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 257335 : 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 257335 : bool found = false;
78 : CachedPower cached_power;
79 257335 : COMPUTE_FOR_CACHE(20);
80 257335 : COMPUTE_FOR_CACHE(19);
81 257335 : COMPUTE_FOR_CACHE(18);
82 257335 : COMPUTE_FOR_CACHE(17);
83 257335 : COMPUTE_FOR_CACHE(16);
84 257335 : COMPUTE_FOR_CACHE(15);
85 257335 : COMPUTE_FOR_CACHE(14);
86 257335 : COMPUTE_FOR_CACHE(13);
87 257335 : COMPUTE_FOR_CACHE(12);
88 257335 : COMPUTE_FOR_CACHE(11);
89 257335 : COMPUTE_FOR_CACHE(10);
90 257335 : COMPUTE_FOR_CACHE(9);
91 257335 : COMPUTE_FOR_CACHE(8);
92 257335 : COMPUTE_FOR_CACHE(7);
93 257335 : COMPUTE_FOR_CACHE(6);
94 257335 : COMPUTE_FOR_CACHE(5);
95 257335 : COMPUTE_FOR_CACHE(4);
96 257335 : COMPUTE_FOR_CACHE(3);
97 257335 : COMPUTE_FOR_CACHE(2);
98 257335 : COMPUTE_FOR_CACHE(1);
99 257335 : if (!found) {
100 0 : UNIMPLEMENTED();
101 : // Silence compiler warnings.
102 0 : cached_power.significand = 0;
103 0 : cached_power.binary_exponent = 0;
104 0 : cached_power.decimal_exponent = 0;
105 : }
106 257335 : *c_mk = DiyFp(cached_power.significand, cached_power.binary_exponent);
107 257335 : *mk = cached_power.decimal_exponent;
108 257335 : ASSERT((alpha <= c_mk->e() + e) && (c_mk->e() + e <= gamma));
109 257335 : }
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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