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Object Shapes is used for accessing instance variables and representing the
"frozenness" of objects. Object instances have a "shape" and the shape
represents some attributes of the object (currently which instance variables are
set and the "frozenness"). Shapes form a tree data structure, and when a new
instance variable is set on an object, that object "transitions" to a new shape
in the shape tree. Each shape has an ID that is used for caching. The shape
structure is independent of class, so objects of different types can have the
same shape.
For example:
```ruby
class Foo
def initialize
# Starts with shape id 0
@a = 1 # transitions to shape id 1
@b = 1 # transitions to shape id 2
end
end
class Bar
def initialize
# Starts with shape id 0
@a = 1 # transitions to shape id 1
@b = 1 # transitions to shape id 2
end
end
foo = Foo.new # `foo` has shape id 2
bar = Bar.new # `bar` has shape id 2
```
Both `foo` and `bar` instances have the same shape because they both set
instance variables of the same name in the same order.
This technique can help to improve inline cache hits as well as generate more
efficient machine code in JIT compilers.
This commit also adds some methods for debugging shapes on objects. See
`RubyVM::Shape` for more details.
For more context on Object Shapes, see [Feature: #18776]
Co-Authored-By: Aaron Patterson <tenderlove@ruby-lang.org>
Co-Authored-By: Eileen M. Uchitelle <eileencodes@gmail.com>
Co-Authored-By: John Hawthorn <john@hawthorn.email>
61 lines
2.1 KiB
C
61 lines
2.1 KiB
C
#ifndef INTERNAL_OBJECT_H /*-*-C-*-vi:se ft=c:*/
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#define INTERNAL_OBJECT_H
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/**
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* @author Ruby developers <ruby-core@ruby-lang.org>
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* @copyright This file is a part of the programming language Ruby.
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* Permission is hereby granted, to either redistribute and/or
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* modify this file, provided that the conditions mentioned in the
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* file COPYING are met. Consult the file for details.
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* @brief Internal header for Object.
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*/
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#include "ruby/ruby.h" /* for VALUE */
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/* object.c */
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VALUE rb_class_search_ancestor(VALUE klass, VALUE super);
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NORETURN(void rb_undefined_alloc(VALUE klass));
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double rb_num_to_dbl(VALUE val);
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VALUE rb_obj_dig(int argc, VALUE *argv, VALUE self, VALUE notfound);
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VALUE rb_immutable_obj_clone(int, VALUE *, VALUE);
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VALUE rb_check_convert_type_with_id(VALUE,int,const char*,ID);
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int rb_bool_expected(VALUE, const char *, int raise);
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static inline void RBASIC_CLEAR_CLASS(VALUE obj);
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static inline void RBASIC_SET_CLASS_RAW(VALUE obj, VALUE klass);
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static inline void RBASIC_SET_CLASS(VALUE obj, VALUE klass);
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RUBY_SYMBOL_EXPORT_BEGIN
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/* object.c (export) */
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int rb_opts_exception_p(VALUE opts, int default_value);
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RUBY_SYMBOL_EXPORT_END
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MJIT_SYMBOL_EXPORT_BEGIN
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CONSTFUNC(VALUE rb_obj_equal(VALUE obj1, VALUE obj2));
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CONSTFUNC(VALUE rb_obj_not(VALUE obj));
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VALUE rb_obj_not_equal(VALUE obj1, VALUE obj2);
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void rb_obj_copy_ivar(VALUE dest, VALUE obj);
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VALUE rb_false(VALUE obj);
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VALUE rb_convert_type_with_id(VALUE v, int t, const char* nam, ID mid);
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VALUE rb_obj_size(VALUE self, VALUE args, VALUE obj);
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VALUE rb_get_freeze_opt(int argc, VALUE *argv);
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MJIT_SYMBOL_EXPORT_END
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static inline void
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RBASIC_SET_CLASS_RAW(VALUE obj, VALUE klass)
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{
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const VALUE *ptr = &RBASIC(obj)->klass;
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*(VALUE *)ptr = klass;
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}
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static inline void
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RBASIC_CLEAR_CLASS(VALUE obj)
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{
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RBASIC_SET_CLASS_RAW(obj, 0);
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}
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static inline void
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RBASIC_SET_CLASS(VALUE obj, VALUE klass)
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{
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VALUE oldv = RBASIC_CLASS(obj);
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RBASIC_SET_CLASS_RAW(obj, klass);
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RB_OBJ_WRITTEN(obj, oldv, klass);
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}
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#endif /* INTERNAL_OBJECT_H */
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