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add Math.signbit #333

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merged 5 commits into from
Nov 18, 2018
Merged

add Math.signbit #333

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d9cba69
add Math.signbit
MaxGraey Nov 13, 2018
5913f9a
minor improvment
MaxGraey Nov 13, 2018
b16b3be
improve portable code
MaxGraey Nov 17, 2018
081d090
handle negative NaNs
MaxGraey Nov 17, 2018
e05a509
simplify
MaxGraey Nov 17, 2018
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2 changes: 2 additions & 0 deletions std/assembly/index.d.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -736,6 +736,8 @@ interface IMath<T> {
round(x: T): T;
/** Returns the sign of `x`, indicating whether the number is positive, negative or zero. */
sign(x: T): T;
/** Returns whether the sign bit of `x` is set */
signbit(x: T): bool;
/** Returns the sine of `x`. */
sin(x: T): T;
/** Returns the hyperbolic sine of `x`. */
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12 changes: 12 additions & 0 deletions std/assembly/math.ts
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Expand Up @@ -992,6 +992,13 @@ export namespace NativeMath {
}
}

@inline
export function signbit(x: f64): bool {
// In ECMAScript all NaN values are indistinguishable from each other
// so we need handle NaN and negative NaN in similar way
return <bool>(<i32>(reinterpret<u64>(x) >>> 63 != 0) & <i32>(x == x));
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Similar to the f32 version, the != 0 instruction can be saved here as well.

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@MaxGraey MaxGraey Nov 17, 2018 •
edited
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I'm not sure. Because without != 0 u64 will be cast (extend op code) to i32 anyway

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Oh, actually != 0 doesn't matter because it has to convert from 64 to 32 bits anyway.

}

export function sin(x: f64): f64 { // TODO
unreachable();
return 0;
Expand Down Expand Up @@ -2046,6 +2053,11 @@ export namespace NativeMathf {
}
}

@inline
export function signbit(x: f32): bool {
return <bool>((reinterpret<u32>(x) >>> 31) & <i32>(x == x));
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This looks like it might result in an unnecessary & 1 to convert from i32 to bool. A better way to write it is: <bool>(reinterpret<u32>(x) >>> 31) & (x == x), as it keeps type conversions to a minimum.

}

export function sin(x: f32): f32 { // TODO
unreachable();
return 0;
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1 change: 1 addition & 0 deletions std/portable/index.d.ts
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Expand Up @@ -517,6 +517,7 @@ interface IMath {
random(): f64;
round(x: f64): f64;
sign(x: f64): f64;
signbit(x: f64): bool;
sin(x: f64): f64;
sinh(x: f64): f64;
sqrt(x: f64): f64;
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8 changes: 7 additions & 1 deletion std/portable/index.js
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Expand Up @@ -4,6 +4,9 @@ var globalScope = typeof window !== "undefined" && window || typeof global !== "

globalScope.ASC_TARGET = 0;

var F64 = new Float64Array(1);
var U64 = new Uint32Array(F64.buffer);

Object.defineProperties(
globalScope["i8"] = function i8(value) { return value << 24 >> 24; }
, {
Expand Down Expand Up @@ -210,7 +213,7 @@ globalScope["isString"] = function isString(arg) {

globalScope["isArray"] = Array.isArray;

globalScope["unchecked"] = function(expr) {
globalScope["unchecked"] = function unchecked(expr) {
return expr;
};

Expand All @@ -223,6 +226,9 @@ globalScope["fmodf"] = function fmodf(x, y) {
};

globalScope["JSMath"] = Math;
globalScope["JSMath"].signbit = function signbit(x) {
F64[0] = x; return Boolean((U64[1] >>> 31) & (x == x));
}

globalScope["memory"] = (() => {
var HEAP = new Uint8Array(0);
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