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author | Arnd Bergmann <arnd@arndb.de> | 2021-05-08 01:07:51 +0300 |
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committer | Arnd Bergmann <arnd@arndb.de> | 2021-05-10 18:50:47 +0300 |
commit | 0652035a57945e14e611dafae2ec5b46a05bc1d1 (patch) | |
tree | 0c34544a7755bc1ee0a822e86458d3ed9215533f /include/linux/unaligned/le_struct.h | |
parent | f12d3ff3f41cc92f67cfaf29697685e8834fe4a4 (diff) | |
download | linux-0652035a57945e14e611dafae2ec5b46a05bc1d1.tar.xz |
asm-generic: unaligned: remove byteshift helpers
In theory, compilers should be able to work this out themselves so we
can use a simpler version based on the swab() helpers.
I have verified that this works on all supported compiler versions
(gcc-4.9 and up, clang-10 and up). Looking at the object code produced by
gcc-11, I found that the impact is mostly a change in inlining decisions
that lead to slightly larger code.
In other cases, this version produces explicit byte swaps in place of
separate byte access, or comparing against pre-swapped constants.
While the source code is clearly simpler, I have not seen an indication
of the new version actually producing better code on Arm, so maybe
we want to skip this after all. From what I can tell, gcc recognizes
the byteswap pattern in the byteshift.h header and can turn it into
explicit instructions, but it does not turn a __builtin_bswap32() back
into individual bytes when that would result in better output, e.g.
when storing a byte-reversed constant.
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Diffstat (limited to 'include/linux/unaligned/le_struct.h')
-rw-r--r-- | include/linux/unaligned/le_struct.h | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/include/linux/unaligned/le_struct.h b/include/linux/unaligned/le_struct.h index 9977987883a6..22f90a4afaa5 100644 --- a/include/linux/unaligned/le_struct.h +++ b/include/linux/unaligned/le_struct.h @@ -34,4 +34,34 @@ static inline void put_unaligned_le64(u64 val, void *p) __put_unaligned_cpu64(val, p); } +static inline u16 get_unaligned_be16(const void *p) +{ + return swab16(__get_unaligned_cpu16((const u8 *)p)); +} + +static inline u32 get_unaligned_be32(const void *p) +{ + return swab32(__get_unaligned_cpu32((const u8 *)p)); +} + +static inline u64 get_unaligned_be64(const void *p) +{ + return swab64(__get_unaligned_cpu64((const u8 *)p)); +} + +static inline void put_unaligned_be16(u16 val, void *p) +{ + __put_unaligned_cpu16(swab16(val), p); +} + +static inline void put_unaligned_be32(u32 val, void *p) +{ + __put_unaligned_cpu32(swab32(val), p); +} + +static inline void put_unaligned_be64(u64 val, void *p) +{ + __put_unaligned_cpu64(swab64(val), p); +} + #endif /* _LINUX_UNALIGNED_LE_STRUCT_H */ |