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| 1 // Copyright (c) 2014, the Dart project authors. Please see the AUTHORS file | |
| 2 // for details. All rights reserved. Use of this source code is governed by a | |
| 3 // BSD-style license that can be found in the LICENSE file. | |
| 4 | |
| 5 part of dart2js.optimizers; | |
| 6 | |
| 7 /** | |
| 8 * Propagates constants throughout the IR, and replaces branches with fixed | |
| 9 * jumps as well as side-effect free expressions with known constant results. | |
| 10 * Should be followed by the [ShrinkingReducer] pass. | |
| 11 * | |
| 12 * Implemented according to 'Constant Propagation with Conditional Branches' | |
| 13 * by Wegman, Zadeck. | |
| 14 */ | |
| 15 class ConstantPropagator implements Pass { | |
| 16 | |
| 17 // Required for type determination in analysis of TypeOperator expressions. | |
| 18 final dart2js.Compiler _compiler; | |
| 19 | |
| 20 // The constant system is used for evaluation of expressions with constant | |
| 21 // arguments. | |
| 22 final dart2js.ConstantSystem _constantSystem; | |
| 23 | |
| 24 ConstantPropagator(this._compiler, this._constantSystem); | |
| 25 | |
| 26 void rewrite(FunctionDefinition root) { | |
| 27 if (root.isAbstract) return; | |
| 28 | |
| 29 // Set all parent pointers. | |
| 30 | |
| 31 new _ParentVisitor().visit(root); | |
| 32 | |
| 33 // Analyze. In this phase, the entire term is analyzed for reachability | |
| 34 // and the constant status of each expression. | |
| 35 | |
| 36 _ConstPropagationVisitor analyzer = | |
| 37 new _ConstPropagationVisitor(_compiler, _constantSystem); | |
| 38 analyzer.analyze(root); | |
| 39 | |
| 40 // Transform. Uses the data acquired in the previous analysis phase to | |
| 41 // replace branches with fixed targets and side-effect-free expressions | |
| 42 // with constant results. | |
| 43 | |
| 44 _TransformingVisitor transformer = new _TransformingVisitor( | |
| 45 analyzer.reachableNodes, analyzer.node2value); | |
| 46 transformer.transform(root); | |
| 47 } | |
| 48 } | |
| 49 | |
| 50 /** | |
| 51 * Uses the information from a preceding analysis pass in order to perform the | |
| 52 * actual transformations on the CPS graph. | |
| 53 */ | |
| 54 class _TransformingVisitor extends RecursiveVisitor { | |
| 55 | |
| 56 final Set<Node> reachable; | |
| 57 final Map<Node, _ConstnessLattice> node2value; | |
| 58 | |
| 59 _TransformingVisitor(this.reachable, this.node2value); | |
| 60 | |
| 61 void transform(FunctionDefinition root) { | |
| 62 visitFunctionDefinition(root); | |
| 63 } | |
| 64 | |
| 65 /// Given an expression with a known constant result and a continuation, | |
| 66 /// replaces the expression by a new LetPrim / InvokeContinuation construct. | |
| 67 /// `unlink` is a closure responsible for unlinking all removed references. | |
| 68 LetPrim constifyExpression(Expression node, | |
| 69 Continuation continuation, | |
| 70 void unlink()) { | |
| 71 _ConstnessLattice cell = node2value[node]; | |
| 72 if (cell == null || !cell.isConstant) { | |
| 73 return null; | |
| 74 } | |
| 75 | |
| 76 assert(continuation.parameters.length == 1); | |
| 77 | |
| 78 // Set up the replacement structure. | |
| 79 | |
| 80 PrimitiveConstantValue primitiveConstant = cell.constant; | |
| 81 ConstantExpression constExp = | |
