| 1 | /** |
| 2 | * Copyright (c) Meta Platforms, Inc. and affiliates. |
| 3 | * |
| 4 | * This source code is licensed under the MIT license found in the |
| 5 | * LICENSE file in the root directory of this source tree. |
| 6 | */ |
| 7 | |
| 8 | import {CompilerError} from '../CompilerError'; |
| 9 | import { |
| 10 | DeclarationId, |
| 11 | Environment, |
| 12 | GeneratedSource, |
| 13 | Identifier, |
| 14 | InstructionId, |
| 15 | Pattern, |
| 16 | Place, |
| 17 | ReactiveFunction, |
| 18 | ReactiveInstruction, |
| 19 | ReactiveScopeBlock, |
| 20 | ReactiveStatement, |
| 21 | ReactiveTerminal, |
| 22 | ReactiveTerminalStatement, |
| 23 | ReactiveValue, |
| 24 | ScopeId, |
| 25 | getHookKind, |
| 26 | isMutableEffect, |
| 27 | } from '../HIR'; |
| 28 | import {assertExhaustive, getOrInsertDefault} from '../Utils/utils'; |
| 29 | import {getPlaceScope, ReactiveScope} from '../HIR/HIR'; |
| 30 | import { |
| 31 | ReactiveFunctionTransform, |
| 32 | ReactiveFunctionVisitor, |
| 33 | Transformed, |
| 34 | eachReactiveValueOperand, |
| 35 | visitReactiveFunction, |
| 36 | } from './visitors'; |
| 37 | import {printPlace} from '../HIR/PrintHIR'; |
| 38 | import {getFunctionCallSignature} from '../Inference/InferMutationAliasingEffects'; |
| 39 | |
| 40 | /* |
| 41 | * This pass prunes reactive scopes that are not necessary to bound downstream computation. |
| 42 | * Specifically, the pass identifies the set of identifiers which may "escape". Values can |
| 43 | * escape in one of two ways: |
| 44 | * * They are directly returned by the function and/or transitively aliased by a return |
| 45 | * value. |
| 46 | * * They are passed as input to a hook. This is because any value passed to a hook may |
| 47 | * have its referenced ultimately stored by React (ie, be aliased by an external value). |
| 48 | * For example, the closure passed to useEffect escapes. |
| 49 | * |
| 50 | * Example to build intuition: |
| 51 | * |
| 52 | * ```javascript |
| 53 | * function Component(props) { |
| 54 | * const a = {}; // not aliased or returned: *not* memoized |
| 55 | * const b = {}; // aliased by c, which is returned: memoized |
| 56 | * const c = [b]; // directly returned: memoized |
| 57 | * return c; |
| 58 | * } |
| 59 | * ``` |
| 60 | * |
| 61 | * However, this logic alone is insufficient for two reasons: |
| 62 | * - Statically memoizing JSX elements *may* be inefficient compared to using dynamic |
| 63 | * memoization with `React.memo()`. Static memoization may be JIT'd and can look at |
| 64 | * the precise props w/o dynamic iteration, but incurs potentially large code-size |
| 65 | * overhead. Dynamic memoization with `React.memo()` incurs potentially increased |
| 66 | * runtime overhead for smaller code size. We plan to experiment with both variants |
| 67 | * for JSX. |
| 68 | * - Because we merge values whose mutations _interleave_ into a single scope, there |
| 69 | * can be cases where a non-escaping value needs to be memoized anyway to avoid breaking |
| 70 | * a memoization input. As a rule, for any scope that has a memoized output, all of that |
| 71 | * scope's transitive dependencies must also be memoized _even if they don't escape_. |
| 72 | * Failing to memoize them would cause the scope to invalidate more often than necessary |
| 73 | * and break downstream memoization. |
| 74 | * |
| 75 | * Example of this second case: |
| 76 | * |
| 77 | * ```javascript |
| 78 | * function Component(props) { |
| 79 | * // a can be independently memoized but it doesn't escape, so naively we may think its |
| 80 | * // safe to not memoize. but not memoizing would break caching of b, which does |
| 81 | * // escape. |
| 82 | * const a = [props.a]; |
| 83 | * |
| 84 | * // b and c are interleaved and grouped into a single scope, |
| 85 | * // but they are independent values. c does not escape, but |
| 86 | * // we need to ensure that a is memoized or else b will invalidate |
| 87 | * // on every render since a is a dependency. |
| 88 | * const b = []; |
| 89 | * const c = {}; |
| 90 | * c.a = a; |
| 91 | * b.push(props.b); |
| 92 | * |
| 93 | * return b; |
| 94 | * } |
| 95 | * ``` |
| 96 | * |
| 97 | * ## Algorithm |
| 98 | * |
| 99 | * 1. First we build up a graph, a mapping of IdentifierId to a node describing all the |
| 100 | * scopes and inputs involved in creating that identifier. Individual nodes are marked |
| 101 | * as definitely aliased, conditionally aliased, or unaliased: |
| 102 | * a. Arrays, objects, function calls all produce a new value and are always marked as aliased |
| 103 | * b. Conditional and logical expressions (and a few others) are conditinally aliased, |
| 104 | * depending on whether their result value is aliased. |
| 105 | * c. JSX is always unaliased (though its props children may be) |
| 106 | * 2. The same pass which builds the graph also stores the set of returned identifiers and set of |
| 107 | * identifiers passed as arguments to hooks. |
| 108 | * 3. We traverse the graph starting from the returned identifiers and mark reachable dependencies |
| 109 | * as escaping, based on the combination of the parent node's type and its children (eg a |
