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[compiler][ez] Clean up duplicate code in propagateScopeDeps #31581

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Dec 16, 2024
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[compiler][ez] Clean up duplicate code in propagateScopeDeps #31581

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82 changes: 58 additions & 24 deletions compiler/packages/babel-plugin-react-compiler/src/HIR/PropagateScopeDependenciesHIR.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -358,6 +358,7 @@ class Context {

#temporaries: ReadonlyMap<IdentifierId, ReactiveScopeDependency>;
#temporariesUsedOutsideScope: ReadonlySet<DeclarationId>;
#processedInstrsInOptional: ReadonlySet<Instruction | Terminal>;

/**
* Tracks the traversal state. See Context.declare for explanation of why this
Expand All @@ -368,9 +369,11 @@ class Context {
constructor(
temporariesUsedOutsideScope: ReadonlySet<DeclarationId>,
temporaries: ReadonlyMap<IdentifierId, ReactiveScopeDependency>,
processedInstrsInOptional: ReadonlySet<Instruction | Terminal>,
) {
this.#temporariesUsedOutsideScope = temporariesUsedOutsideScope;
this.#temporaries = temporaries;
this.#processedInstrsInOptional = processedInstrsInOptional;
}

enterScope(scope: ReactiveScope): void {
Expand Down Expand Up @@ -574,22 +577,49 @@ class Context {
currentScope.reassignments.add(place.identifier);
}
}
enterInnerFn<T>(cb: () => T): T {
const wasInInnerFn = this.inInnerFn;
this.inInnerFn = true;
const result = cb();
this.inInnerFn = wasInInnerFn;
return result;
}

/**
* Skip dependencies that are subexpressions of other dependencies. e.g. if a
* dependency is tracked in the temporaries sidemap, it can be added at
* site-of-use
*/
isDeferredDependency(
instr:
| {kind: HIRValue.Instruction; value: Instruction}
| {kind: HIRValue.Terminal; value: Terminal},
): boolean {
return (
this.#processedInstrsInOptional.has(instr.value) ||
(instr.kind === HIRValue.Instruction &&
this.#temporaries.has(instr.value.lvalue.identifier.id))
);
}
}
enum HIRValue {
Instruction = 1,
Terminal,
}

function handleInstruction(instr: Instruction, context: Context): void {
const {id, value, lvalue} = instr;
if (value.kind === 'LoadLocal') {
if (
value.place.identifier.name === null ||
lvalue.identifier.name !== null ||
context.isUsedOutsideDeclaringScope(lvalue)
) {
context.visitOperand(value.place);
}
} else if (value.kind === 'PropertyLoad') {
if (context.isUsedOutsideDeclaringScope(lvalue)) {
context.visitProperty(value.object, value.property, false);
}
context.declare(lvalue.identifier, {
id,
scope: context.currentScope,
});
if (
context.isDeferredDependency({kind: HIRValue.Instruction, value: instr})
) {
return;
}
if (value.kind === 'PropertyLoad') {
context.visitProperty(value.object, value.property, false);
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Doesn't seem to be a equivalent to the context.isUsedOutsideDeclaringScope(lvalue) check in the new version, is that a semantic change?

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Ahh that's because we already check context.isUsedOutsideDeclaringScope when building the temporaries sidemap. It's a bit awkward, but we need this information when constructing the temporaries sidemap because:

  • context.isUsedOutsideDeclaringScope represents a reordering barrier
  • the whole point of the temporaries sidemap is to represent reorderable / semantically equivalent expressions
  • it's difficult to defer finding reordering barriers because they may affect multiple temporaries entries i.e. PropertyLoads from non-reorderable values

I originally duplicated this code to decouple temporary sidemap construction from dependency collection. But.. I think that made maintaining this code much more difficult. @mvitousek I'd love feedback on how to make this cleaner!

} else if (value.kind === 'StoreLocal') {
context.visitOperand(value.value);
if (value.lvalue.kind === InstructionKind.Reassign) {
Expand Down Expand Up @@ -632,11 +662,6 @@ function handleInstruction(instr: Instruction, context: Context): void {
context.visitOperand(operand);
}
}

context.declare(lvalue.identifier, {
id,
scope: context.currentScope,
});
}

function collectDependencies(
Expand All @@ -645,7 +670,11 @@ function collectDependencies(
temporaries: ReadonlyMap<IdentifierId, ReactiveScopeDependency>,
processedInstrsInOptional: ReadonlySet<Instruction | Terminal>,
): Map<ReactiveScope, Array<ReactiveScopeDependency>> {
const context = new Context(usedOutsideDeclaringScope, temporaries);
const context = new Context(
usedOutsideDeclaringScope,
temporaries,
processedInstrsInOptional,
);

for (const param of fn.params) {
if (param.kind === 'Identifier') {
Expand Down Expand Up @@ -694,16 +723,21 @@ function collectDependencies(
/**
* Recursively visit the inner function to extract dependencies there
*/
const wasInInnerFn = context.inInnerFn;
context.inInnerFn = true;
handleFunction(instr.value.loweredFunc.func);
context.inInnerFn = wasInInnerFn;
} else if (!processedInstrsInOptional.has(instr)) {
const innerFn = instr.value.loweredFunc.func;
context.enterInnerFn(() => {
handleFunction(innerFn);
});
} else {
handleInstruction(instr, context);
}
}

if (!processedInstrsInOptional.has(block.terminal)) {
if (
!context.isDeferredDependency({
kind: HIRValue.Terminal,
value: block.terminal,
})
) {
for (const place of eachTerminalOperand(block.terminal)) {
context.visitOperand(place);
}
Expand Down
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