| 82 new PrimitiveConstantExpression(primitiveConstant); | |
| 83 Constant constant = new Constant(constExp); | |
| 84 LetPrim letPrim = new LetPrim(constant); | |
| 85 InvokeContinuation invoke = | |
| 86 new InvokeContinuation(continuation, <Definition>[constant]); | |
| 87 | |
| 88 invoke.parent = constant.parent = letPrim; | |
| 89 letPrim.body = invoke; | |
| 90 | |
| 91 // Replace the method invocation. | |
| 92 | |
| 93 InteriorNode parent = node.parent; | |
| 94 letPrim.parent = parent; | |
| 95 parent.body = letPrim; | |
| 96 | |
| 97 unlink(); | |
| 98 | |
| 99 return letPrim; | |
| 100 } | |
| 101 | |
| 102 // A branch can be eliminated and replaced by an invocation if only one of | |
| 103 // the possible continuations is reachable. Removal often leads to both dead | |
| 104 // primitives (the condition variable) and dead continuations (the unreachable | |
| 105 // branch), which are both removed by the shrinking reductions pass. | |
| 106 // | |
| 107 // (Branch (IsTrue true) k0 k1) -> (InvokeContinuation k0) | |
| 108 void visitBranch(Branch node) { | |
| 109 bool trueReachable = reachable.contains(node.trueContinuation.definition); | |
| 110 bool falseReachable = reachable.contains(node.falseContinuation.definition); | |
| 111 bool bothReachable = (trueReachable && falseReachable); | |
| 112 bool noneReachable = !(trueReachable || falseReachable); | |
| 113 | |
| 114 if (bothReachable || noneReachable) { | |
| 115 // Nothing to do, shrinking reductions take care of the unreachable case. | |
| 116 super.visitBranch(node); | |
| 117 return; | |
| 118 } | |
| 119 | |
| 120 Continuation successor = (trueReachable) ? | |
| 121 node.trueContinuation.definition : node.falseContinuation.definition; | |
| 122 | |
| 123 // Replace the branch by a continuation invocation. | |
| 124 | |
| 125 assert(successor.parameters.isEmpty); | |
| 126 InvokeContinuation invoke = | |
| 127 new InvokeContinuation(successor, <Definition>[]); | |
| 128 | |
| 129 InteriorNode parent = node.parent; | |
| 130 invoke.parent = parent; | |
| 131 parent.body = invoke; | |
| 132 | |
| 133 // Unlink all removed references. | |
| 134 | |
| 135 node.trueContinuation.unlink(); | |
| 136 node.falseContinuation.unlink(); | |
| 137 IsTrue isTrue = node.condition; | |
| 138 isTrue.value.unlink(); | |
| 139 | |
| 140 visitInvokeContinuation(invoke); | |
| 141 } | |
| 142 | |
| 143 // Side-effect free method calls with constant results can be replaced by | |
| 144 // a LetPrim / InvokeContinuation pair. May lead to dead primitives which | |
| 145 // are removed by the shrinking reductions pass. | |
| 146 // | |
| 147 // (InvokeMethod v0 == v1 k0) | |
| 148 // -> (assuming the result is a constant `true`) | |
| 149 // (LetPrim v2 (Constant true)) | |
| 150 // (InvokeContinuation k0 v2) | |
| 151 void visitInvokeMethod(InvokeMethod node) { | |
| 152 Continuation cont = node.continuation.definition; | |
| 153 LetPrim letPrim = constifyExpression(node, cont, () { | |
| 154 node.receiver.unlink(); | |
| 155 node.continuation.unlink(); | |
| 156 node.arguments.forEach((Reference ref) => ref.unlink()); | |
| 157 }); | |
| 158 | |
| 159 if (letPrim == null) { | |
| 160 super.visitInvokeMethod(node); | |
| 161 } else { | |
| 162 visitLetPrim(letPrim); | |
| 163 } | |
| 164 } | |
