1 // Copyright 2013 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
4
5 #ifndef V8_ARM64_UTILS_ARM64_H_
6 #define V8_ARM64_UTILS_ARM64_H_
7
8 #include <cmath>
9
10 #include "src/arm64/constants-arm64.h"
11 #include "src/utils.h"
12
13 namespace v8 {
14 namespace internal {
15
16 // These are global assumptions in v8.
17 STATIC_ASSERT((static_cast<int32_t>(-1) >> 1) == -1);
18 STATIC_ASSERT((static_cast<uint32_t>(-1) >> 1) == 0x7FFFFFFF);
19
20 uint32_t float_sign(float val);
21 uint32_t float_exp(float val);
22 uint32_t float_mantissa(float val);
23 uint32_t double_sign(double val);
24 uint32_t double_exp(double val);
25 uint64_t double_mantissa(double val);
26
27 float float_pack(uint32_t sign, uint32_t exp, uint32_t mantissa);
28 double double_pack(uint64_t sign, uint64_t exp, uint64_t mantissa);
29
30 // An fpclassify() function for 16-bit half-precision floats.
31 int float16classify(float16 value);
32
33 // Bit counting.
34 int CountLeadingZeros(uint64_t value, int width);
35 int CountLeadingSignBits(int64_t value, int width);
36 int CountTrailingZeros(uint64_t value, int width);
37 int CountSetBits(uint64_t value, int width);
38 int LowestSetBitPosition(uint64_t value);
39 int HighestSetBitPosition(uint64_t value);
40 uint64_t LargestPowerOf2Divisor(uint64_t value);
41 int MaskToBit(uint64_t mask);
42
43
44 template <typename T>
ReverseBytes(T value,int block_bytes_log2)45 T ReverseBytes(T value, int block_bytes_log2) {
46 DCHECK((sizeof(value) == 4) || (sizeof(value) == 8));
47 DCHECK((1U << block_bytes_log2) <= sizeof(value));
48 // Split the 64-bit value into an 8-bit array, where b[0] is the least
49 // significant byte, and b[7] is the most significant.
50 uint8_t bytes[8];
51 uint64_t mask = 0xff00000000000000;
52 for (int i = 7; i >= 0; i--) {
53 bytes[i] = (static_cast<uint64_t>(value) & mask) >> (i * 8);
54 mask >>= 8;
55 }
56
57 // Permutation tables for REV instructions.
58 // permute_table[0] is used by REV16_x, REV16_w
59 // permute_table[1] is used by REV32_x, REV_w
60 // permute_table[2] is used by REV_x
61 DCHECK((0 < block_bytes_log2) && (block_bytes_log2 < 4));
62 static const uint8_t permute_table[3][8] = {{6, 7, 4, 5, 2, 3, 0, 1},
63 {4, 5, 6, 7, 0, 1, 2, 3},
64 {0, 1, 2, 3, 4, 5, 6, 7}};
65 T result = 0;
66 for (int i = 0; i < 8; i++) {
67 result <<= 8;
68 result |= bytes[permute_table[block_bytes_log2 - 1][i]];
69 }
70 return result;
71 }
72
73
74 // NaN tests.
IsSignallingNaN(double num)75 inline bool IsSignallingNaN(double num) {
76 uint64_t raw = bit_cast<uint64_t>(num);
77 if (std::isnan(num) && ((raw & kDQuietNanMask) == 0)) {
78 return true;
79 }
80 return false;
81 }
82
83
IsSignallingNaN(float num)84 inline bool IsSignallingNaN(float num) {
85 uint32_t raw = bit_cast<uint32_t>(num);
86 if (std::isnan(num) && ((raw & kSQuietNanMask) == 0)) {
87 return true;
88 }
89 return false;
90 }
91
IsSignallingNaN(float16 num)92 inline bool IsSignallingNaN(float16 num) {
93 const uint16_t kFP16QuietNaNMask = 0x0200;
94 return (float16classify(num) == FP_NAN) && ((num & kFP16QuietNaNMask) == 0);
95 }
96
97 template <typename T>
IsQuietNaN(T num)98 inline bool IsQuietNaN(T num) {
99 return std::isnan(num) && !IsSignallingNaN(num);
100 }
101
102
103 // Convert the NaN in 'num' to a quiet NaN.
ToQuietNaN(double num)104 inline double ToQuietNaN(double num) {
105 DCHECK(std::isnan(num));
106 return bit_cast<double>(bit_cast<uint64_t>(num) | kDQuietNanMask);
107 }
108
109
ToQuietNaN(float num)110 inline float ToQuietNaN(float num) {
111 DCHECK(std::isnan(num));
112 return bit_cast<float>(bit_cast<uint32_t>(num) |
113 static_cast<uint32_t>(kSQuietNanMask));
114 }
115
116
117 // Fused multiply-add.
FusedMultiplyAdd(double op1,double op2,double a)118 inline double FusedMultiplyAdd(double op1, double op2, double a) {
119 return fma(op1, op2, a);
120 }
121
122
FusedMultiplyAdd(float op1,float op2,float a)123 inline float FusedMultiplyAdd(float op1, float op2, float a) {
124 return fmaf(op1, op2, a);
125 }
126
127 } // namespace internal
128 } // namespace v8
129
130 #endif // V8_ARM64_UTILS_ARM64_H_
131