1
2 /* arm_init.c - NEON optimised filter functions
3 *
4 * Copyright (c) 2018-2022 Cosmin Truta
5 * Copyright (c) 2014,2016 Glenn Randers-Pehrson
6 * Written by Mans Rullgard, 2011.
7 *
8 * This code is released under the libpng license.
9 * For conditions of distribution and use, see the disclaimer
10 * and license in png.h
11 */
12
13 /* This module requires POSIX 1003.1 functions. */
14 #define _POSIX_SOURCE 1
15
16 #include "../pngpriv.h"
17
18 #ifdef PNG_READ_SUPPORTED
19
20 #if PNG_ARM_NEON_OPT > 0
21 #ifdef PNG_ARM_NEON_CHECK_SUPPORTED /* Do run-time checks */
22 /* WARNING: it is strongly recommended that you do not build libpng with
23 * run-time checks for CPU features if at all possible. In the case of the ARM
24 * NEON instructions there is no processor-specific way of detecting the
25 * presence of the required support, therefore run-time detection is extremely
26 * OS specific.
27 *
28 * You may set the macro PNG_ARM_NEON_FILE to the file name of file containing
29 * a fragment of C source code which defines the png_have_neon function. There
30 * are a number of implementations in contrib/arm-neon, but the only one that
31 * has partial support is contrib/arm-neon/linux.c - a generic Linux
32 * implementation which reads /proc/cpufino.
33 */
34 #include <signal.h> /* for sig_atomic_t */
35
36 #ifndef PNG_ARM_NEON_FILE
37 # if defined(__aarch64__) || defined(_M_ARM64)
38 /* ARM Neon is expected to be unconditionally available on ARM64. */
39 # error "PNG_ARM_NEON_CHECK_SUPPORTED must not be defined on ARM64"
40 # elif defined(__ARM_NEON__) || defined(__ARM_NEON)
41 /* ARM Neon is expected to be available on the target CPU architecture. */
42 # error "PNG_ARM_NEON_CHECK_SUPPORTED must not be defined on this CPU arch"
43 # elif defined(__linux__)
44 # define PNG_ARM_NEON_FILE "contrib/arm-neon/linux.c"
45 # else
46 # error "No support for run-time ARM Neon checking; use compile-time options"
47 # endif
48 #endif
49
50 static int png_have_neon(png_structp png_ptr);
51 #ifdef PNG_ARM_NEON_FILE
52 # include PNG_ARM_NEON_FILE
53 #endif
54 #endif /* PNG_ARM_NEON_CHECK_SUPPORTED */
55
56 #ifndef PNG_ALIGNED_MEMORY_SUPPORTED
57 # error "ALIGNED_MEMORY is required; set: -DPNG_ALIGNED_MEMORY_SUPPORTED"
58 #endif
59
60 void
61 png_init_filter_functions_neon(png_structp pp, unsigned int bpp)
62 {
63 /* The switch statement is compiled in for ARM_NEON_API, the call to
64 * png_have_neon is compiled in for ARM_NEON_CHECK. If both are defined
65 * the check is only performed if the API has not set the NEON option on
66 * or off explicitly. In this case the check controls what happens.
67 *
68 * If the CHECK is not compiled in and the option is UNSET the behavior prior
69 * to 1.6.7 was to use the NEON code - this was a bug caused by having the
70 * wrong order of the 'ON' and 'default' cases. UNSET now defaults to OFF,
71 * as documented in png.h
72 */
73 png_debug(1, "in png_init_filter_functions_neon");
74 #ifdef PNG_ARM_NEON_API_SUPPORTED
75 switch ((pp->options >> PNG_ARM_NEON) & 3)
76 {
77 case PNG_OPTION_UNSET:
78 /* Allow the run-time check to execute if it has been enabled -
79 * thus both API and CHECK can be turned on. If it isn't supported
80 * this case will fall through to the 'default' below, which just
81 * returns.
82 */
83 #endif /* PNG_ARM_NEON_API_SUPPORTED */
84 #ifdef PNG_ARM_NEON_CHECK_SUPPORTED
85 {
86 static volatile sig_atomic_t no_neon = -1; /* not checked */
87
88 if (no_neon < 0)
89 no_neon = !png_have_neon(pp);
90
91 if (no_neon)
92 return;
93 }
94 #ifdef PNG_ARM_NEON_API_SUPPORTED
95 break;
96 #endif
97 #endif /* PNG_ARM_NEON_CHECK_SUPPORTED */
98
99 #ifdef PNG_ARM_NEON_API_SUPPORTED
100 default: /* OFF or INVALID */
101 return;
102
103 case PNG_OPTION_ON:
104 /* Option turned on */
105 break;
106 }
107 #endif
108
109 /* IMPORTANT: any new external functions used here must be declared using
110 * PNG_INTERNAL_FUNCTION in ../pngpriv.h. This is required so that the
111 * 'prefix' option to configure works:
112 *
113 * ./configure --with-libpng-prefix=foobar_
114 *
115 * Verify you have got this right by running the above command, doing a build
116 * and examining pngprefix.h; it must contain a #define for every external
117 * function you add. (Notice that this happens automatically for the
118 * initialization function.)
119 */
120 pp->read_filter[PNG_FILTER_VALUE_UP-1] = png_read_filter_row_up_neon;
121
122 if (bpp == 3)
123 {
124 pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub3_neon;
125 pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg3_neon;
126 pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
127 png_read_filter_row_paeth3_neon;
128 }
129
130 else if (bpp == 4)
131 {
132 pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub4_neon;
133 pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg4_neon;
134 pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
135 png_read_filter_row_paeth4_neon;
136 }
137 }
138 #endif /* PNG_ARM_NEON_OPT > 0 */
139 #endif /* READ */