| // Copyright (c) 2012, the Dart project authors. Please see the AUTHORS file |
| // for details. All rights reserved. Use of this source code is governed by a |
| // BSD-style license that can be found in the LICENSE file. |
| |
| part of ssa; |
| |
| abstract class OptimizationPhase { |
| String get name; |
| void visitGraph(HGraph graph); |
| } |
| |
| class SsaOptimizerTask extends CompilerTask { |
| final JavaScriptBackend backend; |
| SsaOptimizerTask(JavaScriptBackend backend) |
| : this.backend = backend, |
| super(backend.compiler); |
| String get name => 'SSA optimizer'; |
| Compiler get compiler => backend.compiler; |
| |
| void runPhases(HGraph graph, List<OptimizationPhase> phases) { |
| for (OptimizationPhase phase in phases) { |
| runPhase(graph, phase); |
| } |
| } |
| |
| void runPhase(HGraph graph, OptimizationPhase phase) { |
| phase.visitGraph(graph); |
| compiler.tracer.traceGraph(phase.name, graph); |
| assert(graph.isValid()); |
| } |
| |
| void optimize(CodegenWorkItem work, HGraph graph) { |
| ConstantSystem constantSystem = compiler.backend.constantSystem; |
| JavaScriptItemCompilationContext context = work.compilationContext; |
| measure(() { |
| SsaDeadCodeEliminator dce; |
| List<OptimizationPhase> phases = <OptimizationPhase>[ |
| // Run trivial instruction simplification first to optimize |
| // some patterns useful for type conversion. |
| new SsaInstructionSimplifier(constantSystem, backend, work), |
| new SsaTypeConversionInserter(compiler), |
| new SsaRedundantPhiEliminator(), |
| new SsaDeadPhiEliminator(), |
| new SsaTypePropagator(compiler), |
| // After type propagation, more instructions can be |
| // simplified. |
| new SsaInstructionSimplifier(constantSystem, backend, work), |
| new SsaCheckInserter(backend, work, context.boundsChecked), |
| new SsaInstructionSimplifier(constantSystem, backend, work), |
| new SsaCheckInserter(backend, work, context.boundsChecked), |
| new SsaTypePropagator(compiler), |
| // Run a dead code eliminator before LICM because dead |
| // interceptors are often in the way of LICM'able instructions. |
| new SsaDeadCodeEliminator(compiler), |
| new SsaGlobalValueNumberer(compiler), |
| // After GVN, some instructions might need their type to be |
| // updated because they now have different inputs. |
| new SsaTypePropagator(compiler), |
| new SsaCodeMotion(), |
| new SsaValueRangeAnalyzer(compiler, constantSystem, work), |
| // Previous optimizations may have generated new |
| // opportunities for instruction simplification. |
| new SsaInstructionSimplifier(constantSystem, backend, work), |
| new SsaCheckInserter(backend, work, context.boundsChecked), |
| new SsaSimplifyInterceptors(compiler, constantSystem, work), |
| dce = new SsaDeadCodeEliminator(compiler)]; |
| runPhases(graph, phases); |
| if (!dce.eliminatedSideEffects) return; |
| phases = <OptimizationPhase>[ |
| new SsaGlobalValueNumberer(compiler), |
| new SsaCodeMotion(), |
| new SsaValueRangeAnalyzer(compiler, constantSystem, work), |
| new SsaInstructionSimplifier(constantSystem, backend, work), |
| new SsaCheckInserter(backend, work, context.boundsChecked), |
| new SsaSimplifyInterceptors(compiler, constantSystem, work), |
| new SsaDeadCodeEliminator(compiler)]; |
| runPhases(graph, phases); |
| }); |
| } |
| } |
| |
| /** |
| * If both inputs to known operations are available execute the operation at |
| * compile-time. |
| */ |
| class SsaInstructionSimplifier extends HBaseVisitor |
| implements OptimizationPhase { |
| final String name = "SsaInstructionSimplifier"; |
| final JavaScriptBackend backend; |
| final CodegenWorkItem work; |
| final ConstantSystem constantSystem; |
| HGraph graph; |
| Compiler get compiler => backend.compiler; |
| |
| SsaInstructionSimplifier(this.constantSystem, this.backend, this.work); |
| |
| void visitGraph(HGraph visitee) { |
| graph = visitee; |
| visitDominatorTree(visitee); |
| } |
| |
| visitBasicBlock(HBasicBlock block) { |
| HInstruction instruction = block.first; |
| while (instruction != null) { |
| HInstruction next = instruction.next; |
| HInstruction replacement = instruction.accept(this); |
| if (replacement != instruction) { |
| block.rewrite(instruction, replacement); |
| |
| // If we can replace [instruction] with [replacement], then |
| // [replacement]'s type can be narrowed. |
| TypeMask newType = replacement.instructionType.intersection( |
| instruction.instructionType, compiler); |
| replacement.instructionType = newType; |
| |
| // If the replacement instruction does not know its |
| // source element, use the source element of the |
| // instruction. |
| if (replacement.sourceElement == null) { |
| replacement.sourceElement = instruction.sourceElement; |
| } |
| if (replacement.sourcePosition == null) { |
| replacement.sourcePosition = instruction.sourcePosition; |
| } |
| if (!replacement.isInBasicBlock()) { |
| // The constant folding can return an instruction that is already |
| // part of the graph (like an input), so we only add the replacement |
| // if necessary. |
| block.addAfter(instruction, replacement); |
| // Visit the replacement as the next instruction in case it |
| // can also be constant folded away. |
| next = replacement; |
| } |
| block.remove(instruction); |
| } |
| instruction = next; |
| } |
| } |
| |
| HInstruction visitInstruction(HInstruction node) { |
| return node; |
| } |
| |
| HInstruction visitBoolify(HBoolify node) { |
| List<HInstruction> inputs = node.inputs; |
| assert(inputs.length == 1); |
| HInstruction input = inputs[0]; |
| if (input.isBoolean(compiler)) return input; |
| // All values that cannot be 'true' are boolified to false. |
| TypeMask mask = input.instructionType; |
| if (!mask.contains(backend.jsBoolClass, compiler)) { |
| return graph.addConstantBool(false, compiler); |
| } |
| return node; |
| } |
| |
| HInstruction visitNot(HNot node) { |
| List<HInstruction> inputs = node.inputs; |
| assert(inputs.length == 1); |
| HInstruction input = inputs[0]; |
| if (input is HConstant) { |
| HConstant constant = input; |
| bool isTrue = constant.constant.isTrue(); |
| return graph.addConstantBool(!isTrue, compiler); |
| } else if (input is HNot) { |
| return input.inputs[0]; |
| } |
| return node; |
| } |
| |
| HInstruction visitInvokeUnary(HInvokeUnary node) { |
| HInstruction folded = |
| foldUnary(node.operation(constantSystem), node.operand); |
| return folded != null ? folded : node; |
| } |
| |
| HInstruction foldUnary(UnaryOperation operation, HInstruction operand) { |
| if (operand is HConstant) { |
| HConstant receiver = operand; |
| Constant folded = operation.fold(receiver.constant); |
| if (folded != null) return graph.addConstant(folded, compiler); |
| } |
| return null; |
