Implement tracking and optimizations of packed arrays

src/elements-kind.cc

+// Copyright 2012 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.
+
+#include "elements-kind.h"
+
+#include "api.h"
+#include "elements.h"
+#include "objects.h"
+
+namespace v8 {
+namespace internal {
+
+
+void PrintElementsKind(FILE* out, ElementsKind kind) {
+  ElementsAccessor* accessor = ElementsAccessor::ForKind(kind);
+  PrintF(out, "%s", accessor->name());
+}
+
+
+ElementsKind GetInitialFastElementsKind() {
+  if (FLAG_packed_arrays) {
+    return FAST_SMI_ELEMENTS;
+  } else {
+    return FAST_HOLEY_SMI_ELEMENTS;
+  }
+}
+
+
+struct InitializeFastElementsKindSequence {
+  static void Construct(
+      ElementsKind **fast_elements_kind_sequence_ptr) {

[Jakob Kummerow, 2012/05/13 21:55:27]

nit: s/ **/** /

[danno, 2012/05/22 11:05:21]

Done.

+    ElementsKind* fast_elements_kind_sequence =
+        new ElementsKind[kFastElementsKindCount];
+    *fast_elements_kind_sequence_ptr = fast_elements_kind_sequence;
+    STATIC_ASSERT(FAST_SMI_ELEMENTS == FIRST_FAST_ELEMENTS_KIND);
+    fast_elements_kind_sequence[0] = FAST_SMI_ELEMENTS;
+    fast_elements_kind_sequence[1] = FAST_HOLEY_SMI_ELEMENTS;
+    fast_elements_kind_sequence[2] = FAST_DOUBLE_ELEMENTS;
+    fast_elements_kind_sequence[3] = FAST_HOLEY_DOUBLE_ELEMENTS;
+    fast_elements_kind_sequence[4] = FAST_ELEMENTS;
+    fast_elements_kind_sequence[5] = FAST_HOLEY_ELEMENTS;
+  }
+};
+
+
+static LazyInstance<ElementsKind*,
+                    InitializeFastElementsKindSequence>::type
+    fast_elements_kind_sequence = LAZY_INSTANCE_INITIALIZER;
+
+
+ElementsKind GetFastElementsKindFromSequenceIndex(int sequence_number) {
+  ASSERT(sequence_number >= 0 &&
+         sequence_number < kFastElementsKindCount);
+  return fast_elements_kind_sequence.Get()[sequence_number];
+}
+
+int GetSequenceIndexFromFastElementsKind(ElementsKind elements_kind) {
+  for (int i = 0; i < kFastElementsKindCount; ++i) {
+    if (fast_elements_kind_sequence.Get()[i] == elements_kind) {
+      return i;
+    }
+  }
+  UNREACHABLE();
+  return 0;
+}
+
+
+ElementsKind GetNextMoreGeneralFastElementsKind(ElementsKind elements_kind,
+                                                bool allow_only_packed) {
+  ASSERT(IsFastElementsKind(elements_kind));
+  ASSERT(elements_kind != TERMINAL_FAST_ELEMENTS_KIND);
+  while (true) {
+    int index =
+        GetSequenceIndexFromFastElementsKind(elements_kind) + 1;
+    elements_kind = GetFastElementsKindFromSequenceIndex(index);
+    if (!IsFastHoleyElementsKind(elements_kind) || !allow_only_packed) {
+      return elements_kind;
+    }
+  }
+  UNREACHABLE();
+  return TERMINAL_FAST_ELEMENTS_KIND;
+}
+
+
+bool IsMoreGeneralElementsKindTransition(ElementsKind from_kind,
+                                         ElementsKind to_kind) {
+  switch (from_kind) {
+    case FAST_SMI_ELEMENTS:
+      return to_kind != FAST_SMI_ELEMENTS;
+    case FAST_HOLEY_SMI_ELEMENTS:
+      return to_kind != FAST_SMI_ELEMENTS &&
+          to_kind != FAST_HOLEY_SMI_ELEMENTS;
+    case FAST_DOUBLE_ELEMENTS:
+      return to_kind != FAST_SMI_ELEMENTS &&
+          to_kind != FAST_HOLEY_SMI_ELEMENTS &&
+          to_kind != FAST_DOUBLE_ELEMENTS;
+    case FAST_HOLEY_DOUBLE_ELEMENTS:
+      return to_kind == FAST_ELEMENTS ||
+          to_kind == FAST_HOLEY_ELEMENTS;
+    case FAST_ELEMENTS:
+      return to_kind == FAST_HOLEY_ELEMENTS;
+    case FAST_HOLEY_ELEMENTS:
+      return false;
+    default:
+      return false;
+  }
+}
+
+
+} }  // namespace v8::internal