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ruby--ruby/include/ruby/internal/core/rarray.h
Peter Zhu a51f30c671 [Feature #18634] Implement Arrays on Variable Width Allocation 
This commit implements arrays on Variable Width Allocation. This allows
longer arrays to be embedded (i.e. contents directly follow the object
header) which improves performance through better cache locality.
2022-03-22 09:42:39 -04:00

609 lines
18 KiB
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#ifndef RBIMPL_RARRAY_H /*-*-C++-*-vi:se ft=cpp:*/
#define RBIMPL_RARRAY_H
/**
* @file
* @author Ruby developers <ruby-core@ruby-lang.org>
* @copyright This file is a part of the programming language Ruby.
* Permission is hereby granted, to either redistribute and/or
* modify this file, provided that the conditions mentioned in the
* file COPYING are met. Consult the file for details.
* @warning Symbols prefixed with either `RBIMPL` or `rbimpl` are
* implementation details. Don't take them as canon. They could
* rapidly appear then vanish. The name (path) of this header file
* is also an implementation detail. Do not expect it to persist
* at the place it is now. Developers are free to move it anywhere
* anytime at will.
* @note To ruby-core: remember that this header can be possibly
* recursively included from extension libraries written in C++.
* Do not expect for instance `__VA_ARGS__` is always available.
* We assume C99 for ruby itself but we don't assume languages of
* extension libraries. They could be written in C++98.
* @brief Defines struct ::RArray.
*/
#include "ruby/internal/arithmetic/long.h"
#include "ruby/internal/attr/artificial.h"
#include "ruby/internal/attr/constexpr.h"
#include "ruby/internal/attr/maybe_unused.h"
#include "ruby/internal/attr/pure.h"
#include "ruby/internal/cast.h"
#include "ruby/internal/core/rbasic.h"
#include "ruby/internal/dllexport.h"
#include "ruby/internal/fl_type.h"
#include "ruby/internal/rgengc.h"
#include "ruby/internal/stdbool.h"
#include "ruby/internal/value.h"
#include "ruby/internal/value_type.h"
#include "ruby/assert.h"
/**
* @private
* @warning Do not touch this macro.
* @warning It is an implementation detail.
* @warning The value of this macro must match for ruby itself and all
* extension libraries, otherwise serious memory corruption shall
* occur.
*/
#ifndef USE_TRANSIENT_HEAP
# define USE_TRANSIENT_HEAP 1
#endif
/**
* Convenient casting macro.
*
* @param obj An object, which is in fact an ::RArray.
* @return The passed object casted to ::RArray.
*/
#define RARRAY(obj) RBIMPL_CAST((struct RArray *)(obj))
/** @cond INTERNAL_MACRO */
#define RARRAY_EMBED_FLAG RARRAY_EMBED_FLAG
#define RARRAY_EMBED_LEN_MASK RARRAY_EMBED_LEN_MASK
#define RARRAY_EMBED_LEN_MAX RARRAY_EMBED_LEN_MAX
#define RARRAY_EMBED_LEN_SHIFT RARRAY_EMBED_LEN_SHIFT
#if USE_TRANSIENT_HEAP
# define RARRAY_TRANSIENT_FLAG RARRAY_TRANSIENT_FLAG
#else
# define RARRAY_TRANSIENT_FLAG 0
#endif
/** @endcond */
#define RARRAY_LEN rb_array_len /**< @alias{rb_array_len} */
#define RARRAY_CONST_PTR rb_array_const_ptr /**< @alias{rb_array_const_ptr} */
#define RARRAY_CONST_PTR_TRANSIENT rb_array_const_ptr_transient /**< @alias{rb_array_const_ptr_transient} */
/** @cond INTERNAL_MACRO */
#if defined(__fcc__) || defined(__fcc_version) || \
defined(__FCC__) || defined(__FCC_VERSION)
/* workaround for old version of Fujitsu C Compiler (fcc) */
# define FIX_CONST_VALUE_PTR(x) ((const VALUE *)(x))
#else
# define FIX_CONST_VALUE_PTR(x) (x)
#endif
#define RARRAY_EMBED_LEN RARRAY_EMBED_LEN
#define RARRAY_LENINT RARRAY_LENINT
#define RARRAY_TRANSIENT_P RARRAY_TRANSIENT_P
#define RARRAY_ASET RARRAY_ASET
#define RARRAY_PTR RARRAY_PTR
/** @endcond */
/**
* @private
*
* Bits that you can set to ::RBasic::flags.