| 165 | |
| 166 // See [visitInvokeMethod]. | |
| 167 void visitConcatenateStrings(ConcatenateStrings node) { | |
| 168 Continuation cont = node.continuation.definition; | |
| 169 LetPrim letPrim = constifyExpression(node, cont, () { | |
| 170 node.continuation.unlink(); | |
| 171 node.arguments.forEach((Reference ref) => ref.unlink()); | |
| 172 }); | |
| 173 | |
| 174 if (letPrim == null) { | |
| 175 super.visitConcatenateStrings(node); | |
| 176 } else { | |
| 177 visitLetPrim(letPrim); | |
| 178 } | |
| 179 } | |
| 180 | |
| 181 // See [visitInvokeMethod]. | |
| 182 void visitTypeOperator(TypeOperator node) { | |
| 183 Continuation cont = node.continuation.definition; | |
| 184 LetPrim letPrim = constifyExpression(node, cont, () { | |
| 185 node.receiver.unlink(); | |
| 186 node.continuation.unlink(); | |
| 187 }); | |
| 188 | |
| 189 if (letPrim == null) { | |
| 190 super.visitTypeOperator(node); | |
| 191 } else { | |
| 192 visitLetPrim(letPrim); | |
| 193 } | |
| 194 } | |
| 195 } | |
| 196 | |
| 197 /** | |
| 198 * Runs an analysis pass on the given function definition in order to detect | |
| 199 * const-ness as well as reachability, both of which are used in the subsequent | |
| 200 * transformation pass. | |
| 201 */ | |
| 202 class _ConstPropagationVisitor extends Visitor { | |
| 203 // The node worklist stores nodes that are both reachable and need to be | |
| 204 // processed, but have not been processed yet. Using a worklist avoids deep | |
| 205 // recursion. | |
| 206 // The node worklist and the reachable set operate in concert: nodes are | |
| 207 // only ever added to the worklist when they have not yet been marked as | |
| 208 // reachable, and adding a node to the worklist is always followed by marking | |
| 209 // it reachable. | |
| 210 // TODO(jgruber): Storing reachability per-edge instead of per-node would | |
| 211 // allow for further optimizations. | |
| 212 final List<Node> nodeWorklist = <Node>[]; | |
| 213 final Set<Node> reachableNodes = new Set<Node>(); | |
| 214 | |
| 215 // The definition workset stores all definitions which need to be reprocessed | |
| 216 // since their lattice value has changed. | |
| 217 final Set<Definition> defWorkset = new Set<Definition>(); | |
| 218 | |
| 219 final dart2js.Compiler compiler; | |
| 220 final dart2js.ConstantSystem constantSystem; | |
| 221 | |
| 222 // Stores the current lattice value for nodes. Note that it contains not only | |
| 223 // definitions as keys, but also expressions such as method invokes. | |
| 224 // Access through [getValue] and [setValue]. | |
| 225 final Map<Node, _ConstnessLattice> node2value = <Node, _ConstnessLattice>{}; | |
| 226 | |
| 227 _ConstPropagationVisitor(this.compiler, this.constantSystem); | |
| 228 | |
| 229 void analyze(FunctionDefinition root) { | |
| 230 reachableNodes.clear(); | |
| 231 defWorkset.clear(); | |
| 232 nodeWorklist.clear(); | |
| 233 | |
| 234 // Initially, only the root node is reachable. | |
| 235 setReachable(root); | |
| 236 | |
| 237 while (true) { | |
| 238 if (nodeWorklist.isNotEmpty) { | |
| 239 // Process a new reachable expression. | |
| 240 Node node = nodeWorklist.removeLast(); | |
| 241 visit(node); | |
| 242 } else if (defWorkset.isNotEmpty) { | |
| 243 // Process all usages of a changed definition. | |
