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31 lines
1.1 KiB
C
31 lines
1.1 KiB
C
/*
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* Copyright 2024 Google LLC
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include "util/math.h"
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#include <stdint.h>
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#include <stdbool.h>
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int ceil_log_two(uint32_t n) {
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// clz stands for Count Leading Zeroes. We use it to find the MSB
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int msb = 31 - __builtin_clz(n);
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// popcount counts the number of set bits in a word (1's)
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bool power_of_two = __builtin_popcount(n) == 1;
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// if not exact power of two, use the next power of two
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// we want to err on the side of caution and want to
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// always round up
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return ((power_of_two) ? msb : (msb + 1));
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}
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