diff options
| author | Matt Turner <mattst88@gmail.com> | 2019-09-04 21:48:56 -0700 |
|---|---|---|
| committer | Tony Cook <tony@develop-help.com> | 2019-10-08 09:27:43 +1100 |
| commit | e8864dba80952684bf3afe83438d4eee0c3939a9 (patch) | |
| tree | ef39f361559ca7cabef294085a643c3742e6d4f5 /zaphod32_hash.h | |
| parent | ee9ac1cd8eb988fea70841eae211b11355711416 (diff) | |
| download | perl-e8864dba80952684bf3afe83438d4eee0c3939a9.tar.gz | |
Clean up U8TO*_LE macro implementations
The code guarded by #ifndef U32_ALIGNMENT_REQUIRED attempts to optimize
byte-swapping by doing unaligned loads, but accessing data through
unaligned pointers is undefined behavior in C. Moreover, compilers are
more than capable of recognizing these open-coded byte-swap patterns and
emitting a bswap instruction, or an unaligned load instruction, or a
combined load, etc. There's no need for multiple paths to attain the
desired result.
See https://rt.perl.org/Ticket/Display.html?id=133495
Diffstat (limited to 'zaphod32_hash.h')
| -rw-r--r-- | zaphod32_hash.h | 35 |
1 files changed, 0 insertions, 35 deletions
diff --git a/zaphod32_hash.h b/zaphod32_hash.h index c9b60ccb32..2fb391a233 100644 --- a/zaphod32_hash.h +++ b/zaphod32_hash.h @@ -74,41 +74,6 @@ #define STMT_END while(0) #endif -#ifndef ZAPHOD32_ALLOW_UNALIGNED_AND_LITTLE_ENDIAN -/* ZAPHOD32_ALLOW_UNALIGNED_AND_LITTLE_ENDIAN only matters if nothing has defined U8TO64_LE etc, - * and when built with Perl these should be defined before this file is loaded. - */ -#ifdef U32_ALIGNMENT_REQUIRED -#define ZAPHOD32_ALLOW_UNALIGNED_AND_LITTLE_ENDIAN 0 -#else -#define ZAPHOD32_ALLOW_UNALIGNED_AND_LITTLE_ENDIAN 1 -#endif -#endif - -#ifndef U8TO32_LE -#if ZAPHOD32_ALLOW_UNALIGNED_AND_LITTLE_ENDIAN -#define U8TO32_LE(ptr) (*((const U32 *)(ptr))) -#else -#define U8TO32_LE(ptr) (\ - (U32)(ptr)[3] << 24 | \ - (U32)(ptr)[2] << 16 | \ - (U32)(ptr)[1] << 8 | \ - (U32)(ptr)[0] \ -) -#endif -#endif - -#ifndef U8TO16_LE -#if ZAPHOD32_ALLOW_UNALIGNED_AND_LITTLE_ENDIAN -#define U8TO16_LE(ptr) (*((const U16 *)(ptr))) -#else -#define U8TO16_LE(ptr) (\ - (U16)(ptr)[1] << 8 | \ - (U16)(ptr)[0] \ -) -#endif -#endif - /* This is two marsaglia xor-shift permutes, with a prime-multiple * sandwiched inside. The end result of doing this twice with different * primes is a completely avalanched v. */ |