[compiler] Represent array accesses with PropertyLoad #32287
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LoweredFunction dependencies were exclusively used for dependency extraction (in `propagateScopeDeps`). Now that we have a `propagateScopeDepsHIR` that recursively traverses into nested functions, we can delete `dependencies` and their associated synthetic `LoadLocal`/`PropertyLoad` instructions.
This removes special casing for `PropertyStore` mutability inference within FunctionExpressions.
(needs cleanup) - Scopes no longer store a flat list of their dependencies. Instead: - Scope terminals are effectively a `goto` for scope dependency instructions (represented as value blocks that terminate with a `goto scopeBlock` for HIR and a series of ReactiveInstructions for ReactiveIR) - Scopes themselves store `dependencies: Array<Place>`, which refer to temporaries written to by scope dependency instructions Next steps: - new pass to dedupe scope dependency instructions after all dependency and scope pruning passes, effectively 'hoisting' dependencies out - more complex dependencies (unary ops like `Boolean` or `Not`, binary ops like `!==` or logical operators)
(draft, needs cleanup) Prior to this PR, our HIR represented property access with numeric literals (e.g. `myVar[0]`) as ComputedLoads. This means that they were subject to some deopts (most notably, not being easily dedupable / hoistable as dependencies). Now, `PropertyLoad`, `PropertyStore`, etc reference numeric and string literals (although not yet string literals that aren't valid babel identifiers). The difference between PropertyLoad and ComputedLoad is fuzzy now (maybe we should rename these). - PropertyLoad: property keys are string and numeric literals, only when the string literals are valid babel identifiers - ComputedLoad: non-valid babel identifier string literals (rare) and other non-literal expressions The biggest feature from this PR is that it trivially enables array-indicing expressions as dependencies. The compiler can also specify global and imported types for arrays (e.g. return value of `useState`) I'm happy to close this if it complicates more than it helps -- alternative options are to entirely rely on instruction reordering-based approaches like ReactiveGraphIR or make dependency-specific parsing + hoisting logic more robust.
This was referenced Feb 1, 2025
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Didn’t look at the code yet but the idea makes totally sense. PropertyLoad for cases of a static property, ComputedLoad for where the index is dynamic. We might want to rename them in a follow up. |
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(draft, needs cleanup)
Prior to this PR, our HIR represented property access with numeric literals (e.g.
myVar[0]) as ComputedLoads. This means that they were subject to some deopts (most notably, not being easily dedupable / hoistable as dependencies).Now,
PropertyLoad,PropertyStore, etc reference numeric and string literals (although not yet string literals that aren't valid babel identifiers). The difference between PropertyLoad and ComputedLoad is fuzzy now (maybe we should rename these).The biggest feature from this PR is that it trivially enables array-indicing expressions as dependencies. The compiler can also specify global and imported types for arrays (e.g. return value of
useState)I'm happy to close this if it complicates more than it helps -- alternative options are to entirely rely on instruction reordering-based approaches like ReactiveGraphIR or make dependency-specific parsing + hoisting logic more robust.
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