| 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 {GeneratedSource} from '../HIR'; |
| 10 | import { |
| 11 | DeclarationId, |
| 12 | Identifier, |
| 13 | InstructionId, |
| 14 | Place, |
| 15 | PrunedReactiveScopeBlock, |
| 16 | ReactiveFunction, |
| 17 | ReactiveScope, |
| 18 | ReactiveInstruction, |
| 19 | ReactiveScopeBlock, |
| 20 | ReactiveValue, |
| 21 | ScopeId, |
| 22 | SpreadPattern, |
| 23 | promoteTemporary, |
| 24 | promoteTemporaryJsxTag, |
| 25 | IdentifierId, |
| 26 | } from '../HIR/HIR'; |
| 27 | import {ReactiveFunctionVisitor, visitReactiveFunction} from './visitors'; |
| 28 | import {eachInstructionValueLValue, eachPatternOperand} from '../HIR/visitors'; |
| 29 | |
| 30 | /** |
| 31 | * Phase 2: Promote identifiers which are used in a place that requires a named variable. |
| 32 | */ |
| 33 | class PromoteTemporaries extends ReactiveFunctionVisitor<State> { |
| 34 | override visitScope(scopeBlock: ReactiveScopeBlock, state: State): void { |
| 35 | for (const dep of scopeBlock.scope.dependencies) { |
| 36 | const {identifier} = dep; |
| 37 | if (identifier.name == null) { |
| 38 | promoteIdentifier(identifier, state); |
| 39 | } |
| 40 | } |
| 41 | /* |
| 42 | * This is technically optional. We could prune ReactiveScopes |
| 43 | * whose outputs are not used in another computation or return |
| 44 | * value. |
| 45 | * Many of our current test fixtures do not return a value, so |
| 46 | * it is better for now to promote (and memoize) every output. |
| 47 | */ |
| 48 | for (const [, declaration] of scopeBlock.scope.declarations) { |
| 49 | if (declaration.identifier.name == null) { |
| 50 | promoteIdentifier(declaration.identifier, state); |
| 51 | } |
| 52 | } |
| 53 | this.traverseScope(scopeBlock, state); |
| 54 | } |
| 55 | |
| 56 | override visitPrunedScope( |
| 57 | scopeBlock: PrunedReactiveScopeBlock, |
| 58 | state: State, |
| 59 | ): void { |
| 60 | for (const [, declaration] of scopeBlock.scope.declarations) { |
| 61 | if ( |
| 62 | declaration.identifier.name == null && |
| 63 | state.pruned.get(declaration.identifier.declarationId) |
| 64 | ?.usedOutsideScope === true |
| 65 | ) { |
| 66 | promoteIdentifier(declaration.identifier, state); |
| 67 | } |
| 68 | } |
| 69 | this.traversePrunedScope(scopeBlock, state); |
| 70 | } |
| 71 | |
| 72 | override visitParam(place: Place, state: State): void { |
| 73 | if (place.identifier.name === null) { |
| 74 | promoteIdentifier(place.identifier, state); |
| 75 | } |
| 76 | } |
| 77 | |
| 78 | override visitValue( |
| 79 | id: InstructionId, |
| 80 | value: ReactiveValue, |
| 81 | state: State, |
| 82 | ): void { |
| 83 | this.traverseValue(id, value, state); |
| 84 | if (value.kind === 'FunctionExpression' || value.kind === 'ObjectMethod') { |
| 85 | this.visitHirFunction(value.loweredFunc.func, state); |
| 86 | } |
| 87 | } |
| 88 | |
| 89 | override visitReactiveFunctionValue( |
| 90 | _id: InstructionId, |
| 91 | _dependencies: Array<Place>, |
| 92 | fn: ReactiveFunction, |
| 93 | state: State, |
| 94 | ): void { |
| 95 | for (const operand of fn.params) { |
| 96 | const place = operand.kind === 'Identifier' ? operand : operand.place; |
| 97 | if (place.identifier.name === null) { |
| 98 | promoteIdentifier(place.identifier, state); |
| 99 | } |
| 100 | } |
| 101 | visitReactiveFunction(fn, this, state); |
| 102 | } |
| 103 | } |
| 104 | |