| 110 | * conditional node with an aliased dep promotes to aliased). |
| 111 | * 4. Finally we prune scopes whose outputs weren't marked. |
| 112 | */ |
| 113 | export function pruneNonEscapingScopes(fn: ReactiveFunction): void { |
| 114 | /* |
| 115 | * First build up a map of which instructions are involved in creating which values, |
| 116 | * and which values are returned. |
| 117 | */ |
| 118 | const state = new State(fn.env); |
| 119 | for (const param of fn.params) { |
| 120 | if (param.kind === 'Identifier') { |
| 121 | state.declare(param.identifier.declarationId); |
| 122 | } else { |
| 123 | state.declare(param.place.identifier.declarationId); |
| 124 | } |
| 125 | } |
| 126 | visitReactiveFunction(fn, new CollectDependenciesVisitor(fn.env, state), []); |
| 127 | |
| 128 | /* |
| 129 | * Then walk outward from the returned values and find all captured operands. |
| 130 | * This forms the set of identifiers which should be memoized. |
| 131 | */ |
| 132 | const memoized = computeMemoizedIdentifiers(state); |
| 133 | |
| 134 | // Prune scopes that do not declare/reassign any escaping values |
| 135 | visitReactiveFunction(fn, new PruneScopesTransform(), memoized); |
| 136 | } |
| 137 | |
| 138 | export type MemoizationOptions = { |
| 139 | memoizeJsxElements: boolean; |
| 140 | forceMemoizePrimitives: boolean; |
| 141 | }; |
| 142 | |
| 143 | // Describes how to determine whether a value should be memoized, relative to dependees and dependencies |
| 144 | enum MemoizationLevel { |
| 145 | // The value should be memoized if it escapes |
| 146 | Memoized = 'Memoized', |
| 147 | /* |
| 148 | * Values that are memoized if their dependencies are memoized (used for logical/ternary and |
| 149 | * other expressions that propagate dependencies wo changing them) |
| 150 | */ |
| 151 | Conditional = 'Conditional', |
| 152 | /* |
| 153 | * Values that cannot be compared with Object.is, but which by default don't need to be memoized |
| 154 | * unless forced |
| 155 | */ |
| 156 | Unmemoized = 'Unmemoized', |
| 157 | // The value will never be memoized: used for values that can be cheaply compared w Object.is |
| 158 | Never = 'Never', |
| 159 | } |
| 160 | |
| 161 | /* |
| 162 | * Given an identifier that appears as an lvalue multiple times with different memoization levels, |
| 163 | * determines the final memoization level. |
| 164 | */ |
| 165 | function joinAliases( |
| 166 | kind1: MemoizationLevel, |
| 167 | kind2: MemoizationLevel, |
| 168 | ): MemoizationLevel { |
| 169 | if ( |
| 170 | kind1 === MemoizationLevel.Memoized || |
| 171 | kind2 === MemoizationLevel.Memoized |
| 172 | ) { |
| 173 | return MemoizationLevel.Memoized; |
| 174 | } else if ( |
| 175 | kind1 === MemoizationLevel.Conditional || |
| 176 | kind2 === MemoizationLevel.Conditional |
| 177 | ) { |
| 178 | return MemoizationLevel.Conditional; |
| 179 | } else if ( |
| 180 | kind1 === MemoizationLevel.Unmemoized || |
| 181 | kind2 === MemoizationLevel.Unmemoized |
| 182 | ) { |
| 183 | return MemoizationLevel.Unmemoized; |
| 184 | } else { |
| 185 | return MemoizationLevel.Never; |
| 186 | } |
| 187 | } |
| 188 | |
| 189 | // A node in the graph describing the memoization level of a given identifier as well as its dependencies and scopes. |
| 190 | type IdentifierNode = { |
| 191 | level: MemoizationLevel; |
| 192 | memoized: boolean; |
| 193 | dependencies: Set<DeclarationId>; |
| 194 | scopes: Set<ScopeId>; |
| 195 | seen: boolean; |
| 196 | }; |
| 197 | |
| 198 | // A scope node describing its dependencies |
| 199 | type ScopeNode = { |
| 200 | dependencies: Array<DeclarationId>; |
| 201 | seen: boolean; |
| 202 | }; |
| 203 | |
| 204 | // Stores the identifier and scope graphs, set of returned identifiers, etc |
| 205 | class State { |
| 206 | env: Environment; |
| 207 | /* |
| 208 | * Maps lvalues for LoadLocal to the identifier being loaded, to resolve indirections |
| 209 | * in subsequent lvalues/rvalues. |
| 210 | * |
| 211 | * NOTE: this pass uses DeclarationId rather than IdentifierId because the pass is not |
| 212 | * aware of control-flow, only data flow via mutation. Instead of precisely modeling |
| 213 | * control flow, we analyze all values that may flow into a particular program variable, |
| 214 | * and then whether that program variable may escape (if so, the values flowing in may |
| 215 | * escape too). Thus we use DeclarationId to captures all values that may flow into |
| 216 | * a particular program variable, regardless of control flow paths. |
| 217 | * |
| 218 | * In the future when we convert to HIR everywhere this pass can account for control |
| 219 | * flow and use SSA ids. |
| 220 | */ |
| 221 | definitions: Map<DeclarationId, DeclarationId> = new Map(); |
| 222 | |
| 223 | identifiers: Map<DeclarationId, IdentifierNode> = new Map(); |
| 224 | scopes: Map<ScopeId, ScopeNode> = new Map(); |
| 225 | escapingValues: Set<DeclarationId> = new Set(); |
| 226 | |
| 227 | constructor(env: Environment) { |
| 228 | this.env = env; |
| 229 | } |
| 230 | |
| 231 | // Declare a new identifier, used for function id and params |
| 232 | declare(id: DeclarationId): void { |
| 233 | this.identifiers.set(id, { |
| 234 | level: MemoizationLevel.Never, |