| 244 Definition def = defWorkset.first; | |
| 245 defWorkset.remove(def); | |
| 246 | |
| 247 // Visit all uses of this definition. This might add new entries to | |
| 248 // [nodeWorklist], for example by visiting a newly-constant usage within | |
| 249 // a branch node. | |
| 250 for (Reference ref = def.firstRef; ref != null; ref = ref.next) { | |
| 251 visit(ref.parent); | |
| 252 } | |
| 253 } else { | |
| 254 break; // Both worklists empty. | |
| 255 } | |
| 256 } | |
| 257 } | |
| 258 | |
| 259 /// If the passed node is not yet reachable, mark it reachable and add it | |
| 260 /// to the work list. | |
| 261 void setReachable(Node node) { | |
| 262 if (!reachableNodes.contains(node)) { | |
| 263 reachableNodes.add(node); | |
| 264 nodeWorklist.add(node); | |
| 265 } | |
| 266 } | |
| 267 | |
| 268 /// Returns the lattice value corresponding to [node], defaulting to unknown. | |
| 269 /// | |
| 270 /// Never returns null. | |
| 271 _ConstnessLattice getValue(Node node) { | |
| 272 _ConstnessLattice value = node2value[node]; | |
| 273 return (value == null) ? _ConstnessLattice.Unknown : value; | |
| 274 } | |
| 275 | |
| 276 /// Joins the passed lattice [updateValue] to the current value of [node], | |
| 277 /// and adds it to the definition work set if it has changed and [node] is | |
| 278 /// a definition. | |
| 279 void setValue(Node node, _ConstnessLattice updateValue) { | |
| 280 _ConstnessLattice oldValue = getValue(node); | |
| 281 _ConstnessLattice newValue = updateValue.join(oldValue); | |
| 282 if (oldValue == newValue) { | |
| 283 return; | |
| 284 } | |
| 285 | |
| 286 // Values may only move in the direction UNKNOWN -> CONSTANT -> NONCONST. | |
| 287 assert(newValue.kind >= oldValue.kind); | |
| 288 | |
| 289 node2value[node] = newValue; | |
| 290 if (node is Definition) { | |
| 291 defWorkset.add(node); | |
| 292 } | |
| 293 } | |
| 294 | |
| 295 // -------------------------- Visitor overrides ------------------------------ | |
| 296 | |
| 297 void visitNode(Node node) { | |
| 298 compiler.internalError(NO_LOCATION_SPANNABLE, | |
| 299 "_ConstPropagationVisitor is stale, add missing visit overrides"); | |
| 300 } | |
| 301 | |
| 302 void visitFunctionDefinition(FunctionDefinition node) { | |
| 303 node.parameters.forEach(visitParameter); | |
| 304 setReachable(node.body); | |
| 305 } | |
| 306 | |
| 307 // Expressions. | |
| 308 | |
| 309 void visitLetPrim(LetPrim node) { | |
| 310 visit(node.primitive); // No reason to delay visits to primitives. | |
| 311 setReachable(node.body); | |
| 312 } | |
| 313 | |
| 314 void visitLetCont(LetCont node) { | |
| 315 // The continuation is only marked as reachable on use. | |
| 316 setReachable(node.body); | |
| 317 } | |
| 318 | |
| 319 void visitInvokeStatic(InvokeStatic node) { | |
| 320 Continuation cont = node.continuation.definition; | |
| 321 setReachable(cont); | |
| 322 | |
| 323 assert(cont.parameters.length == 1); | |
| 324 Parameter returnValue = cont.parameters[0]; | |
| 325 setValue(returnValue, _ConstnessLattice.NonConst); | |
| 326 } | |
| 327 | |
| 328 void visitInvokeContinuation(InvokeContinuation node) { | |
| 329 Continuation cont = node.continuation.definition; | |
| 330 setReachable(cont); | |
| 331 | |
| 332 // Forward the constant status of all continuation invokes to the | |