| 105 | /** |
| 106 | * Phase 3: Now that identifiers which need promotion are promoted, find and promote |
| 107 | * all other Identifier instances of each promoted DeclarationId. |
| 108 | */ |
| 109 | class PromoteAllInstancedOfPromotedTemporaries extends ReactiveFunctionVisitor<State> { |
| 110 | override visitPlace(_id: InstructionId, place: Place, state: State): void { |
| 111 | if ( |
| 112 | place.identifier.name === null && |
| 113 | state.promoted.has(place.identifier.declarationId) |
| 114 | ) { |
| 115 | promoteIdentifier(place.identifier, state); |
| 116 | } |
| 117 | } |
| 118 | override visitLValue( |
| 119 | _id: InstructionId, |
| 120 | _lvalue: Place, |
| 121 | _state: State, |
| 122 | ): void { |
| 123 | this.visitPlace(_id, _lvalue, _state); |
| 124 | } |
| 125 | traverseScopeIdentifiers(scope: ReactiveScope, state: State): void { |
| 126 | for (const [, decl] of scope.declarations) { |
| 127 | if ( |
| 128 | decl.identifier.name === null && |
| 129 | state.promoted.has(decl.identifier.declarationId) |
| 130 | ) { |
| 131 | promoteIdentifier(decl.identifier, state); |
| 132 | } |
| 133 | } |
| 134 | for (const dep of scope.dependencies) { |
| 135 | if ( |
| 136 | dep.identifier.name === null && |
| 137 | state.promoted.has(dep.identifier.declarationId) |
| 138 | ) { |
| 139 | promoteIdentifier(dep.identifier, state); |
| 140 | } |
| 141 | } |
| 142 | for (const reassignment of scope.reassignments) { |
| 143 | if ( |
| 144 | reassignment.name === null && |
| 145 | state.promoted.has(reassignment.declarationId) |
| 146 | ) { |
| 147 | promoteIdentifier(reassignment, state); |
| 148 | } |
| 149 | } |
| 150 | } |
| 151 | override visitScope(scope: ReactiveScopeBlock, state: State): void { |
| 152 | this.traverseScope(scope, state); |
| 153 | this.traverseScopeIdentifiers(scope.scope, state); |
| 154 | } |
| 155 | override visitPrunedScope( |
| 156 | scopeBlock: PrunedReactiveScopeBlock, |
| 157 | state: State, |
| 158 | ): void { |
| 159 | this.traversePrunedScope(scopeBlock, state); |
| 160 | this.traverseScopeIdentifiers(scopeBlock.scope, state); |
| 161 | } |
| 162 | override visitReactiveFunctionValue( |
| 163 | _id: InstructionId, |
| 164 | _dependencies: Array<Place>, |
| 165 | fn: ReactiveFunction, |
| 166 | state: State, |
| 167 | ): void { |
| 168 | visitReactiveFunction(fn, this, state); |
| 169 | } |
| 170 | } |
| 171 | |
| 172 | type JsxExpressionTags = Set<DeclarationId>; |
| 173 | type State = { |
| 174 | tags: JsxExpressionTags; |
| 175 | promoted: Set<DeclarationId>; |
| 176 | pruned: Map< |
| 177 | DeclarationId, |
| 178 | {activeScopes: Array<ScopeId>; usedOutsideScope: boolean} |
| 179 | >; // true if referenced within another scope, false if only accessed outside of scopes |
| 180 | }; |
| 181 | |
| 182 | /** |
| 183 | * Phase 1: checks for pruned variables which need to be promoted, as well as |
| 184 | * usage of identifiers as jsx tags, which need to be promoted differently |
| 185 | */ |
| 186 | class CollectPromotableTemporaries extends ReactiveFunctionVisitor<State> { |
| 187 | activeScopes: Array<ScopeId> = []; |
| 188 | |
| 189 | override visitPlace(_id: InstructionId, place: Place, state: State): void { |
| 190 | if ( |
| 191 | this.activeScopes.length !== 0 && |
| 192 | state.pruned.has(place.identifier.declarationId) |
| 193 | ) { |
| 194 | const prunedPlace = state.pruned.get(place.identifier.declarationId)!; |
