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1 /* | 1 /* |
2 * Copyright (c) 2012, Google Inc. All rights reserved. | 2 * Copyright (c) 2012, Google Inc. All rights reserved. |
3 * | 3 * |
4 * Redistribution and use in source and binary forms, with or without | 4 * Redistribution and use in source and binary forms, with or without |
5 * modification, are permitted provided that the following conditions are | 5 * modification, are permitted provided that the following conditions are |
6 * met: | 6 * met: |
7 * | 7 * |
8 * * Redistributions of source code must retain the above copyright | 8 * * Redistributions of source code must retain the above copyright |
9 * notice, this list of conditions and the following disclaimer. | 9 * notice, this list of conditions and the following disclaimer. |
10 * * Redistributions in binary form must reproduce the above | 10 * * Redistributions in binary form must reproduce the above |
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24 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | 24 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, |
25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | 25 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY |
26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | 26 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT |
27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | 27 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE |
28 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | 28 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
29 */ | 29 */ |
30 | 30 |
31 #ifndef SaturatedArithmetic_h | 31 #ifndef SaturatedArithmetic_h |
32 #define SaturatedArithmetic_h | 32 #define SaturatedArithmetic_h |
33 | 33 |
| 34 #include "wtf/CPU.h" |
34 #include <limits> | 35 #include <limits> |
35 #include <stdint.h> | 36 #include <stdint.h> |
36 | 37 |
| 38 #if CPU(ARM) && COMPILER(GCC) |
| 39 |
| 40 // If we're building ARM on GCC we replace the C++ versions with some |
| 41 // native ARM assembly for speed. |
| 42 #include "wtf/asm/SaturatedArithmeticARM.h" |
| 43 |
| 44 #else |
| 45 |
37 ALWAYS_INLINE int32_t saturatedAddition(int32_t a, int32_t b) | 46 ALWAYS_INLINE int32_t saturatedAddition(int32_t a, int32_t b) |
38 { | 47 { |
39 uint32_t ua = a; | 48 uint32_t ua = a; |
40 uint32_t ub = b; | 49 uint32_t ub = b; |
41 uint32_t result = ua + ub; | 50 uint32_t result = ua + ub; |
42 | 51 |
43 // Can only overflow if the signed bit of the two values match. If the signe
d | 52 // Can only overflow if the signed bit of the two values match. If the |
44 // bit of the result and one of the values differ it did overflow. | 53 // signed bit of the result and one of the values differ it overflowed. |
45 if (!((ua ^ ub) >> 31) & (result ^ ua) >> 31) | 54 |
46 result = std::numeric_limits<int>::max() + (ua >> 31); | 55 if (~(ua ^ ub) & (result ^ ua) & (1 << 31)) |
| 56 return std::numeric_limits<int>::max() + (ua >> 31); |
47 | 57 |
48 return result; | 58 return result; |
49 } | 59 } |
50 | 60 |
51 ALWAYS_INLINE int32_t saturatedSubtraction(int32_t a, int32_t b) | 61 ALWAYS_INLINE int32_t saturatedSubtraction(int32_t a, int32_t b) |
52 { | 62 { |
53 uint32_t ua = a; | 63 uint32_t ua = a; |
54 uint32_t ub = b; | 64 uint32_t ub = b; |
55 uint32_t result = ua - ub; | 65 uint32_t result = ua - ub; |
56 | 66 |
57 // Can only overflow if the signed bit of the two values do not match. If th
e | 67 // Can only overflow if the signed bit of the two input values differ. If |
58 // signed bit of the result and the first value differ it did overflow. | 68 // the signed bit of the result and the first value differ it overflowed. |
59 if ((ua ^ ub) >> 31 & (result ^ ua) >> 31) | 69 |
60 result = std::numeric_limits<int>::max() + (ua >> 31); | 70 if ((ua ^ ub) & (result ^ ua) & (1 << 31)) |
| 71 return std::numeric_limits<int>::max() + (ua >> 31); |
61 | 72 |
62 return result; | 73 return result; |
63 } | 74 } |
64 | 75 |
| 76 inline int getMaxSaturatedSetResultForTesting(int FractionalShift) |
| 77 { |
| 78 // For C version the set function maxes out to max int, this differs from |
| 79 // the ARM asm version, see SaturatedArithmetiARM.h for the equivalent asm |
| 80 // version. |
| 81 return std::numeric_limits<int>::max(); |
| 82 } |
| 83 |
| 84 inline int getMinSaturatedSetResultForTesting(int FractionalShift) |
| 85 { |
| 86 return std::numeric_limits<int>::min(); |
| 87 } |
| 88 |
| 89 ALWAYS_INLINE int saturatedSet(int value, int FractionalShift) |
| 90 { |
| 91 const int intMaxForLayoutUnit = |
| 92 std::numeric_limits<int>::max() >> FractionalShift; |
| 93 |
| 94 const int intMinForLayoutUnit = |
| 95 std::numeric_limits<int>::min() >> FractionalShift; |
| 96 |
| 97 if (value > intMaxForLayoutUnit) |
| 98 return std::numeric_limits<int>::max(); |
| 99 |
| 100 if (value < intMinForLayoutUnit) |
| 101 return std::numeric_limits<int>::min(); |
| 102 |
| 103 return value << FractionalShift; |
| 104 } |
| 105 |
| 106 |
| 107 ALWAYS_INLINE int saturatedSet(unsigned value, int FractionalShift) |
| 108 { |
| 109 const unsigned intMaxForLayoutUnit = |
| 110 std::numeric_limits<int>::max() >> FractionalShift; |
| 111 |
| 112 if (value >= intMaxForLayoutUnit) |
| 113 return std::numeric_limits<int>::max(); |
| 114 |
| 115 return value << FractionalShift; |
| 116 } |
| 117 |
| 118 #endif // CPU(ARM) && COMPILER(GCC) |
65 #endif // SaturatedArithmetic_h | 119 #endif // SaturatedArithmetic_h |
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