| 333 // continuation. Note that this is effectively a phi node in SSA terms. | |
| 334 for (int i = 0; i < node.arguments.length; i++) { | |
| 335 Definition def = node.arguments[i].definition; | |
| 336 _ConstnessLattice cell = getValue(def); | |
| 337 setValue(cont.parameters[i], cell); | |
| 338 } | |
| 339 } | |
| 340 | |
| 341 void visitInvokeMethod(InvokeMethod node) { | |
| 342 Continuation cont = node.continuation.definition; | |
| 343 setReachable(cont); | |
| 344 | |
| 345 /// Sets the value of both the current node and the target continuation | |
| 346 /// parameter. | |
| 347 void setValues(_ConstnessLattice updateValue) { | |
| 348 setValue(node, updateValue); | |
| 349 Parameter returnValue = cont.parameters[0]; | |
| 350 setValue(returnValue, updateValue); | |
| 351 } | |
| 352 | |
| 353 _ConstnessLattice lhs = getValue(node.receiver.definition); | |
| 354 if (lhs.isUnknown) { | |
| 355 // This may seem like a missed opportunity for evaluating short-circuiting | |
| 356 // boolean operations; we are currently skipping these intentionally since | |
| 357 // expressions such as `(new Foo() || true)` may introduce type errors | |
| 358 // and thus evaluation to `true` would not be correct. | |
| 359 // TODO(jgruber): Handle such cases while ensuring that new Foo() and | |
| 360 // a type-check (in checked mode) are still executed. | |
| 361 return; // And come back later. | |
| 362 } else if (lhs.isNonConst) { | |
| 363 setValues(_ConstnessLattice.NonConst); | |
| 364 return; | |
| 365 } else if (!node.selector.isOperator) { | |
| 366 // TODO(jgruber): Handle known methods on constants such as String.length. | |
| 367 setValues(_ConstnessLattice.NonConst); | |
| 368 return; | |
| 369 } | |
| 370 | |
| 371 // Calculate the resulting constant if possible. | |
| 372 ConstantValue result; | |
| 373 String opname = node.selector.name; | |
| 374 if (node.selector.argumentCount == 0) { | |
| 375 // Unary operator. | |
| 376 | |
| 377 if (opname == "unary-") { | |
| 378 opname = "-"; | |
| 379 } | |
| 380 dart2js.UnaryOperation operation = constantSystem.lookupUnary(opname); | |
| 381 if (operation != null) { | |
| 382 result = operation.fold(lhs.constant); | |
| 383 } | |
| 384 } else if (node.selector.argumentCount == 1) { | |
| 385 // Binary operator. | |
| 386 | |
| 387 _ConstnessLattice rhs = getValue(node.arguments[0].definition); | |
| 388 if (!rhs.isConstant) { | |
| 389 setValues(rhs); | |
| 390 return; | |
| 391 } | |
| 392 | |
| 393 dart2js.BinaryOperation operation = constantSystem.lookupBinary(opname); | |
| 394 if (operation != null) { | |
| 395 result = operation.fold(lhs.constant, rhs.constant); | |
| 396 } | |
| 397 } | |
| 398 | |
| 399 // Update value of the continuation parameter. Again, this is effectively | |
| 400 // a phi. | |
| 401 | |
| 402 setValues((result == null) ? | |
| 403 _ConstnessLattice.NonConst : new _ConstnessLattice(result)); | |
| 404 } | |
| 405 | |
| 406 void visitInvokeSuperMethod(InvokeSuperMethod node) { | |
| 407 Continuation cont = node.continuation.definition; | |
| 408 setReachable(cont); | |
| 409 | |
| 410 assert(cont.parameters.length == 1); | |
| 411 Parameter returnValue = cont.parameters[0]; | |
| 412 setValue(returnValue, _ConstnessLattice.NonConst); | |
| 413 } | |
| 414 | |
