ece0eaa3f8
Add benchmark that randomizes whether return should be NULL or pointer
to CHAR. The rationale is on many architectures there is a choice
between a predicate execution option (i.e cmovcc on x86) or a branch.
On x86 the results for cmovcc vs branch are something along the lines
of the following:
perc-zero, Br On Result, Time Br / Time cmov
0.10, 1, ,0.983
0.10, 0, ,1.246
0.25, 1, ,1.035
0.25, 0, ,1.49
0.33, 1, ,1.016
0.33, 0, ,1.579
0.50, 1, ,1.228
0.50, 0, ,1.739
0.66, 1, ,1.039
0.66, 0, ,1.764
0.75, 1, ,0.996
0.75, 0, ,1.642
0.90, 1, ,1.071
0.90, 0, ,1.409
1.00, 1, ,0.937
1.00, 0, ,0.999
Reviewed-by: H.J. Lu <hjl.tools@gmail.com>
389 lines
10 KiB
C
389 lines
10 KiB
C
/* Measure STRCHR functions.
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Copyright (C) 2013-2022 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<https://www.gnu.org/licenses/>. */
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#define TEST_MAIN
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#ifndef WIDE
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# ifdef USE_FOR_STRCHRNUL
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# define TEST_NAME "strchrnul"
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# else
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# define TEST_NAME "strchr"
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# endif /* !USE_FOR_STRCHRNUL */
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#else
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# ifdef USE_FOR_STRCHRNUL
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# define TEST_NAME "wcschrnul"
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# else
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# define TEST_NAME "wcschr"
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# endif /* !USE_FOR_STRCHRNUL */
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#endif /* WIDE */
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#include "bench-string.h"
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#include "json-lib.h"
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#define BIG_CHAR MAX_CHAR
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#ifndef WIDE
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# ifdef USE_FOR_STRCHRNUL
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# undef STRCHR
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# define STRCHR strchrnul
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# define simple_STRCHR simple_STRCHRNUL
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# endif /* !USE_FOR_STRCHRNUL */
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# define MIDDLE_CHAR 127
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# define SMALL_CHAR 23
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#else
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# ifdef USE_FOR_STRCHRNUL
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# undef STRCHR
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# define STRCHR wcschrnul
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# define simple_STRCHR simple_WCSCHRNUL
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# endif /* !USE_FOR_STRCHRNUL */
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# define MIDDLE_CHAR 1121
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# define SMALL_CHAR 851
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#endif /* WIDE */
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#ifdef USE_FOR_STRCHRNUL
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# define DO_RAND_TEST(...)
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#else
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# define DO_RAND_TEST(...) do_rand_test(__VA_ARGS__)
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#endif
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#ifdef USE_FOR_STRCHRNUL
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# define NULLRET(endptr) endptr
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#else
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# define NULLRET(endptr) NULL
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#endif /* !USE_FOR_STRCHRNUL */
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typedef CHAR *(*proto_t) (const CHAR *, int);
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CHAR *
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simple_STRCHR (const CHAR *s, int c)
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{
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for (; *s != (CHAR) c; ++s)
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if (*s == '\0')
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return NULLRET ((CHAR *) s);
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return (CHAR *) s;
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}
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IMPL (simple_STRCHR, 0)
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IMPL (STRCHR, 1)
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#ifndef USE_FOR_STRCHRNUL
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/* Random benchmarks for strchr (if return is CHAR or NULL). The
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rational for the benchmark is returning null/char can be done with
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predicate execution (i.e cmovcc on x86) or a branch. */
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/* Large enough that full history can't be stored in BHT. */
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#define NUM_SEARCH_CHARS 2048
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/* Expectation is usecases of strchr check the return. Otherwise
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strchrnul would almost always be better. Since there is another
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branch coming we want to test the case where a potential branch in
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strchr can be used to skip a later mispredict because of the
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relationship between the two branches. */
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static void __attribute__ ((noinline, noclone))
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do_one_rand_plus_branch_test (json_ctx_t *json_ctx, impl_t *impl,
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const CHAR *s, const CHAR *c)
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{
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size_t i, iters = INNER_LOOP_ITERS_LARGE;
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int must_execute = 0;
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timing_t start, stop, cur;
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TIMING_NOW (start);
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for (i = 0; i < iters; ++i)
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{
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if (CALL (impl, s, c[i % NUM_SEARCH_CHARS]))
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{
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/* We just need something that will force compiler to emit
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a branch instead of conditional execution. */
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++must_execute;
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asm volatile("" : : :);
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}
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}
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TIMING_NOW (stop);
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TIMING_DIFF (cur, start, stop);
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json_element_double (json_ctx, (double)cur / (double)iters);
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}
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static void __attribute__ ((noinline, noclone))
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do_one_rand_test (json_ctx_t *json_ctx, impl_t *impl, const CHAR *s,
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const CHAR *c)
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{
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size_t i, iters = INNER_LOOP_ITERS_LARGE;
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timing_t start, stop, cur;
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TIMING_NOW (start);
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for (i = 0; i < iters; ++i)
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{
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CALL (impl, s, c[i % NUM_SEARCH_CHARS]);
