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[compiler] Foundation of new mutability and aliasing (alternate take)
Alternate take at a new mutability and alising model, aiming to replace `InferReferenceEffects` and `InferMutableRanges`. My initial passes at this were more complicated than necessary, and I've iterated to refine and distill this down to the core concepts. There are two effects that track information flow: `capture` and `alias`: * Given distinct values A and B. After capture A -> B, mutate(B) does *not* modify A. This more precisely captures the semantic of the previous `Store` effect. As an example, `array.push(item)` has the effect `capture item -> array` and `mutate(array)`. The array is modified, not the item. * Given distinct values A and B. After alias A -> B, mutate(B) *does* modify A. This is because B now refers to the same value as A. * Given distinct values A and B, after *either* capture A -> B *or* alias A -> B, transitiveMutate(B) counts as a mutation of A. Conceptually "capture A -> B" means that a reference to A was "captured" (or stored) within A, but there is not a directly aliasing. Whereas "alias A -> B" means literal value aliasing. The idea is that our previous sequential fixpoint loops in InferMutableRanges can instead work by first looking at transitive mutations, then look at non-transitive mutations. And aliasing groups can be built purely based on the `alias` effect. Lots more to do here but the structure is coming together. [ghstack-poisoned]
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@@ -6,6 +6,7 @@
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*/
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import {CompilerError} from '../CompilerError';
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import {AliasingSignature} from '../Inference/InferMutationAliasingEffects';
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import {Effect, ValueKind, ValueReason} from './HIR';
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import {
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BuiltInType,
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@@ -179,6 +180,8 @@ export type FunctionSignature = {
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impure?: boolean;
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canonicalName?: string;
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aliasing?: AliasingSignature | null;
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};
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/*
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@@ -332,6 +335,7 @@ addObject(BUILTIN_SHAPES, BuiltInArrayId, [
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returnValueKind: ValueKind.Mutable,
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noAlias: true,
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mutableOnlyIfOperandsAreMutable: true,
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aliasing: null,
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}),
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],
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[
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+1201
File diff suppressed because it is too large
Load Diff
+5
-17
@@ -48,7 +48,7 @@ import {
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eachTerminalOperand,
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eachTerminalSuccessor,
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} from '../HIR/visitors';
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import {assertExhaustive, retainWhere} from '../Utils/utils';
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import {assertExhaustive, retainWhere, Set_isSuperset} from '../Utils/utils';
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import {
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inferTerminalFunctionEffects,
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inferInstructionFunctionEffects,
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@@ -790,7 +790,7 @@ function inferParam(
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* │ Mutable │───┘
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* └──────────────────────────┘
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*/
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function mergeValues(a: ValueKind, b: ValueKind): ValueKind {
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export function mergeValueKinds(a: ValueKind, b: ValueKind): ValueKind {
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if (a === b) {
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return a;
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} else if (a === ValueKind.MaybeFrozen || b === ValueKind.MaybeFrozen) {
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@@ -832,28 +832,16 @@ function mergeValues(a: ValueKind, b: ValueKind): ValueKind {
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}
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}
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/**
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* @returns `true` if `a` is a superset of `b`.
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*/
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function isSuperset<T>(a: ReadonlySet<T>, b: ReadonlySet<T>): boolean {
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for (const v of b) {
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if (!a.has(v)) {
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return false;
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}
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}
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return true;
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}
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function mergeAbstractValues(
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a: AbstractValue,
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b: AbstractValue,
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): AbstractValue {
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const kind = mergeValues(a.kind, b.kind);
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const kind = mergeValueKinds(a.kind, b.kind);
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if (
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kind === a.kind &&
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kind === b.kind &&
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isSuperset(a.reason, b.reason) &&
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isSuperset(a.context, b.context)
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Set_isSuperset(a.reason, b.reason) &&
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Set_isSuperset(a.context, b.context)
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) {
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return a;
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}
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@@ -121,6 +121,21 @@ export function Set_intersect<T>(sets: Array<ReadonlySet<T>>): Set<T> {
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return result;
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}
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/**
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* @returns `true` if `a` is a superset of `b`.
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*/
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export function Set_isSuperset<T>(
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a: ReadonlySet<T>,
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b: ReadonlySet<T>,
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): boolean {
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for (const v of b) {
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if (!a.has(v)) {
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return false;
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}
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}
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return true;
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}
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export function Iterable_some<T>(
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iter: Iterable<T>,
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pred: (item: T) => boolean,
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