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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 1.6.16 [December 22, 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  
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  #ifdef PNG_ARM_NEON_API_SUPPORTED
70     switch ((pp->options >> PNG_ARM_NEON) & 3)
71     {
72        case PNG_OPTION_UNSET:
73           /* Allow the run-time check to execute if it has been enabled -
74            * thus both API and CHECK can be turned on.  If it isn't supported
75            * this case will fall through to the 'default' below, which just
76            * returns.
77            */
78  #endif /* PNG_ARM_NEON_API_SUPPORTED */
79  #ifdef PNG_ARM_NEON_CHECK_SUPPORTED
80           {
81              static volatile sig_atomic_t no_neon = -1; /* not checked */
82  
83              if (no_neon < 0)
84                 no_neon = !png_have_neon(pp);
85  
86              if (no_neon)
87                 return;
88           }
89  #ifdef PNG_ARM_NEON_API_SUPPORTED
90           break;
91  #endif
92  #endif /* PNG_ARM_NEON_CHECK_SUPPORTED */
93  
94  #ifdef PNG_ARM_NEON_API_SUPPORTED
95        default: /* OFF or INVALID */
96           return;
97  
98        case PNG_OPTION_ON:
99           /* Option turned on */
100           break;
101     }
102  #endif
103  
104     /* IMPORTANT: any new external functions used here must be declared using
105      * PNG_INTERNAL_FUNCTION in ../pngpriv.h.  This is required so that the
106      * 'prefix' option to configure works:
107      *
108      *    ./configure --with-libpng-prefix=foobar_
109      *
110      * Verify you have got this right by running the above command, doing a build
111      * and examining pngprefix.h; it must contain a #define for every external
112      * function you add.  (Notice that this happens automatically for the
113      * initialization function.)
114      */
115     pp->read_filter[PNG_FILTER_VALUE_UP-1] = png_read_filter_row_up_neon;
116  
117     if (bpp == 3)
118     {
119        pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub3_neon;
120        pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg3_neon;
121        pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
122           png_read_filter_row_paeth3_neon;
123     }
124  
125     else if (bpp == 4)
126     {
127        pp->read_filter[PNG_FILTER_VALUE_SUB-1] = png_read_filter_row_sub4_neon;
128        pp->read_filter[PNG_FILTER_VALUE_AVG-1] = png_read_filter_row_avg4_neon;
129        pp->read_filter[PNG_FILTER_VALUE_PAETH-1] =
130            png_read_filter_row_paeth4_neon;
131     }
132  }
133  #endif /* PNG_ARM_NEON_OPT > 0 */
134  #endif /* READ */
135