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bswap.h: add support for built-in bswap functions 

Newer compiler versions, like GCC 10 and Clang 12, have built-in
functions for bswap32 and bswap64. This comes in handy, for example,
when targeting CLANGARM64 on Windows, which would not be supported
without this logic.

Signed-off-by: Dennis Ameling <dennis@dennisameling.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
maint
Dennis Ameling 2025-04-23 08:01:43 +00:00 committed by Junio C Hamano
parent 683c54c999
commit 6547d1c9cb
1 changed files with 13 additions and 1 deletions
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14
compat/bswap.h
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@ -35,7 +35,19 @@ static inline uint64_t default_bswap64(uint64_t val)
#undef bswap32
#undef bswap64

#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))
/**
* __has_builtin is available since Clang 10 and GCC 10.
* Below is a fallback for older compilers.
*/
#ifndef __has_builtin
#define __has_builtin(x) 0
#endif

#if __has_builtin(__builtin_bswap32) && __has_builtin(__builtin_bswap64)
#define bswap32(x) __builtin_bswap32((x))
#define bswap64(x) __builtin_bswap64((x))

#elif defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__))

#define bswap32 git_bswap32
static inline uint32_t git_bswap32(uint32_t x)