1 // Copyright 2012 the V8 project authors. All rights reserved.
2 // Use of this source code is governed by a BSD-style license that can be
3 // found in the LICENSE file.
5 // This file relies on the fact that the following declarations have been made
7 // var $Object = global.Object;
9 // Keep reference to original values of some global properties. This
10 // has the added benefit that the code in this file is isolated from
11 // changes to these properties.
12 var $floor = MathFloor;
15 // Instance class name can only be set on functions. That is the only
16 // purpose for MathConstructor.
17 function MathConstructor() {}
18 var $Math = new MathConstructor();
20 // -------------------------------------------------------------------
22 // ECMA 262 - 15.8.2.1
24 if (%_IsSmi(x)) return x >= 0 ? x : -x;
25 x = TO_NUMBER_INLINE(x);
26 if (x === 0) return 0; // To handle -0.
27 return x > 0 ? x : -x;
30 // ECMA 262 - 15.8.2.2
31 function MathAcos(x) {
32 return %MathAcos(TO_NUMBER_INLINE(x));
35 // ECMA 262 - 15.8.2.3
36 function MathAsin(x) {
37 return %MathAsin(TO_NUMBER_INLINE(x));
40 // ECMA 262 - 15.8.2.4
41 function MathAtan(x) {
42 return %MathAtan(TO_NUMBER_INLINE(x));
45 // ECMA 262 - 15.8.2.5
46 // The naming of y and x matches the spec, as does the order in which
47 // ToNumber (valueOf) is called.
48 function MathAtan2(y, x) {
49 return %MathAtan2(TO_NUMBER_INLINE(y), TO_NUMBER_INLINE(x));
52 // ECMA 262 - 15.8.2.6
53 function MathCeil(x) {
54 return -MathFloor(-x);
57 // ECMA 262 - 15.8.2.7
59 x = MathAbs(x); // Convert to number and get rid of -0.
60 return TrigonometricInterpolation(x, 1);
63 // ECMA 262 - 15.8.2.8
65 return %MathExp(TO_NUMBER_INLINE(x));
68 // ECMA 262 - 15.8.2.9
69 function MathFloor(x) {
70 x = TO_NUMBER_INLINE(x);
71 // It's more common to call this with a positive number that's out
72 // of range than negative numbers; check the upper bound first.
73 if (x < 0x80000000 && x > 0) {
74 // Numbers in the range [0, 2^31) can be floored by converting
75 // them to an unsigned 32-bit value using the shift operator.
76 // We avoid doing so for -0, because the result of Math.floor(-0)
77 // has to be -0, which wouldn't be the case with the shift.
84 // ECMA 262 - 15.8.2.10
86 return %_MathLog(TO_NUMBER_INLINE(x));
89 // ECMA 262 - 15.8.2.11
90 function MathMax(arg1, arg2) { // length == 2
91 var length = %_ArgumentsLength();
93 arg1 = TO_NUMBER_INLINE(arg1);
94 arg2 = TO_NUMBER_INLINE(arg2);
95 if (arg2 > arg1) return arg2;
96 if (arg1 > arg2) return arg1;
98 // Make sure -0 is considered less than +0.
99 return (arg1 === 0 && %_IsMinusZero(arg1)) ? arg2 : arg1;
101 // All comparisons failed, one of the arguments must be NaN.
105 for (var i = 0; i < length; i++) {
106 var n = %_Arguments(i);
107 if (!IS_NUMBER(n)) n = NonNumberToNumber(n);
108 // Make sure +0 is considered greater than -0.
109 if (NUMBER_IS_NAN(n) || n > r || (r === 0 && n === 0 && %_IsMinusZero(r))) {
116 // ECMA 262 - 15.8.2.12
117 function MathMin(arg1, arg2) { // length == 2
118 var length = %_ArgumentsLength();
120 arg1 = TO_NUMBER_INLINE(arg1);
121 arg2 = TO_NUMBER_INLINE(arg2);
122 if (arg2 > arg1) return arg1;
123 if (arg1 > arg2) return arg2;
125 // Make sure -0 is considered less than +0.
126 return (arg1 === 0 && %_IsMinusZero(arg1)) ? arg1 : arg2;
128 // All comparisons failed, one of the arguments must be NaN.
132 for (var i = 0; i < length; i++) {
133 var n = %_Arguments(i);
134 if (!IS_NUMBER(n)) n = NonNumberToNumber(n);
135 // Make sure -0 is considered less than +0.
136 if (NUMBER_IS_NAN(n) || n < r || (r === 0 && n === 0 && %_IsMinusZero(n))) {
143 // ECMA 262 - 15.8.2.13
144 function MathPow(x, y) {
145 return %_MathPow(TO_NUMBER_INLINE(x), TO_NUMBER_INLINE(y));
148 // ECMA 262 - 15.8.2.14
149 var rngstate; // Initialized to a Uint32Array during genesis.
150 function MathRandom() {
151 var r0 = (MathImul(18273, rngstate[0] & 0xFFFF) + (rngstate[0] >>> 16)) | 0;
153 var r1 = (MathImul(36969, rngstate[1] & 0xFFFF) + (rngstate[1] >>> 16)) | 0;
155 var x = ((r0 << 16) + (r1 & 0xFFFF)) | 0;
156 // Division by 0x100000000 through multiplication by reciprocal.
157 return (x < 0 ? (x + 0x100000000) : x) * 2.3283064365386962890625e-10;
160 // ECMA 262 - 15.8.2.15
161 function MathRound(x) {
162 return %RoundNumber(TO_NUMBER_INLINE(x));
165 // ECMA 262 - 15.8.2.16
166 function MathSin(x) {
167 x = x * 1; // Convert to number and deal with -0.
