1 /* 2 * Copyright 2012 Google Inc. 3 * 4 * Use of this source code is governed by a BSD-style license that can be 5 * found in the LICENSE file. 6 */ 7 8 #ifndef SkMathPriv_DEFINED 9 #define SkMathPriv_DEFINED 10 11 #include "SkMath.h" 12 13 #if defined(SK_BUILD_FOR_IOS) && (defined(SK_BUILD_FOR_ARM32) || defined(SK_BUILD_FOR_ARM64)) 14 // iOS on ARM starts processes with the Flush-To-Zero (FTZ) and 15 // Denormals-Are-Zero (DAZ) bits in the fpscr register set. 16 // Algorithms that rely on denormalized numbers need alternative implementations. 17 // This can also be controlled in SSE with the MXCSR register, 18 // x87 with FSTCW/FLDCW, and mips with FCSR. This should be detected at runtime, 19 // or the library built one way or the other more generally (by the build). 20 #define SK_CPU_FLUSH_TO_ZERO 21 #endif 22 23 /** Returns -1 if n < 0, else returns 0 24 */ 25 #define SkExtractSign(n) ((int32_t)(n) >> 31) 26 27 /** If sign == -1, returns -n, else sign must be 0, and returns n. 28 Typically used in conjunction with SkExtractSign(). 29 */ 30 static inline int32_t SkApplySign(int32_t n, int32_t sign) { 31 SkASSERT(sign == 0 || sign == -1); 32 return (n ^ sign) - sign; 33 } 34 35 /** Return x with the sign of y */ 36 static inline int32_t SkCopySign32(int32_t x, int32_t y) { 37 return SkApplySign(x, SkExtractSign(x ^ y)); 38 } 39 40 /** Given a positive value and a positive max, return the value 41 pinned against max. 42 Note: only works as long as max - value doesn't wrap around 43 @return max if value >= max, else value 44 */ 45 static inline unsigned SkClampUMax(unsigned value, unsigned max) { 46 if (value > max) { 47 value = max; 48 } 49 return value; 50 } 51 52 /////////////////////////////////////////////////////////////////////////////// 53 54 /** Return a*b/255, truncating away any fractional bits. Only valid if both 55 a and b are 0..255 56 */ 57 static inline U8CPU SkMulDiv255Trunc(U8CPU a, U8CPU b) { 58 SkASSERT((uint8_t)a == a); 59 SkASSERT((uint8_t)b == b); 60 unsigned prod = a*b + 1; 61 return (prod + (prod >> 8)) >> 8; 62 } 63 64 /** Return (a*b)/255, taking the ceiling of any fractional bits. Only valid if 65 both a and b are 0..255. The expected result equals (a * b + 254) / 255. 66 */ 67 static inline U8CPU SkMulDiv255Ceiling(U8CPU a, U8CPU b) { 68 SkASSERT((uint8_t)a == a); 69 SkASSERT((uint8_t)b == b); 70 unsigned prod = a*b + 255; 71 return (prod + (prod >> 8)) >> 8; 72 } 73 74 /** Just the rounding step in SkDiv255Round: round(value / 255) 75 */ 76 static inline unsigned SkDiv255Round(unsigned prod) { 77 prod += 128; 78 return (prod + (prod >> 8)) >> 8; 79 } 80 81 static inline float SkPinToUnitFloat(float x) { 82 return SkTMin(SkTMax(x, 0.0f), 1.0f); 83 } 84 85 /** 86 * Swap byte order of a 4-byte value, e.g. 0xaarrggbb -> 0xbbggrraa. 87 */ 88 #if defined(_MSC_VER) 89 #include <intrin.h> 90 static inline uint32_t SkBSwap32(uint32_t v) { return _byteswap_ulong(v); } 91 #else 92 static inline uint32_t SkBSwap32(uint32_t v) { return __builtin_bswap32(v); } 93 #endif 94 95 //! Returns the number of leading zero bits (0...32) 96 int SkCLZ_portable(uint32_t); 97 98 #ifndef SkCLZ 99 #if defined(SK_BUILD_FOR_WIN32) 100 #include <intrin.h> 101 102 static inline int SkCLZ(uint32_t mask) { 103 if (mask) { 104 unsigned long index; 105 _BitScanReverse(&index, mask); 106 // Suppress this bogus /analyze warning. The check for non-zero 107 // guarantees that _BitScanReverse will succeed. 