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Merged
merged 9 commits into from
Jun 13, 2020
Merged

modernize loader #1279

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0ff6d5c
modernize loader
MaxGraey May 16, 2020
2076a1e
revert some changes
MaxGraey May 16, 2020
32aec8b
fix
MaxGraey May 16, 2020
2ef43dd
refactor preInstantiate a little
MaxGraey May 17, 2020
9429298
more
MaxGraey May 17, 2020
bd8f35c
remove unnecessary parentesies
MaxGraey May 17, 2020
17a9101
replace str concat to interpolations
MaxGraey May 17, 2020
80d6f93
make validateArrayInfo helper
MaxGraey May 17, 2020
a7b1287
rename validateArrayInfo to getArrayInfo
MaxGraey Jun 2, 2020
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53 changes: 27 additions & 26 deletions lib/loader/index.js
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Original file line number Diff line number Diff line change
Expand Up @@ -44,17 +44,17 @@ const CHUNKSIZE = 1024;
function getStringImpl(buffer, ptr) {
const U32 = new Uint32Array(buffer);
const U16 = new Uint16Array(buffer);
let length = U32[(ptr + SIZE_OFFSET) >>> 2] >>> 1;
let length = U32[ptr + SIZE_OFFSET >>> 2] >>> 1;
let offset = ptr >>> 1;
if (length <= CHUNKSIZE) return String.fromCharCode.apply(String, U16.subarray(offset, offset + length));
const parts = [];
let parts = '';
do {
const last = U16[offset + CHUNKSIZE - 1];
const size = last >= 0xD800 && last < 0xDC00 ? CHUNKSIZE - 1 : CHUNKSIZE;
parts.push(String.fromCharCode.apply(String, U16.subarray(offset, offset += size)));
parts += String.fromCharCode.apply(String, U16.subarray(offset, offset += size));
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@dcodeIO dcodeIO May 16, 2020 •
edited
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Are you sure that this is always faster? Would imagine that it is for smaller strings, but once parts grows bigger, it might slow down substantially.

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On Chrome it should be definitely faster. See this tests:
https://twitter.com/MaxGraey/status/1232045301374111744
https://esbench.com/bench/5e540d53328a52009e8b1b22
It relate to string reversing but it also use same technique as string decoding

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You don't need to do String.fromCharCode.apply(String) could simply do something like

const fromCharCode = String.fromCharCode;

fromCharCode.apply(null, theArray);

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Does this affect performance?

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I don't think so

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@MaxGraey MaxGraey May 17, 2020 •
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@dcodeIO I made micro benchmark which more relate to this case:
https://gist.github.com/MaxGraey/6db5c6c6d7e4a0f45154b73a5e130976

and it seems string concat approach faster in 3 times

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While 4K+ is already a reasonably long string, an interesting measurement there would be how long a string has to be for both approaches to execute in an equal time span, if at all. That would help to inform if it is good enough in any case, or if we'd need another code path to deal with strings longer than X.

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Also, the test string is exclusively ASCII currently, so it might be that engines optimize this differently than strings that have at least one non-LATIN1 character. Both cases would be interesting.

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Based on my benchmarks inside Node, concat is faster than +:
https://github.com/aminya/typescript-optimization#string--vs-concat

length -= size;
} while (length > CHUNKSIZE);
return parts.join("") + String.fromCharCode.apply(String, U16.subarray(offset, offset + length));
return parts + String.fromCharCode.apply(String, U16.subarray(offset, offset + length));
}

/** Prepares the base module prior to instantiation. */
Expand All @@ -70,15 +70,13 @@ function preInstantiate(imports) {
const env = (imports.env = imports.env || {});
env.abort = env.abort || function abort(msg, file, line, colm) {
const memory = extendedExports.memory || env.memory; // prefer exported, otherwise try imported
throw Error("abort: " + getString(memory, msg) + " at " + getString(memory, file) + ":" + line + ":" + colm);
throw Error(`abort: ${getString(memory, msg)} at ${getString(memory, file)}:${line}:${colm}`);
};
env.trace = env.trace || function trace(msg, n) {
env.trace = env.trace || function trace(msg, n, ...args) {
const memory = extendedExports.memory || env.memory;
console.log("trace: " + getString(memory, msg) + (n ? " " : "") + Array.prototype.slice.call(arguments, 2, 2 + n).join(", "));
};
env.seed = env.seed || function seed() {
return Date.now();
console.log(`trace: ${getString(memory, msg)}${n ? " " : ""}${args.slice(0, n).join(", ")}`);
};
env.seed = env.seed || Date.now;
imports.Math = imports.Math || Math;
imports.Date = imports.Date || Date;

