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Add optimized crc32 for Power 8+ processors #478

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Add optimized crc32 for Power 8+ processors #478

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Commits on Apr 6, 2022

  1. Preparation for Power optimizations 

    Optimized functions for Power will make use of GNU indirect functions,
an extension to support different implementations of the same function,
which can be selected during runtime. This will be used to provide
optimized functions for different processor versions.

Since this is a GNU extension, we placed the definition of the Z_IFUNC
macro under `contrib/gcc`. This can be reused by other archs as well.

Author: Matheus Castanho <msc@linux.ibm.com>
Author: Rogerio Alves <rcardoso@linux.ibm.com>
    @mscastanho
    Rogerio Alves authored and mscastanho committed Apr 6, 2022
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  2. Add Power8+ optimized crc32 

    This commit adds an optimized version for the crc32 function based
on crc32-vpmsum from https://github.com/antonblanchard/crc32-vpmsum/

This is the C implementation created by Rogerio Alves <rogealve@br.ibm.com>

It makes use of vector instructions to speed up CRC32 algorithm.
    @grooverdan @mscastanho
    grooverdan authored and mscastanho committed Apr 6, 2022
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  3. Fix clang's behavior on versions >= 7 

    Clang 7 changed the behavior of vec_xxpermdi in order to match GCC's
behavior.  After this change, code that used to work on Clang 6 stopped
to work on Clang >= 7.

Tested on Clang 6, 7, 8 and 9.

Reference: https://bugs.llvm.org/show_bug.cgi?id=38192

Signed-off-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>
    @tuliom @mscastanho
    tuliom authored and mscastanho committed Apr 6, 2022
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