| } |
| |
| HInstruction tryOptimizeLengthInterceptedGetter(HInvokeDynamic node) { |
| HInstruction actualReceiver = node.inputs[1]; |
| if (actualReceiver.isIndexablePrimitive(compiler)) { |
| if (actualReceiver.isConstantString()) { |
| HConstant constantInput = actualReceiver; |
| StringConstant constant = constantInput.constant; |
| return graph.addConstantInt(constant.length, compiler); |
| } else if (actualReceiver.isConstantList()) { |
| HConstant constantInput = actualReceiver; |
| ListConstant constant = constantInput.constant; |
| return graph.addConstantInt(constant.length, compiler); |
| } |
| Element element = backend.jsIndexableLength; |
| var mask = actualReceiver.instructionType; |
| bool isFixedLength = false; |
| if (mask.isContainer && mask.length != null) { |
| // A container on which we have inferred the length. |
| isFixedLength = true; |
| } else if (mask.containsOnly(backend.jsFixedArrayClass) |
| || mask.containsOnlyString(compiler) |
| || backend.isTypedArray(mask)) { |
| isFixedLength = true; |
| } |
| HFieldGet result = new HFieldGet( |
| element, actualReceiver, backend.intType, |
| isAssignable: !isFixedLength); |
| return result; |
| } else if (actualReceiver.isConstantMap()) { |
| HConstant constantInput = actualReceiver; |
| MapConstant constant = constantInput.constant; |
| return graph.addConstantInt(constant.length, compiler); |
| } |
| return null; |
| } |
| |
| HInstruction handleInterceptedCall(HInvokeDynamic node) { |
| // Try constant folding the instruction. |
| Operation operation = node.specializer.operation(constantSystem); |
| if (operation != null) { |
| HInstruction instruction = node.inputs.length == 2 |
| ? foldUnary(operation, node.inputs[1]) |
| : foldBinary(operation, node.inputs[1], node.inputs[2]); |
| if (instruction != null) return instruction; |
| } |
| |
| // Try converting the instruction to a builtin instruction. |
| HInstruction instruction = |
| node.specializer.tryConvertToBuiltin(node, compiler); |
| if (instruction != null) return instruction; |
| |
| Selector selector = node.selector; |
| HInstruction input = node.inputs[1]; |
| |
| if (selector.isCall() || selector.isOperator()) { |
| Element target; |
| if (input.isExtendableArray(compiler)) { |
| if (selector.applies(backend.jsArrayRemoveLast, compiler)) { |
| target = backend.jsArrayRemoveLast; |
| } else if (selector.applies(backend.jsArrayAdd, compiler)) { |
| // The codegen special cases array calls, but does not |
| // inline argument type checks. |
| if (!compiler.enableTypeAssertions) { |
| target = backend.jsArrayAdd; |
| } |
| } |
| } else if (input.isString(compiler)) { |
| if (selector.applies(backend.jsStringSplit, compiler)) { |
| HInstruction argument = node.inputs[2]; |
| if (argument.isString(compiler) && !argument.canBeNull()) { |
| target = backend.jsStringSplit; |
| } |
| } else if (selector.applies(backend.jsStringOperatorAdd, compiler)) { |
| // `operator+` is turned into a JavaScript '+' so we need to |
| // make sure the receiver and the argument are not null. |
| HInstruction argument = node.inputs[2]; |
| if (argument.isString(compiler) |
| && !argument.canBeNull() |
| && !input.canBeNull()) { |
| target = backend.jsStringOperatorAdd; |
| } |
| } else if (selector.applies(backend.jsStringToString, compiler) |
| && !input.canBeNull()) { |
| return input; |
| } |
| } |
| if (target != null) { |
| // TODO(ngeoffray): There is a strong dependency between codegen |
| // and this optimization that the dynamic invoke does not need an |
| // interceptor. We currently need to keep a |
| // HInvokeDynamicMethod and not create a HForeign because |
| // HForeign is too opaque for the SsaCheckInserter (that adds a |
| // bounds check on removeLast). Once we start inlining, the |
| // bounds check will become explicit, so we won't need this |
| // optimization. |
| HInvokeDynamicMethod result = new HInvokeDynamicMethod( |
| node.selector, node.inputs.sublist(1), node.instructionType); |
| result.element = target; |
| return result; |
| } |
| } else if (selector.isGetter()) { |
| if (selector.asUntyped.applies(backend.jsIndexableLength, compiler)) { |
| HInstruction optimized = tryOptimizeLengthInterceptedGetter(node); |
| if (optimized != null) return optimized; |
| } |
| } |
| |
| return node; |
| } |
| |
| HInstruction visitInvokeDynamicMethod(HInvokeDynamicMethod node) { |
| if (node.isInterceptedCall) { |
| HInstruction folded = handleInterceptedCall(node); |
| if (folded != node) return folded; |
| } |
| |
| TypeMask receiverType = node.getDartReceiver(compiler).instructionType; |
| Selector selector = new TypedSelector(receiverType, node.selector); |
| Element element = compiler.world.locateSingleElement(selector); |
| // TODO(ngeoffray): Also fold if it's a getter or variable. |
| if (element != null |
| && element.isFunction() |
| // If we found out that the only target is a [:noSuchMethod:], |
| // we just ignore it. |
| && element.name == selector.name) { |
| FunctionElement method = element; |
| |
| if (method.isNative()) { |
| HInstruction folded = tryInlineNativeMethod(node, method); |
| if (folded != null) return folded; |
| } else { |
| // TODO(ngeoffray): If the method has optional parameters, |
| // we should pass the default values. |
| FunctionSignature parameters = method.computeSignature(compiler); |
| if (parameters.optionalParameterCount == 0 |
| || parameters.parameterCount == node.selector.argumentCount) { |
| node.element = element; |
| } |
| } |
| } |
| return node; |
| } |
| |
| HInstruction tryInlineNativeMethod(HInvokeDynamicMethod node, |
| FunctionElement method) { |
| // Enable direct calls to a native method only if we don't run in checked |
| // mode, where the Dart version may have type annotations on parameters and |
| // return type that it should check. |
| // Also check that the parameters are not functions: it's the callee that |
| // will translate them to JS functions. |
| // |
| // TODO(ngeoffray): There are some cases where we could still inline in |
| // checked mode if we know the arguments have the right type. And we could |
| // do the closure conversion as well as the return type annotation check. |
| |
| if (!node.isInterceptedCall) return null; |
| |
| // TODO(sra): Check for legacy methods with bodies in the native strings. |
| // foo() native 'return something'; |
| // They should not be used. |
| |
| FunctionSignature signature = method.computeSignature(compiler); |
| if (signature.optionalParametersAreNamed) return null; |
| |
| // Return types on native methods don't need to be checked, since the |
| // declaration has to be truthful. |
| |
| // The call site might omit optional arguments. The inlined code must |
