dba54b8888
implementation of the ARM NEON discovery function to be set at build-time and provide sample implementations from the current code in the contrib/arm-neon subdirectory. The __linux__ code has also been changed to compile and link on Android by using /proc/cpuinfo, and the old linux code is in contrib/arm-neon/linux-auxv.c. The new code avoids POSIX and Linux dependencies apart from opening /proc/cpuinfo and is C90 compliant.
84 lines
3.4 KiB
Plaintext
84 lines
3.4 KiB
Plaintext
OPERATING SYSTEM SPECIFIC ARM NEON DETECTION
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--------------------------------------------
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Detection of the ability to exexcute ARM NEON on an ARM processor requires
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operating system support. (The information is not available in user mode.)
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HOW TO USE THIS
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---------------
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This directory contains C code fragments which can be included in arm/arm_init.c
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by setting the macro PNG_ARM_NEON_FILE to the file name in "" or <> at build
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time. This setting is not recorded in pnglibconf.h and can be changed simply by
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rebuilding arm/arm_init.o with the required macro definition.
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For any of this code to be used the ARM NEON code must be enabled and run time
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checks must be supported. I.e.:
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#if PNG_ARM_NEON_OPT > 0
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#ifdef PNG_ARM_NEON_CHECK_SUPPORTED
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This is done in a 'configure' build by passing configure the argument:
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--enable-arm-neon=check
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Apart from the basic Linux implementation in contrib/arm-neon/linux.c this code
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is unsupported. That means that it is not even compiled on a regular basis and
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may be broken in any given minor release.
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FILE FORMAT
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-----------
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Each file documents its testing status as of the last time it was tested (which
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may have been a long time ago):
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STATUS: one of:
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SUPPORTED: This indicates that the file is included in the regularly
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performed test builds and bugs are fixed when discovered.
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COMPILED: This indicates that the code did compile at least once. See the
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more detailed description for the extent to which the result was
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successful.
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TESTED: This means the code was fully compiled into the libpng test programs
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and these were run at least once.
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BUG REPORTS: an email address to which to send reports of problems
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The file is a fragment of C code. It should not define any 'extern' symbols;
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everything should be static. It must define the function:
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static int png_have_neon(png_structp png_ptr);
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That function must return 1 if ARM NEON instructions are supported, 0 if not.
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It must not execute png_error unless it detects a bug. A png_error will prevent
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the reading of the PNG and in the future, writing too.
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BUG REPORTS
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-----------
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If you mail a bug report for any file that is not SUPPORTED there may only be
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limited response. Consider fixing it and sending a patch to fix the problem -
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this is more likely to result in action.
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CONTRIBUTIONS
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-------------
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You may send contributions of new implementations to
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png-mng-implement@sourceforge.net. Please write code in strict C90 C where
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possible. Obviously OS dependencies are to be expected. If you submit code you
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must have the authors permission and it must have a license that is acceptable
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to the current maintainer; in particular that license must permit
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redistribution.
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Please try to make the contribution a single file and give the file a clear and
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unambiguous name that identifies the target OS. If multiple files really are
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required put them all in a sub-directory.
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You must also be prepared to handle bug reports from users of the code, either
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by joining the png-mng-implement mailing list or by providing an email for the
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"BUG REPORTS" entry or both. Please make sure that the header of the file
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contains the STATUS and BUG REPORTS fields as above.
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Please list the OS requirements as precisely as possible. Ideally you should
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also list the environment in which the code has been tested and certainly list
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any environments where you suspect it might not work.
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