1;! HP-PA-1.1 __mpn_submul_1 -- Multiply a limb vector with a limb and
2;! subtract the result from a second limb vector.
3
4;! Copyright (C) 1992-2022 Free Software Foundation, Inc.
5
6;! This file is part of the GNU MP Library.
7
8;! The GNU MP Library is free software; you can redistribute it and/or modify
9;! it under the terms of the GNU Lesser General Public License as published by
10;! the Free Software Foundation; either version 2.1 of the License, or (at your
11;! option) any later version.
12
13;! The GNU MP Library is distributed in the hope that it will be useful, but
14;! WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
15;! or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
16;! License for more details.
17
18;! You should have received a copy of the GNU Lesser General Public License
19;! along with the GNU MP Library. If not, see
20;! <https://www.gnu.org/licenses/>.
21
22
23;! INPUT PARAMETERS
24;! res_ptr r26
25;! s1_ptr r25
26;! size r24
27;! s2_limb r23
28
29;! This runs at 12 cycles/limb on a PA7000. With the used instructions, it
30;! can not become faster due to data cache contention after a store. On the
31;! PA7100 it runs at 11 cycles/limb, and that can not be improved either,
32;! since only the xmpyu does not need the integer pipeline, so the only
33;! dual-issue we will get are addc+xmpyu. Unrolling could gain a cycle/limb
34;! on the PA7100.
35
36;! There are some ideas described in mul_1.s that applies to this code too.
37
38;! It seems possible to make this run as fast as __mpn_addmul_1, if we use
39;! sub,>>= %r29,%r20,%r22
40;! addi 1,%r28,%r28
41;! but that requires reworking the hairy software pipeline...
42
43 .text
44 .export __mpn_submul_1
45__mpn_submul_1:
46 .proc
47 .callinfo frame=64,no_calls
48 .entry
49
50 ldo 64(%r30),%r30
51 fldws,ma 4(%r25),%fr5
52 stw %r23,-16(%r30) ;! move s2_limb ...
53 addib,= -1,%r24,L$just_one_limb
54 fldws -16(%r30),%fr4 ;! ... into fr4
55 add %r0,%r0,%r0 ;! clear carry
56 xmpyu %fr4,%fr5,%fr6
57 fldws,ma 4(%r25),%fr7
58 fstds %fr6,-16(%r30)
59 xmpyu %fr4,%fr7,%fr8
60 ldw -12(%r30),%r20 ;! least significant limb in product
61 ldw -16(%r30),%r28
62
63 fstds %fr8,-16(%r30)
64 addib,= -1,%r24,L$end
65 ldw -12(%r30),%r1
66
67;! Main loop
68L$loop:
69 ldws 0(%r26),%r29
70 fldws,ma 4(%r25),%fr5
71 sub %r29,%r20,%r22
72 add %r22,%r20,%r0
73 stws,ma %r22,4(%r26)
74 addc %r28,%r1,%r20
75 xmpyu %fr4,%fr5,%fr6
76 ldw -16(%r30),%r28
77 fstds %fr6,-16(%r30)
78 addc %r0,%r28,%r28
79 addib,<> -1,%r24,L$loop
80 ldw -12(%r30),%r1
81
82L$end:
83 ldw 0(%r26),%r29
84 sub %r29,%r20,%r22
85 add %r22,%r20,%r0
86 stws,ma %r22,4(%r26)
87 addc %r28,%r1,%r20
88 ldw -16(%r30),%r28
89 ldws 0(%r26),%r29
90 addc %r0,%r28,%r28
91 sub %r29,%r20,%r22
92 add %r22,%r20,%r0
93 stws,ma %r22,4(%r26)
94 addc %r0,%r28,%r28
95 bv 0(%r2)
96 ldo -64(%r30),%r30
97
98L$just_one_limb:
99 xmpyu %fr4,%fr5,%fr6
100 ldw 0(%r26),%r29
101 fstds %fr6,-16(%r30)
102 ldw -12(%r30),%r1
103 ldw -16(%r30),%r28
104 sub %r29,%r1,%r22
105 add %r22,%r1,%r0
106 stw %r22,0(%r26)
107 addc %r0,%r28,%r28
108 bv 0(%r2)
109 ldo -64(%r30),%r30
110
111 .exit
112 .procend
113

source code of glibc/sysdeps/hppa/hppa1.1/submul_1.S