Reduce the memory used by frame elements from two words to one by...

src/frame-element.h

+// Copyright 2009 the V8 project authors. All rights reserved.
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+//       notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+//       copyright notice, this list of conditions and the following
+//       disclaimer in the documentation and/or other materials provided
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef V8_FRAME_ELEMENT_H_
+#define V8_FRAME_ELEMENT_H_
+
+#include "register-allocator-inl.h"
+
+namespace v8 { namespace internal {
+
+// -------------------------------------------------------------------------
+// Virtual frame elements
+//
+// The internal elements of the virtual frames.  There are several kinds of
+// elements:
+//   * Invalid: elements that are uninitialized or not actually part
+//     of the virtual frame.  They should not be read.
+//   * Memory: an element that resides in the actual frame.  Its address is
+//     given by its position in the virtual frame.
+//   * Register: an element that resides in a register.
+//   * Constant: an element whose value is known at compile time.
+
+class FrameElement BASE_EMBEDDED {
+ public:
+  enum SyncFlag {
+    NOT_SYNCED,
+    SYNCED
+  };
+
+  // The default constructor creates an invalid frame element.
+  FrameElement() {
+    value_ = StaticTypeField::encode(StaticType::UNKNOWN_TYPE)
+        | TypeField::encode(INVALID)
+        | CopiedField::encode(false)
+        | SyncedField::encode(false)
+        | DataField::encode(0);
+  }
+
+  // Factory function to construct an invalid frame element.
+  static FrameElement InvalidElement() {
+    FrameElement result;
+    return result;
+  }
+
+  // Factory function to construct an in-memory frame element.
+  static FrameElement MemoryElement() {
+    FrameElement result(MEMORY, no_reg, SYNCED);
+    return result;
+  }
+
+  // Factory function to construct an in-register frame element.
+  static FrameElement RegisterElement(Register reg,
+                                      SyncFlag is_synced,
+                                      StaticType static_type = StaticType()) {
+    return FrameElement(REGISTER, reg, is_synced, static_type);
+  }
+
+  // Factory function to construct a frame element whose value is known at
+  // compile time.
+  static FrameElement ConstantElement(Handle<Object> value,
+                                      SyncFlag is_synced) {
+    FrameElement result(value, is_synced);
+    return result;
+  }
+
+  // Static indirection table for handles to constants.  If a frame
+  // element represents a constant, the data contains an index into
+  // this table of handles to the actual constants.
+  typedef ZoneList<Handle<Object> > ZoneObjectList;
+
+  static ZoneObjectList* ConstantList() {
+    static ZoneObjectList list(10);
+    return &list;
+  }
+
+  // Clear the constants indirection table.
+  static void ClearConstantList() {
+    ConstantList()->Clear();
+  }
+
+  bool is_synced() const { return SyncedField::decode(value_); }
+
+  void set_sync() {
+    ASSERT(type() != MEMORY);
+    value_ = value_ | SyncedField::encode(true);
+  }
+
+  void clear_sync() {
+    ASSERT(type() != MEMORY);
+    value_ = value_ & ~SyncedField::mask();
+  }
+
+  bool is_valid() const { return type() != INVALID; }
+  bool is_memory() const { return type() == MEMORY; }
+  bool is_register() const { return type() == REGISTER; }
+  bool is_constant() const { return type() == CONSTANT; }
+  bool is_copy() const { return type() == COPY; }
+
+  bool is_copied() const { return CopiedField::decode(value_); }
+  void set_copied() { value_ = value_ | CopiedField::encode(true); }
+  void clear_copied() { value_ = value_ & ~CopiedField::mask(); }
+
+  Register reg() const {
+    ASSERT(is_register());
+    uint32_t reg = DataField::decode(value_);
+    Register result;
+    result.code_ = reg;
+    return result;
+  }
+
+  Handle<Object> handle() const {
+    ASSERT(is_constant());
+    return ConstantList()->at(DataField::decode(value_));
+  }
+
+  int index() const {
+    ASSERT(is_copy());
+    return DataField::decode(value_);
+  }
+
+  StaticType static_type() { return StaticType(StaticTypeField::decode(value_)); }

[Kasper Lund, 2009/05/14 11:26:16]

Line too long?

[Mads Ager (chromium), 2009/05/14 11:42:40]

Done.