| 235 | memoized: false, |
| 236 | dependencies: new Set(), |
| 237 | scopes: new Set(), |
| 238 | seen: false, |
| 239 | }); |
| 240 | } |
| 241 | |
| 242 | /* |
| 243 | * Associates the identifier with its scope, if there is one and it is active for the given instruction id: |
| 244 | * - Records the scope and its dependencies |
| 245 | * - Associates the identifier with this scope |
| 246 | */ |
| 247 | visitOperand( |
| 248 | id: InstructionId, |
| 249 | place: Place, |
| 250 | identifier: DeclarationId, |
| 251 | ): void { |
| 252 | const scope = getPlaceScope(id, place); |
| 253 | if (scope !== null) { |
| 254 | let node = this.scopes.get(scope.id); |
| 255 | if (node === undefined) { |
| 256 | node = { |
| 257 | dependencies: [...scope.dependencies].map( |
| 258 | dep => dep.identifier.declarationId, |
| 259 | ), |
| 260 | seen: false, |
| 261 | }; |
| 262 | this.scopes.set(scope.id, node); |
| 263 | } |
| 264 | const identifierNode = this.identifiers.get(identifier); |
| 265 | CompilerError.invariant(identifierNode !== undefined, { |
| 266 | reason: 'Expected identifier to be initialized', |
| 267 | description: `[${id}] operand=${printPlace(place)} for identifier declaration ${identifier}`, |
| 268 | loc: place.loc, |
| 269 | }); |
| 270 | identifierNode.scopes.add(scope.id); |
| 271 | } |
| 272 | } |
| 273 | } |
| 274 | |
| 275 | /* |
| 276 | * Given a state derived from visiting the function, walks the graph from the returned nodes |
| 277 | * to determine which other values should be memoized. Returns a set of all identifiers |
| 278 | * that should be memoized. |
| 279 | */ |
| 280 | function computeMemoizedIdentifiers(state: State): Set<DeclarationId> { |
| 281 | const memoized = new Set<DeclarationId>(); |
| 282 | |
| 283 | // Visit an identifier, optionally forcing it to be memoized |
| 284 | function visit(id: DeclarationId, forceMemoize: boolean = false): boolean { |
| 285 | const node = state.identifiers.get(id); |
| 286 | CompilerError.invariant(node !== undefined, { |
| 287 | reason: `Expected a node for all identifiers, none found for \`${id}\``, |
| 288 | loc: GeneratedSource, |
| 289 | }); |
| 290 | if (node.seen) { |
| 291 | return node.memoized; |
| 292 | } |
| 293 | node.seen = true; |
| 294 | |
| 295 | /* |
| 296 | * Note: in case of cycles we temporarily mark the identifier as non-memoized, |
| 297 | * this is reset later after processing dependencies |
| 298 | */ |
| 299 | node.memoized = false; |
| 300 | |
| 301 | // Visit dependencies, determine if any of them are memoized |
| 302 | let hasMemoizedDependency = false; |
| 303 | for (const dep of node.dependencies) { |
| 304 | const isDepMemoized = visit(dep); |
| 305 | hasMemoizedDependency ||= isDepMemoized; |
| 306 | } |
| 307 | |
| 308 | if ( |
| 309 | node.level === MemoizationLevel.Memoized || |
| 310 | (node.level === MemoizationLevel.Conditional && |
| 311 | (hasMemoizedDependency || forceMemoize)) || |
| 312 | (node.level === MemoizationLevel.Unmemoized && forceMemoize) |
| 313 | ) { |
| 314 | node.memoized = true; |
| 315 | memoized.add(id); |
| 316 | for (const scope of node.scopes) { |
| 317 | forceMemoizeScopeDependencies(scope); |
| 318 | } |
| 319 | } |
| 320 | return node.memoized; |
| 321 | } |
| 322 | |
| 323 | // Force all the scope's optionally-memoizeable dependencies (not "Never") to be memoized |
| 324 | function forceMemoizeScopeDependencies(id: ScopeId): void { |
| 325 | const node = state.scopes.get(id); |
| 326 | CompilerError.invariant(node !== undefined, { |
| 327 | reason: 'Expected a node for all scopes', |
| 328 | loc: GeneratedSource, |
| 329 | }); |
| 330 | if (node.seen) { |
| 331 | return; |
| 332 | } |
| 333 | node.seen = true; |
| 334 | |
| 335 | for (const dep of node.dependencies) { |
| 336 | visit(dep, true); |
| 337 | } |
| 338 | return; |
| 339 | } |
| 340 | |
| 341 | // Walk from the "roots" aka returned identifiers. |
| 342 | for (const value of state.escapingValues) { |
| 343 | visit(value); |
| 344 | } |
| 345 | |
| 346 | return memoized; |
| 347 | } |
| 348 | |
| 349 | type LValueMemoization = { |
| 350 | place: Place; |
| 351 | level: MemoizationLevel; |
| 352 | }; |
| 353 | |
| 354 | function computePatternLValues(pattern: Pattern): Array<LValueMemoization> { |
| 355 | const lvalues: Array<LValueMemoization> = []; |
| 356 | switch (pattern.kind) { |
| 357 | case 'ArrayPattern': { |
| 358 | for (const item of pattern.items) { |
| 359 | if (item.kind === 'Identifier') { |
| 360 | lvalues.push({place: item, level: MemoizationLevel.Conditional}); |
| 361 | } else if (item.kind === 'Spread') { |
| 362 | lvalues.push({place: item.place, level: MemoizationLevel.Memoized}); |
| 363 | } |
| 364 | } |
| 365 | break; |
| 366 | } |
| 367 | case 'ObjectPattern': { |
| 368 | for (const property of pattern.properties) { |
| 369 | if (property.kind === 'ObjectProperty') { |
| 370 | lvalues.push({ |
| 371 | place: property.place, |
| 372 | level: MemoizationLevel.Conditional, |
| 373 | }); |
| 374 | } else { |
| 375 | lvalues.push({ |
| 376 | place: property.place, |
| 377 | level: MemoizationLevel.Memoized, |
| 378 | }); |
| 379 | } |
| 380 | } |
| 381 | break; |
