1/*******************************************************************************
2 *
3 * Copyright (c) 1993 Intel Corporation
4 *
5 * Intel hereby grants you permission to copy, modify, and distribute this
6 * software and its documentation.  Intel grants this permission provided
7 * that the above copyright notice appears in all copies and that both the
8 * copyright notice and this permission notice appear in supporting
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11 * made to this software or documentation, and that the name of Intel
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17 * IMPLIED, INCLUDING, WITHOUT LIMITATION, ANY WARRANTY OF MERCHANTABILITY
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29 ******************************************************************************/
30
31	.file "memchr_ca.s"
32#ifdef	__PIC
33	.pic
34#endif
35#ifdef	__PID
36	.pid
37#endif
38/*
39 * (c) copyright 1988,1993 Intel Corp., all rights reserved
40 */
41
42/*
43	procedure memchr  (optimized assembler version for the CA)
44
45	src_addr = memchr (src_addr, char, max_bytes)
46
47	searching from src_addr for max_bytes bytes, return a pointer to the
48	first byte that contains the indicated byte in the source string.
49	Return null if the byte is not found.
50
51	Undefined behavior will occur if the end of the source string (i.e.
52	the terminating null byte) is in the last two words of the program's
53	allocated memory space.  This is so because, in several cases, memchr
54	will fetch ahead.  Disallowing the fetch ahead would impose a severe
55	performance penalty.
56
57	This program handles two cases:
58
59	1) the argument starts on a word boundary
60	2) the argument doesn't start on a word boundary
61
62	At the time of this writing, only g0 thru g7 and g13 are available
63	for use in this leafproc;  other registers would have to be saved and
64	restored.  These nine registers, plus tricky use of g14 are sufficient
65	to implement the routine.  The registers are used as follows:
66
67	g0  src ptr;  upon return it is a pointer to the matching byte, or null
68	g1  char to seek
69	g2  maximum number of bytes to check
70	g3  char to seek, broadcast to all four bytes
71	g4  word of the source string
72	g5  copy of the word
73	g6  mask to avoid unimportant bytes in first word
74	g7  byte extraction mask
75	g13 return address
76	g14
77*/
78
79	.globl	_memchr
80	.globl	__memchr
81	.leafproc	_memchr, __memchr
82	.align	2
83_memchr:
84#ifndef __PIC
85	lda 	Lrett,g14
86#else
87	lda 	Lrett-(.+8)(ip),g14
88#endif
89__memchr:
90
91	mov	g14,g13		# preserve return address
92	 lda	0xff,g7		# byte extraction mask
93	and	g1,g7,g1	# make char an 8-bit ordinal
94	 lda	0,g14		# conform to register linkage standard
95	cmpibge.f 0,g2,Lnot_found	# do nothing if max_bytes <= 0
96	addo	g0,g2,g2	# compute ending address from start and len
97	and	g0,3,g6		# extract byte offset of src
98	notand	g0,3,g0		# extract word addr of start of src
99	shlo	8,g1,g3		# broadcast the char to four bytes
100	 ld	(g0),g4		# fetch word containing at least first byte
101	or	g1,g3,g3
102	shlo	16,g3,g5
103	cmpo	g1,g7		# is char being sought 0xff?
104	or	g5,g3,g3
105	shlo	3,g6,g6		# get shift count for making mask for first word
106	subi	1,0,g5		# mask initially all ones
107#if __i960_BIG_ENDIAN__
108	shro	g6,g5,g5	# get mask for bytes needed from first word
109#else
110	shlo	g6,g5,g5	# get mask for bytes needed from first word
111#endif
112	notor	g4,g5,g4	# set unneeded bytes to all ones
113	 be.f	Lsearch_for_0xff	# branch if seeking 0xff
114
115Lsearch_for_word_with_char:
116	scanbyte g3,g4		# check for byte with char
117	 lda	4(g0),g0	# pre-increment src word pointer
118	mov	g4,g5		# keep a copy of word
119	ld	(g0),g4		# fetch next word of src
120	 bo.f	Lsearch_for_char	# branch if null found
121	cmpoble.t g0,g2,Lsearch_for_word_with_char	# branch if not null
122
123Lnot_found:
124	mov	0,g0		# char not found.  Return null
125Lexit_code:
126	bx	(g13)		# g0 = addr of char in src (or null);  g14 = 0
127Lrett:
128	ret
129
130Lsearch_for_char:
131	subo	4,g0,g0		# back up the byte pointer
132Lsearch_for_char.a:
133	cmpobe.f g0,g2,Lnot_found	# quit if max_bytes exhausted
134#if __i960_BIG_ENDIAN__
135	rotate	8,g5,g5		# shift word to position next byte
136#endif
137	and	g5,g7,g6	# extract byte
138	cmpo	g1,g6		# is it char?
139	 lda	1(g0),g0	# bump src byte ptr
140#if ! __i960_BIG_ENDIAN__
141	shro	8,g5,g5		# shift word to position next byte
142#endif
143	 bne.t	Lsearch_for_char.a
144	subo	1,g0,g0		# back up the byte pointer
145	 b	Lexit_code
146
147Lsearch_for_0xff:
148	lda	0xf0f0f0f0,g6	# make first comparison mask for char=-1 case.
149	or	g6,g5,g6
150	and	g4,g6,g4	# make unimportant bytes of first word 0x0f
151	 b	Lsearch_for_word_with_char
152
153/* end of memchr */
154