| 415 void visitInvokeConstructor(InvokeConstructor node) { | |
| 416 Continuation cont = node.continuation.definition; | |
| 417 setReachable(cont); | |
| 418 | |
| 419 assert(cont.parameters.length == 1); | |
| 420 Parameter returnValue = cont.parameters[0]; | |
| 421 setValue(returnValue, _ConstnessLattice.NonConst); | |
| 422 } | |
| 423 | |
| 424 void visitConcatenateStrings(ConcatenateStrings node) { | |
| 425 Continuation cont = node.continuation.definition; | |
| 426 setReachable(cont); | |
| 427 | |
| 428 void setValues(_ConstnessLattice updateValue) { | |
| 429 setValue(node, updateValue); | |
| 430 Parameter returnValue = cont.parameters[0]; | |
| 431 setValue(returnValue, updateValue); | |
| 432 } | |
| 433 | |
| 434 // TODO(jgruber): Currently we only optimize if all arguments are string | |
| 435 // constants, but we could also handle cases such as "foo${42}". | |
| 436 bool allStringConstants = node.arguments.every((Reference ref) { | |
| 437 if (!(ref.definition is Constant)) { | |
| 438 return false; | |
| 439 } | |
| 440 Constant constant = ref.definition; | |
| 441 return constant != null && constant.value.isString; | |
| 442 }); | |
| 443 | |
| 444 assert(cont.parameters.length == 1); | |
| 445 if (allStringConstants) { | |
| 446 // All constant, we can concatenate ourselves. | |
| 447 Iterable<String> allStrings = node.arguments.map((Reference ref) { | |
| 448 Constant constant = ref.definition; | |
| 449 StringConstantValue stringConstant = constant.value; | |
| 450 return stringConstant.primitiveValue.slowToString(); | |
| 451 }); | |
| 452 LiteralDartString dartString = new LiteralDartString(allStrings.join()); | |
| 453 ConstantValue constant = new StringConstantValue(dartString); | |
| 454 setValues(new _ConstnessLattice(constant)); | |
| 455 } else { | |
| 456 setValues(_ConstnessLattice.NonConst); | |
| 457 } | |
| 458 } | |
| 459 | |
| 460 void visitBranch(Branch node) { | |
| 461 IsTrue isTrue = node.condition; | |
| 462 _ConstnessLattice conditionCell = getValue(isTrue.value.definition); | |
| 463 | |
| 464 if (conditionCell.isUnknown) { | |
| 465 return; // And come back later. | |
| 466 } else if (conditionCell.isNonConst) { | |
| 467 setReachable(node.trueContinuation.definition); | |
| 468 setReachable(node.falseContinuation.definition); | |
| 469 } else if (conditionCell.isConstant && | |
| 470 !(conditionCell.constant.isBool)) { | |
| 471 // Treat non-bool constants in condition as non-const since they result | |
| 472 // in type errors in checked mode. | |
| 473 // TODO(jgruber): Default to false in unchecked mode. | |
| 474 setReachable(node.trueContinuation.definition); | |
| 475 setReachable(node.falseContinuation.definition); | |
| 476 setValue(isTrue.value.definition, _ConstnessLattice.NonConst); | |
| 477 } else if (conditionCell.isConstant && | |
| 478 conditionCell.constant.isBool) { | |
| 479 BoolConstantValue boolConstant = conditionCell.constant; | |
| 480 setReachable((boolConstant.isTrue) ? | |
| 481 node.trueContinuation.definition : node.falseContinuation.definition); | |
| 482 } | |
| 483 } | |
| 484 | |
| 485 void visitTypeOperator(TypeOperator node) { | |
| 486 Continuation cont = node.continuation.definition; | |
| 487 setReachable(cont); | |
| 488 | |
| 489 void setValues(_ConstnessLattice updateValue) { | |