| 382 | } |
| 383 | default: { |
| 384 | assertExhaustive( |
| 385 | pattern, |
| 386 | `Unexpected pattern kind \`${(pattern as any).kind}\``, |
| 387 | ); |
| 388 | } |
| 389 | } |
| 390 | return lvalues; |
| 391 | } |
| 392 | |
| 393 | /* |
| 394 | * Populates the input state with the set of returned identifiers and information about each |
| 395 | * identifier's and scope's dependencies. |
| 396 | */ |
| 397 | class CollectDependenciesVisitor extends ReactiveFunctionVisitor< |
| 398 | Array<ReactiveScope> |
| 399 | > { |
| 400 | env: Environment; |
| 401 | state: State; |
| 402 | options: MemoizationOptions; |
| 403 | |
| 404 | constructor(env: Environment, state: State) { |
| 405 | super(); |
| 406 | this.env = env; |
| 407 | this.state = state; |
| 408 | this.options = { |
| 409 | memoizeJsxElements: !this.env.config.enableForest, |
| 410 | forceMemoizePrimitives: |
| 411 | this.env.config.enableForest || |
| 412 | this.env.config.enablePreserveExistingMemoizationGuarantees, |
| 413 | }; |
| 414 | } |
| 415 | |
| 416 | /* |
| 417 | * Given a value, returns a description of how it should be memoized: |
| 418 | * - lvalues: optional extra places that are lvalue-like in the sense of |
| 419 | * aliasing the rvalues |
| 420 | * - rvalues: places that are aliased by the instruction's lvalues. |
| 421 | * - level: the level of memoization to apply to this value |
| 422 | */ |
| 423 | computeMemoizationInputs( |
| 424 | value: ReactiveValue, |
| 425 | lvalue: Place | null, |
| 426 | ): { |
| 427 | // can optionally return a custom set of lvalues per instruction |
| 428 | lvalues: Array<LValueMemoization>; |
| 429 | rvalues: Array<Place>; |
| 430 | } { |
| 431 | const env = this.env; |
| 432 | const options = this.options; |
| 433 | |
| 434 | switch (value.kind) { |
| 435 | case 'ConditionalExpression': { |
| 436 | return { |
| 437 | // Only need to memoize if the rvalues are memoized |
| 438 | lvalues: |
| 439 | lvalue !== null |
| 440 | ? [{place: lvalue, level: MemoizationLevel.Conditional}] |
| 441 | : [], |
| 442 | rvalues: [ |
| 443 | // Conditionals do not alias their test value. |
| 444 | ...this.computeMemoizationInputs(value.consequent, null).rvalues, |
| 445 | ...this.computeMemoizationInputs(value.alternate, null).rvalues, |
| 446 | ], |
| 447 | }; |
| 448 | } |
| 449 | case 'LogicalExpression': { |
| 450 | return { |
| 451 | // Only need to memoize if the rvalues are memoized |
| 452 | lvalues: |
| 453 | lvalue !== null |
| 454 | ? [{place: lvalue, level: MemoizationLevel.Conditional}] |
| 455 | : [], |
| 456 | rvalues: [ |
| 457 | ...this.computeMemoizationInputs(value.left, null).rvalues, |
| 458 | ...this.computeMemoizationInputs(value.right, null).rvalues, |
| 459 | ], |
| 460 | }; |
| 461 | } |
| 462 | case 'SequenceExpression': { |
| 463 | for (const instr of value.instructions) { |
| 464 | this.visitValueForMemoization(instr.id, instr.value, instr.lvalue); |
| 465 | } |
| 466 | return { |
| 467 | // Only need to memoize if the rvalues are memoized |
| 468 | lvalues: |
| 469 | lvalue !== null |
| 470 | ? [{place: lvalue, level: MemoizationLevel.Conditional}] |
| 471 | : [], |
| 472 | /* |
| 473 | * Only the final value of the sequence is a true rvalue: |
| 474 | * values from the sequence's instructions are evaluated |
| 475 | * as separate nodes |
| 476 | */ |
| 477 | rvalues: this.computeMemoizationInputs(value.value, null).rvalues, |
| 478 | }; |
| 479 | } |
| 480 | case 'JsxExpression': { |
| 481 | const operands: Array<Place> = []; |
| 482 | if (value.tag.kind === 'Identifier') { |
| 483 | operands.push(value.tag); |
| 484 | } |
| 485 | for (const prop of value.props) { |
| 486 | if (prop.kind === 'JsxAttribute') { |
| 487 | operands.push(prop.place); |
| 488 | } else { |
| 489 | operands.push(prop.argument); |
| 490 | } |
| 491 | } |
| 492 | if (value.children !== null) { |
| 493 | for (const child of value.children) { |
| 494 | operands.push(child); |
| 495 | } |
| 496 | } |
| 497 | const level = options.memoizeJsxElements |
| 498 | ? MemoizationLevel.Memoized |
| 499 | : MemoizationLevel.Unmemoized; |
| 500 | return { |
| 501 | /* |
| 502 | * JSX elements themselves are not memoized unless forced to |
| 503 | * avoid breaking downstream memoization |
| 504 | */ |
| 505 | lvalues: lvalue !== null ? [{place: lvalue, level}] : [], |
| 506 | rvalues: operands, |
| 507 | }; |
| 508 | } |
| 509 | case 'JsxFragment': { |
| 510 | const level = options.memoizeJsxElements |
| 511 | ? MemoizationLevel.Memoized |
| 512 | : MemoizationLevel.Unmemoized; |
| 513 | return { |
| 514 | /* |
| 515 | * JSX elements themselves are not memoized unless forced to |
| 516 | * avoid breaking downstream memoization |
| 517 | */ |
| 518 | lvalues: lvalue !== null ? [{place: lvalue, level}] : [], |
| 519 | rvalues: value.children, |
| 520 | }; |
| 521 | } |
| 522 | case 'NextPropertyOf': |
| 523 | case 'StartMemoize': |
| 524 | case 'FinishMemoize': |
| 525 | case 'Debugger': |
| 526 | case 'ComputedDelete': |
| 527 | case 'PropertyDelete': |
| 528 | case 'LoadGlobal': |
| 529 | case 'MetaProperty': |
| 530 | case 'TemplateLiteral': |
| 531 | case 'Primitive': |
| 532 | case 'JSXText': |