Expand All @@ -98,15 +96,22 @@ function postInstantiate(extendedExports, instance) {
function getInfo(id) {
const U32 = new Uint32Array(memory.buffer);
const count = U32[rttiBase >>> 2];
if ((id >>>= 0) >= count) throw Error("invalid id: " + id);
if ((id >>>= 0) >= count) throw Error(`invalid id: ${id}`);
return U32[(rttiBase + 4 >>> 2) + id * 2];
}

/** Gets and validate runtime type info for the given id for array like objects */
function getArrayInfo(id) {
const info = getInfo(id);
if (!(info & (ARRAYBUFFERVIEW | ARRAY | STATICARRAY))) throw Error(`not an array: ${id}, flags=${info}`);
return info;
}

/** Gets the runtime base id for the given id. */
function getBase(id) {
const U32 = new Uint32Array(memory.buffer);
const count = U32[rttiBase >>> 2];
if ((id >>>= 0) >= count) throw Error("invalid id: " + id);
if ((id >>>= 0) >= count) throw Error(`invalid id: ${id}`);
return U32[(rttiBase + 4 >>> 2) + id * 2 + 1];
}

Expand Down Expand Up @@ -135,7 +140,7 @@ function postInstantiate(extendedExports, instance) {
function __getString(ptr) {
const buffer = memory.buffer;
const id = new Uint32Array(buffer)[ptr + ID_OFFSET >>> 2];
if (id !== STRING_ID) throw Error("not a string: " + ptr);
if (id !== STRING_ID) throw Error(`not a string: ${ptr}`);
return getStringImpl(buffer, ptr);
}

Expand All @@ -157,13 +162,12 @@ function postInstantiate(extendedExports, instance) {
case 3: return new (signed ? BigInt64Array : BigUint64Array)(buffer);
}
}
throw Error("unsupported align: " + alignLog2);
throw Error(`unsupported align: ${alignLog2}`);
}

/** Allocates a new array in the module's memory and returns its retained pointer. */
function __allocArray(id, values) {
const info = getInfo(id);
if (!(info & (ARRAYBUFFERVIEW | ARRAY | STATICARRAY))) throw Error("not an array: " + id + ", flags= " + info);
const info = getArrayInfo(id);
const align = getValueAlign(info);
const length = values.length;
const buf = alloc(length << align, info & STATICARRAY ? id : ARRAYBUFFER_ID);
Expand Down Expand Up @@ -194,8 +198,7 @@ function postInstantiate(extendedExports, instance) {
function __getArrayView(arr) {
const U32 = new Uint32Array(memory.buffer);
const id = U32[arr + ID_OFFSET >>> 2];
const info = getInfo(id);
if (!(info & (ARRAYBUFFERVIEW | ARRAY | STATICARRAY))) throw Error("not an array: " + id + ", flags=" + info);
const info = getArrayInfo(id);
const align = getValueAlign(info);
let buf = info & STATICARRAY
? arr
Expand Down Expand Up @@ -244,8 +247,8 @@ function postInstantiate(extendedExports, instance) {

/** Attach a set of get TypedArray and View functions to the exports. */
function attachTypedArrayFunctions(ctor, name, align) {
extendedExports["__get" + name] = getTypedArray.bind(null, ctor, align);
extendedExports["__get" + name + "View"] = getTypedArrayView.bind(null, ctor, align);
extendedExports[`__get${name}`] = getTypedArray.bind(null, ctor, align);
extendedExports[`__get${name}View`] = getTypedArrayView.bind(null, ctor, align);
}

[
Expand All @@ -271,7 +274,7 @@ function postInstantiate(extendedExports, instance) {
/** Tests whether an object is an instance of the class represented by the specified base id. */
function __instanceof(ptr, baseId) {
const U32 = new Uint32Array(memory.buffer);
let id = U32[(ptr + ID_OFFSET) >>> 2];
let id = U32[ptr + ID_OFFSET >>> 2];
if (id <= U32[rttiBase >>> 2]) {
do if (id == baseId) return true;
while (id = getBase(id));
Expand Down Expand Up @@ -364,9 +367,7 @@ function demangle(exports, extendedExports = {}) {
return ctor.wrap(ctor.prototype.constructor(0, ...args));
};
ctor.prototype = {
valueOf: function valueOf() {
return this[THIS];
}
valueOf() { return this[THIS]; }
};
ctor.wrap = function(thisValue) {
return Object.create(ctor.prototype, { [THIS]: { value: thisValue, writable: false } });
Expand All @@ -383,8 +384,8 @@ function demangle(exports, extendedExports = {}) {
let getter = exports[internalName.replace("set:", "get:")];
let setter = exports[internalName.replace("get:", "set:")];
Object.defineProperty(curr, name, {
get: function() { return getter(this[THIS]); },
set: function(value) { setter(this[THIS], value); },
get() { return getter(this[THIS]); },
set(value) { setter(this[THIS], value); },
enumerable: true
});
}
Expand Down