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src/compiler/representation-change.h

Index: src/compiler/representation-change.h
diff --git a/src/compiler/representation-change.h b/src/compiler/representation-change.h
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+// Copyright 2014 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_REPRESENTATION_CHANGE_H_
+#define V8_COMPILER_REPRESENTATION_CHANGE_H_
+
+#include "src/compiler/js-graph.h"
+#include "src/compiler/machine-operator.h"
+#include "src/compiler/node-properties-inl.h"
+#include "src/compiler/simplified-operator.h"
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+// The types and representations tracked during representation inference
+// and change insertion.
+// TODO(titzer): First, merge MachineRepresentation and RepType.
+// TODO(titzer): Second, Use the real type system instead of RepType.
+enum RepType {
+  // Representations.
+  rBit = 1 << 0,
+  rWord32 = 1 << 1,
+  rWord64 = 1 << 2,
+  rFloat64 = 1 << 3,
+  rTagged = 1 << 4,
+
+  // Types.
+  tBool = 1 << 5,
+  tInt32 = 1 << 6,
+  tUint32 = 1 << 7,
+  tInt64 = 1 << 8,
+  tUint64 = 1 << 9,
+  tNumber = 1 << 10,
+  tAny = 1 << 11
+};
+
+typedef uint16_t RepTypeUnion;
+
+const RepTypeUnion rMask = rBit | rWord32 | rWord64 | rFloat64 | rTagged;
+const RepTypeUnion tMask =
+    tBool | tInt32 | tUint32 | tInt64 | tUint64 | tNumber | tAny;
+const RepType rPtr = kPointerSize == 4 ? rWord32 : rWord64;
+
+
+// Contains logic related to changing the representation of values for constants
+// and other nodes, as well as lowering Simplified->Machine operators.
+// Eagerly folds any representation changes for constants.
+class RepresentationChanger {
+ public:
+  RepresentationChanger(JSGraph* jsgraph, SimplifiedOperatorBuilder* simplified,
+                        MachineOperatorBuilder* machine, Isolate* isolate)
+      : jsgraph_(jsgraph),
+        simplified_(simplified),
+        machine_(machine),
+        isolate_(isolate),
+        testing_type_errors_(false),
+        type_error_(false) {}
+
+
+  Node* GetRepresentationFor(Node* node, RepTypeUnion output_type,
+                             RepTypeUnion use_type) {
+    if (!IsPowerOf2(output_type & rMask)) {
+      // There should be only one output representation.
+      return TypeError(node, output_type, use_type);
+    }
+    if ((use_type & rMask) == (output_type & rMask)) {
+      // Representations are the same. That's a no-op.
+      return node;
+    }
+    if (use_type & rTagged) {
+      return GetTaggedRepresentationFor(node, output_type);
+    } else if (use_type & rFloat64) {
+      return GetFloat64RepresentationFor(node, output_type);
+    } else if (use_type & rWord32) {
+      return GetWord32RepresentationFor(node, output_type);
+    } else if (use_type & rBit) {
+      return GetBitRepresentationFor(node, output_type);
+    } else if (use_type & rWord64) {
+      return GetWord64RepresentationFor(node, output_type);
+    } else {
+      return node;
+    }
+  }
+
+  Node* GetTaggedRepresentationFor(Node* node, RepTypeUnion output_type) {
+    // Eagerly fold representation changes for constants.
+    switch (node->opcode()) {
+      case IrOpcode::kNumberConstant:
+      case IrOpcode::kHeapConstant:
+        return node;  // No change necessary.
+      case IrOpcode::kInt32Constant:
+        if (output_type & tUint32) {
+          uint32_t value = ValueOf<uint32_t>(node->op());
+          return jsgraph()->Constant(static_cast<double>(value));
+        } else if (output_type & tInt32) {
+          int32_t value = ValueOf<int32_t>(node->op());
+          return jsgraph()->Constant(value);
+        } else if (output_type & rBit) {
+          return ValueOf<int32_t>(node->op()) == 0 ? jsgraph()->FalseConstant()
+                                                   : jsgraph()->TrueConstant();
+        } else {
+          return TypeError(node, output_type, rTagged);
+        }
+      case IrOpcode::kFloat64Constant:
+        return jsgraph()->Constant(ValueOf<double>(node->op()));
+      default:
+        break;
+    }
+    // Select the correct X -> Tagged operator.
+    Operator* op;
+    if (output_type & rBit) {
+      op = simplified()->ChangeBitToBool();
+    } else if (output_type & rWord32) {
+      if (output_type & tUint32) {
+        op = simplified()->ChangeUint32ToTagged();
+      } else if (output_type & tInt32) {
+        op = simplified()->ChangeInt32ToTagged();
+      } else {
+        return TypeError(node, output_type, rTagged);
+      }
+    } else if (output_type & rFloat64) {
+      op = simplified()->ChangeFloat64ToTagged();
+    } else {
+      return TypeError(node, output_type, rTagged);
+    }
+    return jsgraph()->graph()->NewNode(op, node);
+  }
+
+  Node* GetFloat64RepresentationFor(Node* node, RepTypeUnion output_type) {
+    // Eagerly fold representation changes for constants.
