fix(code-splitting): make strict transitive init registration deterministic and constant-time#10320
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…nistic and constant-time (#10320) ## Summary Two independent, cheap fixes to the strict-execution-order cross-chunk link pass (review items 3 and 4): - **Cross-target determinism.** `add_transitive_esm_init_depended_symbols` iterated an `FxHashMap` via `.values()`, whose bucket order follows FxHash layout. FxHash is unseeded but hashes differently on 32-bit vs 64-bit, so that order — which flows into the chunk's `depended_symbols` `FxIndexSet` and thence into imported-symbol rename order (the `$1`/`$2` suffixes) in `deconflict_chunk_symbols` — could diverge between native and wasm32/WASI builds. Now iterated sorted by the owning `StmtInfoIdx`, pinning one order everywhere. It is the single hash-ordered site three review passes converged on; every other hash-ordered effect is already sorted before use. - **Quadratic strict-mode hot loop.** `module_is_in_live_chunk` did a linear `chunk.modules.contains` scan, called for every canonical referenced symbol of every included statement under strict — quadratic on large chunks. Replaced with an O(1) `module_to_chunk` + liveness check. The O(1) rewrite is verified semantically equivalent: `add_module_to_chunk` sets `module_to_chunk[m]` and pushes `m` onto `c.modules` together, and every site that later removes a module from a chunk's `modules` list preserves the invariant (`module_to_chunk[m] == Some(c) && c live ⟹ c.modules ∋ m`) by pairing the removal with clearing `module_to_chunk[m]` (unused-runtime sweep), reassigning it to the destination chunk via `add_module_to_chunk` (runtime relocation, runtime→target merge, `apply_common_chunk_merges`), or marking the emptied chunk `Removed`. No site leaves `module_to_chunk` pointed at a still-live chunk that no longer contains the module, so no removed-module set is needed. The invariant is documented in the function's doc comment. ## Behavior / snapshot impact **None.** Zero fixture snapshot changes. The determinism fix is invisible on native 64-bit (its value is native-vs-wasm parity, which the native suite cannot exercise); the O(1) change is a pure performance rewrite with identical results. ## Validation - `cargo test -p rolldown` — 1868 passed; snapshot-stable (zero deltas). The only failures are 5 pre-existing environmental ones unrelated to this change (`cjs_module_lexer_compat` ×3 and `npm_packages/util_deprecate` need an installed `cjs-module-lexer`; `test262` needs the test262 submodule). - `cargo fmt --all --check` — clean. - `cargo clippy -p rolldown --all-targets -- -D warnings` — clean. --- Follow-up to #10104; addresses the two "cheap pre-merge fixes" (items 3 and 4) from the review discussion: #10104 (comment)
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Summary
Two independent, cheap fixes to the strict-execution-order cross-chunk link pass (review items 3 and 4):
add_transitive_esm_init_depended_symbolsiterated anFxHashMapvia.values(), whose bucket order follows FxHash layout. FxHash is unseeded but hashes differently on 32-bit vs 64-bit, so that order — which flows into the chunk'sdepended_symbolsFxIndexSetand thence into imported-symbol rename order (the$1/$2suffixes) indeconflict_chunk_symbols— could diverge between native and wasm32/WASI builds. Now iterated sorted by the owningStmtInfoIdx, pinning one order everywhere. It is the single hash-ordered site three review passes converged on; every other hash-ordered effect is already sorted before use.module_is_in_live_chunkdid a linearchunk.modules.containsscan, called for every canonical referenced symbol of every included statement under strict — quadratic on large chunks. Replaced with an O(1)module_to_chunk+ liveness check.The O(1) rewrite is verified semantically equivalent:
add_module_to_chunksetsmodule_to_chunk[m]and pushesmontoc.modulestogether, and every site that later removes a module from a chunk'smoduleslist preserves the invariant (module_to_chunk[m] == Some(c) && c live ⟹ c.modules ∋ m) by pairing the removal with clearingmodule_to_chunk[m](unused-runtime sweep), reassigning it to the destination chunk viaadd_module_to_chunk(runtime relocation, runtime→target merge,apply_common_chunk_merges), or marking the emptied chunkRemoved. No site leavesmodule_to_chunkpointed at a still-live chunk that no longer contains the module, so no removed-module set is needed. The invariant is documented in the function's doc comment.Behavior / snapshot impact
None. Zero fixture snapshot changes. The determinism fix is invisible on native 64-bit (its value is native-vs-wasm parity, which the native suite cannot exercise); the O(1) change is a pure performance rewrite with identical results.
Validation
cargo test -p rolldown— 1868 passed; snapshot-stable (zero deltas). The only failures are 5 pre-existing environmental ones unrelated to this change (cjs_module_lexer_compat×3 andnpm_packages/util_deprecateneed an installedcjs-module-lexer;test262needs the test262 submodule).cargo fmt --all --check— clean.cargo clippy -p rolldown --all-targets -- -D warnings— clean.Follow-up to #10104; addresses the two "cheap pre-merge fixes" (items 3 and 4) from the review discussion: #10104 (comment)