x86/k7/mul_basecase.asm

dnl  AMD K7 mpn_mul_basecase -- multiply two mpn numbers.

dnl  Copyright 1999-2002 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 K7: approx 4.42 cycles per cross product at around 20x20 limbs (16
C     limbs/loop unrolling).


dnl  K7 UNROLL_COUNT cycles/product (at around 20x20)
dnl           8           4.67
dnl          16           4.59
dnl          32           4.42
dnl  Maximum possible with the current code is 32.
dnl
dnl  At 32 the typical 13-26 limb sizes from the karatsuba code will get
dnl  done with a straight run through a block of code, no inner loop.  Using
dnl  32 gives 1k of code, but the k7 has a 64k L1 code cache.

deflit(UNROLL_COUNT, 32)


C void mpn_mul_basecase (mp_ptr wp,
C                        mp_srcptr xp, mp_size_t xsize,
C                        mp_srcptr yp, mp_size_t ysize);
C
C Calculate xp,xsize multiplied by yp,ysize, storing the result in
C wp,xsize+ysize.
C
C This routine is essentially the same as mpn/generic/mul_basecase.c, but
C it's faster because it does most of the mpn_addmul_1() startup
C calculations only once.  The saving is 15-25% on typical sizes coming from
C the Karatsuba multiply code.

ifdef(`PIC',`
deflit(UNROLL_THRESHOLD, 5)
',`
deflit(UNROLL_THRESHOLD, 5)
')

defframe(PARAM_YSIZE,20)
defframe(PARAM_YP,   16)
defframe(PARAM_XSIZE,12)
defframe(PARAM_XP,   8)
defframe(PARAM_WP,   4)

	TEXT
	ALIGN(32)
PROLOGUE(mpn_mul_basecase)
deflit(`FRAME',0)

	movl	PARAM_XSIZE, %ecx
	movl	PARAM_YP, %eax

	movl	PARAM_XP, %edx
	movl	(%eax), %eax	C yp low limb

	cmpl	$2, %ecx
	ja	L(xsize_more_than_two)
	je	L(two_by_something)


	C one limb by one limb

	mull	(%edx)

	movl	PARAM_WP, %ecx
	movl	%eax, (%ecx)
	movl	%edx, 4(%ecx)
	ret


C -----------------------------------------------------------------------------
L(two_by_something):
deflit(`FRAME',0)
	decl	PARAM_YSIZE
	pushl	%ebx		defframe_pushl(`SAVE_EBX')
	movl	%eax, %ecx	C yp low limb

	movl	PARAM_WP, %ebx
	pushl	%esi		defframe_pushl(`SAVE_ESI')
	movl	%edx, %esi	C xp

	movl	(%edx), %eax	C xp low limb
	jnz	L(two_by_two)


	C two limbs by one limb

	mull	%ecx

	movl	%eax, (%ebx)
	movl	4(%esi), %eax
	movl	%edx, %esi	C carry

	mull	%ecx

	addl	%eax, %esi

	movl	%esi, 4(%ebx)
	movl	SAVE_ESI, %esi

	adcl	$0, %edx

	movl	%edx, 8(%ebx)
	movl	SAVE_EBX, %ebx
	addl	$FRAME, %esp

	ret


C -----------------------------------------------------------------------------
C Could load yp earlier into another register.

	ALIGN(16)
L(two_by_two):
	C eax	xp low limb
	C ebx	wp
	C ecx	yp low limb
	C edx
	C esi	xp
	C edi
	C ebp

dnl  FRAME carries on from previous

	mull	%ecx		C xp[0] * yp[0]

	push	%edi		defframe_pushl(`SAVE_EDI')
	movl	%edx, %edi	C carry, for wp[1]

