1 // Copyright 2014 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. 4 5 // Flags: --harmony-maths 6 7 // Monkey-patch Float32Array. 8 Float32Array = function(x) { this[0] = 0; }; 9 10 assertTrue(isNaN(Math.fround(NaN))); 11 assertTrue(isNaN(Math.fround(function() {}))); 12 assertTrue(isNaN(Math.fround({ toString: function() { return NaN; } }))); 13 assertTrue(isNaN(Math.fround({ valueOf: function() { return "abc"; } }))); 14 assertEquals("Infinity", String(1/Math.fround(0))); 15 assertEquals("-Infinity", String(1/Math.fround(-0))); 16 assertEquals("Infinity", String(Math.fround(Infinity))); 17 assertEquals("-Infinity", String(Math.fround(-Infinity))); 18 19 assertEquals("Infinity", String(Math.fround(1E200))); 20 assertEquals("-Infinity", String(Math.fround(-1E200))); 21 assertEquals("Infinity", String(1/Math.fround(1E-300))); 22 assertEquals("-Infinity", String(1/Math.fround(-1E-300))); 23 24 mantissa_23_shift = Math.pow(2, -23); 25 mantissa_29_shift = Math.pow(2, -23-29); 26 27 // Javascript implementation of IEEE 754 to test double to single conversion. 28 function ieee754float(sign_bit, 29 exponent_bits, 30 mantissa_23_bits, 31 mantissa_29_bits) { 32 this.sign_bit = sign_bit & 1; 33 this.exponent_bits = exponent_bits & ((1 << 11) - 1); 34 this.mantissa_23_bits = mantissa_23_bits & ((1 << 23) - 1); 35 this.mantissa_29_bits = mantissa_29_bits & ((1 << 29) - 1); 36 } 37 38 ieee754float.prototype.returnSpecial = function() { 39 if (mantissa_23_bits == 0 && mantissa_29_bits == 0) return sign * Infinity; 40 return NaN; 41 } 42 43 ieee754float.prototype.toDouble = function() { 44 var sign = this.sign_bit ? -1 : 1; 45 var exponent = this.exponent_bits - 1023; 46 if (exponent == -1023) returnSpecial(); 47 var mantissa = 1 + this.mantissa_23_bits * mantissa_23_shift + 48 this.mantissa_29_bits * mantissa_29_shift; 49 return sign * Math.pow(2, exponent) * mantissa; 50 } 51 52 ieee754float.prototype.toSingle = function() { 53 var sign = this.sign_bit ? -1 : 1; 54 var exponent = this.exponent_bits - 1023; 55 if (exponent == -1023) returnSpecial(); 56 if (exponent > 127) return sign * Infinity; 57 if (exponent < -126) return this.toSingleSubnormal(sign, exponent); 58 var round = this.mantissa_29_bits >> 28; 59 var mantissa = 1 + (this.mantissa_23_bits + round) * mantissa_23_shift; 60 return sign * Math.pow(2, exponent) * mantissa; 61 } 62 63 ieee754float.prototype.toSingleSubnormal = function(sign, exponent) { 64 var shift = -126 - exponent; 65 if (shift > 24) return sign * 0; 66 var round_mask = 1 << (shift - 1); 67 var mantissa_23_bits = this.mantissa_23_bits + (1 << 23); 68 var round = ((mantissa_23_bits & round_mask) != 0) | 0; 69 if (round) { // Round to even if tied. 70 var tied_mask = round_mask - 1; 71 var result_last_bit_mask = 1 << shift; 72 var tied = this.mantissa_29_bits == 0 && 73 (mantissa_23_bits & tied_mask ) == 0; 74 var result_already_even = (mantissa_23_bits & result_last_bit_mask) == 0; 75 if (tied && result_already_even) round = 0; 76 } 77 mantissa_23_bits >>= shift; 78 var mantissa = (mantissa_23_bits + round) * mantissa_23_shift; 79 return sign * Math.pow(2, -126) * mantissa; 80 } 81 82 83 var pi = new ieee754float(0, 0x400, 0x490fda, 0x14442d18); 84 assertEquals(pi.toSingle(), Math.fround(pi.toDouble())); 85 86 function fuzz_mantissa(sign, exp, m1inc, m2inc) { 87 for (var m1 = 0; m1 < (1 << 23); m1 += m1inc) { 88 for (var m2 = 0; m2 < (1 << 29); m2 += m2inc) { 89 var float = new ieee754float(sign, exp, m1, m2); 90 assertEquals(float.toSingle(), Math.fround(float.toDouble())); 91 } 92 } 93 } 94 95 for (var sign = 0; sign < 2; sign++) { 96 for (var exp = 1024 - 170; exp < 1024 + 170; exp++) { 97 fuzz_mantissa(sign, exp, 1337 * exp - sign, 127913 * exp - sign); 98 } 99 } 100