+
+  void set_static_type(StaticType static_type) {
+    value_ = value_ & ~StaticTypeField::mask();
+    value_ = value_ | StaticTypeField::encode(static_type.static_type_);
+  }
+
+  bool Equals(FrameElement other) {
+    if (value_ == other.value_) return true;
+
+    if (type() != other.type() ||
+        is_copied() != other.is_copied() ||
+        is_synced() != other.is_synced()) return false;
+
+    if (is_register()) {
+      if (!reg().is(other.reg())) return false;
+    } else if (is_constant()) {
+      if (!handle().is_identical_to(other.handle())) return false;
+    } else if (is_copy()) {
+      if (index() != other.index()) return false;
+    }
+
+    return true;
+  }
+
+  // Given a pair of non-null frame element pointers, return one of them
+  // as an entry frame candidate or null if they are incompatible.
+  FrameElement* Combine(FrameElement* other) {
+    // If either is invalid, the result is.
+    if (!is_valid()) return this;
+    if (!other->is_valid()) return other;
+
+    // If they do not have the exact same location we reallocate.
+    bool not_same_location =
+        (type() != other->type()) ||
+        (is_register() && !reg().is(other->reg())) ||
+        (is_constant() && !handle().is_identical_to(other->handle())) ||
+        (is_copy() && index() != other->index());
+    if (not_same_location) return NULL;
+
+    // If either is unsynced, the result is.  The result static type is
+    // the merge of the static types.  It's safe to set it on one of the
+    // frame elements, and harmless too (because we are only going to
+    // merge the reaching frames and will ensure that the types are
+    // coherent, and changing the static type does not emit code).
+    FrameElement* result = is_synced() ? other : this;
+    result->set_static_type(static_type().merge(other->static_type()));
+    return result;
+  }
+
+ private:
+  enum Type {
+    INVALID,
+    MEMORY,
+    REGISTER,
+    CONSTANT,
+    COPY
+  };
+
+  // Used to construct memory and register elements.
+  FrameElement(Type type, Register reg, SyncFlag is_synced) {
+    value_ = StaticTypeField::encode(StaticType::UNKNOWN_TYPE)
+        | TypeField::encode(type)
+        | CopiedField::encode(false)
+        | SyncedField::encode(is_synced != NOT_SYNCED)
+        | DataField::encode(reg.code_ > 0 ? reg.code_ : 0);
+  }
+
+  FrameElement(Type type, Register reg, SyncFlag is_synced, StaticType stype) {
+    value_ = StaticTypeField::encode(stype.static_type_)
+        | TypeField::encode(type)
+        | CopiedField::encode(false)
+        | SyncedField::encode(is_synced != NOT_SYNCED)
+        | DataField::encode(reg.code_ > 0 ? reg.code_ : 0);
+  }
+
+  // Used to construct constant elements.
+  FrameElement(Handle<Object> value, SyncFlag is_synced) {
+    value_ = StaticTypeField::encode(StaticType::TypeOf(*value).static_type_)
+        | TypeField::encode(CONSTANT)
+        | CopiedField::encode(false)
+        | SyncedField::encode(is_synced != NOT_SYNCED)
+        | DataField::encode(ConstantList()->length());
+    ConstantList()->Add(value);
+  }
+
+  Type type() const { return TypeField::decode(value_); }
+  void set_type(Type type) {
+    value_ = value_ & ~TypeField::mask();
+    value_ = value_ | TypeField::encode(type);
+  }
+
+  void set_index(int new_index) {
+    ASSERT(is_copy());
+    value_ = value_ & ~DataField::mask();
+    value_ = value_ | DataField::encode(new_index);
+  }
+
+  void set_reg(Register new_reg) {
+    ASSERT(is_register());
+    value_ = value_ & ~DataField::mask();
+    value_ = value_ | DataField::encode(new_reg.code_);
+  }
+
+  // Encode static type, type, copied, synced and data in one 32 bit integer.
+  uint32_t value_;
+
+  class StaticTypeField: public BitField<StaticType::StaticTypeEnum, 0, 3> {};
+  class TypeField: public BitField<Type, 3, 3> {};
+  class CopiedField: public BitField<uint32_t, 6, 1> {};
+  class SyncedField: public BitField<uint32_t, 7, 1> {};
+  class DataField: public BitField<uint32_t, 8, 32 - 9> {};
+
+  friend class VirtualFrame;
+};
+
+} }  // namespace v8::internal
+
+#endif  // V8_FRAME_ELEMENT_H_