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

	mull	%ecx		C xp[1] * yp[0]

	addl	%eax, %edi
	movl	PARAM_YP, %ecx

	adcl	$0, %edx
	movl	4(%ecx), %ecx	C yp[1]
	movl	%edi, 4(%ebx)

	movl	4(%esi), %eax	C xp[1]
	movl	%edx, %edi	C carry, for wp[2]

	mull	%ecx		C xp[1] * yp[1]

	addl	%eax, %edi

	adcl	$0, %edx
	movl	(%esi), %eax	C xp[0]

	movl	%edx, %esi	C carry, for wp[3]

	mull	%ecx		C xp[0] * yp[1]

	addl	%eax, 4(%ebx)
	adcl	%edx, %edi
	movl	%edi, 8(%ebx)

	adcl	$0, %esi
	movl	SAVE_EDI, %edi
	movl	%esi, 12(%ebx)

	movl	SAVE_ESI, %esi
	movl	SAVE_EBX, %ebx
	addl	$FRAME, %esp

	ret


C -----------------------------------------------------------------------------
	ALIGN(16)
L(xsize_more_than_two):

C The first limb of yp is processed with a simple mpn_mul_1 style loop
C inline.  Unrolling this doesn't seem worthwhile since it's only run once
C (whereas the addmul below is run ysize-1 many times).  A call to the
C actual mpn_mul_1 will be slowed down by the call and parameter pushing and
C popping, and doesn't seem likely to be worthwhile on the typical 13-26
C limb operations the Karatsuba code calls here with.

	C eax	yp[0]
	C ebx
	C ecx	xsize
	C edx	xp
	C esi
	C edi
	C ebp

dnl  FRAME doesn't carry on from previous, no pushes yet here
defframe(`SAVE_EBX',-4)
defframe(`SAVE_ESI',-8)
defframe(`SAVE_EDI',-12)
defframe(`SAVE_EBP',-16)
deflit(`FRAME',0)

	subl	$16, %esp
deflit(`FRAME',16)

	movl	%edi, SAVE_EDI
	movl	PARAM_WP, %edi

	movl	%ebx, SAVE_EBX
	movl	%ebp, SAVE_EBP
	movl	%eax, %ebp

	movl	%esi, SAVE_ESI
	xorl	%ebx, %ebx
	leal	(%edx,%ecx,4), %esi	C xp end

	leal	(%edi,%ecx,4), %edi	C wp end of mul1
	negl	%ecx


L(mul1):
	C eax	scratch
	C ebx	carry
	C ecx	counter, negative
	C edx	scratch
	C esi	xp end
	C edi	wp end of mul1
	C ebp	multiplier

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

	mull	%ebp

	addl	%ebx, %eax
	movl	%eax, (%edi,%ecx,4)
	movl	$0, %ebx

	adcl	%edx, %ebx
	incl	%ecx
	jnz	L(mul1)


	movl	PARAM_YSIZE, %edx
	movl	PARAM_XSIZE, %ecx

	movl	%ebx, (%edi)		C final carry
	decl	%edx

	jnz	L(ysize_more_than_one)


	movl	SAVE_EDI, %edi
	movl	SAVE_EBX, %ebx

	movl	SAVE_EBP, %ebp
	movl	SAVE_ESI, %esi
	addl	$FRAME, %esp

	ret


L(ysize_more_than_one):
	cmpl	$UNROLL_THRESHOLD, %ecx
	movl	PARAM_YP, %eax

	jae	L(unroll)


C -----------------------------------------------------------------------------
	C simple addmul looping
	C
	C eax	yp
	C ebx
	C ecx	xsize
	C edx	ysize-1
	C esi	xp end
	C edi	wp end of mul1
	C ebp

	leal	4(%eax,%edx,4), %ebp	C yp end
	negl	%ecx
	negl	%edx

	movl	(%esi,%ecx,4), %eax	C xp low limb
	movl	%edx, PARAM_YSIZE	C -(ysize-1)
	incl	%ecx

	xorl	%ebx, %ebx		C initial carry
	movl	%ecx, PARAM_XSIZE	C -(xsize-1)
	movl	%ebp, PARAM_YP

	movl	(%ebp,%edx,4), %ebp	C yp second lowest limb - multiplier
	jmp	L(simple_outer_entry)


