mirror of https://github.com/mgba-emu/mgba.git
60 lines
1.8 KiB
C
60 lines
1.8 KiB
C
/* Copyright (c) 2013-2015 Jeffrey Pfau
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*
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* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef UTIL_MATH_H
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#define UTIL_MATH_H
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#include "util/common.h"
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static inline uint32_t popcount32(unsigned bits) {
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bits = bits - ((bits >> 1) & 0x55555555);
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bits = (bits & 0x33333333) + ((bits >> 2) & 0x33333333);
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return (((bits + (bits >> 4)) & 0xF0F0F0F) * 0x1010101) >> 24;
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}
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static inline unsigned clz32(uint32_t bits) {
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#if defined(__GNUC__) || __clang__
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return __builtin_clz(bits);
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#else
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static const int table[256] = {
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8, 7, 6, 6, 5, 5, 5, 5, 4, 4, 4, 4, 4, 4, 4, 4,
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3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
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2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
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2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
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0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0
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};
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if (bits & 0xFF000000) {
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return table[bits >> 24];
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} else if (bits & 0x00FF0000) {
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return table[bits >> 16] + 8;
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} else if (bits & 0x0000FF00) {
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return table[bits >> 8] + 16;
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}
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return table[bits] + 24;
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#endif
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}
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static inline uint32_t toPow2(uint32_t bits) {
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if (!bits) {
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return 0;
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}
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unsigned lz = clz32(bits - 1);
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return 1 << (32 - lz);
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}
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#endif
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