| 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, SourceLocation} from '..'; |
| 9 | import { |
| 10 | BlockId, |
| 11 | Effect, |
| 12 | HIRFunction, |
| 13 | Identifier, |
| 14 | IdentifierId, |
| 15 | InstructionId, |
| 16 | isJsxType, |
| 17 | makeInstructionId, |
| 18 | ValueKind, |
| 19 | ValueReason, |
| 20 | Place, |
| 21 | isPrimitiveType, |
| 22 | } from '../HIR/HIR'; |
| 23 | import {Environment} from '../HIR/Environment'; |
| 24 | import { |
| 25 | eachInstructionLValue, |
| 26 | eachInstructionValueOperand, |
| 27 | eachTerminalOperand, |
| 28 | } from '../HIR/visitors'; |
| 29 | import {assertExhaustive, getOrInsertWith} from '../Utils/utils'; |
| 30 | |
| 31 | import {AliasingEffect, MutationReason} from './AliasingEffects'; |
| 32 | |
| 33 | /** |
| 34 | * This pass builds an abstract model of the heap and interprets the effects of the |
| 35 | * given function in order to determine the following: |
| 36 | * - The mutable ranges of all identifiers in the function |
| 37 | * - The externally-visible effects of the function, such as mutations of params and |
| 38 | * context-vars, aliasing between params/context-vars/return-value, and impure side |
| 39 | * effects. |
| 40 | * - The legacy `Effect` to store on each Place. |
| 41 | * |
| 42 | * This pass builds a data flow graph using the effects, tracking an abstract notion |
| 43 | * of "when" each effect occurs relative to the others. It then walks each mutation |
| 44 | * effect against the graph, updating the range of each node that would be reachable |
| 45 | * at the "time" that the effect occurred. |
| 46 | * |
| 47 | * This pass also validates against invalid effects: any function that is reachable |
| 48 | * by being called, or via a Render effect, is validated against mutating globals |
| 49 | * or calling impure code. |
| 50 | * |
| 51 | * Note that this function also populates the outer function's aliasing effects with |
| 52 | * any mutations that apply to its params or context variables. |
| 53 | * |
| 54 | * ## Example |
| 55 | * A function expression such as the following: |
| 56 | * |
| 57 | * ``` |
| 58 | * (x) => { x.y = true } |
| 59 | * ``` |
| 60 | * |
| 61 | * Would populate a `Mutate x` aliasing effect on the outer function. |
| 62 | * |
| 63 | * ## Returned Function Effects |
| 64 | * |
| 65 | * The function returns (if successful) a list of externally-visible effects. |
| 66 | * This is determined by simulating a conditional, transitive mutation against |
| 67 | * each param, context variable, and return value in turn, and seeing which other |
| 68 | * such values are affected. If they're affected, they must be captured, so we |
| 69 | * record a Capture. |
| 70 | * |
| 71 | * The only tricky bit is the return value, which could _alias_ (or even assign) |
| 72 | * one or more of the params/context-vars rather than just capturing. So we have |
| 73 | * to do a bit more tracking for returns. |
| 74 | */ |
| 75 | export function inferMutationAliasingRanges( |
| 76 | fn: HIRFunction, |
| 77 | {isFunctionExpression}: {isFunctionExpression: boolean}, |
| 78 | ): Array<AliasingEffect> { |
| 79 | // The set of externally-visible effects |
| 80 | const functionEffects: Array<AliasingEffect> = []; |
| 81 | |
| 82 | /** |
| 83 | * Part 1: Infer mutable ranges for values. We build an abstract model of |
| 84 | * values, the alias/capture edges between them, and the set of mutations. |
| 85 | * Edges and mutations are ordered, with mutations processed against the |
| 86 | * abstract model only after it is fully constructed by visiting all blocks |
| 87 | * _and_ connecting phis. Phis are considered ordered at the time of the |
| 88 | * phi node. |
| 89 | * |
| 90 | * This should (may?) mean that mutations are able to see the full state |
| 91 | * of the graph and mark all the appropriate identifiers as mutated at |