	C this is offset 0x121 so close enough to aligned
L(simple_outer_top):
	C ebp	ysize counter, negative

	movl	PARAM_YP, %edx
	movl	PARAM_XSIZE, %ecx	C -(xsize-1)
	xorl	%ebx, %ebx		C carry

	movl	%ebp, PARAM_YSIZE
	addl	$4, %edi		C next position in wp

	movl	(%edx,%ebp,4), %ebp	C yp limb - multiplier
	movl	-4(%esi,%ecx,4), %eax	C xp low limb


L(simple_outer_entry):

L(simple_inner):
	C eax	xp limb
	C ebx	carry limb
	C ecx	loop counter (negative)
	C edx	scratch
	C esi	xp end
	C edi	wp end
	C ebp	multiplier

	mull	%ebp

	addl	%eax, %ebx
	adcl	$0, %edx

	addl	%ebx, (%edi,%ecx,4)
	movl	(%esi,%ecx,4), %eax
	adcl	$0, %edx

	incl	%ecx
	movl	%edx, %ebx
	jnz	L(simple_inner)


	mull	%ebp

	movl	PARAM_YSIZE, %ebp
	addl	%eax, %ebx

	adcl	$0, %edx
	addl	%ebx, (%edi)

	adcl	$0, %edx
	incl	%ebp

	movl	%edx, 4(%edi)
	jnz	L(simple_outer_top)


	movl	SAVE_EBX, %ebx
	movl	SAVE_ESI, %esi

	movl	SAVE_EDI, %edi
	movl	SAVE_EBP, %ebp
	addl	$FRAME, %esp

	ret


C -----------------------------------------------------------------------------
C
C The unrolled loop is the same as in mpn_addmul_1(), see that code for some
C comments.
C
C VAR_ADJUST is the negative of how many limbs the leals in the inner loop
C increment xp and wp.  This is used to adjust back xp and wp, and rshifted
C to given an initial VAR_COUNTER at the top of the outer loop.
C
C VAR_COUNTER is for the unrolled loop, running from VAR_ADJUST/UNROLL_COUNT
C up to -1, inclusive.
C
C VAR_JMP is the computed jump into the unrolled loop.
C
C VAR_XP_LOW is the least significant limb of xp, which is needed at the
C start of the unrolled loop.
C
C PARAM_YSIZE is the outer loop counter, going from -(ysize-1) up to -1,
C inclusive.
C
C PARAM_YP is offset appropriately so that the PARAM_YSIZE counter can be
C added to give the location of the next limb of yp, which is the multiplier
C in the unrolled loop.
C
C The trick with VAR_ADJUST means it's only necessary to do one fetch in the
C outer loop to take care of xp, wp and the inner loop counter.

defframe(VAR_COUNTER,  -20)
defframe(VAR_ADJUST,   -24)
defframe(VAR_JMP,      -28)
defframe(VAR_XP_LOW,   -32)
deflit(VAR_EXTRA_SPACE, 16)


L(unroll):
	C eax	yp
	C ebx
	C ecx	xsize
	C edx	ysize-1
	C esi	xp end
	C edi	wp end of mul1
	C ebp

	movl	PARAM_XP, %esi
	movl	4(%eax), %ebp		C multiplier (yp second limb)
	leal	4(%eax,%edx,4), %eax	C yp adjust for ysize indexing

	movl	PARAM_WP, %edi
	movl	%eax, PARAM_YP
	negl	%edx

	movl	%edx, PARAM_YSIZE
	leal	UNROLL_COUNT-2(%ecx), %ebx	C (xsize-1)+UNROLL_COUNT-1
	decl	%ecx				C xsize-1

	movl	(%esi), %eax		C xp low limb
	andl	$-UNROLL_MASK-1, %ebx
	negl	%ecx

	subl	$VAR_EXTRA_SPACE, %esp
deflit(`FRAME',16+VAR_EXTRA_SPACE)
	negl	%ebx
	andl	$UNROLL_MASK, %ecx