108 #pragma warning(suppress : 6102) // Using 'index' from failed function call 109 return index ^ 0x1F; 110 } else { 111 return 32; 112 } 113 } 114 #elif defined(SK_CPU_ARM32) || defined(__GNUC__) || defined(__clang__) 115 static inline int SkCLZ(uint32_t mask) { 116 // __builtin_clz(0) is undefined, so we have to detect that case. 117 return mask ? __builtin_clz(mask) : 32; 118 } 119 #else 120 #define SkCLZ(x) SkCLZ_portable(x) 121 #endif 122 #endif 123 124 /** 125 * Returns the smallest power-of-2 that is >= the specified value. If value 126 * is already a power of 2, then it is returned unchanged. It is undefined 127 * if value is <= 0. 128 */ 129 static inline int SkNextPow2(int value) { 130 SkASSERT(value > 0); 131 return 1 << (32 - SkCLZ(value - 1)); 132 } 133 134 /** 135 * Returns the largest power-of-2 that is <= the specified value. If value 136 * is already a power of 2, then it is returned unchanged. It is undefined 137 * if value is <= 0. 138 */ 139 static inline int SkPrevPow2(int value) { 140 SkASSERT(value > 0); 141 return 1 << (32 - SkCLZ(value >> 1)); 142 } 143 144 /** 145 * Returns the log2 of the specified value, were that value to be rounded up 146 * to the next power of 2. It is undefined to pass 0. Examples: 147 * SkNextLog2(1) -> 0 148 * SkNextLog2(2) -> 1 149 * SkNextLog2(3) -> 2 150 * SkNextLog2(4) -> 2 151 * SkNextLog2(5) -> 3 152 */ 153 static inline int SkNextLog2(uint32_t value) { 154 SkASSERT(value != 0); 155 return 32 - SkCLZ(value - 1); 156 } 157 158 /** 159 * Returns the log2 of the specified value, were that value to be rounded down 160 * to the previous power of 2. It is undefined to pass 0. Examples: 161 * SkPrevLog2(1) -> 0 162 * SkPrevLog2(2) -> 1 163 * SkPrevLog2(3) -> 1 164 * SkPrevLog2(4) -> 2 165 * SkPrevLog2(5) -> 2 166 */ 167 static inline int SkPrevLog2(uint32_t value) { 168 SkASSERT(value != 0); 169 return 32 - SkCLZ(value >> 1); 170 } 171 172 /////////////////////////////////////////////////////////////////////////////// 173 174 /** 175 * Return the next power of 2 >= n. 176 */ 177 static inline uint32_t GrNextPow2(uint32_t n) { 178 return n ? (1 << (32 - SkCLZ(n - 1))) : 1; 179 } 180 181 /** 182 * Returns the next power of 2 >= n or n if the next power of 2 can't be represented by size_t. 183 */ 184 static inline size_t GrNextSizePow2(size_t n) { 185 constexpr int kNumSizeTBits = 8 * sizeof(size_t); 186 constexpr size_t kHighBitSet = size_t(1) << (kNumSizeTBits - 1); 187 188 if (!n) { 189 return 1; 190 } else if (n >= kHighBitSet) { 191 return n; 192 } 193 194 n--; 195 uint32_t shift = 1; 196 while (shift < kNumSizeTBits) { 197 n |= n >> shift; 198 shift <<= 1; 199 } 200 return n + 1; 201 } 202 203 static inline int GrNextPow2(int n) { 204 SkASSERT(n >= 0); // this impl only works for non-neg. 205 return n ? (1 << (32 - SkCLZ(n - 1))) : 1; 206 } 207 #endif 208