| // preserve the number of arguments, so check only the actual arguments. |
| |
| List<HInstruction> inputs = node.inputs.sublist(1); |
| int inputPosition = 1; // Skip receiver. |
| bool canInline = true; |
| signature.forEachParameter((Element element) { |
| if (inputPosition < inputs.length && canInline) { |
| HInstruction input = inputs[inputPosition++]; |
| DartType type = element.computeType(compiler).unalias(compiler); |
| if (type is FunctionType) { |
| canInline = false; |
| } |
| if (compiler.enableTypeAssertions) { |
| // TODO(sra): Check if [input] is guaranteed to pass the parameter |
| // type check. Consider using a strengthened type check to avoid |
| // passing `null` to primitive types since the native methods usually |
| // have non-nullable primitive parameter types. |
| canInline = false; |
| } |
| } |
| }); |
| |
| if (!canInline) return null; |
| |
| // Strengthen instruction type from annotations to help optimize |
| // dependent instructions. |
| native.NativeBehavior nativeBehavior = |
| native.NativeBehavior.ofMethod(method, compiler); |
| TypeMask returnType = |
| TypeMaskFactory.fromNativeBehavior(nativeBehavior, compiler); |
| HInvokeDynamicMethod result = |
| new HInvokeDynamicMethod(node.selector, inputs, returnType); |
| result.element = method; |
| return result; |
| } |
| |
| HInstruction visitBoundsCheck(HBoundsCheck node) { |
| HInstruction index = node.index; |
| if (index.isInteger(compiler)) return node; |
| if (index.isConstant()) { |
| HConstant constantInstruction = index; |
| assert(!constantInstruction.constant.isInt()); |
| if (!constantSystem.isInt(constantInstruction.constant)) { |
| // -0.0 is a double but will pass the runtime integer check. |
| node.staticChecks = HBoundsCheck.ALWAYS_FALSE; |
| } |
| } |
| return node; |
| } |
| |
| HInstruction foldBinary(BinaryOperation operation, |
| HInstruction left, |
| HInstruction right) { |
| if (left is HConstant && right is HConstant) { |
| HConstant op1 = left; |
| HConstant op2 = right; |
| Constant folded = operation.fold(op1.constant, op2.constant); |
| if (folded != null) return graph.addConstant(folded, compiler); |
| } |
| return null; |
| } |
| |
| HInstruction visitInvokeBinary(HInvokeBinary node) { |
| HInstruction left = node.left; |
| HInstruction right = node.right; |
| BinaryOperation operation = node.operation(constantSystem); |
| HConstant folded = foldBinary(operation, left, right); |
| if (folded != null) return folded; |
| return node; |
| } |
| |
| bool allUsersAreBoolifies(HInstruction instruction) { |
| List<HInstruction> users = instruction.usedBy; |
| int length = users.length; |
| for (int i = 0; i < length; i++) { |
| if (users[i] is! HBoolify) return false; |
| } |
| return true; |
| } |
| |
| HInstruction visitRelational(HRelational node) { |
| if (allUsersAreBoolifies(node)) { |
| // TODO(ngeoffray): Call a boolified selector. |
| // This node stays the same, but the Boolify node will go away. |
| } |
| // Note that we still have to call [super] to make sure that we end up |
| // in the remaining optimizations. |
| return super.visitRelational(node); |
| } |
| |
| HInstruction handleIdentityCheck(HRelational node) { |
| HInstruction left = node.left; |
| HInstruction right = node.right; |
| TypeMask leftType = left.instructionType; |
| TypeMask rightType = right.instructionType; |
| |
| // Intersection of int and double return conflicting, so |
| // we don't optimize on numbers to preserve the runtime semantics. |
| if (!(left.isNumberOrNull(compiler) && right.isNumberOrNull(compiler))) { |
| TypeMask intersection = leftType.intersection(rightType, compiler); |
| if (intersection.isEmpty && !intersection.isNullable) { |
| return graph.addConstantBool(false, compiler); |
| } |
| } |
| |
| if (left.isNull() && right.isNull()) { |
| return graph.addConstantBool(true, compiler); |
| } |
| |
| if (left.isConstantBoolean() && right.isBoolean(compiler)) { |
| HConstant constant = left; |
| if (constant.constant.isTrue()) { |
| return right; |
| } else { |
| return new HNot(right, backend.boolType); |
| } |
| } |
| |
| if (right.isConstantBoolean() && left.isBoolean(compiler)) { |
| HConstant constant = right; |
| if (constant.constant.isTrue()) { |
| return left; |
| } else { |
| return new HNot(left, backend.boolType); |
| } |
| } |
| |
| return null; |
| } |
| |
| HInstruction visitIdentity(HIdentity node) { |
| HInstruction newInstruction = handleIdentityCheck(node); |
| return newInstruction == null ? super.visitIdentity(node) : newInstruction; |
| } |
| |
| void simplifyCondition(HBasicBlock block, |
| HInstruction condition, |
| bool value) { |
| condition.dominatedUsers(block.first).forEach((user) { |
| HInstruction newCondition = graph.addConstantBool(value, compiler); |
| user.changeUse(condition, newCondition); |
| }); |
| } |
| |
| HInstruction visitIf(HIf node) { |
| HInstruction condition = node.condition; |
| if (condition.isConstant()) return node; |
| bool isNegated = condition is HNot; |
| |
| if (isNegated) { |
| condition = condition.inputs[0]; |
| } else { |
| // It is possible for LICM to move a negated version of the |
| // condition out of the loop where it used. We still want to |
| // simplify the nested use of the condition in that case, so |
| // we look for all dominating negated conditions and replace |
| // nested uses of them with true or false. |
| Iterable<HInstruction> dominating = condition.usedBy.where((user) => |
| user is HNot && user.dominates(node)); |
| dominating.forEach((hoisted) { |
| simplifyCondition(node.thenBlock, hoisted, false); |
| simplifyCondition(node.elseBlock, hoisted, true); |
| }); |
| } |
| simplifyCondition(node.thenBlock, condition, !isNegated); |
| simplifyCondition(node.elseBlock, condition, isNegated); |
| return node; |
| } |
| |
| HInstruction visitIs(HIs node) { |
| DartType type = node.typeExpression; |
| Element element = type.element; |
| |
| if (!node.isRawCheck) { |
| return node; |
| } else if (element.isTypedef()) { |
| return node; |
| } else if (element == compiler.functionClass) { |
| return node; |
| } |
| |
| if (element == compiler.objectClass || type.treatAsDynamic) { |
| return graph.addConstantBool(true, compiler); |
| } |
| |
| HInstruction expression = node.expression; |
| if (expression.isInteger(compiler)) { |
| if (identical(element, compiler.intClass) |
| || identical(element, compiler.numClass) |
| || Elements.isNumberOrStringSupertype(element, compiler)) { |
| return graph.addConstantBool(true, compiler); |
| } else if (identical(element, compiler.doubleClass)) { |
| // We let the JS semantics decide for that check. Currently |
| // the code we emit will always return true. |
| return node; |
| } else { |
