1
2/* arm_init.c - NEON optimised filter functions
3 *
4 * Copyright (c) 2014 Glenn Randers-Pehrson
5 * Written by Mans Rullgard, 2011.
6 * Last changed in libpng 1.6.10 [March 6, 2014]
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#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 * presense of the required support, therefore run-time detectioon 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#ifndef PNG_ARM_NEON_FILE
35#  ifdef __linux__
36#     define PNG_ARM_NEON_FILE "contrib/arm-neon/linux.c"
37#  endif
38#endif
39
40#ifdef PNG_ARM_NEON_FILE
41
42#include <signal.h> /* for sig_atomic_t */
43static int png_have_neon(png_structp png_ptr);
44#include PNG_ARM_NEON_FILE
45
46#else  /* PNG_ARM_NEON_FILE */
47#  error "PNG_ARM_NEON_FILE undefined: no support for run-time ARM NEON checks"
48#endif /* PNG_ARM_NEON_FILE */
49#endif /* PNG_ARM_NEON_CHECK_SUPPORTED */
50
51#ifndef PNG_ALIGNED_MEMORY_SUPPORTED
52#  error "ALIGNED_MEMORY is required; set: -DPNG_ALIGNED_MEMORY_SUPPORTED"
53#endif
54
55void
56png_init_filter_functions_neon(png_structp pp, unsigned int bpp)
57{
58   /* The switch statement is compiled in for ARM_NEON_API, the call to
59    * png_have_neon is compiled in for ARM_NEON_CHECK.  If both are defined
60    * the check is only performed if the API has not set the NEON option on
61    * or off explicitly.  In this case the check controls what happens.
62    *
63    * If the CHECK is not compiled in and the option is UNSET the behavior prior
64    * to 1.6.7 was to use the NEON code - this was a bug caused by having the
65    * wrong order of the 'ON' and 'default' cases.  UNSET now defaults to OFF,
66    * as documented in png.h
67    */
68#ifdef PNG_ARM_NEON_API_SUPPORTED
69   switch ((pp->options >> PNG_ARM_NEON) & 3)
70   {
71      case PNG_OPTION_UNSET:
72         /* Allow the run-time check to execute if it has been enabled -
73          * thus both API and CHECK can be turned on.  If it isn't supported
74          * this case will fall through to the 'default' below, which just
75          * returns.
76          */
77#endif /* PNG_ARM_NEON_API_SUPPORTED */
78#ifdef PNG_ARM_NEON_CHECK_SUPPORTED
79         {
80            static volatile sig_atomic_t no_neon = -1; /* not checked */
81
82            if (no_neon < 0)
83               no_neon = !png_have_neon(pp);
84
85            if (no_neon)
86               return;
87         }
88#ifdef PNG_ARM_NEON_API_SUPPORTED
89         break;
90#endif
91#endif /* PNG_ARM_NEON_CHECK_SUPPORTED */
92
93#ifdef PNG_ARM_NEON_API_SUPPORTED
94      default: /* OFF or INVALID */
95         return;
96
97      case PNG_OPTION_ON:
98         /* Option turned on */
99         break;
100   }
101#endif
102
103   /* IMPORTANT: any new external functions used here must be declared using
104    * PNG_INTERNAL_FUNCTION in ../pngpriv.h.  This is required so that the
105    * 'prefix' option to configure works:
106    *
107    *    ./configure --with-libpng-prefix=foobar_
108    *
109    * Verify you have got this right by running the above command, doing a build
110    * and examining pngprefix.h; it must contain a #define for every external
111    * function you add.  (Notice that this happens automatically for the
112    * initialization function.)
113    */
114   pp->read_filter[PNG_FILTER_VALUE_UP-1] = png_read_filter_row_up_neon;
115
116   if (bpp == 3)
117   {
118      pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub3_neon;
119      pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg3_neon;
120      pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
121         png_read_filter_row_paeth3_neon;
122   }
123
124   else if (bpp == 4)
125   {
126      pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub4_neon;
127      pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg4_neon;
128      pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
129          png_read_filter_row_paeth4_neon;
130   }
131}
132#endif /* PNG_ARM_NEON_OPT > 0 */
133#endif /* PNG_READ_SUPPORTED */
134