| 92 | * the correct point, accounting for both backward and forward edges. |
| 93 | * Ie a mutation of x accounts for both values that flowed into x, |
| 94 | * and values that x flowed into. |
| 95 | */ |
| 96 | const state = new AliasingState(); |
| 97 | type PendingPhiOperand = {from: Place; into: Place; index: number}; |
| 98 | const pendingPhis = new Map<BlockId, Array<PendingPhiOperand>>(); |
| 99 | const mutations: Array<{ |
| 100 | index: number; |
| 101 | id: InstructionId; |
| 102 | transitive: boolean; |
| 103 | kind: MutationKind; |
| 104 | place: Place; |
| 105 | reason: MutationReason | null; |
| 106 | }> = []; |
| 107 | const renders: Array<{index: number; place: Place}> = []; |
| 108 | |
| 109 | let index = 0; |
| 110 | |
| 111 | const shouldRecordErrors = !isFunctionExpression && fn.env.enableValidations; |
| 112 | |
| 113 | for (const param of [...fn.params, ...fn.context, fn.returns]) { |
| 114 | const place = param.kind === 'Identifier' ? param : param.place; |
| 115 | state.create(place, {kind: 'Object'}); |
| 116 | } |
| 117 | const seenBlocks = new Set<BlockId>(); |
| 118 | for (const block of fn.body.blocks.values()) { |
| 119 | for (const phi of block.phis) { |
| 120 | state.create(phi.place, {kind: 'Phi'}); |
| 121 | for (const [pred, operand] of phi.operands) { |
| 122 | if (!seenBlocks.has(pred)) { |
| 123 | // NOTE: annotation required to actually typecheck and not silently infer `any` |
| 124 | const blockPhis = getOrInsertWith<BlockId, Array<PendingPhiOperand>>( |
| 125 | pendingPhis, |
| 126 | pred, |
| 127 | () => [], |
| 128 | ); |
| 129 | blockPhis.push({from: operand, into: phi.place, index: index++}); |
| 130 | } else { |
| 131 | state.assign(index++, operand, phi.place); |
| 132 | } |
| 133 | } |
| 134 | } |
| 135 | seenBlocks.add(block.id); |
| 136 | |
| 137 | for (const instr of block.instructions) { |
| 138 | if (instr.effects == null) continue; |
| 139 | for (const effect of instr.effects) { |
| 140 | if (effect.kind === 'Create') { |
| 141 | state.create(effect.into, {kind: 'Object'}); |
| 142 | } else if (effect.kind === 'CreateFunction') { |
| 143 | state.create(effect.into, { |
| 144 | kind: 'Function', |
| 145 | function: effect.function.loweredFunc.func, |
| 146 | }); |
| 147 | } else if (effect.kind === 'CreateFrom') { |
| 148 | state.createFrom(index++, effect.from, effect.into); |
| 149 | } else if (effect.kind === 'Assign') { |
| 150 | /** |
| 151 | * TODO: Invariant that the node is not initialized yet |
| 152 | * |
| 153 | * InferFunctionExpressionAliasingEffectSignatures currently infers |
| 154 | * Assign effects in some places that should be Alias, leading to |
| 155 | * Assign effects that reinitialize a value. The end result appears to |
| 156 | * be fine, but we should fix that inference pass so that we add the |
| 157 | * invariant here. |
| 158 | */ |
| 159 | if (!state.nodes.has(effect.into.identifier)) { |
| 160 | state.create(effect.into, {kind: 'Object'}); |
| 161 | } |
| 162 | state.assign(index++, effect.from, effect.into); |
| 163 | } else if (effect.kind === 'Alias') { |
| 164 | state.assign(index++, effect.from, effect.into); |
| 165 | } else if (effect.kind === 'MaybeAlias') { |
| 166 | state.maybeAlias(index++, effect.from, effect.into); |
| 167 | } else if (effect.kind === 'Capture') { |
| 168 | state.capture(index++, effect.from, effect.into); |
| 169 | } else if ( |
| 170 | effect.kind === 'MutateTransitive' || |
| 171 | effect.kind === 'MutateTransitiveConditionally' |
| 172 | ) { |
| 173 | mutations.push({ |
| 174 | index: index++, |
| 175 | id: instr.id, |
| 176 | transitive: true, |
| 177 | kind: |
| 178 | effect.kind === 'MutateTransitive' |
| 179 | ? MutationKind.Definite |
| 180 | : MutationKind.Conditional, |
| 181 | reason: null, |
| 182 | place: effect.value, |