| return graph.addConstantBool(false, compiler); |
| } |
| } else if (expression.isDouble(compiler)) { |
| if (identical(element, compiler.doubleClass) |
| || identical(element, compiler.numClass) |
| || Elements.isNumberOrStringSupertype(element, compiler)) { |
| return graph.addConstantBool(true, compiler); |
| } else if (identical(element, compiler.intClass)) { |
| // We let the JS semantics decide for that check. Currently |
| // the code we emit will return true for a double that can be |
| // represented as a 31-bit integer and for -0.0. |
| return node; |
| } else { |
| return graph.addConstantBool(false, compiler); |
| } |
| } else if (expression.isNumber(compiler)) { |
| if (identical(element, compiler.numClass)) { |
| return graph.addConstantBool(true, compiler); |
| } else { |
| // We cannot just return false, because the expression may be of |
| // type int or double. |
| } |
| } else if (expression.canBePrimitiveNumber(compiler) |
| && identical(element, compiler.intClass)) { |
| // We let the JS semantics decide for that check. |
| return node; |
| // We need the [:hasTypeArguments:] check because we don't have |
| // the notion of generics in the backend. For example, [:this:] in |
| // a class [:A<T>:], is currently always considered to have the |
| // raw type. |
| } else if (!RuntimeTypes.hasTypeArguments(type)) { |
| TypeMask expressionMask = expression.instructionType; |
| TypeMask typeMask = (element == compiler.nullClass) |
| ? new TypeMask.subtype(element) |
| : new TypeMask.nonNullSubtype(element); |
| if (expressionMask.union(typeMask, compiler) == typeMask) { |
| return graph.addConstantBool(true, compiler); |
| } else if (expressionMask.intersection(typeMask, compiler).isEmpty) { |
| return graph.addConstantBool(false, compiler); |
| } |
| } |
| return node; |
| } |
| |
| HInstruction visitTypeConversion(HTypeConversion node) { |
| HInstruction value = node.inputs[0]; |
| DartType type = node.typeExpression; |
| if (type != null) { |
| if (type.kind == TypeKind.MALFORMED_TYPE) { |
| // Malformed types are treated as dynamic statically, but should |
| // throw a type error at runtime. |
| return node; |
| } |
| if (!type.treatAsRaw || type.kind == TypeKind.TYPE_VARIABLE) { |
| return node; |
| } |
| if (type.kind == TypeKind.FUNCTION) { |
| // TODO(johnniwinther): Optimize function type conversions. |
| return node; |
| } |
| } |
| return removeIfCheckAlwaysSucceeds(node, node.checkedType); |
| } |
| |
| HInstruction visitTypeKnown(HTypeKnown node) { |
| return removeIfCheckAlwaysSucceeds(node, node.knownType); |
| } |
| |
| HInstruction removeIfCheckAlwaysSucceeds(HCheck node, TypeMask checkedType) { |
| if (checkedType.containsAll(compiler)) return node; |
| HInstruction input = node.checkedInput; |
| TypeMask inputType = input.instructionType; |
| return inputType.isInMask(checkedType, compiler) ? input : node; |
| } |
| |
| Element findConcreteFieldForDynamicAccess(HInstruction receiver, |
| Selector selector) { |
| TypeMask receiverType = receiver.instructionType; |
| return compiler.world.locateSingleField( |
| new TypedSelector(receiverType, selector)); |
| } |
| |
| HInstruction visitFieldGet(HFieldGet node) { |
| var receiver = node.receiver; |
| if (node.element == backend.jsIndexableLength) { |
| JavaScriptItemCompilationContext context = work.compilationContext; |
| if (context.allocatedFixedLists.contains(receiver)) { |
| // TODO(ngeoffray): checking if the second input is an integer |
| // should not be necessary but it currently makes it easier for |
| // other optimizations to reason about a fixed length constructor |
| // that we know takes an int. |
| if (receiver.inputs[0].isInteger(compiler)) { |
| return receiver.inputs[0]; |
| } |
| } else if (receiver.isConstantList() || receiver.isConstantString()) { |
| return graph.addConstantInt(receiver.constant.length, compiler); |
| } else { |
| var type = receiver.instructionType; |
| if (type.isContainer && type.length != null) { |
| HInstruction constant = graph.addConstantInt(type.length, compiler); |
| if (type.isNullable) { |
| // If the container can be null, we update all uses of the |
| // length access to use the constant instead, but keep the |
| // length access in the graph, to ensure we still have a |
| // null check. |
| node.block.rewrite(node, constant); |
| return node; |
| } else { |
| return constant; |
| } |
| } |
| } |
| } |
| return node; |
| } |
| |
| HInstruction visitIndex(HIndex node) { |
| if (node.receiver.isConstantList() && node.index.isConstantInteger()) { |
| var instruction = node.receiver; |
| List<Constant> entries = instruction.constant.entries; |
| instruction = node.index; |
| int index = instruction.constant.value; |
| if (index >= 0 && index < entries.length) { |
| return graph.addConstant(entries[index], compiler); |
| } |
| } |
| return node; |
| } |
| |
| HInstruction visitInvokeDynamicGetter(HInvokeDynamicGetter node) { |
| if (node.isInterceptedCall) { |
| HInstruction folded = handleInterceptedCall(node); |
| if (folded != node) return folded; |
| } |
| HInstruction receiver = node.getDartReceiver(compiler); |
| Element field = findConcreteFieldForDynamicAccess(receiver, node.selector); |
| if (field == null) return node; |
| return directFieldGet(receiver, field); |
| } |
| |
| HInstruction directFieldGet(HInstruction receiver, Element field) { |
| Modifiers modifiers = field.modifiers; |
| bool isAssignable = !(modifiers.isFinal() || modifiers.isConst()); |
| if (!compiler.resolverWorld.hasInvokedSetter(field, compiler)) { |
| // If no setter is ever used for this field it is only initialized in the |
| // initializer list. |
| isAssignable = false; |
| } |
| if (field.isNative()) { |
| // Some native fields are views of data that may be changed by operations. |
| // E.g. node.firstChild depends on parentNode.removeBefore(n1, n2). |
| // TODO(sra): Refine the effect classification so that native effects are |
| // distinct from ordinary Dart effects. |
| isAssignable = true; |
| } |
| |
| TypeMask type; |
| if (field.getEnclosingClass().isNative()) { |
| type = TypeMaskFactory.fromNativeBehavior( |
| native.NativeBehavior.ofFieldLoad(field, compiler), |
| compiler); |
| } else { |
| type = TypeMaskFactory.inferredTypeForElement(field, compiler); |
| } |
| |
| return new HFieldGet( |
| field, receiver, type, isAssignable: isAssignable); |
| } |
| |
| HInstruction visitInvokeDynamicSetter(HInvokeDynamicSetter node) { |
| if (node.isInterceptedCall) { |
| HInstruction folded = handleInterceptedCall(node); |
| if (folded != node) return folded; |
| } |
| |
| HInstruction receiver = node.getDartReceiver(compiler); |
| Element field = findConcreteFieldForDynamicAccess(receiver, node.selector); |
