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RELEASE.md

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RELEASE.md

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Release Notes

v0.2.0

Performance

Benchmark: time bin/es typescript-test.js (TypeScript compiler self-host, ~1.2MB source)

  • v0.1.x: ~12.5s
  • v0.2.0: ~9.1s
  • Improvement: ~27%

Optimizations

Handle System

  • HandleScope::Add fast path: Added static slots for fixed stack-type singletons (Undefined, Null, Bool), avoiding BlockStack overhead for the most common values.
  • HandleScope constant dedup: Replaced linear scan with open-addressing hash table (ConstantHandleMap) for CONST handle deduplication.
  • BlockStack::Rewind fast path: Same-block rewind now directly resets the cursor pointer without touching the vector.

Property Access

  • PropertyMap::GetDataValue: New method that returns raw JSValue* directly from hash probe, skipping StackPropertyDescriptor construction for data-only lookups.
  • Get__Base raw pointer prototype chain walk: Rewrote the core property lookup ([[Get]]) to traverse the prototype chain using raw JSObject* pointers instead of Handle<JSObject>, eliminating Handle creation per prototype level.
  • GetProperty raw pointer walk: Similarly converted [[GetProperty]] to use raw pointers for prototype chain traversal.
  • PropertyMap::hashmap_raw(): Added raw accessor returning HashMapV2* directly, bypassing Handle creation in hot lookup paths.
  • JSObject::Prototype_raw(): Added raw accessor returning JSValue* for prototype, used in raw pointer chain walks.

Hash Map

  • HashMapV2::Probe pointer-first comparison: Probe now checks pointer equality (e.key == key) before falling back to hash + content comparison, exploiting the common case where the same String* object is reused.
  • HashEqualStringEqual simplification: Removed redundant size check when hashes already match (hash encodes size for JS_STRING type).

Scope Chain

  • EnvironmentRecord::outer_raw(): Added raw accessor for scope chain traversal without Handle creation.
  • GetIdentifierReferenceAndGetValue / PutValue: Rewrote scope chain walk using EnvironmentRecord* raw pointer loop. For declarative environments, directly probes bindings and inlines GetBindingValue / SetMutableBinding, avoiding Handle creation entirely on the common path.
  • GetIdentifierReference: Converted from recursive to iterative with raw pointers.

GC / ExtracGC

  • FunctionDeclarativeEnvironmentRecord bug fix: Fixed uninitialized id member (constructor parameter was shadowing the field). Also fixed operator[] to use the correct static env_recs array with kMaxNumPushed * id offset.
  • ExtracGC cached lookup: Cache FunctionDeclarativeEnvironmentRecord* pointer on AST node (ProgramOrFunctionBody::cached_env_rec_), eliminating std::unordered_map::find() on every function call/return. Profile confirmed __hash_table::find dropped from 1.1% to 0%.

Expression Evaluation

  • EvalExpressionAndGetValue switch dispatch: Directly dispatches common expression types (identifiers, literals, binary, unary, ternary) to their evaluators without going through EvalExpression + GetValue, saving one level of indirection.
  • GetValue fast path: Reordered checks to test IsObject first with likely() hint, as object property references dominate.
  • Completion factory methods: Completion::Normal(), Completion::Throw(), Completion::Return() avoid redundant field initialization.

Runtime

  • Context stack reserve: Pre-allocate context stack capacity to reduce reallocation.
  • Error::InitOk / AddContext: Streamlined error initialization and context setup paths.
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