| 533 | case 'BinaryExpression': |
| 534 | case 'UnaryExpression': { |
| 535 | if (options.forceMemoizePrimitives) { |
| 536 | /** |
| 537 | * Because these instructions produce primitives we usually don't consider |
| 538 | * them as escape points: they are known to copy, not return references. |
| 539 | * However if we're forcing memoization of primitives then we mark these |
| 540 | * instructions as needing memoization and walk their rvalues to ensure |
| 541 | * any scopes transitively reachable from the rvalues are considered for |
| 542 | * memoization. Note: we may still prune primitive-producing scopes if |
| 543 | * they don't ultimately escape at all. |
| 544 | */ |
| 545 | const level = MemoizationLevel.Conditional; |
| 546 | return { |
| 547 | lvalues: lvalue !== null ? [{place: lvalue, level}] : [], |
| 548 | rvalues: [...eachReactiveValueOperand(value)], |
| 549 | }; |
| 550 | } |
| 551 | const level = MemoizationLevel.Never; |
| 552 | return { |
| 553 | // All of these instructions return a primitive value and never need to be memoized |
| 554 | lvalues: lvalue !== null ? [{place: lvalue, level}] : [], |
| 555 | rvalues: [], |
| 556 | }; |
| 557 | } |
| 558 | case 'Await': |
| 559 | case 'TypeCastExpression': { |
| 560 | return { |
| 561 | // Indirection for the inner value, memoized if the value is |
| 562 | lvalues: |
| 563 | lvalue !== null |
| 564 | ? [{place: lvalue, level: MemoizationLevel.Conditional}] |
| 565 | : [], |
| 566 | rvalues: [value.value], |
| 567 | }; |
| 568 | } |
| 569 | case 'IteratorNext': { |
| 570 | return { |
| 571 | // Indirection for the inner value, memoized if the value is |
| 572 | lvalues: |
| 573 | lvalue !== null |
| 574 | ? [{place: lvalue, level: MemoizationLevel.Conditional}] |
| 575 | : [], |
| 576 | rvalues: [value.iterator, value.collection], |
| 577 | }; |
| 578 | } |
| 579 | case 'GetIterator': { |
| 580 | return { |
| 581 | // Indirection for the inner value, memoized if the value is |
| 582 | lvalues: |
| 583 | lvalue !== null |
| 584 | ? [{place: lvalue, level: MemoizationLevel.Conditional}] |
| 585 | : [], |
| 586 | rvalues: [value.collection], |
| 587 | }; |
| 588 | } |
| 589 | case 'LoadLocal': { |
| 590 | return { |
| 591 | // Indirection for the inner value, memoized if the value is |
| 592 | lvalues: |
| 593 | lvalue !== null |
| 594 | ? [{place: lvalue, level: MemoizationLevel.Conditional}] |
| 595 | : [], |
| 596 | rvalues: [value.place], |
| 597 | }; |
| 598 | } |
| 599 | case 'LoadContext': { |
| 600 | return { |
| 601 | // Should never be pruned |
| 602 | lvalues: |
| 603 | lvalue !== null |
| 604 | ? [{place: lvalue, level: MemoizationLevel.Conditional}] |
| 605 | : [], |
| 606 | rvalues: [value.place], |
| 607 | }; |
| 608 | } |
| 609 | case 'DeclareContext': { |
| 610 | const lvalues = [ |
| 611 | {place: value.lvalue.place, level: MemoizationLevel.Memoized}, |
| 612 | ]; |
| 613 | if (lvalue !== null) { |
| 614 | lvalues.push({place: lvalue, level: MemoizationLevel.Unmemoized}); |
| 615 | } |
| 616 | return { |
| 617 | lvalues, |
| 618 | rvalues: [], |
| 619 | }; |
| 620 | } |
| 621 | |
| 622 | case 'DeclareLocal': { |
| 623 | const lvalues = [ |
| 624 | {place: value.lvalue.place, level: MemoizationLevel.Unmemoized}, |
| 625 | ]; |
| 626 | if (lvalue !== null) { |
| 627 | lvalues.push({place: lvalue, level: MemoizationLevel.Unmemoized}); |
| 628 | } |
| 629 | return { |
| 630 | lvalues, |
| 631 | rvalues: [], |
| 632 | }; |
| 633 | } |
| 634 | case 'PrefixUpdate': |
| 635 | case 'PostfixUpdate': { |
| 636 | const lvalues = [ |
| 637 | {place: value.lvalue, level: MemoizationLevel.Conditional}, |
| 638 | ]; |
| 639 | if (lvalue !== null) { |
| 640 | lvalues.push({place: lvalue, level: MemoizationLevel.Conditional}); |
| 641 | } |
| 642 | return { |
| 643 | // Indirection for the inner value, memoized if the value is |
| 644 | lvalues, |
| 645 | rvalues: [value.value], |
| 646 | }; |
| 647 | } |
| 648 | case 'StoreLocal': { |
| 649 | const lvalues = [ |
| 650 | {place: value.lvalue.place, level: MemoizationLevel.Conditional}, |
| 651 | ]; |
| 652 | if (lvalue !== null) { |
| 653 | lvalues.push({place: lvalue, level: MemoizationLevel.Conditional}); |
| 654 | } |
| 655 | return { |
| 656 | // Indirection for the inner value, memoized if the value is |
| 657 | lvalues, |
| 658 | rvalues: [value.value], |
| 659 | }; |
| 660 | } |
| 661 | case 'StoreContext': { |
| 662 | // Should never be pruned |
| 663 | const lvalues = [ |
| 664 | {place: value.lvalue.place, level: MemoizationLevel.Memoized}, |
| 665 | ]; |
| 666 | if (lvalue !== null) { |
| 667 | lvalues.push({place: lvalue, level: MemoizationLevel.Conditional}); |
| 668 | } |
| 669 | |
| 670 | return { |
| 671 | lvalues, |
| 672 | rvalues: [value.value], |
| 673 | }; |
| 674 | } |
| 675 | case 'StoreGlobal': { |
| 676 | const lvalues = []; |
| 677 | if (lvalue !== null) { |
| 678 | lvalues.push({place: lvalue, level: MemoizationLevel.Unmemoized}); |
| 679 | } |
| 680 | |
| 681 | return { |
| 682 | lvalues, |
| 683 | rvalues: [value.value], |
| 684 | }; |
| 685 | } |
| 686 | case 'Destructure': { |
| 687 | // Indirection for the inner value, memoized if the value is |