| if (field == null || !field.isAssignable()) return node; |
| // Use [:node.inputs.last:] in case the call follows the |
| // interceptor calling convention, but is not a call on an |
| // interceptor. |
| HInstruction value = node.inputs.last; |
| if (compiler.enableTypeAssertions) { |
| DartType type = field.computeType(compiler); |
| if (!type.treatAsRaw || type.kind == TypeKind.TYPE_VARIABLE) { |
| // We cannot generate the correct type representation here, so don't |
| // inline this access. |
| return node; |
| } |
| HInstruction other = value.convertType( |
| compiler, |
| type, |
| HTypeConversion.CHECKED_MODE_CHECK); |
| if (other != value) { |
| node.block.addBefore(node, other); |
| value = other; |
| } |
| } |
| return new HFieldSet(field, receiver, value); |
| } |
| |
| HInstruction visitStringConcat(HStringConcat node) { |
| // Simplify string concat: |
| // |
| // "" + R -> R |
| // L + "" -> L |
| // "L" + "R" -> "LR" |
| // (prefix + "L") + "R" -> prefix + "LR" |
| // |
| StringConstant getString(HInstruction instruction) { |
| if (!instruction.isConstantString()) return null; |
| HConstant constant = instruction; |
| return constant.constant; |
| } |
| |
| StringConstant leftString = getString(node.left); |
| if (leftString != null && leftString.value.length == 0) return node.right; |
| |
| StringConstant rightString = getString(node.right); |
| if (rightString == null) return node; |
| if (rightString.value.length == 0) return node.left; |
| |
| HInstruction prefix = null; |
| if (leftString == null) { |
| if (node.left is! HStringConcat) return node; |
| HStringConcat leftConcat = node.left; |
| // Don't undo CSE. |
| if (leftConcat.usedBy.length != 1) return node; |
| prefix = leftConcat.left; |
| leftString = getString(leftConcat.right); |
| if (leftString == null) return node; |
| } |
| |
| HInstruction folded = graph.addConstant( |
| constantSystem.createString( |
| new DartString.concat(leftString.value, rightString.value), |
| node.node), |
| compiler); |
| if (prefix == null) return folded; |
| return new HStringConcat(prefix, folded, node.node, backend.stringType); |
| } |
| |
| HInstruction visitStringify(HStringify node) { |
| HInstruction input = node.inputs[0]; |
| if (input.isString(compiler) && !input.canBeNull()) return input; |
| if (input.isConstant()) { |
| HConstant constant = input; |
| if (!constant.constant.isPrimitive()) return node; |
| PrimitiveConstant primitive = constant.constant; |
| return graph.addConstant(constantSystem.createString( |
| primitive.toDartString(), node.node), compiler); |
| } |
| return node; |
| } |
| |
| HInstruction visitOneShotInterceptor(HOneShotInterceptor node) { |
| return handleInterceptedCall(node); |
| } |
| } |
| |
| class SsaCheckInserter extends HBaseVisitor implements OptimizationPhase { |
| final Set<HInstruction> boundsChecked; |
| final CodegenWorkItem work; |
| final JavaScriptBackend backend; |
| final String name = "SsaCheckInserter"; |
| HGraph graph; |
| |
| SsaCheckInserter(this.backend, |
| this.work, |
| this.boundsChecked); |
| |
| void visitGraph(HGraph graph) { |
| this.graph = graph; |
| visitDominatorTree(graph); |
| } |
| |
| void visitBasicBlock(HBasicBlock block) { |
| HInstruction instruction = block.first; |
| while (instruction != null) { |
| HInstruction next = instruction.next; |
| instruction = instruction.accept(this); |
| instruction = next; |
| } |
| } |
| |
| HBoundsCheck insertBoundsCheck(HInstruction indexNode, |
| HInstruction array, |
| HInstruction indexArgument) { |
| Compiler compiler = backend.compiler; |
| bool isAssignable = |
| !array.isFixedArray(compiler) && !array.isString(compiler); |
| HFieldGet length = new HFieldGet( |
| backend.jsIndexableLength, array, backend.intType, |
| isAssignable: isAssignable); |
| indexNode.block.addBefore(indexNode, length); |
| |
| HBoundsCheck check = new HBoundsCheck( |
| indexArgument, length, array, backend.intType); |
| indexNode.block.addBefore(indexNode, check); |
| // If the index input to the bounds check was not known to be an integer |
| // then we replace its uses with the bounds check, which is known to be an |
| // integer. However, if the input was already an integer we don't do this |
| // because putting in a check instruction might obscure the real nature of |
| // the index eg. if it is a constant. The range information from the |
| // BoundsCheck instruction is attached to the input directly by |
| // visitBoundsCheck in the SsaValueRangeAnalyzer. |
| if (!indexArgument.isInteger(compiler)) { |
| indexArgument.replaceAllUsersDominatedBy(indexNode, check); |
| } |
| boundsChecked.add(indexNode); |
| return check; |
| } |
| |
| void visitIndex(HIndex node) { |
| if (boundsChecked.contains(node)) return; |
| HInstruction index = node.index; |
| index = insertBoundsCheck(node, node.receiver, index); |
| } |
| |
| void visitIndexAssign(HIndexAssign node) { |
| if (boundsChecked.contains(node)) return; |
| HInstruction index = node.index; |
| index = insertBoundsCheck(node, node.receiver, index); |
| } |
| |
| void visitInvokeDynamicMethod(HInvokeDynamicMethod node) { |
| Element element = node.element; |
| if (node.isInterceptedCall) return; |
| if (element != backend.jsArrayRemoveLast) return; |
| if (boundsChecked.contains(node)) return; |
| insertBoundsCheck( |
| node, node.receiver, graph.addConstantInt(0, backend.compiler)); |
| } |
| } |
| |
| class SsaDeadCodeEliminator extends HGraphVisitor implements OptimizationPhase { |
| final String name = "SsaDeadCodeEliminator"; |
| |
| final Compiler compiler; |
| SsaLiveBlockAnalyzer analyzer; |
| bool eliminatedSideEffects = false; |
| SsaDeadCodeEliminator(this.compiler); |
| |
| HInstruction zapInstructionCache; |
| HInstruction get zapInstruction { |
| return (zapInstructionCache == null) |
| ? zapInstructionCache = analyzer.graph.addConstantInt(0, compiler) |
| : zapInstructionCache; |
| } |
| |
| /// Returns whether the next throwing instruction that may have side |
| /// effects after [instruction], throws [NoSuchMethodError] on the |
| /// same receiver of [instruction]. |
| bool hasFollowingThrowingNSM(HInstruction instruction) { |
| HInstruction receiver = instruction.getDartReceiver(compiler); |
| HInstruction current = instruction.next; |
| do { |
| if ((current.getDartReceiver(compiler) == receiver) |
| && current.canThrow()) { |
| return true; |
| } |
| if (current.canThrow() || current.sideEffects.hasSideEffects()) { |
| return false; |
| } |
| if (current.next == null && current is HGoto) { |
| // We do not merge blocks in our SSA graph, so if this block |
| // just jumps to a single predecessor, visit this predecessor. |
| assert(current.block.successors.length == 1); |