| 490 setValue(node, updateValue); | |
| 491 Parameter returnValue = cont.parameters[0]; | |
| 492 setValue(returnValue, updateValue); | |
| 493 } | |
| 494 | |
| 495 if (node.isTypeCast) { | |
| 496 // TODO(jgruber): Add support for `as` casts. | |
| 497 setValues(_ConstnessLattice.NonConst); | |
| 498 } | |
| 499 | |
| 500 _ConstnessLattice cell = getValue(node.receiver.definition); | |
| 501 if (cell.isUnknown) { | |
| 502 return; // And come back later. | |
| 503 } else if (cell.isNonConst) { | |
| 504 setValues(_ConstnessLattice.NonConst); | |
| 505 } else if (node.type.kind == types.TypeKind.INTERFACE) { | |
| 506 // Receiver is a constant, perform is-checks at compile-time. | |
| 507 | |
| 508 types.InterfaceType checkedType = node.type; | |
| 509 ConstantValue constant = cell.constant; | |
| 510 types.DartType constantType = constant.computeType(compiler); | |
| 511 | |
| 512 _ConstnessLattice result = _ConstnessLattice.NonConst; | |
| 513 if (constant.isNull && | |
| 514 checkedType.element != compiler.nullClass && | |
| 515 checkedType.element != compiler.objectClass) { | |
| 516 // `(null is Type)` is true iff Type is in { Null, Object }. | |
| 517 result = new _ConstnessLattice(new FalseConstantValue()); | |
| 518 } else { | |
| 519 // Otherwise, perform a standard subtype check. | |
| 520 result = new _ConstnessLattice( | |
| 521 constantSystem.isSubtype(compiler, constantType, checkedType) | |
| 522 ? new TrueConstantValue() | |
| 523 : new FalseConstantValue()); | |
| 524 } | |
| 525 | |
| 526 setValues(result); | |
| 527 } | |
| 528 } | |
| 529 | |
| 530 void visitSetClosureVariable(SetClosureVariable node) { | |
| 531 setReachable(node.body); | |
| 532 } | |
| 533 | |
| 534 void visitDeclareFunction(DeclareFunction node) { | |
| 535 setReachable(node.definition); | |
| 536 setReachable(node.body); | |
| 537 } | |
| 538 | |
| 539 // Definitions. | |
| 540 void visitLiteralList(LiteralList node) { | |
| 541 // Constant lists are translated into (Constant ListConstant(...)) IR nodes, | |
| 542 // and thus LiteralList nodes are NonConst. | |
| 543 setValue(node, _ConstnessLattice.NonConst); | |
| 544 } | |
| 545 | |
| 546 void visitLiteralMap(LiteralMap node) { | |
| 547 // Constant maps are translated into (Constant MapConstant(...)) IR nodes, | |
| 548 // and thus LiteralMap nodes are NonConst. | |
| 549 setValue(node, _ConstnessLattice.NonConst); | |
| 550 } | |
| 551 | |
| 552 void visitConstant(Constant node) { | |
| 553 setValue(node, new _ConstnessLattice(node.value)); | |
| 554 } | |
| 555 | |
| 556 void visitThis(This node) { | |
| 557 setValue(node, _ConstnessLattice.NonConst); | |
| 558 } | |
| 559 | |
| 560 void visitReifyTypeVar(ReifyTypeVar node) { | |
| 561 setValue(node, _ConstnessLattice.NonConst); | |
| 562 } | |
| 563 | |
| 564 void visitCreateFunction(CreateFunction node) { | |
| 565 setReachable(node.definition); | |
| 566 ConstantValue constant = | |
| 567 new FunctionConstantValue(node.definition.element); | |
| 568 setValue(node, new _ConstnessLattice(constant)); | |
| 569 } | |
| 570 | |
| 571 void visitGetClosureVariable(GetClosureVariable node) { | |
| 572 setValue(node, _ConstnessLattice.NonConst); | |
| 573 } | |
| 574 | |
| 575 void visitParameter(Parameter node) { | |
