1 
2 /* arm_init.c - NEON optimised filter functions
3  *
4  * Copyright (c) 2018 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 /* Below, after checking __linux__, various non-C90 POSIX 1003.1 functions are
14  * called.
15  */
16 #define _POSIX_SOURCE 1
17 
18 #include "../pngpriv.h"
19 
20 #ifdef PNG_READ_SUPPORTED
21 
22 #if PNG_ARM_NEON_OPT > 0
23 #ifdef PNG_ARM_NEON_CHECK_SUPPORTED /* Do run-time checks */
24 /* WARNING: it is strongly recommended that you do not build libpng with
25  * run-time checks for CPU features if at all possible.  In the case of the ARM
26  * NEON instructions there is no processor-specific way of detecting the
27  * presence of the required support, therefore run-time detection is extremely
28  * OS specific.
29  *
30  * You may set the macro PNG_ARM_NEON_FILE to the file name of file containing
31  * a fragment of C source code which defines the png_have_neon function.  There
32  * are a number of implementations in contrib/arm-neon, but the only one that
33  * has partial support is contrib/arm-neon/linux.c - a generic Linux
34  * implementation which reads /proc/cpufino.
35  */
36 #ifndef PNG_ARM_NEON_FILE
37 #  ifdef __linux__
38 #     define PNG_ARM_NEON_FILE "linux.c"
39 #  endif
40 #endif
41 
42 #ifdef PNG_ARM_NEON_FILE
43 
44 #include <signal.h> /* for sig_atomic_t */
45 static int png_have_neon(png_structp png_ptr);
46 #include PNG_ARM_NEON_FILE
47 
48 #else  /* PNG_ARM_NEON_FILE */
49 #  error "PNG_ARM_NEON_FILE undefined: no support for run-time ARM NEON checks"
50 #endif /* PNG_ARM_NEON_FILE */
51 #endif /* PNG_ARM_NEON_CHECK_SUPPORTED */
52 
53 #ifndef PNG_ALIGNED_MEMORY_SUPPORTED
54 #  error "ALIGNED_MEMORY is required; set: -DPNG_ALIGNED_MEMORY_SUPPORTED"
55 #endif
56 
57 void
png_init_filter_functions_neon(png_structp pp,unsigned int bpp)58 png_init_filter_functions_neon(png_structp pp, unsigned int bpp)
59 {
60    /* The switch statement is compiled in for ARM_NEON_API, the call to
61     * png_have_neon is compiled in for ARM_NEON_CHECK.  If both are defined
62     * the check is only performed if the API has not set the NEON option on
63     * or off explicitly.  In this case the check controls what happens.
64     *
65     * If the CHECK is not compiled in and the option is UNSET the behavior prior
66     * to 1.6.7 was to use the NEON code - this was a bug caused by having the
67     * wrong order of the 'ON' and 'default' cases.  UNSET now defaults to OFF,
68     * as documented in png.h
69     */
70    png_debug(1, "in png_init_filter_functions_neon");
71 #ifdef PNG_ARM_NEON_API_SUPPORTED
72    switch ((pp->options >> PNG_ARM_NEON) & 3)
73    {
74       case PNG_OPTION_UNSET:
75          /* Allow the run-time check to execute if it has been enabled -
76           * thus both API and CHECK can be turned on.  If it isn't supported
77           * this case will fall through to the 'default' below, which just
78           * returns.
79           */
80 #endif /* PNG_ARM_NEON_API_SUPPORTED */
81 #ifdef PNG_ARM_NEON_CHECK_SUPPORTED
82          {
83             static volatile sig_atomic_t no_neon = -1; /* not checked */
84 
85             if (no_neon < 0)
86                no_neon = !png_have_neon(pp);
87 
88             if (no_neon)
89                return;
90          }
91 #ifdef PNG_ARM_NEON_API_SUPPORTED
92          break;
93 #endif
94 #endif /* PNG_ARM_NEON_CHECK_SUPPORTED */
95 
96 #ifdef PNG_ARM_NEON_API_SUPPORTED
97       default: /* OFF or INVALID */
98          return;
99 
100       case PNG_OPTION_ON:
101          /* Option turned on */
102          break;
103    }
104 #endif
105 
106    /* IMPORTANT: any new external functions used here must be declared using
107     * PNG_INTERNAL_FUNCTION in ../pngpriv.h.  This is required so that the
108     * 'prefix' option to configure works:
109     *
110     *    ./configure --with-libpng-prefix=foobar_
111     *
112     * Verify you have got this right by running the above command, doing a build
113     * and examining pngprefix.h; it must contain a #define for every external
114     * function you add.  (Notice that this happens automatically for the
115     * initialization function.)
116     */
117    pp->read_filter[PNG_FILTER_VALUE_UP-1] = png_read_filter_row_up_neon;
118 
119    if (bpp == 3)
120    {
121       pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub3_neon;
122       pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg3_neon;
123       pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
124          png_read_filter_row_paeth3_neon;
125    }
126 
127    else if (bpp == 4)
128    {
129       pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub4_neon;
130       pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg4_neon;
131       pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
132           png_read_filter_row_paeth4_neon;
133    }
134 }
135 #endif /* PNG_ARM_NEON_OPT > 0 */
136 #endif /* READ */
137