

	movl	PARAM_CARRY, %ecx
	jmp	L(start_1c)

EPILOGUE()

	ALIGN(16)
PROLOGUE(mpn_modexact_1_odd)
deflit(`FRAME',0)

	xorl	%ecx, %ecx
L(start_1c):
	movl	PARAM_DIVISOR, %eax

	subl	$STACK_SPACE, %esp	FRAME_subl_esp(STACK_SPACE)

	movl	%esi, SAVE_ESI
	movl	PARAM_SRC, %esi

	shrl	%eax			C d/2
	movl	%edi, SAVE_EDI

	andl	$127, %eax

ifdef(`PIC',`
	call	L(movl_eip_edi)
	addl	$_GLOBAL_OFFSET_TABLE_, %edi
	movl	modlimb_invert_table@GOT(%edi), %edi
	movzbl	(%eax,%edi), %edi			C inv 8 bits

',`
dnl non-PIC
	movzbl	modlimb_invert_table(%eax), %edi	C inv 8 bits
')

	xorl	%edx, %edx		C initial extra carry
	leal	(%edi,%edi), %eax	C 2*inv

	imull	%edi, %edi		C inv*inv

	movl	%ebx, SAVE_EBX
	movl	PARAM_SIZE, %ebx

	imull	PARAM_DIVISOR, %edi	C inv*inv*d

	subl	%edi, %eax		C inv = 2*inv - inv*inv*d
	leal	(%eax,%eax), %edi	C 2*inv

	imull	%eax, %eax		C inv*inv

	imull	PARAM_DIVISOR, %eax	C inv*inv*d

	leal	(%esi,%ebx,4), %esi	C src end
	negl	%ebx			C -size

	subl	%eax, %edi		C inv = 2*inv - inv*inv*d

	ASSERT(e,`	C d*inv == 1 mod 2^BITS_PER_MP_LIMB
	movl	PARAM_DIVISOR, %eax
	imull	%edi, %eax
	cmpl	$1, %eax')


C The dependent chain here is
C
C	subl	%edx, %eax       1
C	imull	%edi, %eax       4
C	mull	PARAM_DIVISOR    5
C			       ----
C       total		        10
C
C and this is the measured speed.  No special scheduling is necessary, out
C of order execution hides the load latency.

L(top):
	C eax	scratch (src limb)
	C ebx	counter, limbs, negative
	C ecx	carry bit, 0 or 1
	C edx	carry limb, high of last product
	C esi	&src[size]
	C edi	inverse
	C ebp

	movl	(%esi,%ebx,4), %eax
	subl	%ecx, %eax

	sbbl	%ecx, %ecx
	subl	%edx, %eax

	sbbl	$0, %ecx

	imull	%edi, %eax

	negl	%ecx

	mull	PARAM_DIVISOR

	incl	%ebx
	jnz	L(top)


	movl	SAVE_ESI, %esi
	leal	(%ecx,%edx), %eax

	movl	SAVE_EDI, %edi

	movl	SAVE_EBX, %ebx
	addl	$STACK_SPACE, %esp

	ret


ifdef(`PIC',`
L(movl_eip_edi):
	movl	(%esp), %edi
	ret_internal
')

EPILOGUE()