perf: use FxHashSet for O(1) name lookups in declaration instantiation#5024
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tkshsbcue wants to merge 1 commit intoboa-dev:mainfrom
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perf: use FxHashSet for O(1) name lookups in declaration instantiation#5024tkshsbcue wants to merge 1 commit intoboa-dev:mainfrom
tkshsbcue wants to merge 1 commit intoboa-dev:mainfrom
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Replace Vec with FxHashSet for name-tracking collections in bytecode compiler declaration instantiation. 22 .contains() calls go from O(n) to O(1), eliminating O(n^2) behavior when compiling scripts with many declarations. Affected: global/eval/function declaration instantiation functions.
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@jedel1043 i think you might fight this interesting haha! |
Test262 conformance changes
Fixed tests (2):Broken tests (157):Tested main commit: |
Codecov Report❌ Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## main #5024 +/- ##
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+ Coverage 47.24% 58.74% +11.49%
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Files 476 559 +83
Lines 46892 61462 +14570
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+ Hits 22154 36105 +13951
- Misses 24738 25357 +619 ☔ View full report in Codecov by Sentry. 🚀 New features to boost your workflow:
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do you have benchmark results? 👀 |
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hey hi @zhuzhu81998 these are the benchmarks i compiled
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jedel1043
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A-Performance
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Need to fix formatting first |
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Description
This PR replaces
VecwithFxHashSetfor name-tracking collections in the bytecode compiler's declaration instantiation functions, reducing.contains()lookups from O(n) to O(1).The problem
During script/module/function compilation, the bytecode compiler tracks declared function names, variable names, and parameter bindings using
Vec<Sym>. These vectors are repeatedly checked with.contains()inside loops, creating O(n^2) behavior when a script has many declarations.There are 22
.contains()calls indeclarations.rs, many inside nested loops:The fix
Replace
Vec<Sym>withFxHashSet<Sym>for all name-tracking collections used only for membership checks. Where a collection is also iterated (e.g.,declared_var_namesfor emitting bindings), a parallelFxHashSetis maintained alongside theVec.FxHashSet(fromrustc_hash) is already used elsewhere in the codebase and provides faster hashing thanstd::collections::HashSetfor small integer keys likeSym.Affected functions
global_declaration_instantiation_contextdeclared_function_names,declared_var_namesprepare_eval_declaration_instantiationdeclared_function_names,lexically_declared_namesglobal_declaration_instantiationdeclared_function_names,declared_var_nameseval_declaration_instantiationdeclared_function_names,declared_var_namesfunction_declaration_instantiationfunction_names,parameter_bindings,instantiated_var_namesWhy this matters
Declaration instantiation runs on every script, eval, and function compilation. Real-world JavaScript bundles routinely have hundreds or thousands of declarations. The O(n^2) behavior is particularly visible when:
eval()with significant codeTest plan
cargo checkpassescargo clippy-- no warningscargo test -p boa_engine --lib-- all 958 tests pass