| 195 | if (prunedPlace.activeScopes.indexOf(this.activeScopes.at(-1)!) === -1) { |
| 196 | prunedPlace.usedOutsideScope = true; |
| 197 | } |
| 198 | } |
| 199 | } |
| 200 | |
| 201 | override visitValue( |
| 202 | id: InstructionId, |
| 203 | value: ReactiveValue, |
| 204 | state: State, |
| 205 | ): void { |
| 206 | this.traverseValue(id, value, state); |
| 207 | if (value.kind === 'JsxExpression' && value.tag.kind === 'Identifier') { |
| 208 | state.tags.add(value.tag.identifier.declarationId); |
| 209 | } |
| 210 | } |
| 211 | |
| 212 | override visitPrunedScope( |
| 213 | scopeBlock: PrunedReactiveScopeBlock, |
| 214 | state: State, |
| 215 | ): void { |
| 216 | for (const [_id, decl] of scopeBlock.scope.declarations) { |
| 217 | state.pruned.set(decl.identifier.declarationId, { |
| 218 | activeScopes: [...this.activeScopes], |
| 219 | usedOutsideScope: false, |
| 220 | }); |
| 221 | } |
| 222 | this.visitBlock(scopeBlock.instructions, state); |
| 223 | } |
| 224 | |
| 225 | override visitScope(scopeBlock: ReactiveScopeBlock, state: State): void { |
| 226 | this.activeScopes.push(scopeBlock.scope.id); |
| 227 | this.traverseScope(scopeBlock, state); |
| 228 | this.activeScopes.pop(); |
| 229 | } |
| 230 | } |
| 231 | |
| 232 | type InterState = Map<IdentifierId, [Identifier, boolean]>; |
| 233 | class PromoteInterposedTemporaries extends ReactiveFunctionVisitor<InterState> { |
| 234 | #promotable: State; |
| 235 | #consts: Set<IdentifierId> = new Set(); |
| 236 | #globals: Set<IdentifierId> = new Set(); |
| 237 | |
| 238 | /* |
| 239 | * Unpromoted temporaries will be emitted at their use sites rather than as separate |
| 240 | * declarations. However, this causes errors if an interposing temporary has been |
| 241 | * promoted, or if an interposing instruction has had its lvalues deleted, because such |
| 242 | * temporaries will be emitted as separate statements, which can effectively cause |
| 243 | * code to be reordered, and when that code has side effects that changes program behavior. |
| 244 | * This visitor promotes temporarties that have such interposing instructions to preserve |
| 245 | * source ordering. |
| 246 | */ |
| 247 | constructor(promotable: State, params: Array<Place | SpreadPattern>) { |
| 248 | super(); |
| 249 | params.forEach(param => { |
| 250 | switch (param.kind) { |
| 251 | case 'Identifier': |
| 252 | this.#consts.add(param.identifier.id); |
| 253 | break; |
| 254 | case 'Spread': |
| 255 | this.#consts.add(param.place.identifier.id); |
| 256 | break; |
| 257 | } |
| 258 | }); |
| 259 | this.#promotable = promotable; |
| 260 | } |
| 261 | |
| 262 | override visitPlace( |
| 263 | _id: InstructionId, |
| 264 | place: Place, |
| 265 | state: InterState, |
| 266 | ): void { |
| 267 | const promo = state.get(place.identifier.id); |
| 268 | if (promo) { |
| 269 | const [identifier, needsPromotion] = promo; |
| 270 | if ( |
| 271 | needsPromotion && |
| 272 | identifier.name === null && |
| 273 | !this.#consts.has(identifier.id) |
| 274 | ) { |
| 275 | /* |
| 276 | * If the identifier hasn't been promoted but is marked as needing |
| 277 | * promotion by the logic in `visitInstruction`, and we've seen a |
| 278 | * use of it after said marking, promote it |
| 279 | */ |
| 280 | promoteIdentifier(identifier, this.#promotable); |
| 281 | } |
| 282 | } |
