swab() is massively over complicated and can be simplified by builtins. The compilers provide builtin function to swap bytes. * gcc: https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html * clang: https://clang.llvm.org/docs/LanguageExtensions.html This patch simplify swab() with builtins and fallback for old compilers.
Signed-off-by: Lin Liu <[email protected]> --- Cc: Andrew Cooper <[email protected]> Cc: George Dunlap <[email protected]> Cc: Ian Jackson <[email protected]> Cc: Jan Beulich <[email protected]> Cc: Julien Grall <[email protected]> Cc: Stefano Stabellini <[email protected]> Cc: Wei Liu <[email protected]> Changes in v2: - Add fallback for compilers without __builtin_bswap - Implement with plain C instead of macros --- xen/include/xen/byteswap.h | 93 ++++++++++++++++++++++++++++++++++++++ xen/include/xen/compiler.h | 12 +++++ 2 files changed, 105 insertions(+) create mode 100644 xen/include/xen/byteswap.h diff --git a/xen/include/xen/byteswap.h b/xen/include/xen/byteswap.h new file mode 100644 index 0000000000..848a4bbaee --- /dev/null +++ b/xen/include/xen/byteswap.h @@ -0,0 +1,93 @@ +#ifndef _BYTESWAP_H +#define _BYTESWAP_H + +#include <xen/types.h> + +#if !__has_builtin(__builtin_bswap16) +static always_inline uint16_t __builtin_bswap16(uint16_t val) +{ + return ((val & 0x00FF) << 8) | ((val & 0xFF00) >> 8); +} +#endif + +#if !__has_builtin(__builtin_bswap32) +static always_inline uint32_t __builtin_bswap32(uint32_t val) +{ + return ((val & 0x000000FF) << 24) | + ((val & 0x0000FF00) << 8) | + ((val & 0x00FF0000) >> 8) | + ((val & 0xFF000000) >> 24); +} +#endif + +#if !__has_builtin(__builtin_bswap64) +static always_inline uint64_t __builtin_bswap64(uint64_t val) +{ + return ((val & 0x00000000000000FF) << 56) | + ((val & 0x000000000000FF00) << 40) | + ((val & 0x0000000000FF0000) << 24) | + ((val & 0x00000000FF000000) << 8) | + ((val & 0x000000FF00000000) >> 8) | + ((val & 0x0000FF0000000000) >> 24) | + ((val & 0x00FF000000000000) >> 40) | + ((val & 0xFF00000000000000) >> 56); +} +#endif + +#define bswap16(x) __builtin_bswap16(x) +#define bswap32(x) __builtin_bswap32(x) +#define bswap64(x) __builtin_bswap64(x) + +#define bswap_ul(x) bswap##BITS_PER_LONG(x) + +#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__ + +# ifndef __LITTLE_ENDIAN +# define __LITTLE_ENDIAN 1234 +# endif + +# ifndef __LITTLE_ENDIAN_BITFIELD +# define __LITTLE_ENDIAN_BITFIELD +# endif + +# define cpu_to_le64(x) (x) +# define le64_to_cpu(x) (x) +# define cpu_to_le32(x) (x) +# define le32_to_cpu(x) (x) +# define cpu_to_le16(x) (x) +# define le16_to_cpu(x) (x) +# define cpu_to_be64(x) bswap64(x) +# define be64_to_cpu(x) bswap64(x) +# define cpu_to_be32(x) bswap32(x) +# define be32_to_cpu(x) bswap32(x) +# define cpu_to_be16(x) bswap16(x) +# define be16_to_cpu(x) bswap16(x) + +#elif __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__ + +# ifndef __BIG_ENDIAN +# define __BIG_ENDIAN 4321 +# endif + +# ifndef __BIG_ENDIAN_BITFIELD +# define __BIG_ENDIAN_BITFIELD +# endif + +# define cpu_to_le64(x) bswap64(x) +# define le64_to_cpu(x) bswap64(x) +# define cpu_to_le32(x) bswap32(x) +# define le32_to_cpu(x) bswap32(x) +# define cpu_to_le16(x) bswap16(x) +# define le16_to_cpu(x) bswap16(x) +# define cpu_to_be64(x) (x) +# define be64_to_cpu(x) (x) +# define cpu_to_be32(x) (x) +# define be32_to_cpu(x) (x) +# define cpu_to_be16(x) (x) +# define be16_to_cpu(x) (x) + +#else +# error "Unknown Endianness" +#endif /* __BYTE_ORDER__ */ + +#endif /* _LINUX_BITOPS_H */ diff --git a/xen/include/xen/compiler.h b/xen/include/xen/compiler.h index 696c7eb89e..68f28082a5 100644 --- a/xen/include/xen/compiler.h +++ b/xen/include/xen/compiler.h @@ -179,4 +179,16 @@ # define CLANG_DISABLE_WARN_GCC_COMPAT_END #endif +#if (!defined(__clang__) && (__GNUC__ < 10)) +/* + * Backwards compatibility for GCC < 10. + * All supported versions of Clang support __has_builtin + * */ +#define __has_builtin(x) GCC_has ## x + +#define GCC_has__builtin_bswap16 (CONFIG_GCC_VERSION >= 40800) +#define GCC_has__builtin_bswap32 (CONFIG_GCC_VERSION >= 40400) +#define GCC_has__builtin_bswap64 (CONFIG_GCC_VERSION >= 40400) +#endif + #endif /* __LINUX_COMPILER_H */ -- 2.27.0
