bench: stabilize prefix-source getPrefix() and original() cases

claude · claude · commit 939f57950254 · 2026-04-22T17:00:54.000Z
Both accessors are one-line property reads. At 500 iterations the
work completes in microseconds, putting the measurement at the
timer-resolution / JIT-tier-up noise floor; with no use of the
return value the optimizer is also free to strength-reduce the
loop. Raise the inner iteration count to 50,000 and consume the
return value into a sink so V8 cannot elide the load. RME drops
from unstable to ~1.2%.
diff --git a/benchmark/cases/prefix-source/index.bench.mjs b/benchmark/cases/prefix-source/index.bench.mjs
@@ -29,15 +29,19 @@ export default function register(bench) {
 
 	bench.add("prefix-source: getPrefix()", () => {
 		const ps = new sources.PrefixSource("\t", fixtureCode);
-		for (let i = 0; i < 500; i++) ps.getPrefix();
+		let sink = 0;
+		for (let i = 0; i < 50_000; i++) sink ^= ps.getPrefix().length;
+		if (sink === -1) throw new Error("unreachable");
 	});
 
 	bench.add("prefix-source: original()", () => {
 		const ps = new sources.PrefixSource(
 			"\t",
 			new sources.RawSource(fixtureCode),
 		);
-		for (let i = 0; i < 500; i++) ps.original();
+		let sink = 0;
+		for (let i = 0; i < 50_000; i++) sink ^= ps.original() === ps ? 1 : 0;
+		if (sink === -1) throw new Error("unreachable");
 	});
 
 	bench.add("prefix-source: source() (RawSource child)", () => {