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}
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TIMING_NOW (stop);
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TIMING_DIFF (cur, start, stop);
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json_element_double (json_ctx, (double)cur / (double)iters);
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}
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static void
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do_rand_test (json_ctx_t *json_ctx, size_t align, size_t pos, size_t len,
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float perc_zero)
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{
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size_t i;
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int perc_zero_int;
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CHAR *buf = (CHAR *)buf1;
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CHAR *c = (CHAR *)buf2;
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align &= 127;
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if ((align + len) * sizeof (CHAR) >= page_size)
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return;
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/* Test is only interesting if we can hit both cases. */
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if (pos >= len)
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return;
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/* Segfault if we run the test. */
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if (NUM_SEARCH_CHARS * sizeof (CHAR) > page_size)
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return;
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for (i = 0; i < len; ++i)
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{
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buf[align + i] = 2;
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}
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buf[align + len] = 0;
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buf[align + pos] = 1;
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perc_zero_int = perc_zero * RAND_MAX;
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for (i = 0; i < NUM_SEARCH_CHARS; ++i)
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{
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if (rand () > perc_zero_int)
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c[i] = 0;
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else
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c[i] = 1;
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}
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{
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json_element_object_begin (json_ctx);
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json_attr_uint (json_ctx, "rand", 1);
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json_attr_uint (json_ctx, "branch", 1);
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json_attr_double (json_ctx, "perc-zero", perc_zero);
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json_attr_uint (json_ctx, "length", len);
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json_attr_uint (json_ctx, "pos", pos);
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json_attr_uint (json_ctx, "alignment", align);
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json_array_begin (json_ctx, "timings");
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FOR_EACH_IMPL (impl, 0)
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do_one_rand_plus_branch_test (json_ctx, impl, buf + align, c);
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json_array_end (json_ctx);
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json_element_object_end (json_ctx);
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}
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{
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json_element_object_begin (json_ctx);
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json_attr_uint (json_ctx, "rand", 1);
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json_attr_uint (json_ctx, "branch", 0);
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json_attr_double (json_ctx, "perc-zero", perc_zero);
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json_attr_uint (json_ctx, "length", len);
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json_attr_uint (json_ctx, "pos", pos);
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json_attr_uint (json_ctx, "alignment", align);
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json_array_begin (json_ctx, "timings");
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FOR_EACH_IMPL (impl, 0)
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do_one_rand_test (json_ctx, impl, buf + align, c);
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json_array_end (json_ctx);
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json_element_object_end (json_ctx);
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}
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}
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#endif
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static void
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do_one_test (json_ctx_t *json_ctx, impl_t *impl, const CHAR *s, int c,
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const CHAR *exp_res)
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{
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size_t i, iters = INNER_LOOP_ITERS_LARGE;
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timing_t start, stop, cur;
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const CHAR *res = CALL (impl, s, c);
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if (res != exp_res)
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{
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error (0, 0, "Wrong result in function %s %p != %p", impl->name, res,
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exp_res);
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ret = 1;
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return;
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}
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TIMING_NOW (start);
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for (i = 0; i < iters; ++i)
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{
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CALL (impl, s, c);
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}
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TIMING_NOW (stop);
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TIMING_DIFF (cur, start, stop);
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json_element_double (json_ctx, (double)cur / (double)iters);
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}
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static void
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do_test (json_ctx_t *json_ctx, size_t align, size_t pos, size_t len,
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int seek_char, int max_char)
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/* For wcschr: align here means align not in bytes,
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but in wchar_ts, in bytes it will equal to align * (sizeof (wchar_t))
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len for wcschr here isn't in bytes but it's number of wchar_t symbols. */
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{
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size_t i;
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CHAR *result;
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CHAR *buf = (CHAR *) buf1;
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align &= 127;
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if ((align + len) * sizeof (CHAR) >= page_size)
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return;
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for (i = 0; i < len; ++i)
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{
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buf[align + i] = 32 + 23 * i % max_char;
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if (buf[align + i] == seek_char)
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buf[align + i] = seek_char + 1;
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else if (buf[align + i] == 0)
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buf[align + i] = 1;
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}
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buf[align + len] = 0;
