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src/compiler/operator.h

+// Copyright 2013 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef V8_COMPILER_OPERATOR_H_
+#define V8_COMPILER_OPERATOR_H_
+
+#include "src/v8.h"
+
+#include "src/assembler.h"
+#include "src/ostreams.h"
+#include "src/unique.h"
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+// An operator represents description of the "computation" of a node in the
+// compiler IR. A computation takes values (i.e. data) as input and produces
+// zero or more values as output. The side-effects of a computation must be
+// captured by additional control and data dependencies which are part of the
+// IR graph.
+// Operators are immutable and describe the statically-known parts of a
+// computation. Thus they can be safely shared by many different nodes in the
+// IR graph, or even globally between graphs. Operators can have "static
+// parameters" which are compile-time constant parameters to the operator, such
+// as the name for a named field access, the ID of a runtime function, etc.
+// Static parameters are private to the operator and only semantically
+// meaningful to the operator itself.
+class Operator : public ZoneObject {
+ public:
+  Operator(uint8_t opcode, uint16_t properties)
+      : opcode_(opcode), properties_(properties) {}
+  virtual ~Operator() {}
+
+  // Properties inform the operator-independent optimizer about legal
+  // transformations for nodes that have this operator.
+  enum Property {
+    kNoProperties = 0,
+    kReducible    = 1 << 0,  // Participates in strength reduction.
+    kCommutative  = 1 << 1,  // OP(a, b) == OP(b, a) for all inputs.
+    kAssociative  = 1 << 2,  // OP(a, OP(b,c)) == OP(OP(a,b), c) for all inputs.
+    kIdempotent   = 1 << 3,  // OP(a); OP(a) == OP(a).
+
+    kNoRead       = 1 << 4,  // Has no scheduling dependency on Effects
+    kNoWrite      = 1 << 5,  // Does not modify any Effects and thereby
+                             // create new scheduling dependencies.
+    kNoThrow      = 1 << 6,  // Can never generate an exception.
+
+    kFoldable     = kNoRead | kNoWrite,
+    kEliminatable = kNoWrite | kNoThrow,
+    kPure         = kNoRead | kNoWrite | kNoThrow | kIdempotent
+  };
+
+  // A small integer unique to all instances of a particular kind of operator,
+  // useful for quick matching for specific kinds of operators. For fast access
+  // the opcode is stored directly in the operator object.
+  inline uint8_t opcode() const { return opcode_; }
+
+  // Returns a constant string representing the mnemonic of the operator,
+  // without the static parameters. Useful for debugging.
+  virtual const char* mnemonic() = 0;
+
+  // Check if this operator equals another operator. Equivalent operators can
+  // be merged, and nodes with equivalent operators and equivalent inputs
+  // can be merged.
+  virtual bool Equals(Operator* other) = 0;
+
+  // Compute a hashcode to speed up equivalence-set checking.
+  // Equal operators should always have equal hashcodes, and unequal operators
+  // should have unequal hashcodes with high probability.
+  virtual int HashCode() = 0;
+
+  // Check whether this operator has the given property.
+  inline bool HasProperty(Property property) const {
+    return (properties_ & static_cast<int>(property)) == property;
+  }
+
+  // Number of data inputs to the operator, for verifying graph structure.
+  virtual int InputCount() = 0;
+
+  // Number of data outputs from the operator, for verifying graph structure.
+  virtual int OutputCount() = 0;
+
+  inline Property properties() { return static_cast<Property>(properties_); }
+
+  // TODO(titzer): API for input and output types, for typechecking graph.
+ private:
+  // Print the full operator into the given stream, including any
+  // static parameters. Useful for debugging and visualizing the IR.
+  virtual OStream& PrintTo(OStream& os) const = 0;  // NOLINT
+  friend OStream& operator<<(OStream& os, const Operator& op);
+
+  uint8_t opcode_;
+  uint16_t properties_;
+};
+
+OStream& operator<<(OStream& os, const Operator& op);
+
+// An implementation of Operator that has no static parameters. Such operators
+// have just a name, an opcode, and a fixed number of inputs and outputs.
+// They can represented by singletons and shared globally.
+class SimpleOperator : public Operator {
+ public:
+  SimpleOperator(uint8_t opcode,
+                 uint16_t properties,
+                 int input_count,
+                 int output_count,
+                 const char* mnemonic)
+    : Operator(opcode, properties),
+      input_count_(input_count),
+      output_count_(output_count),
+      mnemonic_(mnemonic) { }
+
+  virtual const char* mnemonic() { return mnemonic_; }
+  virtual bool Equals(Operator* that) { return opcode() == that->opcode(); }
+  virtual int HashCode() { return opcode(); }
+  virtual int InputCount() { return input_count_; }
+  virtual int OutputCount() { return output_count_; }
+
+ private:
+  virtual OStream& PrintTo(OStream& os) const {  // NOLINT
+    return os << mnemonic_;
+  }
+
+  int input_count_;
+  int output_count_;
+  const char* mnemonic_;
+};
+
+// Template specialization implements a kind of type class for dealing with the
+// static parameters of Operator1 automatically.
+template <typename T>
+struct StaticParameterTraits {
+  static OStream& PrintTo(OStream& os, T val) {  // NOLINT
+    return os << "??";
+  }
+  static int HashCode(T a) { return 0; }
+  static bool Equals(T a, T b) {
+    return false;  // Not every T has a ==. By default, be conservative.