| 183 | }); |
| 184 | } else if ( |
| 185 | effect.kind === 'Mutate' || |
| 186 | effect.kind === 'MutateConditionally' |
| 187 | ) { |
| 188 | mutations.push({ |
| 189 | index: index++, |
| 190 | id: instr.id, |
| 191 | transitive: false, |
| 192 | kind: |
| 193 | effect.kind === 'Mutate' |
| 194 | ? MutationKind.Definite |
| 195 | : MutationKind.Conditional, |
| 196 | reason: effect.kind === 'Mutate' ? (effect.reason ?? null) : null, |
| 197 | place: effect.value, |
| 198 | }); |
| 199 | } else if ( |
| 200 | effect.kind === 'MutateFrozen' || |
| 201 | effect.kind === 'MutateGlobal' || |
| 202 | effect.kind === 'Impure' |
| 203 | ) { |
| 204 | if (shouldRecordErrors) { |
| 205 | fn.env.recordError(effect.error); |
| 206 | } |
| 207 | functionEffects.push(effect); |
| 208 | } else if (effect.kind === 'Render') { |
| 209 | renders.push({index: index++, place: effect.place}); |
| 210 | functionEffects.push(effect); |
| 211 | } |
| 212 | } |
| 213 | } |
| 214 | const blockPhis = pendingPhis.get(block.id); |
| 215 | if (blockPhis != null) { |
| 216 | for (const {from, into, index} of blockPhis) { |
| 217 | state.assign(index, from, into); |
| 218 | } |
| 219 | } |
| 220 | if (block.terminal.kind === 'return') { |
| 221 | state.assign(index++, block.terminal.value, fn.returns); |
| 222 | } |
| 223 | |
| 224 | if ( |
| 225 | (block.terminal.kind === 'maybe-throw' || |
| 226 | block.terminal.kind === 'return') && |
| 227 | block.terminal.effects != null |
| 228 | ) { |
| 229 | for (const effect of block.terminal.effects) { |
| 230 | if (effect.kind === 'Alias') { |
| 231 | state.assign(index++, effect.from, effect.into); |
| 232 | } else { |
| 233 | CompilerError.invariant(effect.kind === 'Freeze', { |
| 234 | reason: `Unexpected '${effect.kind}' effect for MaybeThrow terminal`, |
| 235 | loc: block.terminal.loc, |
| 236 | }); |
| 237 | } |
| 238 | } |
| 239 | } |
| 240 | } |
| 241 | |
| 242 | for (const mutation of mutations) { |
| 243 | state.mutate( |
| 244 | mutation.index, |
| 245 | mutation.place.identifier, |
| 246 | makeInstructionId(mutation.id + 1), |
| 247 | mutation.transitive, |
| 248 | mutation.kind, |
| 249 | mutation.place.loc, |
| 250 | mutation.reason, |
| 251 | shouldRecordErrors ? fn.env : null, |
| 252 | ); |
| 253 | } |
| 254 | for (const render of renders) { |
| 255 | state.render( |
| 256 | render.index, |
| 257 | render.place.identifier, |
| 258 | shouldRecordErrors ? fn.env : null, |
| 259 | ); |
| 260 | } |
| 261 | for (const param of [...fn.context, ...fn.params]) { |
| 262 | const place = param.kind === 'Identifier' ? param : param.place; |
| 263 | |
| 264 | const node = state.nodes.get(place.identifier); |
| 265 | if (node == null) { |
| 266 | continue; |
| 267 | } |
| 268 | let mutated = false; |
| 269 | if (node.local != null) { |
| 270 | if (node.local.kind === MutationKind.Conditional) { |
| 271 | mutated = true; |
| 272 | functionEffects.push({ |
| 273 | kind: 'MutateConditionally', |
| 274 | value: {...place, loc: node.local.loc}, |
| 275 | }); |
| 276 | } else if (node.local.kind === MutationKind.Definite) { |
| 277 | mutated = true; |
| 278 | functionEffects.push({ |
| 279 | kind: 'Mutate', |
| 280 | value: {...place, loc: node.local.loc}, |
| 281 | reason: node.mutationReason, |
| 282 | }); |
| 283 | } |
| 284 | } |
| 285 | if (node.transitive != null) { |
| 286 | if (node.transitive.kind === MutationKind.Conditional) { |
| 287 | mutated = true; |
| 288 | functionEffects.push({ |
| 289 | kind: 'MutateTransitiveConditionally', |
| 290 | value: {...place, loc: node.transitive.loc}, |
| 291 | }); |
| 292 | } else if (node.transitive.kind === MutationKind.Definite) { |
| 293 | mutated = true; |
| 294 | functionEffects.push({ |
| 295 | kind: 'MutateTransitive', |
| 296 | value: {...place, loc: node.transitive.loc}, |
| 297 | }); |
| 298 | } |
| 299 | } |