| current = current.block.successors[0].first; |
| } else { |
| current = current.next; |
| } |
| } while (current != null); |
| return false; |
| } |
| |
| bool isDeadCode(HInstruction instruction) { |
| if (!instruction.usedBy.isEmpty) return false; |
| if (instruction.sideEffects.hasSideEffects()) return false; |
| if (instruction.canThrow() |
| && instruction.onlyThrowsNSM() |
| && hasFollowingThrowingNSM(instruction)) { |
| return true; |
| } |
| return !instruction.canThrow() |
| && instruction is !HParameterValue |
| && instruction is !HLocalSet; |
| } |
| |
| void visitGraph(HGraph graph) { |
| analyzer = new SsaLiveBlockAnalyzer(graph); |
| analyzer.analyze(); |
| visitPostDominatorTree(graph); |
| cleanPhis(graph); |
| } |
| |
| void visitBasicBlock(HBasicBlock block) { |
| bool isDeadBlock = analyzer.isDeadBlock(block); |
| block.isLive = !isDeadBlock; |
| // Start from the last non-control flow instruction in the block. |
| HInstruction instruction = block.last.previous; |
| while (instruction != null) { |
| var previous = instruction.previous; |
| if (isDeadBlock) { |
| eliminatedSideEffects = eliminatedSideEffects || |
| instruction.sideEffects.hasSideEffects(); |
| removeUsers(instruction); |
| block.remove(instruction); |
| } else if (isDeadCode(instruction)) { |
| block.remove(instruction); |
| } |
| instruction = previous; |
| } |
| } |
| |
| void cleanPhis(HGraph graph) { |
| L: for (HBasicBlock block in graph.blocks) { |
| List<HBasicBlock> predecessors = block.predecessors; |
| if (predecessors.length < 2) continue L; |
| // Find the index of the single live predecessor if it exists. |
| int indexOfLive = -1; |
| for (int i = 0; i < predecessors.length; i++) { |
| if (predecessors[i].isLive) { |
| if (indexOfLive >= 0) continue L; |
| indexOfLive = i; |
| } |
| } |
| // Run through the phis of the block and replace them with their input |
| // that comes from the only live predecessor if that dominates the phi. |
| block.forEachPhi((HPhi phi) { |
| HInstruction replacement = (indexOfLive >= 0) |
| ? phi.inputs[indexOfLive] : zapInstruction; |
| if (replacement.dominates(phi)) { |
| block.rewrite(phi, replacement); |
| block.removePhi(phi); |
| } |
| }); |
| } |
| } |
| |
| void removeUsers(HInstruction instruction) { |
| instruction.usedBy.forEach((user) { |
| removeInput(user, instruction); |
| }); |
| instruction.usedBy.clear(); |
| } |
| |
| void removeInput(HInstruction user, HInstruction input) { |
| List<HInstruction> inputs = user.inputs; |
| for (int i = 0, length = inputs.length; i < length; i++) { |
| if (input == inputs[i]) { |
| HInstruction zap = zapInstruction; |
| inputs[i] = zap; |
| zap.usedBy.add(user); |
| } |
| } |
| } |
| } |
| |
| class SsaLiveBlockAnalyzer extends HBaseVisitor { |
| final HGraph graph; |
| final Set<HBasicBlock> live = new Set<HBasicBlock>(); |
| final List<HBasicBlock> worklist = <HBasicBlock>[]; |
| SsaLiveBlockAnalyzer(this.graph); |
| |
| bool isDeadBlock(HBasicBlock block) => !live.contains(block); |
| |
| void analyze() { |
| markBlockLive(graph.entry); |
| while (!worklist.isEmpty) { |
| HBasicBlock live = worklist.removeLast(); |
| live.last.accept(this); |
| } |
| } |
| |
| void markBlockLive(HBasicBlock block) { |
| if (!live.contains(block)) { |
| worklist.add(block); |
| live.add(block); |
| } |
| } |
| |
| void visitControlFlow(HControlFlow instruction) { |
| instruction.block.successors.forEach(markBlockLive); |
| } |
| |
| void visitIf(HIf instruction) { |
| HInstruction condition = instruction.condition; |
| if (condition.isConstant()) { |
| if (condition.isConstantTrue()) { |
| markBlockLive(instruction.thenBlock); |
| } else { |
| markBlockLive(instruction.elseBlock); |
| } |
| } else { |
| visitControlFlow(instruction); |
| } |
| } |
| } |
| |
| class SsaDeadPhiEliminator implements OptimizationPhase { |
| final String name = "SsaDeadPhiEliminator"; |
| |
| void visitGraph(HGraph graph) { |
| final List<HPhi> worklist = <HPhi>[]; |
| // A set to keep track of the live phis that we found. |
| final Set<HPhi> livePhis = new Set<HPhi>(); |
| |
| // Add to the worklist all live phis: phis referenced by non-phi |
| // instructions. |
| for (final block in graph.blocks) { |
| block.forEachPhi((HPhi phi) { |
| for (final user in phi.usedBy) { |
| if (user is !HPhi) { |
| worklist.add(phi); |
| livePhis.add(phi); |
| break; |
| } |
| } |
| }); |
| } |
| |
| // Process the worklist by propagating liveness to phi inputs. |
| while (!worklist.isEmpty) { |
| HPhi phi = worklist.removeLast(); |
| for (final input in phi.inputs) { |
| if (input is HPhi && !livePhis.contains(input)) { |
| worklist.add(input); |
| livePhis.add(input); |
| } |
| } |
| } |
| |
| // Remove phis that are not live. |
| // Traverse in reverse order to remove phis with no uses before the |
| // phis that they might use. |
| // NOTICE: Doesn't handle circular references, but we don't currently |
| // create any. |
| List<HBasicBlock> blocks = graph.blocks; |
| for (int i = blocks.length - 1; i >= 0; i--) { |
| HBasicBlock block = blocks[i]; |
| HPhi current = block.phis.first; |
| HPhi next = null; |
| while (current != null) { |
| next = current.next; |
| if (!livePhis.contains(current) |
| // TODO(ahe): Not sure the following is correct. |
| && current.usedBy.isEmpty) { |
| block.removePhi(current); |
| } |
| current = next; |
| } |
| } |
| } |
| } |
| |
| class SsaRedundantPhiEliminator implements OptimizationPhase { |
| final String name = "SsaRedundantPhiEliminator"; |
| |
| void visitGraph(HGraph graph) { |
| final List<HPhi> worklist = <HPhi>[]; |
| |
| // Add all phis in the worklist. |
| for (final block in graph.blocks) { |
| block.forEachPhi((HPhi phi) => worklist.add(phi)); |
| } |
| |
| while (!worklist.isEmpty) { |
| HPhi phi = worklist.removeLast(); |
| |
| // If the phi has already been processed, continue. |
| if (!phi.isInBasicBlock()) continue; |
| |
| // Find if the inputs of the phi are the same instruction. |
| // The builder ensures that phi.inputs[0] cannot be the phi |
| // itself. |
| assert(!identical(phi.inputs[0], phi)); |
| HInstruction candidate = phi.inputs[0]; |
| for (int i = 1; i < phi.inputs.length; i++) { |
| HInstruction input = phi.inputs[i]; |
| // If the input is the phi, the phi is still candidate for |
| // elimination. |
| if (!identical(input, candidate) && !identical(input, phi)) { |
| candidate = null; |
| break; |
| } |
| } |
| |
| // If the inputs are not the same, continue. |
| if (candidate == null) continue; |
| |
| // Because we're updating the users of this phi, we may have new |
| // phis candidate for elimination. Add phis that used this phi |
| // to the worklist. |
| for (final user in phi.usedBy) { |
| if (user is HPhi) worklist.add(user); |
