| // Copyright 2019 The Fuchsia Authors. All rights reserved. | |
| // Use of this source code is governed by a BSD-style license that can be | |
| // found in the LICENSE file. | |
| #include "util.h" | |
| #include <assert.h> | |
| // | |
| // | |
| // | |
| #if defined(_MSC_VER) && !defined(__clang__) | |
| #include <intrin.h> | |
| #endif | |
| // | |
| // | |
| // | |
| bool | |
| is_pow2_u32(uint32_t n) | |
| { | |
| return n && !(n & (n - 1)); | |
| } | |
| // | |
| // | |
| // | |
| uint32_t | |
| pow2_ru_u32(uint32_t n) | |
| { | |
| assert(n <= 0x80000000U); | |
| n--; | |
| n |= n >> 1; | |
| n |= n >> 2; | |
| n |= n >> 4; | |
| n |= n >> 8; | |
| n |= n >> 16; | |
| n++; | |
| return n; | |
| } | |
| // | |
| // | |
| // | |
| uint32_t | |
| pow2_rd_u32(uint32_t n) | |
| { | |
| assert(n > 0); | |
| return 1u << msb_idx_u32(n); | |
| } | |
| // | |
| // ASSUMES NON-ZERO | |
| // | |
| uint32_t | |
| msb_idx_u32(uint32_t n) | |
| { | |
| assert(n > 0); | |
| #if defined(_MSC_VER) && !defined(__clang__) | |
| uint32_t index; | |
| _BitScanReverse((unsigned long *)&index, n); | |
| return index; | |
| #elif defined(__GNUC__) | |
| return __builtin_clz(n) ^ 31; | |
| #else | |
| #error "No msb_index()" | |
| #endif | |
| } | |
| // | |
| // | |
| // |