| 300 | if (mutated) { |
| 301 | place.effect = Effect.Capture; |
| 302 | } |
| 303 | } |
| 304 | |
| 305 | /** |
| 306 | * Part 2 |
| 307 | * Add legacy operand-specific effects based on instruction effects and mutable ranges. |
| 308 | * Also fixes up operand mutable ranges, making sure that start is non-zero if the value |
| 309 | * is mutated (depended on by later passes like InferReactiveScopeVariables which uses this |
| 310 | * to filter spurious mutations of globals, which we now guard against more precisely) |
| 311 | */ |
| 312 | for (const block of fn.body.blocks.values()) { |
| 313 | for (const phi of block.phis) { |
| 314 | // TODO: we don't actually set these effects today! |
| 315 | phi.place.effect = Effect.Store; |
| 316 | const isPhiMutatedAfterCreation: boolean = |
| 317 | phi.place.identifier.mutableRange.end > |
| 318 | (block.instructions.at(0)?.id ?? block.terminal.id); |
| 319 | for (const operand of phi.operands.values()) { |
| 320 | operand.effect = isPhiMutatedAfterCreation |
| 321 | ? Effect.Capture |
| 322 | : Effect.Read; |
| 323 | } |
| 324 | if ( |
| 325 | isPhiMutatedAfterCreation && |
| 326 | phi.place.identifier.mutableRange.start === 0 |
| 327 | ) { |
| 328 | /* |
| 329 | * TODO: ideally we'd construct a precise start range, but what really |
| 330 | * matters is that the phi's range appears mutable (end > start + 1) |
| 331 | * so we just set the start to the previous instruction before this block |
| 332 | */ |
| 333 | const firstInstructionIdOfBlock = |
| 334 | block.instructions.at(0)?.id ?? block.terminal.id; |
| 335 | phi.place.identifier.mutableRange.start = makeInstructionId( |
| 336 | firstInstructionIdOfBlock - 1, |
| 337 | ); |
| 338 | } |
| 339 | } |
| 340 | for (const instr of block.instructions) { |
| 341 | for (const lvalue of eachInstructionLValue(instr)) { |
| 342 | lvalue.effect = Effect.ConditionallyMutate; |
| 343 | if (lvalue.identifier.mutableRange.start === 0) { |
| 344 | lvalue.identifier.mutableRange.start = instr.id; |
| 345 | } |
| 346 | if (lvalue.identifier.mutableRange.end === 0) { |
| 347 | lvalue.identifier.mutableRange.end = makeInstructionId( |
| 348 | Math.max(instr.id + 1, lvalue.identifier.mutableRange.end), |
| 349 | ); |
| 350 | } |
| 351 | } |
| 352 | for (const operand of eachInstructionValueOperand(instr.value)) { |
| 353 | operand.effect = Effect.Read; |
| 354 | } |
| 355 | if (instr.effects == null) { |
| 356 | continue; |
| 357 | } |
| 358 | const operandEffects = new Map<IdentifierId, Effect>(); |
| 359 | for (const effect of instr.effects) { |
| 360 | switch (effect.kind) { |
| 361 | case 'Assign': |
| 362 | case 'Alias': |
| 363 | case 'Capture': |
| 364 | case 'CreateFrom': |
| 365 | case 'MaybeAlias': { |
| 366 | const isMutatedOrReassigned = |
| 367 | effect.into.identifier.mutableRange.end > instr.id; |
| 368 | if (isMutatedOrReassigned) { |
| 369 | operandEffects.set(effect.from.identifier.id, Effect.Capture); |
| 370 | operandEffects.set(effect.into.identifier.id, Effect.Store); |
| 371 | } else { |
| 372 | operandEffects.set(effect.from.identifier.id, Effect.Read); |
| 373 | operandEffects.set(effect.into.identifier.id, Effect.Store); |
| 374 | } |
| 375 | break; |
| 376 | } |
| 377 | case 'CreateFunction': |
| 378 | case 'Create': { |
| 379 | break; |
| 380 | } |
| 381 | case 'Mutate': { |
| 382 | operandEffects.set(effect.value.identifier.id, Effect.Store); |
| 383 | break; |
| 384 | } |
| 385 | case 'Apply': { |
| 386 | CompilerError.invariant(false, { |
| 387 | reason: `[AnalyzeFunctions] Expected Apply effects to be replaced with more precise effects`, |
| 388 | loc: effect.function.loc, |
| 389 | }); |
| 390 | } |
| 391 | case 'MutateTransitive': |
| 392 | case 'MutateConditionally': |
| 393 | case 'MutateTransitiveConditionally': { |
| 394 | operandEffects.set( |