*
* @warning These enums are not the only bits we use for arrays.
*
* @internal
*
* Unlike strings, flag usages for arrays are scattered across the entire
* source codes. @shyouhei doesn't know the complete list. But what is listed
* here is at least incomplete.
*/
enum ruby_rarray_flags {
/**
* This flag has something to do with memory footprint. If the array is
* "small" enough, ruby tries to be creative to abuse padding bits of
* struct ::RArray for storing its contents. This flag denotes that
* situation.
*
* @warning This bit has to be considered read-only. Setting/clearing
* this bit without corresponding fix up must cause immediate
* SEGV. Also, internal structures of an array change
* dynamically and transparently throughout of its lifetime.
* Don't assume it being persistent.
*
* @internal
*
* 3rd parties must not be aware that there even is more than one way to
* store array elements. It was a bad idea to expose this to them.
*/
RARRAY_EMBED_FLAG = RUBY_FL_USER1,
/* RUBY_FL_USER2 is for ELTS_SHARED */
/**
* When an array employs embedded strategy (see ::RARRAY_EMBED_FLAG), these
* bits are used to store the number of elements actually filled into
* ::RArray::ary.
*
* @internal
*
* 3rd parties must not be aware that there even is more than one way to
* store array elements. It was a bad idea to expose this to them.
*/
#if USE_RVARGC
RARRAY_EMBED_LEN_MASK = RUBY_FL_USER8 | RUBY_FL_USER7 | RUBY_FL_USER6 |
RUBY_FL_USER5 | RUBY_FL_USER4 | RUBY_FL_USER3
#else
RARRAY_EMBED_LEN_MASK = RUBY_FL_USER4 | RUBY_FL_USER3
#endif
#if USE_TRANSIENT_HEAP
,
/**
* This flag has something to do with an array's "transiency". A transient
* array is an array of young generation (of generational GC), who stores
* its elements inside of dedicated memory pages called a transient heap.
* Not every young generation share that storage scheme, but elder
* generations must no join.
*
* @internal
*
* 3rd parties must not be aware that there even is more than one way to
* store array elements. It was a bad idea to expose this to them.
*/
RARRAY_TRANSIENT_FLAG = RUBY_FL_USER13
#endif
};
/**
* This is an enum because GDB wants it (rather than a macro). People need not
* bother.
*/
enum ruby_rarray_consts {
/** Where ::RARRAY_EMBED_LEN_MASK resides. */
RARRAY_EMBED_LEN_SHIFT = RUBY_FL_USHIFT + 3
#if !USE_RVARGC
,
/** Max possible number elements that can be embedded. */
RARRAY_EMBED_LEN_MAX = RBIMPL_EMBED_LEN_MAX_OF(VALUE)
#endif
};
/** Ruby's array. */
struct RArray {
/** Basic part, including flags and class. */
struct RBasic basic;
/** Array's specific fields. */
union {
/**
* Arrays that use separated memory region for elements use this
* pattern.
*/
struct {
/** Number of elements of the array. */
long len;
/** Auxiliary info. */
union {
/**
* Capacity of `*ptr`. A continuous memory region of at least
* `capa` elements is expected to exist at `*ptr`. This can be
* bigger than `len`.
*/
long capa;
/**
* Parent of the array. Nowadays arrays can share their
* backend memory regions each other, constructing gigantic
* nest of objects. This situation is called "shared", and
* this is the field to control such properties.
*/
#if defined(__clang__) /* <- clang++ is sane */ || \
!defined(__cplusplus) /* <- C99 is sane */ || \
(__cplusplus > 199711L) /* <- C++11 is sane */
const
#endif
VALUE shared_root;
} aux;
/**
* Pointer to the C array that holds the elements of the array. In
* the old days each array had dedicated memory regions. That is
* no longer true today, but there still are arrays of such
* properties. This field could be used to point such things.
*/
const VALUE *ptr;
} heap;
/**
* Embedded elements. When an array is short enough, it uses this area
* to store its elements. In this case the length is encoded into the
* flags.
*/
#if USE_RVARGC
/* This is a length 1 array because:
* 1. GCC has a bug that does not optimize C flexible array members
* (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102452)
* 2. Zero length arrays are not supported by all compilers
*/
const VALUE ary[1];
#else
const VALUE ary[RARRAY_EMBED_LEN_MAX];
#endif
} as;
};
RBIMPL_SYMBOL_EXPORT_BEGIN()
/**
* @private
*
* Declares a section of code where raw pointers are used. This is an
* implementation detail of #RARRAY_PTR_USE. People don't use it directly.
