arm_init.c revision 4d3acf4ec42bf6e838f9060103aff98fbf170794 
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 */
44static 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
56void
57png_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