| 395 | effect.value.identifier.id, |
| 396 | Effect.ConditionallyMutate, |
| 397 | ); |
| 398 | break; |
| 399 | } |
| 400 | case 'Freeze': { |
| 401 | operandEffects.set(effect.value.identifier.id, Effect.Freeze); |
| 402 | break; |
| 403 | } |
| 404 | case 'ImmutableCapture': { |
| 405 | // no-op, Read is the default |
| 406 | break; |
| 407 | } |
| 408 | case 'Impure': |
| 409 | case 'Render': |
| 410 | case 'MutateFrozen': |
| 411 | case 'MutateGlobal': { |
| 412 | // no-op |
| 413 | break; |
| 414 | } |
| 415 | default: { |
| 416 | assertExhaustive( |
| 417 | effect, |
| 418 | `Unexpected effect kind ${(effect as any).kind}`, |
| 419 | ); |
| 420 | } |
| 421 | } |
| 422 | } |
| 423 | for (const lvalue of eachInstructionLValue(instr)) { |
| 424 | const effect = |
| 425 | operandEffects.get(lvalue.identifier.id) ?? |
| 426 | Effect.ConditionallyMutate; |
| 427 | lvalue.effect = effect; |
| 428 | } |
| 429 | for (const operand of eachInstructionValueOperand(instr.value)) { |
| 430 | if ( |
| 431 | operand.identifier.mutableRange.end > instr.id && |
| 432 | operand.identifier.mutableRange.start === 0 |
| 433 | ) { |
| 434 | operand.identifier.mutableRange.start = instr.id; |
| 435 | } |
| 436 | const effect = operandEffects.get(operand.identifier.id) ?? Effect.Read; |
| 437 | operand.effect = effect; |
| 438 | } |
| 439 | |
| 440 | /** |
| 441 | * This case is targeted at hoisted functions like: |
| 442 | * |
| 443 | * ``` |
| 444 | * x(); |
| 445 | * function x() { ... } |
| 446 | * ``` |
| 447 | * |
| 448 | * Which turns into: |
| 449 | * |
| 450 | * t0 = DeclareContext HoistedFunction x |
| 451 | * t1 = LoadContext x |
| 452 | * t2 = CallExpression t1 ( ) |
| 453 | * t3 = FunctionExpression ... |
| 454 | * t4 = StoreContext Function x = t3 |
| 455 | * |
| 456 | * If the function had captured mutable values, it would already have its |
| 457 | * range extended to include the StoreContext. But if the function doesn't |
| 458 | * capture any mutable values its range won't have been extended yet. We |
| 459 | * want to ensure that the value is memoized along with the context variable, |
| 460 | * not independently of it (bc of the way we do codegen for hoisted functions). |
| 461 | * So here we check for StoreContext rvalues and if they haven't already had |
| 462 | * their range extended to at least this instruction, we extend it. |
| 463 | */ |
| 464 | if ( |
| 465 | instr.value.kind === 'StoreContext' && |
| 466 | instr.value.value.identifier.mutableRange.end <= instr.id |
| 467 | ) { |
| 468 | instr.value.value.identifier.mutableRange.end = makeInstructionId( |
| 469 | instr.id + 1, |
| 470 | ); |
| 471 | } |
| 472 | } |
| 473 | if (block.terminal.kind === 'return') { |
| 474 | block.terminal.value.effect = isFunctionExpression |
| 475 | ? Effect.Read |
| 476 | : Effect.Freeze; |
| 477 | } else { |
| 478 | for (const operand of eachTerminalOperand(block.terminal)) { |
| 479 | operand.effect = Effect.Read; |
| 480 | } |
| 481 | } |
| 482 | } |
| 483 | |
| 484 | /** |
| 485 | * Part 3 |
| 486 | * Finish populating the externally visible effects. Above we bubble-up the side effects |
| 487 | * (MutateFrozen/MutableGlobal/Impure/Render) as well as mutations of context variables. |
| 488 | * Here we populate an effect to create the return value as well as populating alias/capture |
| 489 | * effects for how data flows between the params, context vars, and return. |
| 490 | */ |
| 491 | const returns = fn.returns.identifier; |
| 492 | functionEffects.push({ |
| 493 | kind: 'Create', |
| 494 | into: fn.returns, |
| 495 | value: isPrimitiveType(returns) |
| 496 | ? ValueKind.Primitive |
| 497 | : isJsxType(returns.type) |
| 498 | ? ValueKind.Frozen |
| 499 | : ValueKind.Mutable, |
| 500 | reason: ValueReason.KnownReturnSignature, |
| 501 | }); |
| 502 | /** |
