dnl IBM POWER mpn_submul_1 -- Multiply a limb vector with a limb and subtract
dnl the result from a second limb vector.
dnl Copyright 1992, 1994, 1999-2001 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/.
dnl INPUT PARAMETERS
dnl res_ptr r3
dnl s1_ptr r4
dnl size r5
dnl s2_limb r6
dnl The POWER architecture has no unsigned 32x32->64 bit multiplication
dnl instruction. To obtain that operation, we have to use the 32x32->64
dnl signed multiplication instruction, and add the appropriate compensation to
dnl the high limb of the result. We add the multiplicand if the multiplier
dnl has its most significant bit set, and we add the multiplier if the
dnl multiplicand has its most significant bit set. We need to preserve the
dnl carry flag between each iteration, so we have to compute the compensation
dnl carefully (the natural, srai+and doesn't work). Since all POWER can
dnl branch in zero cycles, we use conditional branches for the compensation.
include(`../config.m4')
ASM_START()
PROLOGUE(mpn_submul_1)
cal 3,-4(3)
l 0,0(4)
cmpi 0,6,0
mtctr 5
mul 9,0,6
srai 7,0,31
and 7,7,6
mfmq 11
cax 9,9,7
l 7,4(3)
sf 8,11,7 C add res_limb
a 11,8,11 C invert cy (r11 is junk)
blt Lneg
Lpos: bdz Lend
Lploop: lu 0,4(4)
stu 8,4(3)
cmpi 0,0,0
mul 10,0,6
mfmq 0
ae 11,0,9 C low limb + old_cy_limb + old cy
l 7,4(3)
aze 10,10 C propagate cy to new cy_limb
sf 8,11,7 C add res_limb
a 11,8,11 C invert cy (r11 is junk)
bge Lp0
cax 10,10,6 C adjust high limb for negative limb from s1
Lp0: bdz Lend0
lu 0,4(4)
stu 8,4(3)
cmpi 0,0,0
mul 9,0,6
mfmq 0
ae 11,0,10
l 7,4(3)
aze 9,9
sf 8,11,7
a 11,8,11 C invert cy (r11 is junk)
bge Lp1
cax 9,9,6 C adjust high limb for negative limb from s1
Lp1: bdn Lploop
b Lend
Lneg: cax 9,9,0
bdz Lend
Lnloop: lu 0,4(4)
stu 8,4(3)
cmpi 0,0,0
mul 10,0,6
mfmq 7
ae 11,7,9
l 7,4(3)
ae 10,10,0 C propagate cy to new cy_limb
sf 8,11,7 C add res_limb
a 11,8,11 C invert cy (r11 is junk)
bge Ln0
cax 10,10,6 C adjust high limb for negative limb from s1
Ln0: bdz Lend0
lu 0,4(4)
stu 8,4(3)
cmpi 0,0,0
mul 9,0,6
mfmq 7
ae 11,7,10
l 7,4(3)
ae 9,9,0 C propagate cy to new cy_limb
sf 8,11,7 C add res_limb
a 11,8,11 C invert cy (r11 is junk)
bge Ln1
cax 9,9,6 C adjust high limb for negative limb from s1
Ln1: bdn Lnloop
b Lend
Lend0: cal 9,0(10)
Lend: st 8,4(3)
aze 3,9
br
EPILOGUE(mpn_submul_1)