05beab6b1f
Review URL: http://codereview.chromium.org/1102002 git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@4191 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
120 lines
4.9 KiB
C++
120 lines
4.9 KiB
C++
// Copyright 2010 the V8 project authors. All rights reserved.
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// Redistribution and use in source and binary forms, with or without
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// modification, are permitted provided that the following conditions are
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// met:
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//
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// * Redistributions of source code must retain the above copyright
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// notice, this list of conditions and the following disclaimer.
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// * Redistributions in binary form must reproduce the above
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// copyright notice, this list of conditions and the following
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// disclaimer in the documentation and/or other materials provided
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// with the distribution.
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// * Neither the name of Google Inc. nor the names of its
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// contributors may be used to endorse or promote products derived
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// from this software without specific prior written permission.
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//
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// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
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// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
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// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
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// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
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// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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#ifndef V8_CACHED_POWERS_H_
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#define V8_CACHED_POWERS_H_
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#include "diy-fp.h"
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namespace v8 {
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namespace internal {
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struct CachedPower {
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uint64_t significand;
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int16_t binary_exponent;
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int16_t decimal_exponent;
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};
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// The following defines implement the interface between this file and the
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// generated 'powers_ten.h'.
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// GRISU_CACHE_NAME(1) contains all possible cached powers.
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// GRISU_CACHE_NAME(i) contains GRISU_CACHE_NAME(1) where only every 'i'th
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// element is kept. More formally GRISU_CACHE_NAME(i) contains the elements j*i
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// with 0 <= j < k with k such that j*k < the size of GRISU_CACHE_NAME(1).
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// The higher 'i' is the fewer elements we use.
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// Given that there are less elements, the exponent-distance between two
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// elements in the cache grows. The variable GRISU_CACHE_MAX_DISTANCE(i) stores
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// the maximum distance between two elements.
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#define GRISU_CACHE_STRUCT CachedPower
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#define GRISU_CACHE_NAME(i) kCachedPowers##i
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#define GRISU_CACHE_MAX_DISTANCE(i) kCachedPowersMaxDistance##i
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#define GRISU_CACHE_OFFSET kCachedPowerOffset
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#define GRISU_UINT64_C V8_2PART_UINT64_C
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// The following include imports the precompiled cached powers.
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#include "powers-ten.h" // NOLINT
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static const double kD_1_LOG2_10 = 0.30102999566398114; // 1 / lg(10)
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// We can't use a function since we reference variables depending on the 'i'.
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// This way the compiler is able to see at compile time that only one
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// cache-array variable is used and thus can remove all the others.
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#define COMPUTE_FOR_CACHE(i) \
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if (!found && (gamma - alpha + 1 >= GRISU_CACHE_MAX_DISTANCE(i))) { \
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int kQ = DiyFp::kSignificandSize; \
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double k = ceiling((alpha - e + kQ - 1) * kD_1_LOG2_10); \
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int index = (GRISU_CACHE_OFFSET + static_cast<int>(k) - 1) / i + 1; \
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cached_power = GRISU_CACHE_NAME(i)[index]; \
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found = true; \
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} \
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static void GetCachedPower(int e, int alpha, int gamma, int* mk, DiyFp* c_mk) {
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// The following if statement should be optimized by the compiler so that only
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// one array is referenced and the others are not included in the object file.
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bool found = false;
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CachedPower cached_power;
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COMPUTE_FOR_CACHE(20);
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COMPUTE_FOR_CACHE(19);
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COMPUTE_FOR_CACHE(18);
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COMPUTE_FOR_CACHE(17);
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COMPUTE_FOR_CACHE(16);
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COMPUTE_FOR_CACHE(15);
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COMPUTE_FOR_CACHE(14);
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COMPUTE_FOR_CACHE(13);
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COMPUTE_FOR_CACHE(12);
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COMPUTE_FOR_CACHE(11);
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COMPUTE_FOR_CACHE(10);
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COMPUTE_FOR_CACHE(9);
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COMPUTE_FOR_CACHE(8);
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COMPUTE_FOR_CACHE(7);
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COMPUTE_FOR_CACHE(6);
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COMPUTE_FOR_CACHE(5);
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COMPUTE_FOR_CACHE(4);
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COMPUTE_FOR_CACHE(3);
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COMPUTE_FOR_CACHE(2);
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COMPUTE_FOR_CACHE(1);
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if (!found) {
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UNIMPLEMENTED();
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// Silence compiler warnings.
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cached_power.significand = 0;
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cached_power.binary_exponent = 0;
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cached_power.decimal_exponent = 0;
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}
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*c_mk = DiyFp(cached_power.significand, cached_power.binary_exponent);
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*mk = cached_power.decimal_exponent;
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ASSERT((alpha <= c_mk->e() + e) && (c_mk->e() + e <= gamma));
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}
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#undef GRISU_REDUCTION
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#undef GRISU_CACHE_STRUCT
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#undef GRISU_CACHE_NAME
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#undef GRISU_CACHE_MAX_DISTANCE
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#undef GRISU_CACHE_OFFSET
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#undef GRISU_UINT64_C
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} } // namespace v8::internal
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#endif // V8_CACHED_POWERS_H_
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