| 503 | * Determine precise data-flow effects by simulating transitive mutations of the params/ |
| 504 | * captures and seeing what other params/context variables are affected. Anything that |
| 505 | * would be transitively mutated needs a capture relationship. |
| 506 | */ |
| 507 | const tracked: Array<Place> = []; |
| 508 | for (const param of [...fn.params, ...fn.context, fn.returns]) { |
| 509 | const place = param.kind === 'Identifier' ? param : param.place; |
| 510 | tracked.push(place); |
| 511 | } |
| 512 | for (const into of tracked) { |
| 513 | const mutationIndex = index++; |
| 514 | state.mutate( |
| 515 | mutationIndex, |
| 516 | into.identifier, |
| 517 | null, |
| 518 | true, |
| 519 | MutationKind.Conditional, |
| 520 | into.loc, |
| 521 | null, |
| 522 | null, |
| 523 | ); |
| 524 | for (const from of tracked) { |
| 525 | if ( |
| 526 | from.identifier.id === into.identifier.id || |
| 527 | from.identifier.id === fn.returns.identifier.id |
| 528 | ) { |
| 529 | continue; |
| 530 | } |
| 531 | const fromNode = state.nodes.get(from.identifier); |
| 532 | CompilerError.invariant(fromNode != null, { |
| 533 | reason: `Expected a node to exist for all parameters and context variables`, |
| 534 | loc: into.loc, |
| 535 | }); |
| 536 | if (fromNode.lastMutated === mutationIndex) { |
| 537 | if (into.identifier.id === fn.returns.identifier.id) { |
| 538 | // The return value could be any of the params/context variables |
| 539 | functionEffects.push({ |
| 540 | kind: 'Alias', |
| 541 | from, |
| 542 | into, |
| 543 | }); |
| 544 | } else { |
| 545 | // Otherwise params/context-vars can only capture each other |
| 546 | functionEffects.push({ |
| 547 | kind: 'Capture', |
| 548 | from, |
| 549 | into, |
| 550 | }); |
| 551 | } |
| 552 | } |
| 553 | } |
| 554 | } |
| 555 | |
| 556 | return functionEffects; |
| 557 | } |
| 558 | |
| 559 | function appendFunctionErrors(env: Environment | null, fn: HIRFunction): void { |
| 560 | if (env == null) return; |
| 561 | for (const effect of fn.aliasingEffects ?? []) { |
| 562 | switch (effect.kind) { |
| 563 | case 'Impure': |
| 564 | case 'MutateFrozen': |
| 565 | case 'MutateGlobal': { |
| 566 | env.recordError(effect.error); |
| 567 | break; |
| 568 | } |
| 569 | } |
| 570 | } |
| 571 | } |
| 572 | |
| 573 | export enum MutationKind { |
| 574 | None = 0, |
| 575 | Conditional = 1, |
| 576 | Definite = 2, |
| 577 | } |
| 578 | |
| 579 | type Node = { |
| 580 | id: Identifier; |
| 581 | createdFrom: Map<Identifier, number>; |
| 582 | captures: Map<Identifier, number>; |
| 583 | aliases: Map<Identifier, number>; |
| 584 | maybeAliases: Map<Identifier, number>; |
| 585 | edges: Array<{ |
| 586 | index: number; |
| 587 | node: Identifier; |
| 588 | kind: 'capture' | 'alias' | 'maybeAlias'; |
| 589 | }>; |
| 590 | transitive: {kind: MutationKind; loc: SourceLocation} | null; |
| 591 | local: {kind: MutationKind; loc: SourceLocation} | null; |
| 592 | lastMutated: number; |
| 593 | mutationReason: MutationReason | null; |
| 594 | value: |
| 595 | | {kind: 'Object'} |
| 596 | | {kind: 'Phi'} |
| 597 | | {kind: 'Function'; function: HIRFunction}; |
| 598 | }; |
| 599 | class AliasingState { |
| 600 | nodes: Map<Identifier, Node> = new Map(); |
| 601 | |
| 602 | create(place: Place, value: Node['value']): void { |
| 603 | this.nodes.set(place.identifier, { |
| 604 | id: place.identifier, |
| 605 | createdFrom: new Map(), |
| 606 | captures: new Map(), |
| 607 | aliases: new Map(), |
| 608 | maybeAliases: new Map(), |
| 609 | edges: [], |
| 610 | transitive: null, |
| 611 | local: null, |
| 612 | lastMutated: 0, |
| 613 | mutationReason: null, |
| 614 | value, |
| 615 | }); |
| 616 | } |
| 617 | |
| 618 | createFrom(index: number, from: Place, into: Place): void { |
| 619 | this.create(into, {kind: 'Object'}); |
| 620 | const fromNode = this.nodes.get(from.identifier); |
