tilegx: provide optimized strnlen, strstr, and strcasestr

System Internals / glibc - Chris Metcalf [tilera.com] - 6 October 2014 10:19 UTC

strnlen() is based on the existing tile strlen() with length checking added. It speeds up by up to 5x, but on average across the benchtest corpus by around 35%. No regressions are seen.

strstr() does 8-byte aligned loads and compares using a 2-byte filter on the first two bytes of the needle and then testing the remaining bytes in needle using memcmp(). It speeds up about 5x in the best case (for "found" needles), about 2x looking at benchtest as a whole, with some slowdowns as much as 45%. on a few cases (including the "fail" case for 128KB search).

strcasestr() is based on strstr() but uses a SIMD tolower routine to convert 8-bytes to lower case in 5 instructions. It also uses a 2-byte filter and then strncasecmp() for the remaining bytes. strncasecmp() is not optimized for SIMD, so there is futher room for improvement. However, it is still up to 16x faster for "found" needles, averaging 2x faster on the whole corpus of benchtests. It does slow down by up to 35% on a few cases, similarly to strstr().

c86f7b8 tilegx: provide optimized strnlen, strstr, and strcasestr
ChangeLog | 5 +
sysdeps/tile/tilegx/strcasestr.c | 55 +++++++
sysdeps/tile/tilegx/string-endian.h | 22 ++-
sysdeps/tile/tilegx/strnlen.c | 58 ++++++++
sysdeps/tile/tilegx/strstr.c | 271 +++++++++++++++++++++++++++++++++++
5 files changed, 406 insertions(+), 5 deletions(-)

Upstream: sourceware.org

  • Share