To make a strtok faster and improve performance in general we need to do one
additional change.
A comment:
/* It doesn't make sense to send libc-internal strcspn calls through a PLT.
The speedup we get from using SSE4.2 instruction is likely eaten away
by the indirect call in the PLT. */
Does not make sense at all because nobody bothered to check it. Gap
between these implementations is quite big, when haystack is empty a
sse2 is around 40 cycles slower because it needs to populate a lookup
table and difference only increases with size. That is much bigger than
plt slowdown which is few cycles.
Even benchtest show a gap which also may be reverse by branch
misprediction but my internal benchmark shown.
simple_strspn stupid_strspn __strspn_sse42 __strspn_sse2
Length 0, alignment 0, acc len 6: 18.6562 35.2344 17.0469 61.6719
Length 6, alignment 0, acc len 6: 59.5469 72.5781 16.4219 73.625
This patch also handles strpbrk which is implemented by including a
x86_64/multiarch/strcspn.S file.
* sysdeps/x86_64/multiarch/strspn.S: Remove plt indirection.
* sysdeps/x86_64/multiarch/strcspn.S: Likewise.
+2015-05-12 Ondřej Bílka <neleai@seznam.cz>
+
+ * sysdeps/x86_64/multiarch/strcspn.S: Remove plt indirection.
+ * sysdeps/x86_64/multiarch/strspn.S: Likewise.
+
2015-05-12 Roland McGrath <roland@hack.frob.com>
* posix/uname-values.h: New file.
# undef END
# define END(name) \
cfi_endproc; .size STRCSPN_SSE2, .-STRCSPN_SSE2
-# undef libc_hidden_builtin_def
-/* It doesn't make sense to send libc-internal strcspn calls through a PLT.
- The speedup we get from using SSE4.2 instruction is likely eaten away
- by the indirect call in the PLT. */
-# define libc_hidden_builtin_def(name) \
- .globl __GI_STRCSPN; __GI_STRCSPN = STRCSPN_SSE2
#endif
-
#endif /* HAVE_SSE4_SUPPORT */
#ifdef USE_AS_STRPBRK
# undef END
# define END(name) \
cfi_endproc; .size __strspn_sse2, .-__strspn_sse2
-# undef libc_hidden_builtin_def
-/* It doesn't make sense to send libc-internal strspn calls through a PLT.
- The speedup we get from using SSE4.2 instruction is likely eaten away
- by the indirect call in the PLT. */
-# define libc_hidden_builtin_def(name) \
- .globl __GI_strspn; __GI_strspn = __strspn_sse2
#endif
#endif /* HAVE_SSE4_SUPPORT */