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if (pos < len)
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{
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buf[align + pos] = seek_char;
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result = buf + align + pos;
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}
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else if (seek_char == 0)
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result = buf + align + len;
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else
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result = NULLRET (buf + align + len);
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json_element_object_begin (json_ctx);
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json_attr_uint (json_ctx, "rand", 0);
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json_attr_uint (json_ctx, "length", len);
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json_attr_uint (json_ctx, "pos", pos);
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json_attr_uint (json_ctx, "seek_char", seek_char);
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json_attr_uint (json_ctx, "max_char", max_char);
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json_attr_uint (json_ctx, "alignment", align);
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json_array_begin (json_ctx, "timings");
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FOR_EACH_IMPL (impl, 0)
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do_one_test (json_ctx, impl, buf + align, seek_char, result);
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json_array_end (json_ctx);
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json_element_object_end (json_ctx);
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}
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int
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test_main (void)
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{
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json_ctx_t json_ctx;
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size_t i;
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test_init ();
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json_init (&json_ctx, 0, stdout);
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json_document_begin (&json_ctx);
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json_attr_string (&json_ctx, "timing_type", TIMING_TYPE);
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json_attr_object_begin (&json_ctx, "functions");
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json_attr_object_begin (&json_ctx, TEST_NAME);
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json_attr_string (&json_ctx, "bench-variant", "");
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json_array_begin (&json_ctx, "ifuncs");
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FOR_EACH_IMPL (impl, 0)
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json_element_string (&json_ctx, impl->name);
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json_array_end (&json_ctx);
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json_array_begin (&json_ctx, "results");
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for (i = 1; i < 8; ++i)
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{
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do_test (&json_ctx, 0, 16 << i, 2048, SMALL_CHAR, MIDDLE_CHAR);
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do_test (&json_ctx, i, 16 << i, 2048, SMALL_CHAR, MIDDLE_CHAR);
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}
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for (i = 1; i < 8; ++i)
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{
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do_test (&json_ctx, 0, 16 << i, 4096, SMALL_CHAR, MIDDLE_CHAR);
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do_test (&json_ctx, i, 16 << i, 4096, SMALL_CHAR, MIDDLE_CHAR);
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}
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for (i = 1; i < 8; ++i)
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{
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do_test (&json_ctx, i, 64, 256, SMALL_CHAR, MIDDLE_CHAR);
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do_test (&json_ctx, i, 64, 256, SMALL_CHAR, BIG_CHAR);
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}
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for (i = 0; i < 8; ++i)
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{
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do_test (&json_ctx, 16 * i, 256, 512, SMALL_CHAR, MIDDLE_CHAR);
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do_test (&json_ctx, 16 * i, 256, 512, SMALL_CHAR, BIG_CHAR);
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}
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for (i = 0; i < 32; ++i)
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{
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do_test (&json_ctx, 0, i, i + 1, SMALL_CHAR, MIDDLE_CHAR);
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do_test (&json_ctx, 0, i, i + 1, SMALL_CHAR, BIG_CHAR);
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}
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for (i = 1; i < 8; ++i)
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{
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do_test (&json_ctx, 0, 16 << i, 2048, 0, MIDDLE_CHAR);
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do_test (&json_ctx, i, 16 << i, 2048, 0, MIDDLE_CHAR);
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}
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for (i = 1; i < 8; ++i)
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{
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do_test (&json_ctx, 0, 16 << i, 4096, 0, MIDDLE_CHAR);
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do_test (&json_ctx, i, 16 << i, 4096, 0, MIDDLE_CHAR);
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}
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for (i = 1; i < 8; ++i)
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{
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do_test (&json_ctx, i, 64, 256, 0, MIDDLE_CHAR);
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do_test (&json_ctx, i, 64, 256, 0, BIG_CHAR);
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}
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for (i = 0; i < 8; ++i)
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{
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do_test (&json_ctx, 16 * i, 256, 512, 0, MIDDLE_CHAR);
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do_test (&json_ctx, 16 * i, 256, 512, 0, BIG_CHAR);
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}
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for (i = 0; i < 32; ++i)
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{
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do_test (&json_ctx, 0, i, i + 1, 0, MIDDLE_CHAR);
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do_test (&json_ctx, 0, i, i + 1, 0, BIG_CHAR);
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}
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DO_RAND_TEST(&json_ctx, 0, 15, 16, 0.0);
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DO_RAND_TEST(&json_ctx, 0, 15, 16, 0.1);
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DO_RAND_TEST(&json_ctx, 0, 15, 16, 0.25);
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DO_RAND_TEST(&json_ctx, 0, 15, 16, 0.33);
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DO_RAND_TEST(&json_ctx, 0, 15, 16, 0.5);
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DO_RAND_TEST(&json_ctx, 0, 15, 16, 0.66);
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DO_RAND_TEST(&json_ctx, 0, 15, 16, 0.75);
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DO_RAND_TEST(&json_ctx, 0, 15, 16, 0.9);
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DO_RAND_TEST(&json_ctx, 0, 15, 16, 1.0);
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json_array_end (&json_ctx);
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json_attr_object_end (&json_ctx);
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json_attr_object_end (&json_ctx);
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json_document_end (&json_ctx);
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return ret;
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}
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#include <support/test-driver.c>
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