| } |
| phi.block.rewrite(phi, candidate); |
| phi.block.removePhi(phi); |
| } |
| } |
| } |
| |
| class GvnWorkItem { |
| final HBasicBlock block; |
| final ValueSet valueSet; |
| GvnWorkItem(this.block, this.valueSet); |
| } |
| |
| class SsaGlobalValueNumberer implements OptimizationPhase { |
| final String name = "SsaGlobalValueNumberer"; |
| final Compiler compiler; |
| final Set<int> visited; |
| |
| List<int> blockChangesFlags; |
| List<int> loopChangesFlags; |
| |
| SsaGlobalValueNumberer(this.compiler) : visited = new Set<int>(); |
| |
| void visitGraph(HGraph graph) { |
| computeChangesFlags(graph); |
| moveLoopInvariantCode(graph); |
| List<GvnWorkItem> workQueue = |
| <GvnWorkItem>[new GvnWorkItem(graph.entry, new ValueSet())]; |
| do { |
| GvnWorkItem item = workQueue.removeLast(); |
| visitBasicBlock(item.block, item.valueSet, workQueue); |
| } while (!workQueue.isEmpty); |
| } |
| |
| void moveLoopInvariantCode(HGraph graph) { |
| for (int i = graph.blocks.length - 1; i >= 0; i--) { |
| HBasicBlock block = graph.blocks[i]; |
| if (block.isLoopHeader()) { |
| int changesFlags = loopChangesFlags[block.id]; |
| HLoopInformation info = block.loopInformation; |
| // Iterate over all blocks of this loop. Note that blocks in |
| // inner loops are not visited here, but we know they |
| // were visited before because we are iterating in post-order. |
| // So instructions that are GVN'ed in an inner loop are in their |
| // loop entry, and [info.blocks] contains this loop entry. |
| moveLoopInvariantCodeFromBlock(block, block, changesFlags); |
| for (HBasicBlock other in info.blocks) { |
| moveLoopInvariantCodeFromBlock(other, block, changesFlags); |
| } |
| } |
| } |
| } |
| |
| void moveLoopInvariantCodeFromBlock(HBasicBlock block, |
| HBasicBlock loopHeader, |
| int changesFlags) { |
| assert(block.parentLoopHeader == loopHeader || block == loopHeader); |
| HBasicBlock preheader = loopHeader.predecessors[0]; |
| int dependsFlags = SideEffects.computeDependsOnFlags(changesFlags); |
| HInstruction instruction = block.first; |
| bool isLoopAlwaysTaken() { |
| HInstruction instruction = loopHeader.last; |
| assert(instruction is HGoto || instruction is HLoopBranch); |
| return instruction is HGoto |
| || instruction.inputs[0].isConstantTrue(); |
| } |
| bool firstInstructionInLoop = block == loopHeader |
| // Compensate for lack of code motion. |
| || (blockChangesFlags[loopHeader.id] == 0 |
| && isLoopAlwaysTaken() |
| && loopHeader.successors[0] == block); |
| while (instruction != null) { |
| HInstruction next = instruction.next; |
| if (instruction.useGvn() |
| && (!instruction.canThrow() || firstInstructionInLoop) |
| && !instruction.sideEffects.dependsOn(dependsFlags)) { |
| bool loopInvariantInputs = true; |
| List<HInstruction> inputs = instruction.inputs; |
| for (int i = 0, length = inputs.length; i < length; i++) { |
| if (isInputDefinedAfterDominator(inputs[i], preheader)) { |
| loopInvariantInputs = false; |
| break; |
| } |
| } |
| |
| // If the inputs are loop invariant, we can move the |
| // instruction from the current block to the pre-header block. |
| if (loopInvariantInputs) { |
| block.detach(instruction); |
| preheader.moveAtExit(instruction); |
| } else { |
| firstInstructionInLoop = false; |
| } |
| } |
| int oldChangesFlags = changesFlags; |
| changesFlags |= instruction.sideEffects.getChangesFlags(); |
| if (oldChangesFlags != changesFlags) { |
| dependsFlags = SideEffects.computeDependsOnFlags(changesFlags); |
| } |
| instruction = next; |
| } |
| } |
| |
| bool isInputDefinedAfterDominator(HInstruction input, |
| HBasicBlock dominator) { |
| return input.block.id > dominator.id; |
| } |
| |
| void visitBasicBlock( |
| HBasicBlock block, ValueSet values, List<GvnWorkItem> workQueue) { |
| HInstruction instruction = block.first; |
| if (block.isLoopHeader()) { |
| int flags = loopChangesFlags[block.id]; |
| values.kill(flags); |
| } |
| while (instruction != null) { |
| HInstruction next = instruction.next; |
| int flags = instruction.sideEffects.getChangesFlags(); |
| assert(flags == 0 || !instruction.useGvn()); |
| values.kill(flags); |
| if (instruction.useGvn()) { |
| HInstruction other = values.lookup(instruction); |
| if (other != null) { |
| assert(other.gvnEquals(instruction) && instruction.gvnEquals(other)); |
| block.rewriteWithBetterUser(instruction, other); |
| block.remove(instruction); |
| } else { |
| values.add(instruction); |
| } |
| } |
| instruction = next; |
| } |
| |
| List<HBasicBlock> dominatedBlocks = block.dominatedBlocks; |
| for (int i = 0, length = dominatedBlocks.length; i < length; i++) { |
| HBasicBlock dominated = dominatedBlocks[i]; |
| // No need to copy the value set for the last child. |
| ValueSet successorValues = (i == length - 1) ? values : values.copy(); |
| // If we have no values in our set, we do not have to kill |
| // anything. Also, if the range of block ids from the current |
| // block to the dominated block is empty, there is no blocks on |
| // any path from the current block to the dominated block so we |
| // don't have to do anything either. |
| assert(block.id < dominated.id); |
| if (!successorValues.isEmpty && block.id + 1 < dominated.id) { |
| visited.clear(); |
| List<HBasicBlock> workQueue = <HBasicBlock>[dominated]; |
| int changesFlags = 0; |
| do { |
| HBasicBlock current = workQueue.removeLast(); |
| changesFlags |= |
| getChangesFlagsForDominatedBlock(block, current, workQueue); |
| } while (!workQueue.isEmpty); |
| successorValues.kill(changesFlags); |
| } |
| workQueue.add(new GvnWorkItem(dominated, successorValues)); |
| } |
| } |
| |
| void computeChangesFlags(HGraph graph) { |
| // Create the changes flags lists. Make sure to initialize the |
| // loop changes flags list to zero so we can use bitwise or when |
| // propagating loop changes upwards. |
| final int length = graph.blocks.length; |
| blockChangesFlags = new List<int>(length); |
| loopChangesFlags = new List<int>(length); |
| for (int i = 0; i < length; i++) loopChangesFlags[i] = 0; |
| |
| // Run through all the basic blocks in the graph and fill in the |
| // changes flags lists. |
| for (int i = length - 1; i >= 0; i--) { |
| final HBasicBlock block = graph.blocks[i]; |
| final int id = block.id; |
| |
| // Compute block changes flags for the block. |
| int changesFlags = 0; |
| HInstruction instruction = block.first; |
| while (instruction != null) { |
| changesFlags |= instruction.sideEffects.getChangesFlags(); |
| instruction = instruction.next; |
| } |
| assert(blockChangesFlags[id] == null); |
| blockChangesFlags[id] = changesFlags; |
| |
| // Loop headers are part of their loop, so update the loop |
| // changes flags accordingly. |