	movl	%ebx, VAR_ADJUST
	movl	%ecx, %edx
	shll	$4, %ecx

	sarl	$UNROLL_LOG2, %ebx

	C 17 code bytes per limb
ifdef(`PIC',`
	call	L(pic_calc)
L(unroll_here):
',`
	leal	L(unroll_entry) (%ecx,%edx,1), %ecx
')
	negl	%edx

	movl	%eax, VAR_XP_LOW
	movl	%ecx, VAR_JMP
	leal	4(%edi,%edx,4), %edi	C wp and xp, adjust for unrolling,
	leal	4(%esi,%edx,4), %esi	C  and start at second limb
	jmp	L(unroll_outer_entry)


ifdef(`PIC',`
L(pic_calc):
	C See mpn/x86/README about old gas bugs
	leal	(%ecx,%edx,1), %ecx
	addl	$L(unroll_entry)-L(unroll_here), %ecx
	addl	(%esp), %ecx
	ret_internal
')


C --------------------------------------------------------------------------
	ALIGN(32)
L(unroll_outer_top):
	C ebp	ysize counter, negative

	movl	VAR_ADJUST, %ebx
	movl	PARAM_YP, %edx

	movl	VAR_XP_LOW, %eax
	movl	%ebp, PARAM_YSIZE	C store incremented ysize counter

	leal	4(%edi,%ebx,4), %edi
	leal	(%esi,%ebx,4), %esi
	sarl	$UNROLL_LOG2, %ebx

	movl	(%edx,%ebp,4), %ebp	C yp next multiplier
	movl	VAR_JMP, %ecx

L(unroll_outer_entry):
	mull	%ebp

	testb	$1, %cl		C and clear carry bit
	movl	%ebx, VAR_COUNTER
	movl	$0, %ebx

	movl	$0, %ecx
	cmovz(	%eax, %ecx)	C eax into low carry, zero into high carry limb
	cmovnz(	%eax, %ebx)

	C Extra fetch of VAR_JMP is bad, but registers are tight
	jmp	*VAR_JMP


C -----------------------------------------------------------------------------
	ALIGN(32)
L(unroll_top):
	C eax	xp limb
	C ebx	carry high
	C ecx	carry low
	C edx	scratch
	C esi	xp+8
	C edi	wp
	C ebp	yp multiplier limb
	C
	C VAR_COUNTER  loop counter, negative
	C
	C 17 bytes each limb

L(unroll_entry):

deflit(CHUNK_COUNT,2)
forloop(`i', 0, UNROLL_COUNT/CHUNK_COUNT-1, `
	deflit(`disp0', eval(i*CHUNK_COUNT*4 ifelse(UNROLL_BYTES,256,-128)))
	deflit(`disp1', eval(disp0 + 4))

Zdisp(	movl,	disp0,(%esi), %eax)
	adcl	%edx, %ebx

	mull	%ebp

Zdisp(	addl,	%ecx, disp0,(%edi))
	movl	$0, %ecx

	adcl	%eax, %ebx


	movl	disp1(%esi), %eax
	adcl	%edx, %ecx

	mull	%ebp

	addl	%ebx, disp1(%edi)
	movl	$0, %ebx

	adcl	%eax, %ecx
')


	incl	VAR_COUNTER
	leal	UNROLL_BYTES(%esi), %esi
	leal	UNROLL_BYTES(%edi), %edi

	jnz	L(unroll_top)


	C eax
	C ebx	zero
	C ecx	low
	C edx	high
	C esi
	C edi	wp, pointing at second last limb)
	C ebp
	C
	C carry flag to be added to high

deflit(`disp0', ifelse(UNROLL_BYTES,256,-128))
deflit(`disp1', eval(disp0-0 + 4))

	movl	PARAM_YSIZE, %ebp
	adcl	$0, %edx
	addl	%ecx, disp0(%edi)

	adcl	$0, %edx
	incl	%ebp

	movl	%edx, disp1(%edi)
	jnz	L(unroll_outer_top)


	movl	SAVE_ESI, %esi
	movl	SAVE_EBP, %ebp

	movl	SAVE_EDI, %edi
	movl	SAVE_EBX, %ebx
	addl	$FRAME, %esp

	ret

EPILOGUE()