| 688 | const lvalues = []; |
| 689 | if (lvalue !== null) { |
| 690 | lvalues.push({place: lvalue, level: MemoizationLevel.Conditional}); |
| 691 | } |
| 692 | lvalues.push(...computePatternLValues(value.lvalue.pattern)); |
| 693 | return { |
| 694 | lvalues: lvalues, |
| 695 | rvalues: [value.value], |
| 696 | }; |
| 697 | } |
| 698 | case 'ComputedLoad': |
| 699 | case 'PropertyLoad': { |
| 700 | const level = MemoizationLevel.Conditional; |
| 701 | return { |
| 702 | // Indirection for the inner value, memoized if the value is |
| 703 | lvalues: lvalue !== null ? [{place: lvalue, level}] : [], |
| 704 | /* |
| 705 | * Only the object is aliased to the result, and the result only needs to be |
| 706 | * memoized if the object is |
| 707 | */ |
| 708 | rvalues: [value.object], |
| 709 | }; |
| 710 | } |
| 711 | case 'ComputedStore': { |
| 712 | /* |
| 713 | * The object being stored to acts as an lvalue (it aliases the value), but |
| 714 | * the computed key is not aliased |
| 715 | */ |
| 716 | const lvalues = [ |
| 717 | {place: value.object, level: MemoizationLevel.Conditional}, |
| 718 | ]; |
| 719 | if (lvalue !== null) { |
| 720 | lvalues.push({place: lvalue, level: MemoizationLevel.Conditional}); |
| 721 | } |
| 722 | return { |
| 723 | lvalues, |
| 724 | rvalues: [value.value], |
| 725 | }; |
| 726 | } |
| 727 | case 'OptionalExpression': { |
| 728 | // Indirection for the inner value, memoized if the value is |
| 729 | const lvalues = []; |
| 730 | if (lvalue !== null) { |
| 731 | lvalues.push({place: lvalue, level: MemoizationLevel.Conditional}); |
| 732 | } |
| 733 | return { |
| 734 | lvalues: lvalues, |
| 735 | rvalues: [ |
| 736 | ...this.computeMemoizationInputs(value.value, null).rvalues, |
| 737 | ], |
| 738 | }; |
| 739 | } |
| 740 | case 'TaggedTemplateExpression': { |
| 741 | const signature = getFunctionCallSignature( |
| 742 | env, |
| 743 | value.tag.identifier.type, |
| 744 | ); |
| 745 | let lvalues = []; |
| 746 | if (lvalue !== null) { |
| 747 | lvalues.push({place: lvalue, level: MemoizationLevel.Memoized}); |
| 748 | } |
| 749 | if (signature?.noAlias === true) { |
| 750 | return { |
| 751 | lvalues, |
| 752 | rvalues: [], |
| 753 | }; |
| 754 | } |
| 755 | const operands = [...eachReactiveValueOperand(value)]; |
| 756 | lvalues.push( |
| 757 | ...operands |
| 758 | .filter(operand => isMutableEffect(operand.effect, operand.loc)) |
| 759 | .map(place => ({place, level: MemoizationLevel.Memoized})), |
| 760 | ); |
| 761 | return { |
| 762 | lvalues, |
| 763 | rvalues: operands, |
| 764 | }; |
| 765 | } |
| 766 | case 'CallExpression': { |
| 767 | const signature = getFunctionCallSignature( |
| 768 | env, |
| 769 | value.callee.identifier.type, |
| 770 | ); |
| 771 | let lvalues = []; |
| 772 | if (lvalue !== null) { |
| 773 | lvalues.push({place: lvalue, level: MemoizationLevel.Memoized}); |
| 774 | } |
| 775 | if (signature?.noAlias === true) { |
| 776 | return { |
| 777 | lvalues, |
| 778 | rvalues: [], |
| 779 | }; |
| 780 | } |
| 781 | const operands = [...eachReactiveValueOperand(value)]; |
| 782 | lvalues.push( |
| 783 | ...operands |
| 784 | .filter(operand => isMutableEffect(operand.effect, operand.loc)) |
| 785 | .map(place => ({place, level: MemoizationLevel.Memoized})), |
| 786 | ); |
| 787 | return { |
| 788 | lvalues, |
| 789 | rvalues: operands, |
| 790 | }; |
| 791 | } |
| 792 | case 'MethodCall': { |
| 793 | const signature = getFunctionCallSignature( |
| 794 | env, |
| 795 | value.property.identifier.type, |
| 796 | ); |
| 797 | let lvalues = []; |
| 798 | if (lvalue !== null) { |
| 799 | lvalues.push({place: lvalue, level: MemoizationLevel.Memoized}); |
| 800 | } |
| 801 | if (signature?.noAlias === true) { |
| 802 | return { |
| 803 | lvalues, |
| 804 | rvalues: [], |
| 805 | }; |
| 806 | } |
| 807 | const operands = [...eachReactiveValueOperand(value)]; |
| 808 | lvalues.push( |
| 809 | ...operands |
| 810 | .filter(operand => isMutableEffect(operand.effect, operand.loc)) |
| 811 | .map(place => ({place, level: MemoizationLevel.Memoized})), |
| 812 | ); |
| 813 | return { |
| 814 | lvalues, |
| 815 | rvalues: operands, |
| 816 | }; |
| 817 | } |
| 818 | case 'RegExpLiteral': |
| 819 | case 'ObjectMethod': |
| 820 | case 'FunctionExpression': |
| 821 | case 'ArrayExpression': |
| 822 | case 'NewExpression': |
| 823 | case 'ObjectExpression': |
| 824 | case 'PropertyStore': { |
| 825 | /* |
| 826 | * All of these instructions may produce new values which must be memoized if |
| 827 | * reachable from a return value. Any mutable rvalue may alias any other rvalue |
| 828 | */ |
| 829 | const operands = [...eachReactiveValueOperand(value)]; |
| 830 | const lvalues = operands |
| 831 | .filter(operand => isMutableEffect(operand.effect, operand.loc)) |
| 832 | .map(place => ({place, level: MemoizationLevel.Memoized})); |
| 833 | if (lvalue !== null) { |
| 834 | lvalues.push({place: lvalue, level: MemoizationLevel.Memoized}); |
| 835 | } |
| 836 | return { |
| 837 | lvalues, |
| 838 | rvalues: operands, |
| 839 | }; |
| 840 | } |
| 841 | case 'UnsupportedNode': { |
| 842 | const lvalues = []; |
| 843 | if (lvalue !== null) { |
