1 /* Copyright 2019 Google LLC. All Rights Reserved.
2
3 Licensed under the Apache License, Version 2.0 (the "License");
4 you may not use this file except in compliance with the License.
5 You may obtain a copy of the License at
6
7 http://www.apache.org/licenses/LICENSE-2.0
8
9 Unless required by applicable law or agreed to in writing, software
10 distributed under the License is distributed on an "AS IS" BASIS,
11 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 See the License for the specific language governing permissions and
13 limitations under the License.
14 ==============================================================================*/
15
16 #ifndef RUY_RUY_SIZE_UTIL_H_
17 #define RUY_RUY_SIZE_UTIL_H_
18
19 #include <type_traits>
20
21 #include "ruy/check_macros.h"
22
23 #ifdef _WIN32
24 #include <intrin.h>
25 #endif
26
27 namespace ruy {
28
29 template <typename Integer>
floor_log2(Integer n)30 inline Integer floor_log2(Integer n) {
31 static_assert(std::is_integral<Integer>::value, "");
32 static_assert(std::is_signed<Integer>::value, "");
33 static_assert(sizeof(Integer) == 4 || sizeof(Integer) == 8, "");
34
35 RUY_DCHECK_GE(n, 1);
36 #ifdef _MSC_VER
37 unsigned long result; // NOLINT[runtime/int]
38 if (sizeof(Integer) == 4) {
39 _BitScanReverse(&result, n);
40 } else {
41 #if defined(_M_X64) || defined(_M_ARM64)
42 // _BitScanReverse64 is supported only on 64-bit MSVC platforms
43 _BitScanReverse64(&result, static_cast<unsigned __int64>(n));
44 #else
45 // Emulate using 32-bit _BitScanReverse
46 const uint32_t n_hi = uint64_t(n) >> 32;
47 if (n_hi == 0) {
48 _BitScanReverse(&result, static_cast<unsigned long>(n));
49 } else {
50 _BitScanReverse(&result, static_cast<unsigned long>(n_hi));
51 result += 32;
52 }
53 #endif // defined(_M_X64) || defined(_M_ARM64)
54 }
55 return result;
56 #else
57 if (sizeof(Integer) == 4) {
58 return 31 - __builtin_clz(n);
59 } else {
60 return 63 - __builtin_clzll(n);
61 }
62 #endif
63 }
64
65 template <typename Integer>
ceil_log2(Integer n)66 Integer ceil_log2(Integer n) {
67 RUY_DCHECK_GE(n, 1);
68 return n == 1 ? 0 : floor_log2(n - 1) + 1;
69 }
70
71 template <typename Integer>
is_pot(Integer value)72 constexpr bool is_pot(Integer value) {
73 return (value > 0) && ((value & (value - 1)) == 0);
74 }
75
76 template <typename Integer>
pot_log2(Integer n)77 Integer pot_log2(Integer n) {
78 RUY_DCHECK(is_pot(n));
79 return floor_log2(n);
80 }
81
82 template <typename Integer>
round_down_pot(Integer value)83 Integer round_down_pot(Integer value) {
84 return static_cast<Integer>(1) << floor_log2(value);
85 }
86
87 template <typename Integer>
round_up_pot(Integer value)88 Integer round_up_pot(Integer value) {
89 return static_cast<Integer>(1) << ceil_log2(value);
90 }
91
92 template <typename Integer, typename Modulo>
round_down_pot(Integer value,Modulo modulo)93 Integer round_down_pot(Integer value, Modulo modulo) {
94 RUY_DCHECK_EQ(modulo & (modulo - 1), 0);
95 return value & ~(modulo - 1);
96 }
97
98 template <typename Integer, typename Modulo>
round_up_pot(Integer value,Modulo modulo)99 Integer round_up_pot(Integer value, Modulo modulo) {
100 return round_down_pot(value + modulo - 1, modulo);
101 }
102
103 } // namespace ruy
104
105 #endif // RUY_RUY_SIZE_UTIL_H_
106