| 621 | const toNode = this.nodes.get(into.identifier); |
| 622 | if (fromNode == null || toNode == null) { |
| 623 | return; |
| 624 | } |
| 625 | fromNode.edges.push({index, node: into.identifier, kind: 'alias'}); |
| 626 | if (!toNode.createdFrom.has(from.identifier)) { |
| 627 | toNode.createdFrom.set(from.identifier, index); |
| 628 | } |
| 629 | } |
| 630 | |
| 631 | capture(index: number, from: Place, into: Place): void { |
| 632 | const fromNode = this.nodes.get(from.identifier); |
| 633 | const toNode = this.nodes.get(into.identifier); |
| 634 | if (fromNode == null || toNode == null) { |
| 635 | return; |
| 636 | } |
| 637 | fromNode.edges.push({index, node: into.identifier, kind: 'capture'}); |
| 638 | if (!toNode.captures.has(from.identifier)) { |
| 639 | toNode.captures.set(from.identifier, index); |
| 640 | } |
| 641 | } |
| 642 | |
| 643 | assign(index: number, from: Place, into: Place): void { |
| 644 | const fromNode = this.nodes.get(from.identifier); |
| 645 | const toNode = this.nodes.get(into.identifier); |
| 646 | if (fromNode == null || toNode == null) { |
| 647 | return; |
| 648 | } |
| 649 | fromNode.edges.push({index, node: into.identifier, kind: 'alias'}); |
| 650 | if (!toNode.aliases.has(from.identifier)) { |
| 651 | toNode.aliases.set(from.identifier, index); |
| 652 | } |
| 653 | } |
| 654 | |
| 655 | maybeAlias(index: number, from: Place, into: Place): void { |
| 656 | const fromNode = this.nodes.get(from.identifier); |
| 657 | const toNode = this.nodes.get(into.identifier); |
| 658 | if (fromNode == null || toNode == null) { |
| 659 | return; |
| 660 | } |
| 661 | fromNode.edges.push({index, node: into.identifier, kind: 'maybeAlias'}); |
| 662 | if (!toNode.maybeAliases.has(from.identifier)) { |
| 663 | toNode.maybeAliases.set(from.identifier, index); |
| 664 | } |
| 665 | } |
| 666 | |
| 667 | render(index: number, start: Identifier, env: Environment | null): void { |
| 668 | const seen = new Set<Identifier>(); |
| 669 | const queue: Array<Identifier> = [start]; |
| 670 | while (queue.length !== 0) { |
| 671 | const current = queue.pop()!; |
| 672 | if (seen.has(current)) { |
| 673 | continue; |
| 674 | } |
| 675 | seen.add(current); |
| 676 | const node = this.nodes.get(current); |
| 677 | if (node == null || node.transitive != null || node.local != null) { |
| 678 | continue; |
| 679 | } |
| 680 | if (node.value.kind === 'Function') { |
| 681 | appendFunctionErrors(env, node.value.function); |
| 682 | } |
| 683 | for (const [alias, when] of node.createdFrom) { |
| 684 | if (when >= index) { |
| 685 | continue; |
| 686 | } |
| 687 | queue.push(alias); |
| 688 | } |
| 689 | for (const [alias, when] of node.aliases) { |
| 690 | if (when >= index) { |
| 691 | continue; |
| 692 | } |
| 693 | queue.push(alias); |
| 694 | } |
| 695 | for (const [capture, when] of node.captures) { |
| 696 | if (when >= index) { |
| 697 | continue; |
| 698 | } |
| 699 | queue.push(capture); |
| 700 | } |
| 701 | } |
| 702 | } |
| 703 | |
| 704 | mutate( |
| 705 | index: number, |
| 706 | start: Identifier, |
| 707 | // Null is used for simulated mutations |
| 708 | end: InstructionId | null, |
| 709 | transitive: boolean, |
| 710 | startKind: MutationKind, |
| 711 | loc: SourceLocation, |
| 712 | reason: MutationReason | null, |
| 713 | env: Environment | null, |
| 714 | ): void { |
| 715 | const seen = new Map<Identifier, MutationKind>(); |
| 716 | const queue: Array<{ |
| 717 | place: Identifier; |
| 718 | transitive: boolean; |
| 719 | direction: 'backwards' | 'forwards'; |
| 720 | kind: MutationKind; |
| 721 | }> = [{place: start, transitive, direction: 'backwards', kind: startKind}]; |
| 722 | while (queue.length !== 0) { |
| 723 | const {place: current, transitive, direction, kind} = queue.pop()!; |
| 724 | const previousKind = seen.get(current); |
