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update default memory access for armv6

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Now uses `memcpy()` (method 0) by default
fix #490
This commit is contained in:
Yann Collet 2021-02-02 06:40:22 -08:00
parent f2c52f1236
commit a470f2ef95
1 changed files with 7 additions and 8 deletions
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15
xxhash.h
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@ -1135,8 +1135,8 @@ XXH_PUBLIC_API XXH128_hash_t XXH128(const void* data, size_t len, XXH64_hash_t s
* - `XXH_FORCE_MEMORY_ACCESS=1`: `__attribute__((packed))`
* @par
* Depends on compiler extensions and is therefore not portable.
* This method is safe if your compiler supports it, and *generally* as
* fast or faster than `memcpy`.
* This method is safe _if_ your compiler supports it,
* and *generally* as fast or faster than `memcpy`.
*
* - `XXH_FORCE_MEMORY_ACCESS=2`: Direct cast
* @par
@ -1144,7 +1144,7 @@ XXH_PUBLIC_API XXH128_hash_t XXH128(const void* data, size_t len, XXH64_hash_t s
* compiler, but it violates the C standard as it directly dereferences an
* unaligned pointer. It can generate buggy code on targets which do not
* support unaligned memory accesses, but in some circumstances, it's the
* only known way to get the most performance (example: GCC + ARMv6).
* only known way to get the most performance.
*
* - `XXH_FORCE_MEMORY_ACCESS=3`: Byteshift
* @par
@ -1152,7 +1152,6 @@ XXH_PUBLIC_API XXH128_hash_t XXH128(const void* data, size_t len, XXH64_hash_t s
* inline small `memcpy()` calls, and it might also be faster on big-endian
* systems which lack a native byteswap instruction. However, some compilers
* will emit literal byteshifts even if the target supports unaligned access.
*
* .
*
* @warning
@ -1255,10 +1254,10 @@ XXH_PUBLIC_API XXH128_hash_t XXH128(const void* data, size_t len, XXH64_hash_t s
*/
#ifndef XXH_FORCE_MEMORY_ACCESS /* can be defined externally, on command line for example */
# if !defined(__clang__) && defined(__GNUC__) && defined(__ARM_FEATURE_UNALIGNED) && defined(__ARM_ARCH) && (__ARM_ARCH == 6)
# define XXH_FORCE_MEMORY_ACCESS 2
# elif !defined(__clang__) && ((defined(__INTEL_COMPILER) && !defined(_WIN32)) || \
(defined(__GNUC__) && (defined(__ARM_ARCH) && __ARM_ARCH >= 7)))
/* prefer __packed__ structures (method 1) for gcc on armv7 and armv8 */
# if !defined(__clang__) && ( \
(defined(__INTEL_COMPILER) && !defined(_WIN32)) || \
(defined(__GNUC__) && (defined(__ARM_ARCH) && __ARM_ARCH >= 7)) )
# define XXH_FORCE_MEMORY_ACCESS 1
# endif
#endif