OLD | NEW |
---|---|
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 |
(...skipping 29 matching lines...) Expand all Loading... | |
40 #define IS_POWER_OF_TWO(x) (((x) & ((x) - 1)) == 0) | 40 #define IS_POWER_OF_TWO(x) (((x) & ((x) - 1)) == 0) |
41 | 41 |
42 // Returns true iff x is a power of 2 (or zero). Cannot be used with the | 42 // Returns true iff x is a power of 2 (or zero). Cannot be used with the |
43 // maximally negative value of the type T (the -1 overflows). | 43 // maximally negative value of the type T (the -1 overflows). |
44 template <typename T> | 44 template <typename T> |
45 static inline bool IsPowerOf2(T x) { | 45 static inline bool IsPowerOf2(T x) { |
46 return IS_POWER_OF_TWO(x); | 46 return IS_POWER_OF_TWO(x); |
47 } | 47 } |
48 | 48 |
49 | 49 |
50 // X must be a power of 2. Returns the number of trailing zeros. | |
51 template <typename T> | |
52 static inline int WhichPowerOf2(T x) { | |
Søren Thygesen Gjesse
2010/06/14 07:56:47
Shouldn't there be a test case for this?
Erik Corry
2010/06/14 21:05:46
Assert added.
| |
53 ASSERT(IsPowerOf2(x)); | |
54 if (x < 0) return 31; | |
55 if (x == 0) return 32; | |
56 int bits = 0; | |
57 if (x >= 0x10000) { | |
58 bits += 16; | |
59 x >>= 16; | |
60 } | |
61 if (x >= 0x100) { | |
62 bits += 8; | |
63 x >>= 8; | |
64 } | |
65 if (x >= 0x10) { | |
66 bits += 4; | |
67 x >>= 4; | |
68 } | |
69 switch (x) { | |
70 case 1: return bits; | |
71 case 2: return bits + 1; | |
72 case 4: return bits + 2; | |
73 case 8: return bits + 3; | |
74 default: UNREACHABLE(); | |
75 } | |
76 return 0; | |
77 } | |
78 | |
79 | |
50 // The C++ standard leaves the semantics of '>>' undefined for | 80 // The C++ standard leaves the semantics of '>>' undefined for |
51 // negative signed operands. Most implementations do the right thing, | 81 // negative signed operands. Most implementations do the right thing, |
52 // though. | 82 // though. |
53 static inline int ArithmeticShiftRight(int x, int s) { | 83 static inline int ArithmeticShiftRight(int x, int s) { |
54 return x >> s; | 84 return x >> s; |
55 } | 85 } |
56 | 86 |
57 | 87 |
58 // Compute the 0-relative offset of some absolute value x of type T. | 88 // Compute the 0-relative offset of some absolute value x of type T. |
59 // This allows conversion of Addresses and integral types into | 89 // This allows conversion of Addresses and integral types into |
(...skipping 641 matching lines...) Expand 10 before | Expand all | Expand 10 after Loading... | |
701 | 731 |
702 Dest dest; | 732 Dest dest; |
703 memcpy(&dest, &source, sizeof(dest)); | 733 memcpy(&dest, &source, sizeof(dest)); |
704 return dest; | 734 return dest; |
705 } | 735 } |
706 | 736 |
707 } } // namespace v8::internal | 737 } } // namespace v8::internal |
708 | 738 |
709 | 739 |
710 #endif // V8_UTILS_H_ | 740 #endif // V8_UTILS_H_ |
OLD | NEW |