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Side by Side Diff: src/cached_powers.h

Issue 804005: Revert grisu commits. (Closed) Base URL: http://v8.googlecode.com/svn/branches/bleeding_edge/
Patch Set: Created 10 years, 9 months ago
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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 int k = ceiling((alpha - e + kQ - 1) * kD_1_LOG2_10); \
69 int index = (GRISU_CACHE_OFFSET + 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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