1/*
2 * Copyright (c) 2017 Imagination Technologies.
3 *
4 * All rights reserved.
5 *
6 * Redistribution and use in source and binary forms, with or without
7 * modification, are permitted provided that the following conditions
8 * are met:
9 *
10 *      * Redistributions of source code must retain the above copyright
11 *        notice, this list of conditions and the following disclaimer.
12 *      * Redistributions in binary form must reproduce the above copyright
13 *        notice, this list of conditions and the following disclaimer
14 *        in the documentation and/or other materials provided with
15 *        the distribution.
16 *      * Neither the name of Imagination Technologies nor the names of its
17 *        contributors may be used to endorse or promote products derived
18 *        from this software without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
21 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
22 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
23 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
24 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
25 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
26 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
30 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31 */
32
33#include <string.h>
34
35#define op_t        unsigned long int
36#define op_size     sizeof (op_t)
37
38#if __mips64
39typedef struct
40{
41  op_t B0:8, B1:8, B2:8, B3:8, B4:8, B5:8, B6:8, B7:8;
42} bits_t;
43#else
44typedef struct
45{
46  op_t B0:8, B1:8, B2:8, B3:8;
47} bits_t;
48#endif
49
50typedef union
51{
52  op_t v;
53  bits_t b;
54} bitfields_t;
55
56#define DO_BYTE(i)                  \
57  if (a.b.B##i != ch) {             \
58    if(a.b.B##i == '\0') return 0;  \
59    p++;                            \
60  } else                            \
61    return (char *)p;
62
63#define DO_WORD(w, cnt) {                            \
64  op_t val = w[cnt] ^ mask_c;                        \
65  if ((((w[cnt] - mask_1) & ~w[cnt]) & mask_128) ||  \
66    (((val - mask_1) & ~val) & mask_128)) {          \
67    return do_bytes(w + cnt, ch);                    \
68  }                                                  \
69}
70
71static inline char * __attribute__ ((always_inline))
72do_bytes (const op_t* w, unsigned char ch)
73{
74  bitfields_t a;
75  unsigned char* p = (unsigned char *) w;
76  a.v = *w;
77#if __mips64
78  DO_BYTE(0)
79  DO_BYTE(1)
80  DO_BYTE(2)
81  DO_BYTE(3)
82  DO_BYTE(4)
83  DO_BYTE(5)
84  DO_BYTE(6)
85  DO_BYTE(7)
86#else
87  DO_BYTE(0)
88  DO_BYTE(1)
89  DO_BYTE(2)
90  DO_BYTE(3)
91#endif
92  return (char *)p;
93}
94
95char* strchr(const char* s, int c) __overloadable
96{
97  const op_t *w;
98  op_t mask_1, mask_128, mask_c;
99  const unsigned char ch = c;
100  unsigned char* p = (unsigned char *) s;
101
102  /*
103   * Check byte by byte till initial alignment
104   */
105  for ( ; *p != ch && ((size_t) p % op_size) != 0; p++)
106    if (*p == '\0')
107      return 0;
108
109  if (*p != ch) {
110    w = (const op_t *) p;
111
112    mask_c = ch | (ch << 8);
113    mask_c |= mask_c << 16;
114    __asm__ volatile (
115      "li %0, 0x01010101 \n\t"
116      : "=r" (mask_1)
117    );
118#if __mips64
119    mask_1 |= mask_1 << 32;
120    mask_c |= mask_c << 32;
121#endif
122    mask_128 = mask_1 << 7;
123
124    /*
125     * Check word/dword wize after initial alignment till character match
126     * or end of string
127     */
128    while (1) {
129      DO_WORD(w, 0)
130      DO_WORD(w, 1)
131      DO_WORD(w, 2)
132      DO_WORD(w, 3)
133      w += 4;
134    }
135  }
136
137  return (char *)p;
138}
139