mirror of
https://github.com/vercel-labs/scriptc.git
synced 2026-11-08 08:44:37 +08:00
Chris Tate
2cbce33cd3
An instance of a compiled class reaches untyped code as a capsule, which a property site sent to its helper on every read: the helper normalizes the capsule, tests each class's key in turn, and loads the field. A read site now emits the helper's plain field branches inline. A capsule whose key pointer is one of those classes' keys loads the field from its instance and shares the inline hits' conversion. A branch is emitted only when its field holds a plain dyn cell and every subclass the helper's normalization can rebox the key to reads the same field from the same slot. Getters, bag properties, unset fields and other capsules keep the helper.
63 lines
1.6 KiB
JavaScript
63 lines
1.6 KiB
JavaScript
// Untyped reads and writes of class instances at property sites: base and
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// subclass instances, subclass instances returned where the base class is
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// the inferred type, a subclass that redeclares an inherited field, a
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// getter, fields set after construction and fields never set.
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class Point {
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constructor(x, y) {
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this.x = x;
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this.y = y;
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}
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}
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class Tagged extends Point {
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constructor(x, y, tag) {
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super(x, y);
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this.tag = tag;
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}
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}
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class Shifted extends Point {
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label = "s";
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x = 100;
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}
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class Gauge {
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get x() {
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return 9;
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}
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}
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class Late {
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constructor(set) {
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if (set) this.x = "late";
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}
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}
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function make(i) {
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if (i % 3 === 0) return new Point(i, -i);
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if (i % 3 === 1) return new Tagged(i, i * 2, "t" + i);
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return new Shifted(i, 0);
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}
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function readX(o) {
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return o.x;
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}
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function readY(o) {
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return o.y;
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}
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function writeX(o, v) {
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o.x = v;
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}
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const values = [];
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for (let i = 0; i < 9; i++) values.push(make(i));
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values.push(new Gauge(), new Late(true), new Late(false), { x: "plain", y: 1 }, { y: 2, x: "swapped" });
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let sum = 0;
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for (let round = 0; round < 3; round++) {
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for (const v of values) {
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const x = readX(v);
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sum += typeof x === "number" ? x : x === undefined ? 1000 : x.length;
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const y = readY(v);
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if (typeof y === "number") sum += y;
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}
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for (let i = 0; i < 9; i++) writeX(values[i], round * 10 + i);
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}
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console.log(sum);
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console.log(values.map((v) => String(readX(v))).join(" "));
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console.log(values.map((v) => String(readY(v))).join(" "));
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writeX(values[1], "changed");
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console.log(readX(values[1]), readX(values[2]), values[2].label, values[1].tag);
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