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) 1992-2021 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