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| 1 // Copyright 2010 the V8 project authors. All rights reserved. | |
| 2 // Redistribution and use in source and binary forms, with or without | |
| 3 // modification, are permitted provided that the following conditions are | |
| 4 // met: | |
| 5 // | |
| 6 // * Redistributions of source code must retain the above copyright | |
| 7 // notice, this list of conditions and the following disclaimer. | |
| 8 // * Redistributions in binary form must reproduce the above | |
| 9 // copyright notice, this list of conditions and the following | |
| 10 // disclaimer in the documentation and/or other materials provided | |
| 11 // with the distribution. | |
| 12 // * Neither the name of Google Inc. nor the names of its | |
| 13 // contributors may be used to endorse or promote products derived | |
| 14 // from this software without specific prior written permission. | |
| 15 // | |
| 16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS | |
| 17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT | |
| 18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR | |
| 19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT | |
| 20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, | |
| 21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT | |
| 22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
| 23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
| 24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
| 25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE | |
| 26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
| 27 | |
| 28 #ifndef V8_CACHED_POWERS_H_ | |
| 29 #define V8_CACHED_POWERS_H_ | |
| 30 | |
| 31 #include "diy_fp.h" | |
| 32 | |
| 33 namespace v8 { | |
| 34 namespace internal { | |
| 35 | |
| 36 struct CachedPower { | |
| 37 uint64_t significand; | |
| 38 int16_t binary_exponent; | |
| 39 int16_t decimal_exponent; | |
| 40 }; | |
| 41 | |
| 42 // The following defines implement the interface between this file and the | |
| 43 // generated 'powers_ten.h'. | |
| 44 // GRISU_CACHE_NAME(1) contains all possible cached powers. | |
| 45 // GRISU_CACHE_NAME(i) contains GRISU_CACHE_NAME(1) where only every 'i'th | |
| 46 // element is kept. More formally GRISU_CACHE_NAME(i) contains the elements j*i | |
| 47 // with 0 <= j < k with k such that j*k < the size of GRISU_CACHE_NAME(1). | |
| 48 // The higher 'i' is the fewer elements we use. | |
| 49 // Given that there are less elements, the exponent-distance between two | |
| 50 // elements in the cache grows. The variable GRISU_CACHE_MAX_DISTANCE(i) stores | |
| 51 // the maximum distance between two elements. | |
| 52 #define GRISU_CACHE_STRUCT CachedPower | |
| 53 #define GRISU_CACHE_NAME(i) kCachedPowers##i | |
| 54 #define GRISU_CACHE_MAX_DISTANCE(i) kCachedPowersMaxDistance##i | |
| 55 #define GRISU_CACHE_OFFSET kCachedPowerOffset | |
| 56 #define GRISU_UINT64_C V8_2PART_UINT64_C | |
| 57 // The following include imports the precompiled cached powers. | |
| 58 #include "powers_ten.h" // NOLINT | |
| 59 | |
| 60 static const double kD_1_LOG2_10 = 0.30102999566398114; // 1 / lg(10) | |
| 61 | |
| 62 // We can't use a function since we reference variables depending on the 'i'. | |
| 63 // This way the compiler is able to see at compile time that only one | |
| 64 // cache-array variable is used and thus can remove all the others. | |
| 65 #define COMPUTE_FOR_CACHE(i) \ | |
| 66 if (!found && (gamma - alpha + 1 >= GRISU_CACHE_MAX_DISTANCE(i))) { \ | |
| 67 int kQ = DiyFp::kSignificandSize; \ | |
| 68 double k = ceiling((alpha - e + kQ - 1) * kD_1_LOG2_10); \ | |
| 69 int index = (GRISU_CACHE_OFFSET + static_cast<int>(k) - 1) / i + 1; \ | |
| 70 cached_power = GRISU_CACHE_NAME(i)[index]; \ | |
| 71 found = true; \ | |
| 72 } \ | |
| 73 | |
| 74 static void GetCachedPower(int e, int alpha, int gamma, int* mk, DiyFp* c_mk) { | |
| 75 // The following if statement should be optimized by the compiler so that only | |
| 76 // one array is referenced and the others are not included in the object file. | |
| 77 bool found = false; | |
| 78 CachedPower cached_power; | |
| 79 COMPUTE_FOR_CACHE(20); | |
| 80 COMPUTE_FOR_CACHE(19); | |
| 81 COMPUTE_FOR_CACHE(18); | |
| 82 COMPUTE_FOR_CACHE(17); | |
| 83 COMPUTE_FOR_CACHE(16); | |
| 84 COMPUTE_FOR_CACHE(15); | |
| 85 COMPUTE_FOR_CACHE(14); | |
| 86 COMPUTE_FOR_CACHE(13); | |
| 87 COMPUTE_FOR_CACHE(12); | |
| 88 COMPUTE_FOR_CACHE(11); | |
| 89 COMPUTE_FOR_CACHE(10); | |
| 90 COMPUTE_FOR_CACHE(9); | |
| 91 COMPUTE_FOR_CACHE(8); | |
| 92 COMPUTE_FOR_CACHE(7); | |
| 93 COMPUTE_FOR_CACHE(6); | |
| 94 COMPUTE_FOR_CACHE(5); | |
| 95 COMPUTE_FOR_CACHE(4); | |
| 96 COMPUTE_FOR_CACHE(3); | |
| 97 COMPUTE_FOR_CACHE(2); | |
| 98 COMPUTE_FOR_CACHE(1); | |
| 99 if (!found) { | |
| 100 UNIMPLEMENTED(); | |
| 101 // Silence compiler warnings. | |
| 102 cached_power.significand = 0; | |
| 103 cached_power.binary_exponent = 0; | |
| 104 cached_power.decimal_exponent = 0; | |
| 105 } | |
| 106 *c_mk = DiyFp(cached_power.significand, cached_power.binary_exponent); | |
| 107 *mk = cached_power.decimal_exponent; | |
| 108 ASSERT((alpha <= c_mk->e() + e) && (c_mk->e() + e <= gamma)); | |
| 109 } | |
| 110 #undef GRISU_REDUCTION | |
| 111 #undef GRISU_CACHE_STRUCT | |
| 112 #undef GRISU_CACHE_NAME | |
| 113 #undef GRISU_CACHE_MAX_DISTANCE | |
| 114 #undef GRISU_CACHE_OFFSET | |
| 115 #undef GRISU_UINT64_C | |
| 116 | |
| 117 } } // namespace v8::internal | |
| 118 | |
| 119 #endif // V8_CACHED_POWERS_H_ | |
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