diff options
Diffstat (limited to 'src/fns.c')
| -rw-r--r-- | src/fns.c | 43 |
1 files changed, 25 insertions, 18 deletions
diff --git a/src/fns.c b/src/fns.c index 0af9b725c7a..94505eda444 100644 --- a/src/fns.c +++ b/src/fns.c @@ -439,17 +439,29 @@ If string STR1 is greater, the value is a positive number N; } /* Check whether the platform allows access to unaligned addresses for - size_t integers without trapping or undue penalty (a few cycles is OK). + size_t integers without trapping or undue penalty (a few cycles is OK), + and that a word-sized memcpy can be used to generate such an access. This whitelist is incomplete but since it is only used to improve performance, omitting cases is safe. */ -#if defined __x86_64__|| defined __amd64__ \ - || defined __i386__ || defined __i386 \ - || defined __arm64__ || defined __aarch64__ \ - || defined __powerpc__ || defined __powerpc \ - || defined __ppc__ || defined __ppc \ - || defined __s390__ || defined __s390x__ +#if (defined __x86_64__|| defined __amd64__ \ + || defined __i386__ || defined __i386 \ + || defined __arm64__ || defined __aarch64__ \ + || defined __powerpc__ || defined __powerpc \ + || defined __ppc__ || defined __ppc \ + || defined __s390__ || defined __s390x__) \ + && defined __OPTIMIZE__ #define HAVE_FAST_UNALIGNED_ACCESS 1 + +/* Load a word from a possibly unaligned address. */ +static inline size_t +load_unaligned_size_t (const void *p) +{ + size_t x; + memcpy (&x, p, sizeof x); + return x; +} + #else #define HAVE_FAST_UNALIGNED_ACCESS 0 #endif @@ -497,17 +509,12 @@ Symbols are also allowed; their print names are used instead. */) if (HAVE_FAST_UNALIGNED_ACCESS) { /* First compare entire machine words. */ - typedef size_t word_t; - int ws = sizeof (word_t); - const word_t *w1 = (const word_t *) SDATA (string1); - const word_t *w2 = (const word_t *) SDATA (string2); - while (b < nb - ws + 1) - { - if (UNALIGNED_LOAD_SIZE (w1, b / ws) - != UNALIGNED_LOAD_SIZE (w2, b / ws)) - break; - b += ws; - } + int ws = sizeof (size_t); + const char *w1 = SSDATA (string1); + const char *w2 = SSDATA (string2); + while (b < nb - ws + 1 && load_unaligned_size_t (w1 + b) + == load_unaligned_size_t (w2 + b)) + b += ws; } /* Scan forward to the differing byte. */ |