Initial prototype of object layout generation.

src/objects.layout

+# Copyright 2013 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.
+
+# This file contains the description for V8's heap object layouts in a
+# JSON-esque domain-specific language. Modify this file and re-run the
+# generator script to change the generated files.
+
+{ types: [  # Begin main types dictionary here.
+
+###
+#
+# Each 'type' can have the following properties:
+#  - 'name' (mandatory): The name in Pascal-case.
+#  - 'base' (mandatory): The parent type in Pascal-case.
+#  - 'fields' (mandatory): A list of all contained fields.
+#  - 'comment': A comment to be displayed for the class.
+#
+# Each 'field' can have the following properties:
+#  - 'name' (mandatory): The name in lower-case.
+#  - 'type': The type of the field, defaults to 'Object'.
+#  - 'comment': A comment to be displayed for the accessor.
+#  - 'bitfield': A list of fields encoded within this field.
+#
+# Known primitive types to be used: tBool, tSmi
+#
+###
+
+{ name: "Box",
+  base: "Struct",
+  comment: "A simple one-element struct, useful where SMIs need to be boxed.",
+  fields: [
+    { name: "value", comment: "the boxed contents." },

[titzer, 2013/09/02 08:32:10]

I guess a field without a type is just assumed to be tagged?

+  ],
+},
+
+{ name: "AliasedArgumentsEntry",
+  base: "Struct",
+  comment: [
+    "Representation of a slow alias as part of a non-strict arguments objects.",
+    "For fast aliases (if HasNonStrictArgumentsElements()):",
+    " - the parameter map contains an index into the context",
+    " - all attributes of the element have default values",
+    "For slow aliases (if HasDictionaryArgumentsElements()):",
+    " - the parameter map contains no fast alias mapping (i.e. the hole)",
+    " - this struct (in the slow backing store) contains an index into the context",
+    " - all attributes are available as part if the property details",
+  ],
+  fields: [
+    { name: "aliased_context_slot", type: tSmi },
+  ],
+},
+
+{ name: "DeclaredAccessorInfo",
+  base: "AccessorInfo",
+  fields: [
+    { name: "descriptor", type: "DeclaredAccessorDescriptor" },
+  ],
+},
+
+{ name: "ExecutableAccessorInfo",
+  base: "AccessorInfo",
+  comment: [
+    "An accessor must have a getter, but can have no setter.",
+    "",
+    "When setting a property, V8 searches accessors in prototypes.",
+    "If an accessor was found and it does not have a setter,",
+    "the request is ignored.",
+    "",
+    "If the accessor in the prototype has the READ_ONLY property attribute, then",
+    "a new value is added to the local object when the property is set.",
+    "This shadows the accessor in the prototype.",
+  ],
+  fields: [
+    { name: "getter" },
+    { name: "setter" },
+    { name: "data" },
+  ],
+},
+
+{ name: "FunctionTemplateInfo",
+  base: "TemplateInfo",
+  fields: [
+    { name: "serial_number" },
+    { name: "call_code" },
+    { name: "property_accessors" },
+    { name: "prototype_template" },
+    { name: "parent_template" },
+    { name: "named_property_handler" },
+    { name: "indexed_property_handler" },
+    { name: "instance_template" },
+    { name: "class_name" },
+    { name: "signature" },
+    { name: "instance_call_handler" },
+    { name: "access_check_info" },
+    { name: "flag", type: tSmi, bitfield: [

[titzer, 2013/09/02 08:32:10]

Should we by default pack bools into a bitfield? And if we want a particular
boolean unpacked for fast access, then we could have an "unpacked" attribute.

+      { name: "hidden_prototype", type: tBool },
+      { name: "undetectable", type: tBool },
+      { name: "needs_access_check", type: tBool },
+      { name: "read_only_prototype", type: tBool },
+      { name: "remove_prototype", type: tBool },
+    ]},
+    { name: "length", type: tSmi },
+  ],
+},
+
+{ name: "ObjectTemplateInfo",
+  base: "TemplateInfo",
+  fields: [
+    { name: "constructor" },
+    { name: "internal_field_count" },
+  ],
+},
+
+{ name: "SignatureInfo",
+  base: "Struct",
+  fields: [
+    { name: "receiver" },
+    { name: "args" },
+  ],
+},
+
+{ name: "TypeSwitchInfo",
+  base: "Struct",
+  fields: [
+    { name: "types" },
+  ],
+},
+
+]}  # End main types dictionary here.