| 844 | lvalues.push({place: lvalue, level: MemoizationLevel.Never}); |
| 845 | } |
| 846 | return { |
| 847 | lvalues, |
| 848 | rvalues: [], |
| 849 | }; |
| 850 | } |
| 851 | default: { |
| 852 | assertExhaustive( |
| 853 | value, |
| 854 | `Unexpected value kind \`${(value as any).kind}\``, |
| 855 | ); |
| 856 | } |
| 857 | } |
| 858 | } |
| 859 | |
| 860 | visitValueForMemoization( |
| 861 | id: InstructionId, |
| 862 | value: ReactiveValue, |
| 863 | lvalue: Place | null, |
| 864 | ): void { |
| 865 | const state = this.state; |
| 866 | // Determe the level of memoization for this value and the lvalues/rvalues |
| 867 | const aliasing = this.computeMemoizationInputs(value, lvalue); |
| 868 | |
| 869 | // Associate all the rvalues with the instruction's scope if it has one |
| 870 | for (const operand of aliasing.rvalues) { |
| 871 | const operandId = |
| 872 | state.definitions.get(operand.identifier.declarationId) ?? |
| 873 | operand.identifier.declarationId; |
| 874 | state.visitOperand(id, operand, operandId); |
| 875 | } |
| 876 | |
| 877 | // Add the operands as dependencies of all lvalues. |
| 878 | for (const {place: lvalue, level} of aliasing.lvalues) { |
| 879 | const lvalueId = |
| 880 | state.definitions.get(lvalue.identifier.declarationId) ?? |
| 881 | lvalue.identifier.declarationId; |
| 882 | let node = state.identifiers.get(lvalueId); |
| 883 | if (node === undefined) { |
| 884 | node = { |
| 885 | level: MemoizationLevel.Never, |
| 886 | memoized: false, |
| 887 | dependencies: new Set(), |
| 888 | scopes: new Set(), |
| 889 | seen: false, |
| 890 | }; |
| 891 | state.identifiers.set(lvalueId, node); |
| 892 | } |
| 893 | node.level = joinAliases(node.level, level); |
| 894 | /* |
| 895 | * This looks like NxM iterations but in practice all instructions with multiple |
| 896 | * lvalues have only a single rvalue |
| 897 | */ |
| 898 | for (const operand of aliasing.rvalues) { |
| 899 | const operandId = |
| 900 | state.definitions.get(operand.identifier.declarationId) ?? |
| 901 | operand.identifier.declarationId; |
| 902 | if (operandId === lvalueId) { |
| 903 | continue; |
| 904 | } |
| 905 | node.dependencies.add(operandId); |
| 906 | } |
| 907 | |
| 908 | state.visitOperand(id, lvalue, lvalueId); |
| 909 | } |
| 910 | |
| 911 | if (value.kind === 'LoadLocal' && lvalue !== null) { |
| 912 | state.definitions.set( |
| 913 | lvalue.identifier.declarationId, |
| 914 | value.place.identifier.declarationId, |
| 915 | ); |
| 916 | } else if (value.kind === 'CallExpression' || value.kind === 'MethodCall') { |
| 917 | let callee = |
| 918 | value.kind === 'CallExpression' ? value.callee : value.property; |
| 919 | if (getHookKind(state.env, callee.identifier) != null) { |
| 920 | const signature = getFunctionCallSignature( |
| 921 | this.env, |
| 922 | callee.identifier.type, |
| 923 | ); |
| 924 | /* |
| 925 | * Hook values are assumed to escape by default since they can be inputs |
| 926 | * to reactive scopes in the hook. However if the hook is annotated as |
| 927 | * noAlias we know that the arguments cannot escape and don't need to |
| 928 | * be memoized. |
| 929 | */ |
| 930 | if (signature && signature.noAlias === true) { |
| 931 | return; |
| 932 | } |
| 933 | for (const operand of value.args) { |
| 934 | const place = operand.kind === 'Spread' ? operand.place : operand; |
| 935 | state.escapingValues.add(place.identifier.declarationId); |
| 936 | } |
| 937 | } |
| 938 | } |
| 939 | } |
| 940 | |
| 941 | override visitInstruction( |
| 942 | instruction: ReactiveInstruction, |
| 943 | _scopes: Array<ReactiveScope>, |
| 944 | ): void { |
| 945 | this.visitValueForMemoization( |
| 946 | instruction.id, |
| 947 | instruction.value, |
| 948 | instruction.lvalue, |
| 949 | ); |
| 950 | } |
| 951 | |
| 952 | override visitTerminal( |
| 953 | stmt: ReactiveTerminalStatement<ReactiveTerminal>, |
| 954 | scopes: Array<ReactiveScope>, |
| 955 | ): void { |
| 956 | this.traverseTerminal(stmt, scopes); |
| 957 | if (stmt.terminal.kind === 'return') { |
| 958 | this.state.escapingValues.add( |
| 959 | stmt.terminal.value.identifier.declarationId, |
| 960 | ); |
| 961 | |
| 962 | /* |
| 963 | * If the return is within a scope, then those scopes must be evaluated |
| 964 | * with the return and should be considered dependencies of the returned |
| 965 | * value. |
| 966 | * |
| 967 | * This ensures that if those scopes have dependencies that those deps |
| 968 | * are also memoized. |
| 969 | */ |
| 970 | const identifierNode = this.state.identifiers.get( |
| 971 | stmt.terminal.value.identifier.declarationId, |
| 972 | ); |
| 973 | CompilerError.invariant(identifierNode !== undefined, { |
| 974 | reason: 'Expected identifier to be initialized', |
| 975 | loc: stmt.terminal.loc, |
| 976 | }); |
| 977 | for (const scope of scopes) { |
| 978 | identifierNode.scopes.add(scope.id); |
| 979 | } |
| 980 | } |
| 981 | } |
| 982 | |
| 983 | override visitScope( |
| 984 | scope: ReactiveScopeBlock, |
| 985 | scopes: Array<ReactiveScope>, |
| 986 | ): void { |
| 987 | /* |
| 988 | * If a scope reassigns any variables, set the chain of active scopes as a dependency |
| 989 | * of those variables. This ensures that if the variable escapes that we treat the |
