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1 // Copyright 2006-2008 the V8 project authors. All rights reserved. | 1 // Copyright 2006-2008 the V8 project authors. All rights reserved. |
2 // Redistribution and use in source and binary forms, with or without | 2 // Redistribution and use in source and binary forms, with or without |
3 // modification, are permitted provided that the following conditions are | 3 // modification, are permitted provided that the following conditions are |
4 // met: | 4 // met: |
5 // | 5 // |
6 // * Redistributions of source code must retain the above copyright | 6 // * Redistributions of source code must retain the above copyright |
7 // notice, this list of conditions and the following disclaimer. | 7 // notice, this list of conditions and the following disclaimer. |
8 // * Redistributions in binary form must reproduce the above | 8 // * Redistributions in binary form must reproduce the above |
9 // copyright notice, this list of conditions and the following | 9 // copyright notice, this list of conditions and the following |
10 // disclaimer in the documentation and/or other materials provided | 10 // disclaimer in the documentation and/or other materials provided |
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52 // This is incredibly slow on Intel x86. The reason is that rounding | 52 // This is incredibly slow on Intel x86. The reason is that rounding |
53 // towards zero is implied by the C standard. This means that the | 53 // towards zero is implied by the C standard. This means that the |
54 // status register of the FPU has to be changed with the 'fldcw' | 54 // status register of the FPU has to be changed with the 'fldcw' |
55 // instruction. This completely stalls the pipeline and takes many | 55 // instruction. This completely stalls the pipeline and takes many |
56 // hundreds of clock cycles. | 56 // hundreds of clock cycles. |
57 return static_cast<int>(x); | 57 return static_cast<int>(x); |
58 #endif | 58 #endif |
59 } | 59 } |
60 | 60 |
61 | 61 |
62 // The fast double-to-unsigned-int conversion routine does not guarantee | |
63 // rounding towards zero. | |
64 static inline unsigned int FastD2UI(double x) { | |
65 // There is no unsigned version of lrint, so there is no fast path | |
66 // in this function as there is in FastD2I. Using lrint doesn't work | |
67 // for values of 2^31 and above. | |
68 | |
69 // Convert "small enough" doubles to uint32_t by fixing the 32 | |
70 // least significant non-fractional bits in the low 32 bits of the | |
71 // double, and reading them from there. | |
72 const double k2Pow52 = 4503599627370496.0; | |
73 bool negative = x < 0; | |
74 if (negative) { x = -x; } | |
Mads Ager (chromium)
2010/03/03 13:16:50
Remove the braces or split on multiple lines.
| |
75 if (x < k2Pow52) { | |
76 x += k2Pow52; | |
77 uint32_t result; | |
78 memcpy(&result, &x, sizeof(result)); // Copy low 32 bits. | |
79 return negative ? ~result + 1 : result; | |
80 } | |
81 // Large number (outside uint32 range), Infinity or NaN. | |
82 return 0x80000000u; // Return integer indefinite. | |
83 } | |
84 | |
85 | |
62 static inline double DoubleToInteger(double x) { | 86 static inline double DoubleToInteger(double x) { |
63 if (isnan(x)) return 0; | 87 if (isnan(x)) return 0; |
64 if (!isfinite(x) || x == 0) return x; | 88 if (!isfinite(x) || x == 0) return x; |
65 return (x >= 0) ? floor(x) : ceil(x); | 89 return (x >= 0) ? floor(x) : ceil(x); |
66 } | 90 } |
67 | 91 |
68 | 92 |
69 int32_t NumberToInt32(Object* number) { | 93 int32_t NumberToInt32(Object* number) { |
70 if (number->IsSmi()) return Smi::cast(number)->value(); | 94 if (number->IsSmi()) return Smi::cast(number)->value(); |
71 return DoubleToInt32(number->Number()); | 95 return DoubleToInt32(number->Number()); |
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86 if (!isfinite(x) || x == 0) return 0; | 110 if (!isfinite(x) || x == 0) return 0; |
87 if (x < 0 || x >= two32) x = modulo(x, two32); | 111 if (x < 0 || x >= two32) x = modulo(x, two32); |
88 x = (x >= 0) ? floor(x) : ceil(x) + two32; | 112 x = (x >= 0) ? floor(x) : ceil(x) + two32; |
89 return (int32_t) ((x >= two31) ? x - two32 : x); | 113 return (int32_t) ((x >= two31) ? x - two32 : x); |
90 } | 114 } |
91 | 115 |
92 | 116 |
93 } } // namespace v8::internal | 117 } } // namespace v8::internal |
94 | 118 |
95 #endif // V8_CONVERSIONS_INL_H_ | 119 #endif // V8_CONVERSIONS_INL_H_ |
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