| 576 if (node.parent is FunctionDefinition) { | |
| 577 // Functions may escape and thus their parameters must be initialized to | |
| 578 // NonConst. | |
| 579 setValue(node, _ConstnessLattice.NonConst); | |
| 580 } else if (node.parent is Continuation) { | |
| 581 // Continuations on the other hand are local, and parameters are | |
| 582 // initialized to Unknown. | |
| 583 setValue(node, _ConstnessLattice.Unknown); | |
| 584 } else { | |
| 585 compiler.internalError(node.hint, "Unexpected parent of Parameter"); | |
| 586 } | |
| 587 } | |
| 588 | |
| 589 void visitContinuation(Continuation node) { | |
| 590 node.parameters.forEach((Parameter p) { | |
| 591 setValue(p, _ConstnessLattice.Unknown); | |
| 592 defWorkset.add(p); | |
| 593 }); | |
| 594 | |
| 595 if (node.body != null) { | |
| 596 setReachable(node.body); | |
| 597 } | |
| 598 } | |
| 599 | |
| 600 // Conditions. | |
| 601 | |
| 602 void visitIsTrue(IsTrue node) { | |
| 603 Branch branch = node.parent; | |
| 604 visitBranch(branch); | |
| 605 } | |
| 606 } | |
| 607 | |
| 608 /// Represents the constant-state of a variable at some point in the program. | |
| 609 /// UNKNOWN: may be some as yet undetermined constant. | |
| 610 /// CONSTANT: is a constant as stored in the local field. | |
| 611 /// NONCONST: not a constant. | |
| 612 class _ConstnessLattice { | |
| 613 static const int UNKNOWN = 0; | |
| 614 static const int CONSTANT = 1; | |
| 615 static const int NONCONST = 2; | |
| 616 | |
| 617 final int kind; | |
| 618 final ConstantValue constant; | |
| 619 | |
| 620 static final _ConstnessLattice Unknown = | |
| 621 new _ConstnessLattice._internal(UNKNOWN, null); | |
| 622 static final _ConstnessLattice NonConst = | |
| 623 new _ConstnessLattice._internal(NONCONST, null); | |
| 624 | |
| 625 _ConstnessLattice._internal(this.kind, this.constant); | |
| 626 _ConstnessLattice(this.constant) : kind = CONSTANT { | |
| 627 assert(this.constant != null); | |
| 628 } | |
| 629 | |
| 630 bool get isUnknown => (kind == UNKNOWN); | |
| 631 bool get isConstant => (kind == CONSTANT); | |
| 632 bool get isNonConst => (kind == NONCONST); | |
| 633 | |
| 634 int get hashCode => kind | (constant.hashCode << 2); | |
| 635 bool operator==(_ConstnessLattice that) => | |
| 636 (that.kind == this.kind && that.constant == this.constant); | |
| 637 | |
| 638 String toString() { | |
| 639 switch (kind) { | |
| 640 case UNKNOWN: return "Unknown"; | |
| 641 case CONSTANT: return "Constant: $constant"; | |
| 642 case NONCONST: return "Non-constant"; | |
| 643 default: assert(false); | |
| 644 } | |
| 645 return null; | |
| 646 } | |
| 647 | |
| 648 /// Compute the join of two values in the lattice. | |
| 649 _ConstnessLattice join(_ConstnessLattice that) { | |
| 650 assert(that != null); | |
| 651 | |
| 652 if (this.isNonConst || that.isUnknown) { | |
| 653 return this; | |
| 654 } | |
| 655 | |
| 656 if (this.isUnknown || that.isNonConst) { | |
| 657 return that; | |
| 658 } | |
| 659 | |
| 660 if (this.constant == that.constant) { | |
| 661 return this; | |
| 662 } | |
| 663 | |
| 664 return NonConst; | |
| 665 } | |
| 666 } | |
| OLD | NEW |
|---|
Chromium Code Reviews
Issue 694353007:
Move dart2js from sdk/lib/_internal/compiler to pkg/compiler (Closed)
Base URL: https://dart.googlecode.com/svn/branches/bleeding_edge/dart