| 990 | * reassignment scopes — and importantly their dependencies — as needing memoization. |
| 991 | */ |
| 992 | for (const reassignment of scope.scope.reassignments) { |
| 993 | const identifierNode = this.state.identifiers.get( |
| 994 | reassignment.declarationId, |
| 995 | ); |
| 996 | CompilerError.invariant(identifierNode !== undefined, { |
| 997 | reason: 'Expected identifier to be initialized', |
| 998 | loc: reassignment.loc, |
| 999 | }); |
| 1000 | for (const scope of scopes) { |
| 1001 | identifierNode.scopes.add(scope.id); |
| 1002 | } |
| 1003 | identifierNode.scopes.add(scope.scope.id); |
| 1004 | } |
| 1005 | |
| 1006 | this.traverseScope(scope, [...scopes, scope.scope]); |
| 1007 | } |
| 1008 | } |
| 1009 | |
| 1010 | // Prune reactive scopes that do not have any memoized outputs |
| 1011 | class PruneScopesTransform extends ReactiveFunctionTransform< |
| 1012 | Set<DeclarationId> |
| 1013 | > { |
| 1014 | prunedScopes: Set<ScopeId> = new Set(); |
| 1015 | /** |
| 1016 | * Track reassignments so we can correctly set `pruned` flags for |
| 1017 | * inlined useMemos. |
| 1018 | */ |
| 1019 | reassignments: Map<DeclarationId, Set<Identifier>> = new Map(); |
| 1020 | |
| 1021 | override transformScope( |
| 1022 | scopeBlock: ReactiveScopeBlock, |
| 1023 | state: Set<DeclarationId>, |
| 1024 | ): Transformed<ReactiveStatement> { |
| 1025 | this.visitScope(scopeBlock, state); |
| 1026 | |
| 1027 | /** |
| 1028 | * Scopes may initially appear "empty" because the value being memoized |
| 1029 | * is early-returned from within the scope. For now we intentionaly keep |
| 1030 | * these scopes, and let them get pruned later by PruneUnusedScopes |
| 1031 | * _after_ handling the early-return case in PropagateEarlyReturns. |
| 1032 | * |
| 1033 | * Also keep the scope if an early return was created by some earlier pass, |
| 1034 | * which may happen in alternate compiler configurations. |
| 1035 | */ |
| 1036 | if ( |
| 1037 | (scopeBlock.scope.declarations.size === 0 && |
| 1038 | scopeBlock.scope.reassignments.size === 0) || |
| 1039 | scopeBlock.scope.earlyReturnValue !== null |
| 1040 | ) { |
| 1041 | return {kind: 'keep'}; |
| 1042 | } |
| 1043 | |
| 1044 | const hasMemoizedOutput = |
| 1045 | Array.from(scopeBlock.scope.declarations.values()).some(decl => |
| 1046 | state.has(decl.identifier.declarationId), |
| 1047 | ) || |
| 1048 | Array.from(scopeBlock.scope.reassignments).some(identifier => |
| 1049 | state.has(identifier.declarationId), |
| 1050 | ); |
| 1051 | if (hasMemoizedOutput) { |
| 1052 | return {kind: 'keep'}; |
| 1053 | } else { |
| 1054 | this.prunedScopes.add(scopeBlock.scope.id); |
| 1055 | return { |
| 1056 | kind: 'replace-many', |
| 1057 | value: scopeBlock.instructions, |
| 1058 | }; |
| 1059 | } |
| 1060 | } |
| 1061 | |
| 1062 | /** |
| 1063 | * If we pruned the scope for a non-escaping value, we know it doesn't |
| 1064 | * need to be memoized. Remove associated `Memoize` instructions so that |
| 1065 | * we don't report false positives on "missing" memoization of these values. |
| 1066 | */ |
| 1067 | override transformInstruction( |
| 1068 | instruction: ReactiveInstruction, |
| 1069 | state: Set<DeclarationId>, |
| 1070 | ): Transformed<ReactiveStatement> { |
| 1071 | this.traverseInstruction(instruction, state); |
| 1072 | |
| 1073 | const value = instruction.value; |
| 1074 | if (value.kind === 'StoreLocal' && value.lvalue.kind === 'Reassign') { |
| 1075 | // Complex cases of useMemo inlining result in a temporary that is reassigned |
| 1076 | const ids = getOrInsertDefault( |
| 1077 | this.reassignments, |
| 1078 | value.lvalue.place.identifier.declarationId, |
| 1079 | new Set(), |
| 1080 | ); |
| 1081 | ids.add(value.value.identifier); |
| 1082 | } else if ( |
| 1083 | value.kind === 'LoadLocal' && |
| 1084 | value.place.identifier.scope != null && |
| 1085 | instruction.lvalue != null && |
| 1086 | instruction.lvalue.identifier.scope == null |
| 1087 | ) { |
| 1088 | /* |
| 1089 | * Simpler cases result in a direct assignment to the original lvalue, with a |
| 1090 | * LoadLocal |
| 1091 | */ |
| 1092 | const ids = getOrInsertDefault( |
| 1093 | this.reassignments, |
| 1094 | instruction.lvalue.identifier.declarationId, |
| 1095 | new Set(), |
| 1096 | ); |
| 1097 | ids.add(value.place.identifier); |
| 1098 | } else if (value.kind === 'FinishMemoize') { |
| 1099 | let decls; |
| 1100 | if (value.decl.identifier.scope == null) { |
| 1101 | /** |
| 1102 | * If the manual memo was a useMemo that got inlined, iterate through |
| 1103 | * all reassignments to the iife temporary to ensure they're memoized. |
| 1104 | */ |
| 1105 | decls = this.reassignments.get(value.decl.identifier.declarationId) ?? [ |
| 1106 | value.decl.identifier, |
| 1107 | ]; |
| 1108 | } else { |
| 1109 | decls = [value.decl.identifier]; |
| 1110 | } |
| 1111 | |
| 1112 | if ( |
| 1113 | [...decls].every( |
| 1114 | decl => decl.scope == null || this.prunedScopes.has(decl.scope.id), |
| 1115 | ) |
| 1116 | ) { |
| 1117 | value.pruned = true; |
| 1118 | } |
| 1119 | } |
| 1120 | |
| 1121 | return {kind: 'keep'}; |
| 1122 | } |
| 1123 | } |