| 283 | } |
| 284 | |
| 285 | override visitInstruction( |
| 286 | instruction: ReactiveInstruction, |
| 287 | state: InterState, |
| 288 | ): void { |
| 289 | for (const lval of eachInstructionValueLValue(instruction.value)) { |
| 290 | CompilerError.invariant(lval.identifier.name != null, { |
| 291 | reason: |
| 292 | 'PromoteInterposedTemporaries: Assignment targets not expected to be temporaries', |
| 293 | loc: instruction.loc, |
| 294 | }); |
| 295 | } |
| 296 | |
| 297 | switch (instruction.value.kind) { |
| 298 | case 'CallExpression': |
| 299 | case 'MethodCall': |
| 300 | case 'Await': |
| 301 | case 'PropertyStore': |
| 302 | case 'PropertyDelete': |
| 303 | case 'ComputedStore': |
| 304 | case 'ComputedDelete': |
| 305 | case 'PostfixUpdate': |
| 306 | case 'PrefixUpdate': |
| 307 | case 'StoreLocal': |
| 308 | case 'StoreContext': |
| 309 | case 'StoreGlobal': |
| 310 | case 'Destructure': { |
| 311 | let constStore = false; |
| 312 | |
| 313 | if ( |
| 314 | (instruction.value.kind === 'StoreContext' || |
| 315 | instruction.value.kind === 'StoreLocal') && |
| 316 | (instruction.value.lvalue.kind === 'Const' || |
| 317 | instruction.value.lvalue.kind === 'HoistedConst') |
| 318 | ) { |
| 319 | /* |
| 320 | * If an identifier is const, we don't need to worry about it |
| 321 | * being mutated between being loaded and being used |
| 322 | */ |
| 323 | this.#consts.add(instruction.value.lvalue.place.identifier.id); |
| 324 | constStore = true; |
| 325 | } |
| 326 | if ( |
| 327 | instruction.value.kind === 'Destructure' && |
| 328 | (instruction.value.lvalue.kind === 'Const' || |
| 329 | instruction.value.lvalue.kind === 'HoistedConst') |
| 330 | ) { |
| 331 | [...eachPatternOperand(instruction.value.lvalue.pattern)].forEach( |
| 332 | ident => this.#consts.add(ident.identifier.id), |
| 333 | ); |
| 334 | constStore = true; |
| 335 | } |
| 336 | if (instruction.value.kind === 'MethodCall') { |
| 337 | // Treat property of method call as constlike so we don't promote it. |
| 338 | this.#consts.add(instruction.value.property.identifier.id); |
| 339 | } |
| 340 | |
| 341 | super.visitInstruction(instruction, state); |
| 342 | if ( |
| 343 | !constStore && |
| 344 | (instruction.lvalue == null || |
| 345 | instruction.lvalue.identifier.name != null) |
| 346 | ) { |
| 347 | /* |
| 348 | * If we've stripped the lvalue or promoted the lvalue, then we will emit this instruction |
| 349 | * as a statement in codegen. |
| 350 | * |
| 351 | * If this instruction will be emitted directly as a statement rather than as a temporary |
| 352 | * during codegen, then it can interpose between the defs and the uses of other temporaries. |
| 353 | * Since this instruction could potentially mutate those defs, it's not safe to relocate |
| 354 | * the definition of those temporaries to after this instruction. Mark all those temporaries |
| 355 | * as needing promotion, but don't promote them until we actually see them being used. |
| 356 | */ |
| 357 | for (const [key, [ident, _]] of state.entries()) { |
| 358 | state.set(key, [ident, true]); |
| 359 | } |
| 360 | } |
| 361 | if (instruction.lvalue && instruction.lvalue.identifier.name === null) { |
| 362 | // Add this instruction's lvalue to the state, initially not marked as needing promotion |
| 363 | state.set(instruction.lvalue.identifier.id, [ |
| 364 | instruction.lvalue.identifier, |
