diff options
| -rw-r--r-- | meson.build | 4 | ||||
| -rw-r--r-- | src/util/fast_urem_by_const.h | 74 | ||||
| -rw-r--r-- | src/util/meson.build | 1 | ||||
| -rw-r--r-- | src/util/tests/fast_urem_by_const/fast_urem_by_const_test.cpp | 99 | ||||
| -rw-r--r-- | src/util/tests/fast_urem_by_const/meson.build | 32 |
5 files changed, 210 insertions, 0 deletions
diff --git a/meson.build b/meson.build index 2cefbb3f204..cd994c73b72 100644 --- a/meson.build +++ b/meson.build @@ -834,6 +834,10 @@ if cc.compiles('int foo(void) __attribute__((__noreturn__));', name : '__attribute__((__noreturn__))') pre_args += '-DHAVE_FUNC_ATTRIBUTE_NORETURN' endif +if cc.compiles('__uint128_t foo(void) { return 0; }', + name : '__uint128_t') + pre_args += '-DHAVE_UINT128' +endif # TODO: this is very incomplete if ['linux', 'cygwin', 'gnu'].contains(host_machine.system()) diff --git a/src/util/fast_urem_by_const.h b/src/util/fast_urem_by_const.h new file mode 100644 index 00000000000..beb253d2291 --- /dev/null +++ b/src/util/fast_urem_by_const.h @@ -0,0 +1,74 @@ +/* + * Copyright © 2010 Valve Software + * + * Permission is hereby granted, free of charge, to any person obtaining a + * copy of this software and associated documentation files (the "Software"), + * to deal in the Software without restriction, including without limitation + * the rights to use, copy, modify, merge, publish, distribute, sublicense, + * and/or sell copies of the Software, and to permit persons to whom the + * Software is furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice (including the next + * paragraph) shall be included in all copies or substantial portions of the + * Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS + * IN THE SOFTWARE. + */ + +#include <stdint.h> + +/* + * Code for fast 32-bit unsigned remainder, based off of "Faster Remainder by + * Direct Computation: Applications to Compilers and Software Libraries," + * available at https://arxiv.org/pdf/1902.01961.pdf. + * + * util_fast_urem32(n, d, REMAINDER_MAGIC(d)) returns the same thing as + * n % d for any unsigned n and d, however it compiles down to only a few + * multiplications, so it should be faster than plain uint32_t modulo if the + * same divisor is used many times. + */ + +#define REMAINDER_MAGIC(divisor) \ + ((uint64_t) ~0ull / (divisor) + 1) + +/* + * Get bits 64-96 of a 32x64-bit multiply. If __int128_t is available, we use + * it, which usually compiles down to one instruction on 64-bit architectures. + * Otherwise on 32-bit architectures we usually get four instructions (one + * 32x32->64 multiply, one 32x32->32 multiply, and one 64-bit add). + */ + +static inline uint32_t +_mul32by64_hi(uint32_t a, uint64_t b) +{ +#ifdef HAVE_UINT128 + return ((__uint128_t) b * a) >> 64; +#else + /* + * Let b = b0 + 2^32 * b1. Then a * b = a * b0 + 2^32 * a * b1. We would + * have to do a 96-bit addition to get the full result, except that only + * one term has non-zero lower 32 bits, which means that to get the high 32 + * bits, we only have to add the high 64 bits of each term. Unfortunately, + * we have to do the 64-bit addition in case the low 32 bits overflow. + */ + uint32_t b0 = (uint32_t) b; + uint32_t b1 = b >> 32; + return ((((uint64_t) a * b0) >> 32) + (uint64_t) a * b1) >> 32; +#endif +} + +static inline uint32_t +util_fast_urem32(uint32_t n, uint32_t d, uint64_t magic) +{ + uint64_t lowbits = magic * n; + uint32_t result = _mul32by64_hi(d, lowbits); + assert(result == n % d); + return result; +} + diff --git a/src/util/meson.build b/src/util/meson.build index dbb903218f2..23f8c68c701 100644 --- a/src/util/meson.build +++ b/src/util/meson.build @@ -208,6 +208,7 @@ if with_tests ) subdir('tests/fast_idiv_by_const') + subdir('tests/fast_urem_by_const') subdir('tests/hash_table') subdir('tests/string_buffer') subdir('tests/vma') diff --git a/src/util/tests/fast_urem_by_const/fast_urem_by_const_test.cpp b/src/util/tests/fast_urem_by_const/fast_urem_by_const_test.cpp new file mode 100644 index 00000000000..752cd8cd393 --- /dev/null +++ b/src/util/tests/fast_urem_by_const/fast_urem_by_const_test.cpp @@ -0,0 +1,99 @@ +/* + * Copyright © 2018 Intel Corporation + * Copyright © 2019 Valve Corporation + * + * Permission is hereby granted, free of charge, to any person obtaining a + * copy of this software and associated documentation files (the "Software"), + * to deal in the Software without restriction, including without limitation + * the rights to use, copy, modify, merge, publish, distribute, sublicense, + * and/or sell copies of the Software, and to permit persons to whom the + * Software is furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice (including the next + * paragraph) shall be included in all copies or substantial portions of the + * Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS + * IN THE SOFTWARE. + */ + +#undef NDEBUG + +#include <gtest/gtest.h> +#include "util/fast_urem_by_const.h" + +#define RAND_TEST_ITERATIONS 100000 + +static uint32_t +rand_uint(unsigned min) +{ + /* Make sure we get some small and large numbers and powers of two every + * once in a while + */ + int k = rand() % 64; + if (k == 17) { + return min + (rand() % 16); + } else if (k == 42) { + return UINT32_MAX - (rand() % 16); + } else if (k == 9) { + uint32_t r; + do { + r = 1ull << (rand() % 32); + } while (r < min); + return r; + } + + if (min == 0) { + uint32_t r = 0; + for (unsigned i = 0; i < 4; i++) + r |= ((uint32_t)rand() & 0xf) << i * 8; + return r >> (31 - (rand() % 32)); + } else { + uint64_t r; + do { + r = rand_uint(0); + } while (r < min); + return r; + } +} + +static void +test_case(uint32_t n, uint32_t d) +{ + assert(d >= 1); + uint64_t magic = REMAINDER_MAGIC(d); + /* Note: there's already an assert inside util_fast_urem32(), so the + * EXPECT_EQ is only here to make sure the test fails with a wrong result + * even if asserts are disabled. Ideally we could disable the assert just + * for the test to get a better error message, but that doesn't seem too + * easy. + */ + EXPECT_EQ(util_fast_urem32(n, d, magic), n % d); +} + +TEST(fast_urem_by_const, random) +{ + for (unsigned i = 0; i < RAND_TEST_ITERATIONS; i++) { + uint64_t n = rand_uint(0); + uint64_t d = rand_uint(1); + test_case(n, d); + } +} + +TEST(fast_urem_by_const, special_cases) +{ + test_case(0, 1); + test_case(0, UINT32_MAX); + test_case(UINT32_MAX, 1); + test_case(1, UINT32_MAX); + test_case(UINT32_MAX, UINT32_MAX); + test_case(UINT32_MAX, UINT32_MAX - 1); + test_case(UINT32_MAX - 1, UINT32_MAX - 1); + test_case(UINT32_MAX - 2, UINT32_MAX - 1); +} + diff --git a/src/util/tests/fast_urem_by_const/meson.build b/src/util/tests/fast_urem_by_const/meson.build new file mode 100644 index 00000000000..8bae51f0a83 --- /dev/null +++ b/src/util/tests/fast_urem_by_const/meson.build @@ -0,0 +1,32 @@ +# Copyright © 2018 Intel Corporation +# Copyright © 2010 Valve Corporation + +# Permission is hereby granted, free of charge, to any person obtaining a copy +# of this software and associated documentation files (the "Software"), to deal +# in the Software without restriction, including without limitation the rights +# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell +# copies of the Software, and to permit persons to whom the Software is +# furnished to do so, subject to the following conditions: + +# The above copyright notice and this permission notice shall be included in +# all copies or substantial portions of the Software. + +# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR +# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, +# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE +# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER +# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, +# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE +# SOFTWARE. + +test( + 'fast_urem_by_const', + executable( + 'fast_urem_by_const_test', + 'fast_urem_by_const_test.cpp', + dependencies : [dep_thread, dep_dl, idep_gtest], + include_directories : inc_common, + link_with : [libmesa_util], + ), + suite : ['util'], +) |