| if (block.isLoopHeader()) { |
| loopChangesFlags[id] |= changesFlags; |
| } |
| |
| // Propagate loop changes flags upwards. |
| HBasicBlock parentLoopHeader = block.parentLoopHeader; |
| if (parentLoopHeader != null) { |
| loopChangesFlags[parentLoopHeader.id] |= (block.isLoopHeader()) |
| ? loopChangesFlags[id] |
| : changesFlags; |
| } |
| } |
| } |
| |
| int getChangesFlagsForDominatedBlock(HBasicBlock dominator, |
| HBasicBlock dominated, |
| List<HBasicBlock> workQueue) { |
| int changesFlags = 0; |
| List<HBasicBlock> predecessors = dominated.predecessors; |
| for (int i = 0, length = predecessors.length; i < length; i++) { |
| HBasicBlock block = predecessors[i]; |
| int id = block.id; |
| // If the current predecessor block is on the path from the |
| // dominator to the dominated, it must have an id that is in the |
| // range from the dominator to the dominated. |
| if (dominator.id < id && id < dominated.id && !visited.contains(id)) { |
| visited.add(id); |
| changesFlags |= blockChangesFlags[id]; |
| // Loop bodies might not be on the path from dominator to dominated, |
| // but they can invalidate values. |
| changesFlags |= loopChangesFlags[id]; |
| workQueue.add(block); |
| } |
| } |
| return changesFlags; |
| } |
| } |
| |
| // This phase merges equivalent instructions on different paths into |
| // one instruction in a dominator block. It runs through the graph |
| // post dominator order and computes a ValueSet for each block of |
| // instructions that can be moved to a dominator block. These |
| // instructions are the ones that: |
| // 1) can be used for GVN, and |
| // 2) do not use definitions of their own block. |
| // |
| // A basic block looks at its sucessors and finds the intersection of |
| // these computed ValueSet. It moves all instructions of the |
| // intersection into its own list of instructions. |
| class SsaCodeMotion extends HBaseVisitor implements OptimizationPhase { |
| final String name = "SsaCodeMotion"; |
| |
| List<ValueSet> values; |
| |
| void visitGraph(HGraph graph) { |
| values = new List<ValueSet>(graph.blocks.length); |
| for (int i = 0; i < graph.blocks.length; i++) { |
| values[graph.blocks[i].id] = new ValueSet(); |
| } |
| visitPostDominatorTree(graph); |
| } |
| |
| void visitBasicBlock(HBasicBlock block) { |
| List<HBasicBlock> successors = block.successors; |
| |
| // Phase 1: get the ValueSet of all successors (if there are more than one), |
| // compute the intersection and move the instructions of the intersection |
| // into this block. |
| if (successors.length > 1) { |
| ValueSet instructions = values[successors[0].id]; |
| for (int i = 1; i < successors.length; i++) { |
| ValueSet other = values[successors[i].id]; |
| instructions = instructions.intersection(other); |
| } |
| |
| if (!instructions.isEmpty) { |
| List<HInstruction> list = instructions.toList(); |
| for (HInstruction instruction in list) { |
| // Move the instruction to the current block. |
| instruction.block.detach(instruction); |
| block.moveAtExit(instruction); |
| // Go through all successors and rewrite their instruction |
| // to the shared one. |
| for (final successor in successors) { |
| HInstruction toRewrite = values[successor.id].lookup(instruction); |
| if (toRewrite != instruction) { |
| successor.rewriteWithBetterUser(toRewrite, instruction); |
| successor.remove(toRewrite); |
| } |
| } |
| } |
| } |
| } |
| |
| // Don't try to merge instructions to a dominator if we have |
| // multiple predecessors. |
| if (block.predecessors.length != 1) return; |
| |
| // Phase 2: Go through all instructions of this block and find |
| // which instructions can be moved to a dominator block. |
| ValueSet set_ = values[block.id]; |
| HInstruction instruction = block.first; |
| int flags = 0; |
| while (instruction != null) { |
| int dependsFlags = SideEffects.computeDependsOnFlags(flags); |
| flags |= instruction.sideEffects.getChangesFlags(); |
| |
| HInstruction current = instruction; |
| instruction = instruction.next; |
| |
| // TODO(ngeoffray): this check is needed because we currently do |
| // not have flags to express 'Gvn'able', but not movable. |
| if (current is HCheck) continue; |
| if (!current.useGvn()) continue; |
| if (current.sideEffects.dependsOn(dependsFlags)) continue; |
| |
| bool canBeMoved = true; |
| for (final HInstruction input in current.inputs) { |
| if (input.block == block) { |
| canBeMoved = false; |
| break; |
| } |
| } |
| if (!canBeMoved) continue; |
| |
| // This is safe because we are running after GVN. |
| // TODO(ngeoffray): ensure GVN has been run. |
| set_.add(current); |
| } |
| } |
| } |
| |
| class SsaTypeConversionInserter extends HBaseVisitor |
| implements OptimizationPhase { |
| final String name = "SsaTypeconversionInserter"; |
| final Compiler compiler; |
| |
| SsaTypeConversionInserter(this.compiler); |
| |
| void visitGraph(HGraph graph) { |
| visitDominatorTree(graph); |
| } |
| |
| // Update users of [input] that are dominated by [:dominator.first:] |
| // to use [newInput] instead. |
| void changeUsesDominatedBy(HBasicBlock dominator, |
| HInstruction input, |
| TypeMask convertedType) { |
| Setlet<HInstruction> dominatedUsers = input.dominatedUsers(dominator.first); |
| if (dominatedUsers.isEmpty) return; |
| |
| HTypeKnown newInput = new HTypeKnown(convertedType, input); |
| dominator.addBefore(dominator.first, newInput); |
| dominatedUsers.forEach((HInstruction user) { |
| user.changeUse(input, newInput); |
| }); |
| } |
| |
| void visitIs(HIs instruction) { |
| DartType type = instruction.typeExpression; |
| Element element = type.element; |
| if (!instruction.isRawCheck) { |
| return; |
| } else if (element.isTypedef()) { |
| return; |
| } |
| |
| List<HInstruction> ifUsers = <HInstruction>[]; |
| List<HInstruction> notIfUsers = <HInstruction>[]; |
| for (HInstruction user in instruction.usedBy) { |
| if (user is HIf) { |
| ifUsers.add(user); |
| } else if (user is HNot) { |
| for (HInstruction notUser in user.usedBy) { |
| if (notUser is HIf) notIfUsers.add(notUser); |
| } |
| } |
| } |
| |
| if (ifUsers.isEmpty && notIfUsers.isEmpty) return; |
| |
| TypeMask convertedType = new TypeMask.nonNullSubtype(element); |
| HInstruction input = instruction.expression; |
| for (HIf ifUser in ifUsers) { |
| changeUsesDominatedBy(ifUser.thenBlock, input, convertedType); |
| // TODO(ngeoffray): Also change uses for the else block on a type |
| // that knows it is not of a specific type. |
| } |
| |
| for (HIf ifUser in notIfUsers) { |
| changeUsesDominatedBy(ifUser.elseBlock, input, convertedType); |
| // TODO(ngeoffray): Also change uses for the then block on a type |
| // that knows it is not of a specific type. |
| } |
| } |
| } |