168 if (%_IsMinusZero(x)) return x;
169 return TrigonometricInterpolation(x, 0);
172 // ECMA 262 - 15.8.2.17
173 function MathSqrt(x) {
174 return %_MathSqrt(TO_NUMBER_INLINE(x));
177 // ECMA 262 - 15.8.2.18
178 function MathTan(x) {
179 return MathSin(x) / MathCos(x);
182 // Non-standard extension.
183 function MathImul(x, y) {
184 return %NumberImul(TO_NUMBER_INLINE(x), TO_NUMBER_INLINE(y));
188 var kInversePiHalf = 0.636619772367581343; // 2 / pi
189 var kInversePiHalfS26 = 9.48637384723993156e-9; // 2 / pi / (2^26)
191 var kTwoStepThreshold = 1 << 27;
193 var kPiHalf = 1.570796326794896780; // 0x192d4454fb21f93f
194 // We use two parts for pi/2 to emulate a higher precision.
195 // pi_half_1 only has 26 significant bits for mantissa.
196 // Note that pi_half > pi_half_1 + pi_half_2
197 var kPiHalf1 = 1.570796325802803040; // 0x00000054fb21f93f
198 var kPiHalf2 = 9.920935796805404252e-10; // 0x3326a611460b113e
200 var kSamples; // Initialized to a number during genesis.
201 var kIndexConvert; // Initialized to kSamples / (pi/2) during genesis.
202 var kSinTable; // Initialized to a Float64Array during genesis.
203 var kCosXIntervalTable; // Initialized to a Float64Array during genesis.
205 // This implements sine using the following algorithm.
206 // 1) Multiplication takes care of to-number conversion.
207 // 2) Reduce x to the first quadrant [0, pi/2].
208 // Conveniently enough, in case of +/-Infinity, we get NaN.
209 // Note that we try to use only 26 instead of 52 significant bits for
210 // mantissa to avoid rounding errors when multiplying. For very large
211 // input we therefore have additional steps.
212 // 3) Replace x by (pi/2-x) if x was in the 2nd or 4th quadrant.
213 // 4) Do a table lookup for the closest samples to the left and right of x.
214 // 5) Find the derivatives at those sampling points by table lookup:
215 // dsin(x)/dx = cos(x) = sin(pi/2-x) for x in [0, pi/2].
216 // 6) Use cubic spline interpolation to approximate sin(x).
217 // 7) Negate the result if x was in the 3rd or 4th quadrant.
218 // 8) Get rid of -0 by adding 0.
219 function TrigonometricInterpolation(x, phase) {
220 if (x < 0 || x > kPiHalf) {
222 while (x < -kTwoStepThreshold || x > kTwoStepThreshold) {
223 // Let's assume this loop does not terminate.
224 // All numbers x in each loop forms a set S.
225 // (1) abs(x) > 2^27 for all x in S.
226 // (2) abs(multiple) != 0 since (2^27 * inverse_pi_half_s26) > 1
227 // (3) multiple is rounded down in 2^26 steps, so the rounding error is
228 // at most max(ulp, 2^26).
229 // (4) so for x > 2^27, we subtract at most (1+pi/4)x and at least
231 // (5) The subtraction results in x' so that abs(x') <= abs(x)*pi/4.
232 // Note that this difference cannot be simply rounded off.
233 // Set S cannot exist since (5) violates (1). Loop must terminate.
234 multiple = MathFloor(x * kInversePiHalfS26) * kS26;
235 x = x - multiple * kPiHalf1 - multiple * kPiHalf2;
237 multiple = MathFloor(x * kInversePiHalf);
238 x = x - multiple * kPiHalf1 - multiple * kPiHalf2;
241 var double_index = x * kIndexConvert;
242 if (phase & 1) double_index = kSamples - double_index;
243 var index = double_index | 0;
244 var t1 = double_index - index;
246 var y1 = kSinTable[index];
247 var y2 = kSinTable[index + 1];
249 return (t2 * y1 + t1 * y2 +
250 t1 * t2 * ((kCosXIntervalTable[index] - dy) * t2 +
251 (dy - kCosXIntervalTable[index + 1]) * t1))
252 * (1 - (phase & 2)) + 0;
255 // -------------------------------------------------------------------
257 function SetUpMath() {
258 %CheckIsBootstrapping();
260 %SetPrototype($Math, $Object.prototype);
261 %SetProperty(global, "Math", $Math, DONT_ENUM);
262 %FunctionSetInstanceClassName(MathConstructor, 'Math');
264 // Set up math constants.
265 InstallConstants($Math, $Array(
266 // ECMA-262, section 15.8.1.1.
267 "E", 2.7182818284590452354,
268 // ECMA-262, section 15.8.1.2.
269 "LN10", 2.302585092994046,
270 // ECMA-262, section 15.8.1.3.
271 "LN2", 0.6931471805599453,
272 // ECMA-262, section 15.8.1.4.
273 "LOG2E", 1.4426950408889634,
274 "LOG10E", 0.4342944819032518,
275 "PI", 3.1415926535897932,
276 "SQRT1_2", 0.7071067811865476,
277 "SQRT2", 1.4142135623730951
280 // Set up non-enumerable functions of the Math object and
282 InstallFunctions($Math, DONT_ENUM, $Array(
283 "random", MathRandom,
304 %SetInlineBuiltinFlag(MathCeil);
305 %SetInlineBuiltinFlag(MathRandom);
306 %SetInlineBuiltinFlag(MathSin);
307 %SetInlineBuiltinFlag(MathCos);
308 %SetInlineBuiltinFlag(MathTan);
309 %SetInlineBuiltinFlag(TrigonometricInterpolation);