+    switch (node->opcode()) {
+      case IrOpcode::kNumberConstant:
+        return jsgraph()->Float64Constant(ValueOf<double>(node->op()));
+      case IrOpcode::kInt32Constant:
+        if (output_type & tUint32) {
+          uint32_t value = ValueOf<uint32_t>(node->op());
+          return jsgraph()->Float64Constant(static_cast<double>(value));
+        } else {
+          int32_t value = ValueOf<int32_t>(node->op());
+          return jsgraph()->Float64Constant(value);
+        }
+      case IrOpcode::kFloat64Constant:
+        return node;  // No change necessary.
+      default:
+        break;
+    }
+    // Select the correct X -> Float64 operator.
+    Operator* op;
+    if (output_type & rWord32) {
+      if (output_type & tUint32) {
+        op = machine()->ConvertUint32ToFloat64();
+      } else if (output_type & tInt32) {
+        op = machine()->ConvertInt32ToFloat64();
+      } else {
+        return TypeError(node, output_type, rFloat64);
+      }
+    } else if (output_type & rTagged) {
+      op = simplified()->ChangeTaggedToFloat64();
+    } else {
+      return TypeError(node, output_type, rFloat64);
+    }
+    return jsgraph()->graph()->NewNode(op, node);
+  }
+
+  Node* GetWord32RepresentationFor(Node* node, RepTypeUnion output_type) {
+    // Eagerly fold representation changes for constants.
+    switch (node->opcode()) {
+      case IrOpcode::kInt32Constant:
+        return node;  // No change necessary.
+      case IrOpcode::kNumberConstant:
+      case IrOpcode::kFloat64Constant: {
+        if (output_type & tUint32) {
+          int32_t value = static_cast<int32_t>(
+              static_cast<uint32_t>(ValueOf<double>(node->op())));
+          return jsgraph()->Int32Constant(value);
+        } else if (output_type & tInt32) {
+          int32_t value = FastD2I(ValueOf<double>(node->op()));
+          return jsgraph()->Int32Constant(value);
+        } else {
+          return TypeError(node, output_type, rWord32);
+        }
+      }
+      default:
+        break;
+    }
+    // Select the correct X -> Word32 operator.
+    Operator* op = NULL;
+    if (output_type & rFloat64) {
+      // TODO(turbofan): could have cheaper float64 conversions that don't do
+      // the full JavaScript truncation here.
+      if (output_type & tUint32) {
+        op = machine()->ConvertFloat64ToUint32();
+      } else if (output_type & tInt32) {
+        op = machine()->ConvertFloat64ToInt32();
+      } else {
+        return TypeError(node, output_type, rWord32);
+      }
+    } else if (output_type & rTagged) {
+      if (output_type & tUint32) {
+        op = simplified()->ChangeTaggedToUint32();
+      } else if (output_type & tInt32) {
+        op = simplified()->ChangeTaggedToInt32();
+      } else {
+        return TypeError(node, output_type, rWord32);
+      }
+    } else if (output_type & rBit) {
+      return node;  // Sloppy comparison -> word32.
+    } else {
+      return TypeError(node, output_type, rWord32);
+    }
+    return jsgraph()->graph()->NewNode(op, node);
+  }
+
+  Node* GetBitRepresentationFor(Node* node, RepTypeUnion output_type) {
+    // Eagerly fold representation changes for constants.
+    switch (node->opcode()) {
+      case IrOpcode::kInt32Constant: {
+        int32_t value = ValueOf<int32_t>(node->op());
+        if (value == 0 || value == 1) return node;
+        return jsgraph()->OneConstant();  // value != 0
+      }
+      case IrOpcode::kHeapConstant: {
+        Handle<Object> handle = ValueOf<Handle<Object> >(node->op());
+        ASSERT(*handle == isolate()->heap()->true_value() ||
+               *handle == isolate()->heap()->false_value());
+        return jsgraph()->Int32Constant(
+            *handle == isolate()->heap()->true_value() ? 1 : 0);
+      }
+      default:
+        break;
+    }
+    // Select the correct X -> Bit operator.
+    Operator* op;
+    if (output_type & rWord32) {
+      return node;  // No change necessary.
+    } else if (output_type & rWord64) {
+      return node;  // TODO(titzer): No change necessary, on 64-bit.
+    } else if (output_type & rTagged) {
+      op = simplified()->ChangeBoolToBit();
+    } else {
+      return TypeError(node, output_type, rBit);
+    }
+    return jsgraph()->graph()->NewNode(op, node);
+  }
+
+  Node* GetWord64RepresentationFor(Node* node, RepTypeUnion output_type) {
+    if (output_type & rBit) {
+      return node;  // Sloppy comparison -> word64
+    }
+    // Can't really convert Word64 to anything else. Purported to be internal.
