1dnl  Intel P6 mpn_mod_34lsub1 -- remainder modulo 2^24-1.
2
3dnl  Copyright 2000-2002, 2004 Free Software Foundation, Inc.
4
5dnl  This file is part of the GNU MP Library.
6dnl
7dnl  The GNU MP Library is free software; you can redistribute it and/or modify
8dnl  it under the terms of either:
9dnl
10dnl    * the GNU Lesser General Public License as published by the Free
11dnl      Software Foundation; either version 3 of the License, or (at your
12dnl      option) any later version.
13dnl
14dnl  or
15dnl
16dnl    * the GNU General Public License as published by the Free Software
17dnl      Foundation; either version 2 of the License, or (at your option) any
18dnl      later version.
19dnl
20dnl  or both in parallel, as here.
21dnl
22dnl  The GNU MP Library is distributed in the hope that it will be useful, but
23dnl  WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
24dnl  or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
25dnl  for more details.
26dnl
27dnl  You should have received copies of the GNU General Public License and the
28dnl  GNU Lesser General Public License along with the GNU MP Library.  If not,
29dnl  see https://www.gnu.org/licenses/.
30
31include(`../config.m4')
32
33
34C P6: 2.0 cycles/limb
35
36C TODO
37C  Experiments with more unrolling indicate that 1.5 c/l is possible on P6-13
38C  with the current carry handling scheme.
39
40C mp_limb_t mpn_mod_34lsub1 (mp_srcptr src, mp_size_t size)
41C
42C Groups of three limbs are handled, with carry bits from 0mod3 into 1mod3
43C into 2mod3, but at that point going into a separate carries total so we
44C don't keep the carry flag live across the loop control.  Avoiding decl
45C lets us get to 2.0 c/l, as compared to the generic x86 code at 3.66.
46C
47
48defframe(PARAM_SIZE, 8)
49defframe(PARAM_SRC,  4)
50
51dnl  re-use parameter space
52define(SAVE_EBX, `PARAM_SIZE')
53define(SAVE_ESI, `PARAM_SRC')
54
55	TEXT
56	ALIGN(16)
57PROLOGUE(mpn_mod_34lsub1)
58deflit(`FRAME',0)
59
60	movl	PARAM_SIZE, %ecx
61	movl	PARAM_SRC, %edx
62
63	subl	$2, %ecx		C size-2
64	movl	(%edx), %eax		C src[0]
65	ja	L(three_or_more)
66	jb	L(one)
67
68	C size==2
69
70	movl	4(%edx), %ecx		C src[1]
71
72	movl	%eax, %edx		C src[0]
73	shrl	$24, %eax		C src[0] high
74
75	andl	$0xFFFFFF, %edx		C src[0] low
76
77	addl	%edx, %eax
78	movl	%ecx, %edx		C src[1]
79	shrl	$16, %ecx		C src[1] high
80
81	andl	$0xFFFF, %edx
82	addl	%ecx, %eax
83
84	shll	$8, %edx		C src[1] low
85
86	addl	%edx, %eax
87L(one):
88	ret
89
90
91L(three_or_more):
92	C eax	src[0], initial acc 0mod3
93	C ebx
94	C ecx	size-2
95	C edx	src
96	C esi
97	C edi
98	C ebp
99
100	movl	%ebx, SAVE_EBX
101	movl	4(%edx), %ebx		C src[1], initial 1mod3
102	subl	$3, %ecx		C size-5
103
104	movl	%esi, SAVE_ESI
105	movl	8(%edx), %esi		C src[2], initial 2mod3
106
107	pushl	%edi	FRAME_pushl()
108	movl	$0, %edi		C initial carries 0mod3
109	jng	L(done)			C if size < 6
110
111
112L(top):
113	C eax	acc 0mod3
114	C ebx	acc 1mod3
115	C ecx	counter, limbs
116	C edx	src
117	C esi	acc 2mod3
118	C edi	carrys into 0mod3
119	C ebp
120
121	addl	12(%edx), %eax
122	adcl	16(%edx), %ebx
123	adcl	20(%edx), %esi
124	leal	12(%edx), %edx
125	adcl	$0, %edi
126
127	subl	$3, %ecx
128	jg	L(top)			C at least 3 more to process
129
130
131L(done):
132	C ecx is -2, -1 or 0 representing 0, 1 or 2 more limbs respectively
133	cmpl	$-1, %ecx
134	jl	L(done_0)		C if -2, meaning 0 more limbs
135
136	C 1 or 2 more limbs
137	movl	$0, %ecx
138	je	L(done_1)		C if -1, meaning 1 more limb only
139	movl	16(%edx), %ecx
140L(done_1):
141	addl	12(%edx), %eax		C 0mod3
142	adcl	%ecx, %ebx		C 1mod3
143	adcl	$0, %esi		C 2mod3
144	adcl	$0, %edi		C carries 0mod3
145
146L(done_0):
147	C eax	acc 0mod3
148	C ebx	acc 1mod3
149	C ecx
150	C edx
151	C esi	acc 2mod3
152	C edi	carries 0mod3
153	C ebp
154
155	movl	%eax, %ecx		C 0mod3
156	shrl	$24, %eax		C 0mod3 high initial total
157
158	andl	$0xFFFFFF, %ecx		C 0mod3 low
159	movl	%edi, %edx		C carries
160	shrl	$24, %edi		C carries high
161
162	addl	%ecx, %eax		C add 0mod3 low
163	andl	$0xFFFFFF, %edx		C carries 0mod3 low
164	movl	%ebx, %ecx		C 1mod3
165
166	shrl	$16, %ebx		C 1mod3 high
167	addl	%edi, %eax		C add carries high
168	addl	%edx, %eax		C add carries 0mod3 low
169
170	andl	$0xFFFF, %ecx		C 1mod3 low mask
171	addl	%ebx, %eax		C add 1mod3 high
172	movl	SAVE_EBX, %ebx
173
174	shll	$8, %ecx		C 1mod3 low
175	movl	%esi, %edx		C 2mod3
176	popl	%edi	FRAME_popl()
177
178	shrl	$8, %esi		C 2mod3 high
179	andl	$0xFF, %edx		C 2mod3 low mask
180	addl	%ecx, %eax		C add 1mod3 low
181
182	shll	$16, %edx		C 2mod3 low
183	addl	%esi, %eax		C add 2mod3 high
184	movl	SAVE_ESI, %esi
185
186	addl	%edx, %eax		C add 2mod3 low
187
188	ret
189
190EPILOGUE()
191