1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
|
/*
* Copyright 2006 The Android Open Source Project
*
* Use of this source code is governed by a BSD-style license that can be
* found in the LICENSE file.
*/
#ifndef SkMath_DEFINED
#define SkMath_DEFINED
#include "SkTypes.h"
// 64bit -> 32bit utilities
/**
* Return true iff the 64bit value can exactly be represented in signed 32bits
*/
static inline bool sk_64_isS32(int64_t value) {
return (int32_t)value == value;
}
/**
* Return the 64bit argument as signed 32bits, asserting in debug that the arg
* exactly fits in signed 32bits. In the release build, no checks are preformed
* and the return value if the arg does not fit is undefined.
*/
static inline int32_t sk_64_asS32(int64_t value) {
SkASSERT(sk_64_isS32(value));
return (int32_t)value;
}
// Handy util that can be passed two ints, and will automatically promote to
// 64bits before the multiply, so the caller doesn't have to remember to cast
// e.g. (int64_t)a * b;
static inline int64_t sk_64_mul(int64_t a, int64_t b) {
return a * b;
}
///////////////////////////////////////////////////////////////////////////////
/**
* Computes numer1 * numer2 / denom in full 64 intermediate precision.
* It is an error for denom to be 0. There is no special handling if
* the result overflows 32bits.
*/
static inline int32_t SkMulDiv(int32_t numer1, int32_t numer2, int32_t denom) {
SkASSERT(denom);
int64_t tmp = sk_64_mul(numer1, numer2) / denom;
return sk_64_asS32(tmp);
}
/**
* Computes (numer1 << shift) / denom in full 64 intermediate precision.
* It is an error for denom to be 0. There is no special handling if
* the result overflows 32bits.
*/
int32_t SkDivBits(int32_t numer, int32_t denom, int shift);
/**
* Return the integer square root of value, with a bias of bitBias
*/
int32_t SkSqrtBits(int32_t value, int bitBias);
/** Return the integer square root of n, treated as a SkFixed (16.16)
*/
#define SkSqrt32(n) SkSqrtBits(n, 15)
//! Returns the number of leading zero bits (0...32)
int SkCLZ_portable(uint32_t);
#ifndef SkCLZ
#if defined(_MSC_VER) && _MSC_VER >= 1400
#include <intrin.h>
static inline int SkCLZ(uint32_t mask) {
if (mask) {
DWORD index;
_BitScanReverse(&index, mask);
return index ^ 0x1F;
} else {
return 32;
}
}
#elif defined(SK_CPU_ARM) || defined(__GNUC__) || defined(__clang__)
static inline int SkCLZ(uint32_t mask) {
// __builtin_clz(0) is undefined, so we have to detect that case.
return mask ? __builtin_clz(mask) : 32;
}
#else
#define SkCLZ(x) SkCLZ_portable(x)
#endif
#endif
/**
* Returns (value < 0 ? 0 : value) efficiently (i.e. no compares or branches)
*/
static inline int SkClampPos(int value) {
return value & ~(value >> 31);
}
/** Given an integer and a positive (max) integer, return the value
* pinned against 0 and max, inclusive.
* @param value The value we want returned pinned between [0...max]
* @param max The positive max value
* @return 0 if value < 0, max if value > max, else value
*/
static inline int SkClampMax(int value, int max) {
// ensure that max is positive
SkASSERT(max >= 0);
if (value < 0) {
value = 0;
}
if (value > max) {
value = max;
}
return value;
}
/**
* Returns the smallest power-of-2 that is >= the specified value. If value
* is already a power of 2, then it is returned unchanged. It is undefined
* if value is <= 0.
*/
static inline int SkNextPow2(int value) {
SkASSERT(value > 0);
return 1 << (32 - SkCLZ(value - 1));
}
/**
* Returns the log2 of the specified value, were that value to be rounded up
* to the next power of 2. It is undefined to pass 0. Examples:
* SkNextLog2(1) -> 0
* SkNextLog2(2) -> 1
* SkNextLog2(3) -> 2
* SkNextLog2(4) -> 2
* SkNextLog2(5) -> 3
*/
static inline int SkNextLog2(uint32_t value) {
SkASSERT(value != 0);
return 32 - SkCLZ(value - 1);
}
/**
* Returns true if value is a power of 2. Does not explicitly check for
* value <= 0.
*/
static inline bool SkIsPow2(int value) {
return (value & (value - 1)) == 0;
}
///////////////////////////////////////////////////////////////////////////////
/**
* SkMulS16(a, b) multiplies a * b, but requires that a and b are both int16_t.
* With this requirement, we can generate faster instructions on some
* architectures.
*/
#ifdef SK_ARM_HAS_EDSP
static inline int32_t SkMulS16(S16CPU x, S16CPU y) {
SkASSERT((int16_t)x == x);
SkASSERT((int16_t)y == y);
int32_t product;
asm("smulbb %0, %1, %2 \n"
: "=r"(product)
: "r"(x), "r"(y)
);
return product;
}
#else
#ifdef SK_DEBUG
static inline int32_t SkMulS16(S16CPU x, S16CPU y) {
SkASSERT((int16_t)x == x);
SkASSERT((int16_t)y == y);
return x * y;
}
#else
#define SkMulS16(x, y) ((x) * (y))
#endif
#endif
/**
* Return a*b/((1 << shift) - 1), rounding any fractional bits.
* Only valid if a and b are unsigned and <= 32767 and shift is > 0 and <= 8
*/
static inline unsigned SkMul16ShiftRound(U16CPU a, U16CPU b, int shift) {
SkASSERT(a <= 32767);
SkASSERT(b <= 32767);
SkASSERT(shift > 0 && shift <= 8);
unsigned prod = SkMulS16(a, b) + (1 << (shift - 1));
return (prod + (prod >> shift)) >> shift;
}
/**
* Return a*b/255, rounding any fractional bits.
* Only valid if a and b are unsigned and <= 32767.
*/
static inline U8CPU SkMulDiv255Round(U16CPU a, U16CPU b) {
SkASSERT(a <= 32767);
SkASSERT(b <= 32767);
unsigned prod = SkMulS16(a, b) + 128;
return (prod + (prod >> 8)) >> 8;
}
/**
* Stores numer/denom and numer%denom into div and mod respectively.
*/
template <typename In, typename Out>
inline void SkTDivMod(In numer, In denom, Out* div, Out* mod) {
#ifdef SK_CPU_ARM
// If we wrote this as in the else branch, GCC won't fuse the two into one
// divmod call, but rather a div call followed by a divmod. Silly! This
// version is just as fast as calling __aeabi_[u]idivmod manually, but with
// prettier code.
//
// This benches as around 2x faster than the code in the else branch.
const In d = numer/denom;
*div = static_cast<Out>(d);
*mod = static_cast<Out>(numer-d*denom);
#else
// On x86 this will just be a single idiv.
*div = static_cast<Out>(numer/denom);
*mod = static_cast<Out>(numer%denom);
#endif // SK_CPU_ARM
}
#endif
|
