dnl  PowerPC-32 mpn_modexact_1_odd -- mpn by limb exact remainder.

dnl  Copyright 2002, 2003, 2005, 2006 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/limb

C 603e:             ?

C 604e:             6.0

C 75x (G3):         6.0-13.0, depending on divisor

C 7400,7410 (G4):   6.0-13.0, depending on divisor

C 744x,745x (G4+):  8.0-10.0, depending on divisor

C power4/ppc970:   12.0

C power5:          12.0

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 For PIC, the inverse is established arithmetically since it measures about

C 5 cycles faster than the nonsense needed to access binvert_limb_table in

C SVR4 or Darwin style PIC.  AIX might be better, since it avoids bl/mflr to

C get at the GOT/TOC/whatever.

C

C Using divwu for size==1 measured about 10 cycles slower on 604e, or about

C 3-5 cycles faster on 750.  For now it doesn't seem worth bothering with.

C

C The loop allows an early-out on mullw for the inverse, and on mulhwu for

C the divisor.  So the fastest is for instance divisor==1 (inverse==-1), and

C the slowest is anything giving a full 32-bits in both, such as

C divisor==0xDEADBEEF (inverse==0x904B300F).  These establish the stated

C range above for 750 and 7400.

ASM_START()

EXTERN(binvert_limb_table)

PROLOGUE(mpn_modexact_1_odd)

	li	r6, 0

PROLOGUE(mpn_modexact_1c_odd)

	mtctr	r4			C size

ifdef(`PIC_SLOW',`

C Load from our table with PIC is so slow on Linux and Darwin that we avoid it

	rlwinm	r7, r5, 1,28,28		C (divisor << 1) & 8

	rlwinm	r8, r5, 2,28,28		C (divisor << 2) & 8

	xor	r7, r7, r8		C ((divisor << 1) ^ (divisor << 2)) & 8

	rlwinm	r4, r5, 0,28,31		C divisor low 4 bits, speedup mullw

	xor	r4, r4, r7		C inverse, 4 bits

	mullw	r7, r4, r4		C i*i

	slwi	r4, r4, 1		C 2*i

	rlwinm	r8, r5, 0,24,31		C divisor low 8 bits, speedup mullw

	mullw	r7, r7, r8		C i*i*d

	sub	r4, r4, r7		C inverse, 8 bits

',`

	LEA(	r7, binvert_limb_table)

	rlwinm	r4, r5, 31,25,31	C (divisor/2) & 0x7F

	lbzx	r4, r4,r7		C inverse, 8 bits

')

	mullw	r7, r4, r4		C i*i

	slwi	r4, r4, 1		C 2*i

	mullw	r7, r5, r7		C i*i*d   [i*i is 16 bits, so second operand]

	sub	r4, r4, r7		C inverse, 16 bits

	mullw	r7, r4, r4		C i*i

	slwi	r4, r4, 1		C 2*i

	mullw	r7, r7, r5		C i*i*d

	lwz	r0, 0(r3)		C src[0]

	sub	r4, r4, r7		C inverse, 32 bits

	subfc	r7, r6, r0		C l = src[0] - carry

	mullw	r7, r7, r4		C q = l * inverse

	bdz	L(one)

	lwzu	r0, 4(r3)		C src[1]

	mulhwu	r6, r7, r5		C carry = high(q*divisor)

	subfe	r7, r6, r0		C l = src[1] - carry

	bdz	L(two)

L(top):

	mullw	r7, r7, r4		C q = l * inverse

	lwzu	r0, 4(r3)		C src[i]

	mulhwu	r6, r7, r5		C carry = high(q*divisor)

	subfe	r7, r6, r0		C l = src[i] - carry

	bdnz	L(top)

L(two):	mullw	r7, r7, r4		C q = l * inverse

L(one):	subfe	r3, r3, r3		C ca 0 or -1

	mulhwu	r6, r7, r5		C carry = high(q*divisor)

	subf	r3, r3, r6		C carry + ca

	blr

EPILOGUE(mpn_modexact_1c_odd)

EPILOGUE(mpn_modexact_1_odd)

ASM_END()