1 
2 /* arm_init.c - NEON optimised filter functions
3  *
4  * Copyright (c) 2014,2016 Glenn Randers-Pehrson
5  * Written by Mans Rullgard, 2011.
6  * Last changed in libpng 1.6.22 [May 26, 2016]
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 /* Below, after checking __linux__, various non-C90 POSIX 1003.1 functions are
13  * called.
14  */
15 #define _POSIX_SOURCE 1
16 
17 #include "../pngpriv.h"
18 
19 #ifdef PNG_READ_SUPPORTED
20 
21 #if PNG_ARM_NEON_OPT > 0
22 #ifdef PNG_ARM_NEON_CHECK_SUPPORTED /* Do run-time checks */
23 /* WARNING: it is strongly recommended that you do not build libpng with
24  * run-time checks for CPU features if at all possible.  In the case of the ARM
25  * NEON instructions there is no processor-specific way of detecting the
26  * presence of the required support, therefore run-time detection is extremely
27  * OS specific.
28  *
29  * You may set the macro PNG_ARM_NEON_FILE to the file name of file containing
30  * a fragment of C source code which defines the png_have_neon function.  There
31  * are a number of implementations in contrib/arm-neon, but the only one that
32  * has partial support is contrib/arm-neon/linux.c - a generic Linux
33  * implementation which reads /proc/cpufino.
34  */
35 #ifndef PNG_ARM_NEON_FILE
36 #  ifdef __linux__
37 #     define PNG_ARM_NEON_FILE "contrib/arm-neon/linux.c"
38 #  endif
39 #endif
40 
41 #ifdef PNG_ARM_NEON_FILE
42 
43 #include <signal.h> /* for sig_atomic_t */
44 static int png_have_neon(png_structp png_ptr);
45 #include PNG_ARM_NEON_FILE
46 
47 #else  /* PNG_ARM_NEON_FILE */
48 #  error "PNG_ARM_NEON_FILE undefined: no support for run-time ARM NEON checks"
49 #endif /* PNG_ARM_NEON_FILE */
50 #endif /* PNG_ARM_NEON_CHECK_SUPPORTED */
51 
52 #ifndef PNG_ALIGNED_MEMORY_SUPPORTED
53 #  error "ALIGNED_MEMORY is required; set: -DPNG_ALIGNED_MEMORY_SUPPORTED"
54 #endif
55 
56 void
png_init_filter_functions_neon(png_structp pp,unsigned int bpp)57 png_init_filter_functions_neon(png_structp pp, unsigned int bpp)
58 {
59    /* The switch statement is compiled in for ARM_NEON_API, the call to
60     * png_have_neon is compiled in for ARM_NEON_CHECK.  If both are defined
61     * the check is only performed if the API has not set the NEON option on
62     * or off explicitly.  In this case the check controls what happens.
63     *
64     * If the CHECK is not compiled in and the option is UNSET the behavior prior
65     * to 1.6.7 was to use the NEON code - this was a bug caused by having the
66     * wrong order of the 'ON' and 'default' cases.  UNSET now defaults to OFF,
67     * as documented in png.h
68     */
69    png_debug(1, "in png_init_filter_functions_neon");
70 #ifdef PNG_ARM_NEON_API_SUPPORTED
71    switch ((pp->options >> PNG_ARM_NEON) & 3)
72    {
73       case PNG_OPTION_UNSET:
74          /* Allow the run-time check to execute if it has been enabled -
75           * thus both API and CHECK can be turned on.  If it isn't supported
76           * this case will fall through to the 'default' below, which just
77           * returns.
78           */
79 #endif /* PNG_ARM_NEON_API_SUPPORTED */
80 #ifdef PNG_ARM_NEON_CHECK_SUPPORTED
81          {
82             static volatile sig_atomic_t no_neon = -1; /* not checked */
83 
84             if (no_neon < 0)
85                no_neon = !png_have_neon(pp);
86 
87             if (no_neon)
88                return;
89          }
90 #ifdef PNG_ARM_NEON_API_SUPPORTED
91          break;
92 #endif
93 #endif /* PNG_ARM_NEON_CHECK_SUPPORTED */
94 
95 #ifdef PNG_ARM_NEON_API_SUPPORTED
96       default: /* OFF or INVALID */
97          return;
98 
99       case PNG_OPTION_ON:
100          /* Option turned on */
101          break;
102    }
103 #endif
104 
105    /* IMPORTANT: any new external functions used here must be declared using
106     * PNG_INTERNAL_FUNCTION in ../pngpriv.h.  This is required so that the
107     * 'prefix' option to configure works:
108     *
109     *    ./configure --with-libpng-prefix=foobar_
110     *
111     * Verify you have got this right by running the above command, doing a build
112     * and examining pngprefix.h; it must contain a #define for every external
113     * function you add.  (Notice that this happens automatically for the
114     * initialization function.)
115     */
116    pp->read_filter[PNG_FILTER_VALUE_UP-1] = png_read_filter_row_up_neon;
117 
118    if (bpp == 3)
119    {
120       pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub3_neon;
121       pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg3_neon;
122       pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
123          png_read_filter_row_paeth3_neon;
124    }
125 
126    else if (bpp == 4)
127    {
128       pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub4_neon;
129       pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg4_neon;
130       pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
131           png_read_filter_row_paeth4_neon;
132    }
133 }
134 #endif /* PNG_ARM_NEON_OPT > 0 */
135 #endif /* READ */
136