| 725 | if (previousKind != null && previousKind >= kind) { |
| 726 | continue; |
| 727 | } |
| 728 | seen.set(current, kind); |
| 729 | const node = this.nodes.get(current); |
| 730 | if (node == null) { |
| 731 | continue; |
| 732 | } |
| 733 | node.mutationReason ??= reason; |
| 734 | node.lastMutated = Math.max(node.lastMutated, index); |
| 735 | if (end != null) { |
| 736 | node.id.mutableRange.end = makeInstructionId( |
| 737 | Math.max(node.id.mutableRange.end, end), |
| 738 | ); |
| 739 | } |
| 740 | if ( |
| 741 | node.value.kind === 'Function' && |
| 742 | node.transitive == null && |
| 743 | node.local == null |
| 744 | ) { |
| 745 | appendFunctionErrors(env, node.value.function); |
| 746 | } |
| 747 | if (transitive) { |
| 748 | if (node.transitive == null || node.transitive.kind < kind) { |
| 749 | node.transitive = {kind, loc}; |
| 750 | } |
| 751 | } else { |
| 752 | if (node.local == null || node.local.kind < kind) { |
| 753 | node.local = {kind, loc}; |
| 754 | } |
| 755 | } |
| 756 | /** |
| 757 | * all mutations affect "forward" edges by the rules: |
| 758 | * - Capture a -> b, mutate(a) => mutate(b) |
| 759 | * - Alias a -> b, mutate(a) => mutate(b) |
| 760 | */ |
| 761 | for (const edge of node.edges) { |
| 762 | if (edge.index >= index) { |
| 763 | break; |
| 764 | } |
| 765 | queue.push({ |
| 766 | place: edge.node, |
| 767 | transitive, |
| 768 | direction: 'forwards', |
| 769 | // Traversing a maybeAlias edge always downgrades to conditional mutation |
| 770 | kind: edge.kind === 'maybeAlias' ? MutationKind.Conditional : kind, |
| 771 | }); |
| 772 | } |
| 773 | for (const [alias, when] of node.createdFrom) { |
| 774 | if (when >= index) { |
| 775 | continue; |
| 776 | } |
| 777 | queue.push({ |
| 778 | place: alias, |
| 779 | transitive: true, |
| 780 | direction: 'backwards', |
| 781 | kind, |
| 782 | }); |
| 783 | } |
| 784 | if (direction === 'backwards' || node.value.kind !== 'Phi') { |
| 785 | /** |
| 786 | * all mutations affect backward alias edges by the rules: |
| 787 | * - Alias a -> b, mutate(b) => mutate(a) |
| 788 | * - Alias a -> b, mutateTransitive(b) => mutate(a) |
| 789 | * |
| 790 | * However, if we reached a phi because one of its inputs was mutated |
| 791 | * (and we're advancing "forwards" through that node's edges), then |
| 792 | * we know we've already processed the mutation at its source. The |
| 793 | * phi's other inputs can't be affected. |
| 794 | */ |
| 795 | for (const [alias, when] of node.aliases) { |
| 796 | if (when >= index) { |
| 797 | continue; |
| 798 | } |
| 799 | queue.push({ |
| 800 | place: alias, |
| 801 | transitive, |
| 802 | direction: 'backwards', |
| 803 | kind, |
| 804 | }); |
| 805 | } |
| 806 | /** |
| 807 | * MaybeAlias indicates potential data flow from unknown function calls, |
| 808 | * so we downgrade mutations through these aliases to consider them |
| 809 | * conditional. This means we'll consider them for mutation *range* |
| 810 | * purposes but not report validation errors for mutations, since |
| 811 | * we aren't sure that the `from` value could actually be aliased. |
| 812 | */ |
| 813 | for (const [alias, when] of node.maybeAliases) { |
| 814 | if (when >= index) { |
| 815 | continue; |
| 816 | } |
| 817 | queue.push({ |
| 818 | place: alias, |
| 819 | transitive, |
| 820 | direction: 'backwards', |
| 821 | kind: MutationKind.Conditional, |
| 822 | }); |
| 823 | } |
| 824 | } |
| 825 | /** |
| 826 | * but only transitive mutations affect captures |
| 827 | */ |
| 828 | if (transitive) { |
| 829 | for (const [capture, when] of node.captures) { |
| 830 | if (when >= index) { |
| 831 | continue; |
| 832 | } |
| 833 | queue.push({ |
| 834 | place: capture, |
| 835 | transitive, |
| 836 | direction: 'backwards', |
| 837 | kind, |
| 838 | }); |
| 839 | } |
| 840 | } |
| 841 | } |
| 842 | } |
| 843 | } |