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;! HP-PA-1.1 __mpn_submul_1 -- Multiply a limb vector with a limb and
;! subtract the result from a second limb vector.
;! Copyright (C) 1992-2020 Free Software Foundation, Inc.
;! This file is part of the GNU MP Library.
;! The GNU MP Library is free software; you can redistribute it and/or modify
;! it under the terms of the GNU Lesser General Public License as published by
;! the Free Software Foundation; either version 2.1 of the License, or (at your
;! option) any later version.
;! The GNU MP Library is distributed in the hope that it will be useful, but
;! WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
;! or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
;! License for more details.
;! You should have received a copy of the GNU Lesser General Public License
;! along with the GNU MP Library. If not, see
;! <https://www.gnu.org/licenses/>.
;! INPUT PARAMETERS
;! res_ptr r26
;! s1_ptr r25
;! size r24
;! s2_limb r23
;! This runs at 12 cycles/limb on a PA7000. With the used instructions, it
;! can not become faster due to data cache contention after a store. On the
;! PA7100 it runs at 11 cycles/limb, and that can not be improved either,
;! since only the xmpyu does not need the integer pipeline, so the only
;! dual-issue we will get are addc+xmpyu. Unrolling could gain a cycle/limb
;! on the PA7100.
;! There are some ideas described in mul_1.s that applies to this code too.
;! It seems possible to make this run as fast as __mpn_addmul_1, if we use
;! sub,>>= %r29,%r20,%r22
;! addi 1,%r28,%r28
;! but that requires reworking the hairy software pipeline...
.text
.export __mpn_submul_1
__mpn_submul_1:
.proc
.callinfo frame=64,no_calls
.entry
ldo 64(%r30),%r30
fldws,ma 4(%r25),%fr5
stw %r23,-16(%r30) ;! move s2_limb ...
addib,= -1,%r24,L$just_one_limb
fldws -16(%r30),%fr4 ;! ... into fr4
add %r0,%r0,%r0 ;! clear carry
xmpyu %fr4,%fr5,%fr6
fldws,ma 4(%r25),%fr7
fstds %fr6,-16(%r30)
xmpyu %fr4,%fr7,%fr8
ldw -12(%r30),%r20 ;! least significant limb in product
ldw -16(%r30),%r28
fstds %fr8,-16(%r30)
addib,= -1,%r24,L$end
ldw -12(%r30),%r1
;! Main loop
L$loop:
ldws 0(%r26),%r29
fldws,ma 4(%r25),%fr5
sub %r29,%r20,%r22
add %r22,%r20,%r0
stws,ma %r22,4(%r26)
addc %r28,%r1,%r20
xmpyu %fr4,%fr5,%fr6
ldw -16(%r30),%r28
fstds %fr6,-16(%r30)
addc %r0,%r28,%r28
addib,<> -1,%r24,L$loop
ldw -12(%r30),%r1
L$end:
ldw 0(%r26),%r29
sub %r29,%r20,%r22
add %r22,%r20,%r0
stws,ma %r22,4(%r26)
addc %r28,%r1,%r20
ldw -16(%r30),%r28
ldws 0(%r26),%r29
addc %r0,%r28,%r28
sub %r29,%r20,%r22
add %r22,%r20,%r0
stws,ma %r22,4(%r26)
addc %r0,%r28,%r28
bv 0(%r2)
ldo -64(%r30),%r30
L$just_one_limb:
xmpyu %fr4,%fr5,%fr6
ldw 0(%r26),%r29
fstds %fr6,-16(%r30)
ldw -12(%r30),%r1
ldw -16(%r30),%r28
sub %r29,%r1,%r22
add %r22,%r1,%r0
stw %r22,0(%r26)
addc %r0,%r28,%r28
bv 0(%r2)
ldo -64(%r30),%r30
.exit
.procend
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