diff options
| -rw-r--r-- | benchtests/bench-strchr.c | 143 |
1 files changed, 143 insertions, 0 deletions
diff --git a/benchtests/bench-strchr.c b/benchtests/bench-strchr.c index 203900d4ad..54640bde7e 100644 --- a/benchtests/bench-strchr.c +++ b/benchtests/bench-strchr.c @@ -54,6 +54,11 @@ #endif /* WIDE */ #ifdef USE_FOR_STRCHRNUL +# define DO_RAND_TEST(...) +#else +# define DO_RAND_TEST(...) do_rand_test(__VA_ARGS__) +#endif +#ifdef USE_FOR_STRCHRNUL # define NULLRET(endptr) endptr #else # define NULLRET(endptr) NULL @@ -74,6 +79,133 @@ simple_STRCHR (const CHAR *s, int c) IMPL (simple_STRCHR, 0) IMPL (STRCHR, 1) +#ifndef USE_FOR_STRCHRNUL +/* Random benchmarks for strchr (if return is CHAR or NULL). The + rational for the benchmark is returning null/char can be done with + predicate execution (i.e cmovcc on x86) or a branch. */ + + +/* Large enough that full history can't be stored in BHT. */ +#define NUM_SEARCH_CHARS 2048 + +/* Expectation is usecases of strchr check the return. Otherwise + strchrnul would almost always be better. Since there is another + branch coming we want to test the case where a potential branch in + strchr can be used to skip a later mispredict because of the + relationship between the two branches. */ +static void __attribute__ ((noinline, noclone)) +do_one_rand_plus_branch_test (json_ctx_t *json_ctx, impl_t *impl, + const CHAR *s, const CHAR *c) +{ + size_t i, iters = INNER_LOOP_ITERS_LARGE; + int must_execute = 0; + timing_t start, stop, cur; + TIMING_NOW (start); + for (i = 0; i < iters; ++i) + { + if (CALL (impl, s, c[i % NUM_SEARCH_CHARS])) + { + /* We just need something that will force compiler to emit + a branch instead of conditional execution. */ + ++must_execute; + asm volatile("" : : :); + } + } + TIMING_NOW (stop); + + TIMING_DIFF (cur, start, stop); + + json_element_double (json_ctx, (double)cur / (double)iters); +} + +static void __attribute__ ((noinline, noclone)) +do_one_rand_test (json_ctx_t *json_ctx, impl_t *impl, const CHAR *s, + const CHAR *c) +{ + size_t i, iters = INNER_LOOP_ITERS_LARGE; + timing_t start, stop, cur; + TIMING_NOW (start); + for (i = 0; i < iters; ++i) + { + CALL (impl, s, c[i % NUM_SEARCH_CHARS]); + } + TIMING_NOW (stop); + + TIMING_DIFF (cur, start, stop); + + json_element_double (json_ctx, (double)cur / (double)iters); +} + +static void +do_rand_test (json_ctx_t *json_ctx, size_t align, size_t pos, size_t len, + float perc_zero) +{ + size_t i; + int perc_zero_int; + CHAR *buf = (CHAR *)buf1; + CHAR *c = (CHAR *)buf2; + align &= 127; + if ((align + len) * sizeof (CHAR) >= page_size) + return; + + /* Test is only interesting if we can hit both cases. */ + if (pos >= len) + return; + + /* Segfault if we run the test. */ + if (NUM_SEARCH_CHARS * sizeof (CHAR) > page_size) + return; + + for (i = 0; i < len; ++i) + { + buf[align + i] = 2; + } + buf[align + len] = 0; + buf[align + pos] = 1; + + perc_zero_int = perc_zero * RAND_MAX; + for (i = 0; i < NUM_SEARCH_CHARS; ++i) + { + if (rand () > perc_zero_int) + c[i] = 0; + else + c[i] = 1; + } + { + json_element_object_begin (json_ctx); + json_attr_uint (json_ctx, "rand", 1); + json_attr_uint (json_ctx, "branch", 1); + json_attr_double (json_ctx, "perc-zero", perc_zero); + json_attr_uint (json_ctx, "length", len); + json_attr_uint (json_ctx, "pos", pos); + json_attr_uint (json_ctx, "alignment", align); + json_array_begin (json_ctx, "timings"); + + FOR_EACH_IMPL (impl, 0) + do_one_rand_plus_branch_test (json_ctx, impl, buf + align, c); + + json_array_end (json_ctx); + json_element_object_end (json_ctx); + } + { + json_element_object_begin (json_ctx); + json_attr_uint (json_ctx, "rand", 1); + json_attr_uint (json_ctx, "branch", 0); + json_attr_double (json_ctx, "perc-zero", perc_zero); + json_attr_uint (json_ctx, "length", len); + json_attr_uint (json_ctx, "pos", pos); + json_attr_uint (json_ctx, "alignment", align); + json_array_begin (json_ctx, "timings"); + + FOR_EACH_IMPL (impl, 0) + do_one_rand_test (json_ctx, impl, buf + align, c); + + json_array_end (json_ctx); + json_element_object_end (json_ctx); + } +} +#endif + static void do_one_test (json_ctx_t *json_ctx, impl_t *impl, const CHAR *s, int c, const CHAR *exp_res) @@ -136,6 +268,7 @@ do_test (json_ctx_t *json_ctx, size_t align, size_t pos, size_t len, result = NULLRET (buf + align + len); json_element_object_begin (json_ctx); + json_attr_uint (json_ctx, "rand", 0); json_attr_uint (json_ctx, "length", len); json_attr_uint (json_ctx, "pos", pos); json_attr_uint (json_ctx, "seek_char", seek_char); @@ -234,6 +367,16 @@ test_main (void) do_test (&json_ctx, 0, i, i + 1, 0, BIG_CHAR); } + DO_RAND_TEST(&json_ctx, 0, 15, 16, 0.0); + DO_RAND_TEST(&json_ctx, 0, 15, 16, 0.1); + DO_RAND_TEST(&json_ctx, 0, 15, 16, 0.25); + DO_RAND_TEST(&json_ctx, 0, 15, 16, 0.33); + DO_RAND_TEST(&json_ctx, 0, 15, 16, 0.5); + DO_RAND_TEST(&json_ctx, 0, 15, 16, 0.66); + DO_RAND_TEST(&json_ctx, 0, 15, 16, 0.75); + DO_RAND_TEST(&json_ctx, 0, 15, 16, 0.9); + DO_RAND_TEST(&json_ctx, 0, 15, 16, 1.0); + json_array_end (&json_ctx); json_attr_object_end (&json_ctx); json_attr_object_end (&json_ctx); |