+  }
+};
+
+template <>
+struct StaticParameterTraits<ExternalReference> {
+  static OStream& PrintTo(OStream& os, ExternalReference val) {  // NOLINT
+    os << val.address();
+    const Runtime::Function* function =
+        Runtime::FunctionForEntry(val.address());
+    if (function != NULL) {
+      os << " <" << function->name << ".entry>";
+    }
+    return os;
+  }
+  static int HashCode(ExternalReference a) {
+    return reinterpret_cast<intptr_t>(a.address()) & 0xFFFFFFFF;
+  }
+  static bool Equals(ExternalReference a, ExternalReference b) {
+    return a == b;
+  }
+};
+
+// Specialization for static parameters of type {int}.
+template <>
+struct StaticParameterTraits<int> {
+  static OStream& PrintTo(OStream& os, int val) {  // NOLINT
+    return os << val;
+  }
+  static int HashCode(int a) { return a; }
+  static bool Equals(int a, int b) {
+    return a == b;
+  }
+};
+
+// Specialization for static parameters of type {double}.
+template <>
+struct StaticParameterTraits<double> {
+  static OStream& PrintTo(OStream& os, double val) {  // NOLINT
+    return os << val;
+  }
+  static int HashCode(double a) {
+    return static_cast<int>(BitCast<int64_t>(a));
+  }
+  static bool Equals(double a, double b) {
+    return BitCast<int64_t>(a) == BitCast<int64_t>(b);
+  }
+};
+
+// Specialization for static parameters of type {PrintableUnique<Object>}.
+template <>
+struct StaticParameterTraits<PrintableUnique<Object> > {
+  static OStream& PrintTo(OStream& os, PrintableUnique<Object> val) {  // NOLINT
+    return os << val.string();
+  }
+  static int HashCode(PrintableUnique<Object> a) { return a.Hashcode(); }
+  static bool Equals(PrintableUnique<Object> a, PrintableUnique<Object> b) {
+    return a == b;
+  }
+};
+
+// Specialization for static parameters of type {PrintableUnique<Name>}.
+template <>
+struct StaticParameterTraits<PrintableUnique<Name> > {
+  static OStream& PrintTo(OStream& os, PrintableUnique<Name> val) {  // NOLINT
+    return os << val.string();
+  }
+  static int HashCode(PrintableUnique<Name> a) { return a.Hashcode(); }
+  static bool Equals(PrintableUnique<Name> a, PrintableUnique<Name> b) {
+    return a == b;
+  }
+};
+
+#if DEBUG
+// Specialization for static parameters of type {Handle<Object>} to prevent any
+// direct usage of Handles in constants.
+template <>
+struct StaticParameterTraits<Handle<Object> > {
+  static OStream& PrintTo(OStream& os, Handle<Object> val) {  // NOLINT
+    UNREACHABLE();  // Should use PrintableUnique<Object> instead
+    return os;
+  }
+  static int HashCode(Handle<Object> a) {
+    UNREACHABLE();  // Should use PrintableUnique<Object> instead
+    return 0;
+  }
+  static bool Equals(Handle<Object> a, Handle<Object> b) {
+    UNREACHABLE();  // Should use PrintableUnique<Object> instead
+    return false;
+  }
+};
+#endif
+
+// A templatized implementation of Operator that has one static parameter of
+// type {T}. If a specialization of StaticParameterTraits<{T}> exists, then
+// operators of this kind can automatically be hashed, compared, and printed.
+template <typename T>
+class Operator1 : public Operator {
+ public:
+  Operator1(uint8_t opcode,
+            uint16_t properties,
+            int input_count,
+            int output_count,
+            const char* mnemonic,
+            T parameter)
+    : Operator(opcode, properties),
+      input_count_(input_count),
+      output_count_(output_count),
+      mnemonic_(mnemonic),
+      parameter_(parameter) {}
+
+  const T& parameter() const { return parameter_; }
+
+  virtual const char* mnemonic() { return mnemonic_; }
+  virtual bool Equals(Operator* other) {
+    if (opcode() != other->opcode()) return false;
+    Operator1<T>* that = static_cast<Operator1<T>* >(other);
+    T temp1 = this->parameter_;
+    T temp2 = that->parameter_;
+    return StaticParameterTraits<T>::Equals(temp1, temp2);
+  }
+  virtual int HashCode() {
+    return opcode() + 33 * StaticParameterTraits<T>::HashCode(this->parameter_);
+  }
+  virtual int InputCount() { return input_count_; }
+  virtual int OutputCount() { return output_count_; }
+  virtual OStream& PrintParameter(OStream& os) const {  // NOLINT
+    return StaticParameterTraits<T>::PrintTo(os << "[", parameter_) << "]";
+  }
+
+ private:
+  virtual OStream& PrintTo(OStream& os) const {  // NOLINT
+    return PrintParameter(os << mnemonic_);
+  }
+
+  int input_count_;
+  int output_count_;
+  const char* mnemonic_;
+  T parameter_;
+};
+
+// Type definitions for operators with specific types of parameters.
+typedef Operator1<PrintableUnique<Name> > NameOperator;
+
+} } }  // namespace v8::internal::compiler
+
+#endif  // V8_COMPILER_OPERATOR_H_