mirror of
https://github.com/vercel-labs/scriptc.git
synced 2026-10-26 06:34:20 +08:00
Chris Tate
2bb7e7ec7a
An array's length is at most 2^32 - 1 (the runtime's SCR_ARR_MAX_LENGTH). On 64-bit targets the length loads now carry that range (`!range`), so LLVM folds a length converted to double and back to an integer, and simplifies the comparisons that use it. A length stored into an int32 local or used as an index no longer goes through double: tsc-ts has 18% fewer int/double conversion instructions.
56 lines
2.0 KiB
TypeScript
56 lines
2.0 KiB
TypeScript
import { mkdtemp, readFile, rm, writeFile } from "node:fs/promises";
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import { tmpdir } from "node:os";
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import { join } from "node:path";
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import { expect, test } from "vitest";
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import { compile } from "../src/index.js";
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async function emit(source: string, outputKind: "llvm" | "asm"): Promise<string> {
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const dir = await mkdtemp(join(tmpdir(), "scriptc-array-length-range-"));
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try {
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const entry = join(dir, "main.ts");
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const outPath = join(dir, outputKind === "llvm" ? "main.ll" : "main.s");
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await writeFile(entry, source);
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const result = await compile(entry, { outDir: dir, outPath, outputKind });
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expect(result.ok, JSON.stringify(result.diagnostics)).toBe(true);
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return await readFile(outPath, "utf8");
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} finally {
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await rm(dir, { recursive: true, force: true });
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}
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}
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const source = `
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class Signature {
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parameters: string[];
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rest: boolean;
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constructor(parameters: string[], rest: boolean) {
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this.parameters = parameters;
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this.rest = rest;
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}
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}
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function count(signature: Signature): number {
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const length = signature.parameters.length;
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if (signature.rest) return length + signature.parameters[length - 1]!.length;
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return length;
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}
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const signature = new Signature(["a", "bb"], process.argv.length > 1);
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console.log(count(signature), count(new Signature(["x"], false)));
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`;
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test.runIf(process.arch === "x64" || process.arch === "arm64")(
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"array length loads carry the range of a JS array length",
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async () => {
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const llvm = await emit(source, "llvm");
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const body = /^define internal double @sc_bf_count\([^]*?^}/m.exec(llvm)?.[0] ?? "";
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expect(body).toMatch(/= load i64, ptr %\S+(, !tbaa !\d+)?, !range !\{i64 0, i64 4294967296\}/);
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},
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);
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test.runIf(process.arch === "x64")(
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"a length used as an index is not converted to double and back",
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async () => {
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const asm = await emit(source, "asm");
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const body = /^sc_bf_count:[^]*?\.cfi_endproc/m.exec(asm)?.[0] ?? "";
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expect(body).not.toMatch(/cvtsi2sd|cvttsd2si/);
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},
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);
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