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Use ARM crc32 instructions if the ARM architecture has them.

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The ARM crc32 instructions will be used only if an architecture is
explicitly specified at compile time that has those instructions.
For example, -march=armv8.1-a or -march=armv8-a+crc, or if the
machine being compiled on has the instructions, -march=native.
This commit is contained in:
Mark Adler 2019-02-17 20:45:53 -08:00
parent 52fc78baf2
commit deb44b5742
1 changed files with 7 additions and 3 deletions
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10
crc32.c
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@ -618,11 +618,15 @@ const z_crc_t FAR * ZEXPORT get_crc_table()
}
/* =========================================================================
* Use ARM machine instructions if requested. This will compute the CRC about
* Use ARM machine instructions if available. This will compute the CRC about
* ten times faster than the braided calculation. This code does not check for
* the presence of the CRC instruction. Compile with care.
* the presence of the CRC instruction at run time. __ARM_FEATURE_CRC32 will
* only be defined if the compilation specifies an ARM processor architecture
* that has the instructions. For example, compiling with -march=armv8.1-a or
* -march=armv8-a+crc, or -march=native if the compile machine has the crc32
* instructions.
*/
#if defined(Z_ARM_CRC32) && defined(__aarch64__) && W == 8
#if defined(__aarch64__) && defined(__ARM_FEATURE_CRC32) && W == 8
/*
Constants empirically determined to maximize speed. These values are from