conversions-inl.h revision a7e24c173cf37484693b9abb38e494fa7bd7baeb 
1// Copyright 2006-2008 the V8 project authors. All rights reserved.
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27
28#ifndef V8_CONVERSIONS_INL_H_
29#define V8_CONVERSIONS_INL_H_
30
31#include <math.h>
32#include <float.h>         // required for DBL_MAX and on Win32 for finite()
33#include <stdarg.h>
34
35// ----------------------------------------------------------------------------
36// Extra POSIX/ANSI functions for Win32/MSVC.
37
38#include "conversions.h"
39#include "platform.h"
40
41namespace v8 {
42namespace internal {
43
44// The fast double-to-int conversion routine does not guarantee
45// rounding towards zero.
46static inline int FastD2I(double x) {
47#ifdef __USE_ISOC99
48  // The ISO C99 standard defines the lrint() function which rounds a
49  // double to an integer according to the current rounding direction.
50  return lrint(x);
51#else
52  // This is incredibly slow on Intel x86. The reason is that rounding
53  // towards zero is implied by the C standard. This means that the
54  // status register of the FPU has to be changed with the 'fldcw'
55  // instruction. This completely stalls the pipeline and takes many
56  // hundreds of clock cycles.
57  return static_cast<int>(x);
58#endif
59}
60
61
62static inline double DoubleToInteger(double x) {
63  if (isnan(x)) return 0;
64  if (!isfinite(x) || x == 0) return x;
65  return (x >= 0) ? floor(x) : ceil(x);
66}
67
68
69int32_t NumberToInt32(Object* number) {
70  if (number->IsSmi()) return Smi::cast(number)->value();
71  return DoubleToInt32(number->Number());
72}
73
74
75uint32_t NumberToUint32(Object* number) {
76  if (number->IsSmi()) return Smi::cast(number)->value();
77  return DoubleToUint32(number->Number());
78}
79
80
81int32_t DoubleToInt32(double x) {
82  int32_t i = FastD2I(x);
83  if (FastI2D(i) == x) return i;
84  static const double two32 = 4294967296.0;
85  static const double two31 = 2147483648.0;
86  if (!isfinite(x) || x == 0) return 0;
87  if (x < 0 || x >= two32) x = fmod(x, two32);
88  x = (x >= 0) ? floor(x) : ceil(x) + two32;
89  return (int32_t) ((x >= two31) ? x - two32 : x);
90}
91
92
93} }  // namespace v8::internal
94
95#endif  // V8_CONVERSIONS_INL_H_
96