+    return TypeError(node, output_type, rWord64);
+  }
+
+  static RepType TypeForMachineRepresentation(MachineRepresentation rep) {
+    // TODO(titzer): merge MachineRepresentation and RepType.
+    switch (rep) {
+      case kMachineWord8:
+        return rWord32;
+      case kMachineWord16:
+        return rWord32;
+      case kMachineWord32:
+        return rWord32;
+      case kMachineWord64:
+        return rWord64;
+      case kMachineFloat64:
+        return rFloat64;
+      case kMachineTagged:
+        return rTagged;
+      default:
+        UNREACHABLE();
+        return static_cast<RepType>(0);
+    }
+  }
+
+  Operator* Int32OperatorFor(IrOpcode::Value opcode) {
+    switch (opcode) {
+      case IrOpcode::kNumberAdd:
+        return machine()->Int32Add();
+      case IrOpcode::kNumberSubtract:
+        return machine()->Int32Sub();
+      case IrOpcode::kNumberEqual:
+        return machine()->Word32Equal();
+      case IrOpcode::kNumberLessThan:
+        return machine()->Int32LessThan();
+      case IrOpcode::kNumberLessThanOrEqual:
+        return machine()->Int32LessThanOrEqual();
+      default:
+        UNREACHABLE();
+        return NULL;
+    }
+  }
+
+  Operator* Uint32OperatorFor(IrOpcode::Value opcode) {
+    switch (opcode) {
+      case IrOpcode::kNumberAdd:
+        return machine()->Int32Add();
+      case IrOpcode::kNumberSubtract:
+        return machine()->Int32Sub();
+      case IrOpcode::kNumberEqual:
+        return machine()->Word32Equal();
+      case IrOpcode::kNumberLessThan:
+        return machine()->Uint32LessThan();
+      case IrOpcode::kNumberLessThanOrEqual:
+        return machine()->Uint32LessThanOrEqual();
+      default:
+        UNREACHABLE();
+        return NULL;
+    }
+  }
+
+  Operator* Float64OperatorFor(IrOpcode::Value opcode) {
+    switch (opcode) {
+      case IrOpcode::kNumberAdd:
+        return machine()->Float64Add();
+      case IrOpcode::kNumberSubtract:
+        return machine()->Float64Sub();
+      case IrOpcode::kNumberMultiply:
+        return machine()->Float64Mul();
+      case IrOpcode::kNumberDivide:
+        return machine()->Float64Div();
+      case IrOpcode::kNumberModulus:
+        return machine()->Float64Mod();
+      case IrOpcode::kNumberEqual:
+        return machine()->Float64Equal();
+      case IrOpcode::kNumberLessThan:
+        return machine()->Float64LessThan();
+      case IrOpcode::kNumberLessThanOrEqual:
+        return machine()->Float64LessThanOrEqual();
+      default:
+        UNREACHABLE();
+        return NULL;
+    }
+  }
+
+  RepType TypeForField(const FieldAccess& access) {
+    RepType tElement = static_cast<RepType>(0);  // TODO(titzer)
+    RepType rElement = TypeForMachineRepresentation(access.representation);
+    return static_cast<RepType>(tElement | rElement);
+  }
+
+  RepType TypeForElement(const ElementAccess& access) {
+    RepType tElement = static_cast<RepType>(0);  // TODO(titzer)
+    RepType rElement = TypeForMachineRepresentation(access.representation);
+    return static_cast<RepType>(tElement | rElement);
+  }
+
+  RepType TypeForBasePointer(Node* node) {
+    Type* upper = NodeProperties::GetBounds(node).upper;
+    if (upper->Is(Type::UntaggedPtr())) return rPtr;
+    return static_cast<RepType>(tAny | rTagged);
+  }
+
+ private:
+  JSGraph* jsgraph_;
+  SimplifiedOperatorBuilder* simplified_;
+  MachineOperatorBuilder* machine_;
+  Isolate* isolate_;
+
+  friend class RepresentationChangerTester;  // accesses the below fields.
+
+  bool testing_type_errors_;  // If {true}, don't abort on a type error.
+  bool type_error_;           // Set when a type error is detected.
+
+  Node* TypeError(Node* node, RepTypeUnion output_type, RepTypeUnion use) {
+    type_error_ = true;
+    if (!testing_type_errors_) {
+      UNREACHABLE();  // TODO(titzer): report nicer type error
+    }
+    return node;
+  }
+
+  JSGraph* jsgraph() { return jsgraph_; }
+  Isolate* isolate() { return isolate_; }
+  SimplifiedOperatorBuilder* simplified() { return simplified_; }
+  MachineOperatorBuilder* machine() { return machine_; }
+};
+}
+}
+}  // namespace v8::internal::compiler
+
+#endif  // V8_COMPILER_REPRESENTATION_CHANGE_H_