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dnl HP-PA 1.1 mpn_submul_1 -- Multiply a limb vector with a limb and subtract
dnl the result from a second limb vector.
dnl Copyright 1992, 1993, 1994, 2000, 2001, 2002 Free Software Foundation,
dnl Inc.
dnl This file is part of the GNU MP Library.
dnl The GNU MP Library is free software; you can redistribute it and/or modify
dnl it under the terms of the GNU Lesser General Public License as published
dnl by the Free Software Foundation; either version 2.1 of the License, or (at
dnl your option) any later version.
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 Lesser General Public
dnl License for more details.
dnl You should have received a copy of the GNU Lesser General Public License
dnl along with the GNU MP Library; see the file COPYING.LIB. If not, write to
dnl the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
dnl MA 02111-1307, USA.
include(`../config.m4')
C INPUT PARAMETERS
C res_ptr r26
C s1_ptr r25
C size r24
C s2_limb r23
C This runs at 12 cycles/limb on a PA7000. With the used instructions, it can
C not become faster due to data cache contention after a store. On the PA7100
C it runs at 11 cycles/limb.
C There are some ideas described in mul_1.asm that applies to this code too.
C It seems possible to make this run as fast as mpn_addmul_1, if we use
C sub,>>= %r29,%r19,%r22
C addi 1,%r28,%r28
C but that requires reworking the hairy software pipeline...
ASM_START()
PROLOGUE(mpn_submul_1)
C .callinfo frame=64,no_calls
ldo 64(%r30),%r30
fldws,ma 4(%r25),%fr5
stw %r23,-16(%r30) C move s2_limb ...
addib,= -1,%r24,L(just_one_limb)
fldws -16(%r30),%fr4 C ... into fr4
add %r0,%r0,%r0 C clear carry
xmpyu %fr4,%fr5,%fr6
fldws,ma 4(%r25),%fr7
fstds %fr6,-16(%r30)
xmpyu %fr4,%fr7,%fr8
ldw -12(%r30),%r19 C least significant limb in product
ldw -16(%r30),%r28
fstds %fr8,-16(%r30)
addib,= -1,%r24,L(end)
ldw -12(%r30),%r1
C Main loop
.label L(loop)
ldws 0(%r26),%r29
fldws,ma 4(%r25),%fr5
sub %r29,%r19,%r22
add %r22,%r19,%r0
stws,ma %r22,4(%r26)
addc %r28,%r1,%r19
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
.label L(end)
ldw 0(%r26),%r29
sub %r29,%r19,%r22
add %r22,%r19,%r0
stws,ma %r22,4(%r26)
addc %r28,%r1,%r19
ldw -16(%r30),%r28
ldws 0(%r26),%r29
addc %r0,%r28,%r28
sub %r29,%r19,%r22
add %r22,%r19,%r0
stws,ma %r22,4(%r26)
addc %r0,%r28,%r28
bv 0(%r2)
ldo -64(%r30),%r30
.label 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
EPILOGUE()
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