Add unboxed slot-number lane to equality operators#2602
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===, !==, == and != now take the same per-node numeric lane the relational operators gained in sebastienros#2574/sebastienros#2578: when both operands resolve to slot-stored numbers (or a numeric constant), the comparison runs on raw doubles without materializing either side. Both operands are runtime-proven Numbers, so the IEEE compare is spec-exact for all four operators (IsLooselyEqual defers to IsStrictlyEqual for same-type operands; NaN == NaN is false, +0 == -0 is true); any non-number operand declines to the generic coercing path before any side effect. The dominant win is allocation: a loop test like `i === 50000` was re-boxing the counter into a JsNumber on every iteration once it exceeded the small-int cache. LoopDispatchBenchmarks A/B (default job, adjacent runs): | row | base | lanes | |-----------------|---------------------|---------------------| | StrictEqualTest | 5.967 ms / 2,808 KB | 3.710 ms / 3.26 KB | | LooseEqualTest | 5.523 ms / 2,808 KB | 3.777 ms / 3.27 KB | -38% / -32% time, -99.9% allocation (Gen0 eliminated). Untouched rows byte-identical alloc; time deltas were sign-mixed and traced to window drift via an A/B/A re-run on identical bits. New LoopDispatch rows (StrictEqualTest/LooseEqualTest/ModuloEqualTest) pin the shapes; ModuloEqualTest (the stopwatch.js if-chain shape) is deliberately not covered yet - its left side is a modulo expression, not an identifier. EqualityLaneTests pin NaN/signed-zero semantics, mid-loop type-change decline, BigInt/mixed-type bail and value positions. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
lahma
enabled auto-merge (squash)
July 9, 2026 05:55
This was referenced Jul 13, 2026
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What
===,!==,==and!=now take the same per-node unboxed numeric lane the relational operatorsgained in #2574/#2578: when both operands resolve to slot-stored numbers (or a numeric constant), the
comparison runs on raw doubles without materializing either side.
Why
A loop test like
i === 50000re-boxed the counter into aJsNumberon every iteration once itexceeded the small-int cache — the equality operators were the only comparison family without the lane.
Semantics
Both operands are runtime-proven Numbers (
TryGetNumberSlotonly succeeds for number-holdingbindings), so the IEEE compare is spec-exact for all four operators:
IsLooselyEqualdefers toIsStrictlyEqualfor same-type operands,NaN == NaNis false,+0 == -0is true. BigInt isexcluded by the JsNumber gates; any non-number operand declines to the generic coercing path before
any side effect.
Results
LoopDispatchBenchmarks A/B (default job, adjacent runs; new rows added by this PR):
Gen0 eliminated on both rows; untouched rows byte-identical allocation, time deltas sign-mixed and
resolved as window drift via an A/B/A on identical bits.
ModuloEqualTest(the stopwatch.js if-chain shape) is added as a baseline row but deliberately notcovered here — its left side is a modulo expression, not an identifier (see the follow-up PR).
Tests
EqualityLaneTestspin NaN/signed-zero semantics, mid-loop type-change decline, BigInt/mixed-typebail, and value positions.
Gating
All-TFM build ✅ · Jint.Tests net10+net472 ✅ · PublicInterface ×2 ✅ · Test262 99,260/0 ✅
🤖 Generated with Claude Code