| 365 | false, |
| 366 | ]); |
| 367 | } |
| 368 | break; |
| 369 | } |
| 370 | case 'DeclareContext': |
| 371 | case 'DeclareLocal': { |
| 372 | if ( |
| 373 | instruction.value.lvalue.kind === 'Const' || |
| 374 | instruction.value.lvalue.kind === 'HoistedConst' |
| 375 | ) { |
| 376 | this.#consts.add(instruction.value.lvalue.place.identifier.id); |
| 377 | } |
| 378 | super.visitInstruction(instruction, state); |
| 379 | break; |
| 380 | } |
| 381 | case 'LoadContext': |
| 382 | case 'LoadLocal': { |
| 383 | if (instruction.lvalue && instruction.lvalue.identifier.name === null) { |
| 384 | if (this.#consts.has(instruction.value.place.identifier.id)) { |
| 385 | this.#consts.add(instruction.lvalue.identifier.id); |
| 386 | } |
| 387 | state.set(instruction.lvalue.identifier.id, [ |
| 388 | instruction.lvalue.identifier, |
| 389 | false, |
| 390 | ]); |
| 391 | } |
| 392 | super.visitInstruction(instruction, state); |
| 393 | break; |
| 394 | } |
| 395 | case 'PropertyLoad': |
| 396 | case 'ComputedLoad': { |
| 397 | if (instruction.lvalue) { |
| 398 | if (this.#globals.has(instruction.value.object.identifier.id)) { |
| 399 | this.#globals.add(instruction.lvalue.identifier.id); |
| 400 | this.#consts.add(instruction.lvalue.identifier.id); |
| 401 | } |
| 402 | if (instruction.lvalue.identifier.name === null) { |
| 403 | state.set(instruction.lvalue.identifier.id, [ |
| 404 | instruction.lvalue.identifier, |
| 405 | false, |
| 406 | ]); |
| 407 | } |
| 408 | } |
| 409 | super.visitInstruction(instruction, state); |
| 410 | break; |
| 411 | } |
| 412 | case 'LoadGlobal': { |
| 413 | instruction.lvalue && |
| 414 | this.#globals.add(instruction.lvalue.identifier.id); |
| 415 | super.visitInstruction(instruction, state); |
| 416 | break; |
| 417 | } |
| 418 | default: { |
| 419 | super.visitInstruction(instruction, state); |
| 420 | } |
| 421 | } |
| 422 | } |
| 423 | } |
| 424 | |
| 425 | export function promoteUsedTemporaries(fn: ReactiveFunction): void { |
| 426 | const state: State = { |
| 427 | tags: new Set(), |
| 428 | promoted: new Set(), |
| 429 | pruned: new Map(), |
| 430 | }; |
| 431 | visitReactiveFunction(fn, new CollectPromotableTemporaries(), state); |
| 432 | for (const operand of fn.params) { |
| 433 | const place = operand.kind === 'Identifier' ? operand : operand.place; |
| 434 | if (place.identifier.name === null) { |
| 435 | promoteIdentifier(place.identifier, state); |
| 436 | } |
| 437 | } |
| 438 | visitReactiveFunction(fn, new PromoteTemporaries(), state); |
| 439 | |
| 440 | visitReactiveFunction( |
| 441 | fn, |
| 442 | new PromoteInterposedTemporaries(state, fn.params), |
| 443 | new Map(), |
| 444 | ); |
| 445 | visitReactiveFunction( |
| 446 | fn, |
| 447 | new PromoteAllInstancedOfPromotedTemporaries(), |
| 448 | state, |
| 449 | ); |
| 450 | } |
| 451 | |
| 452 | function promoteIdentifier(identifier: Identifier, state: State): void { |
| 453 | CompilerError.invariant(identifier.name === null, { |
| 454 | reason: |
| 455 | 'promoteTemporary: Expected to be called only for temporary variables', |
| 456 | loc: GeneratedSource, |
| 457 | }); |
| 458 | if (state.tags.has(identifier.declarationId)) { |
| 459 | promoteTemporaryJsxTag(identifier); |
| 460 | } else { |
| 461 | promoteTemporary(identifier); |
| 462 | } |
| 463 | state.promoted.add(identifier.declarationId); |
| 464 | } |