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      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
     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