*
* @param[in] ary An object of ::RArray.
* @return `ary`'s backend C array.
*/
VALUE *rb_ary_ptr_use_start(VALUE ary);
/**
* @private
*
* Declares an end of a section formerly started by rb_ary_ptr_use_start().
* This is an implementation detail of #RARRAY_PTR_USE. People don't use it
* directly.
*
* @param[in] a An object of ::RArray.
*/
void rb_ary_ptr_use_end(VALUE a);
#if USE_TRANSIENT_HEAP
/**
* Destructively converts an array of transient backend into ordinal one.
*
* @param[out] a An object of ::RArray.
* @pre `a` must be a transient array.
* @post `a` gets out of transient heap, destructively.
*/
void rb_ary_detransient(VALUE a);
#endif
RBIMPL_SYMBOL_EXPORT_END()
RBIMPL_ATTR_PURE_UNLESS_DEBUG()
RBIMPL_ATTR_ARTIFICIAL()
/**
* Queries the length of the array.
*
* @param[in] ary Array in question.
* @return Its number of elements.
* @pre `ary` must be an instance of ::RArray, and must has its
* ::RARRAY_EMBED_FLAG flag set.
*
* @internal
*
* This was a macro before. It was inevitable to be public, since macros are
* global constructs. But should it be forever? Now that it is a function,
* @shyouhei thinks it could just be eliminated, hidden into implementation
* details.
*/
static inline long
RARRAY_EMBED_LEN(VALUE ary)
{
RBIMPL_ASSERT_TYPE(ary, RUBY_T_ARRAY);
RBIMPL_ASSERT_OR_ASSUME(RB_FL_ANY_RAW(ary, RARRAY_EMBED_FLAG));
VALUE f = RBASIC(ary)->flags;
f &= RARRAY_EMBED_LEN_MASK;
f >>= RARRAY_EMBED_LEN_SHIFT;
return RBIMPL_CAST((long)f);
}
RBIMPL_ATTR_PURE_UNLESS_DEBUG()
/**
* Queries the length of the array.
*
* @param[in] a Array in question.
* @return Its number of elements.
* @pre `a` must be an instance of ::RArray.
*/
static inline long
rb_array_len(VALUE a)
{
RBIMPL_ASSERT_TYPE(a, RUBY_T_ARRAY);
if (RB_FL_ANY_RAW(a, RARRAY_EMBED_FLAG)) {
return RARRAY_EMBED_LEN(a);
}
else {
return RARRAY(a)->as.heap.len;
}
}
RBIMPL_ATTR_ARTIFICIAL()
/**
* Identical to rb_array_len(), except it differs for the return type.
*
* @param[in] ary Array in question.
* @exception rb_eRangeError Too long.
* @return Its number of elements.
* @pre `ary` must be an instance of ::RArray.
*
* @internal
*
* This API seems redundant but has actual usages.
*/
static inline int
RARRAY_LENINT(VALUE ary)
{
return rb_long2int(RARRAY_LEN(ary));
}
RBIMPL_ATTR_PURE_UNLESS_DEBUG()
RBIMPL_ATTR_ARTIFICIAL()
/**
* Queries if the array is a transient array.
*
* @param[in] ary Array in question.
* @retval true Yes it is.
* @retval false No it isn't.
* @pre `ary` must be an instance of ::RArray.
*
* @internal
*
* @shyouhei doesn't understand the benefit of this function called from
* extension libraries.
*/
static inline bool
RARRAY_TRANSIENT_P(VALUE ary)
{
RBIMPL_ASSERT_TYPE(ary, RUBY_T_ARRAY);
#if USE_TRANSIENT_HEAP
return RB_FL_ANY_RAW(ary, RARRAY_TRANSIENT_FLAG);
#else
return false;
#endif
}
RBIMPL_ATTR_PURE_UNLESS_DEBUG()
/**
* @private
*
* This is an implementation detail of RARRAY_PTR(). People do not use it
* directly.
*
* @param[in] a An object of ::RArray.
* @return Its backend storage.
*/
static inline const VALUE *
rb_array_const_ptr_transient(VALUE a)
{
RBIMPL_ASSERT_TYPE(a, RUBY_T_ARRAY);
if (RB_FL_ANY_RAW(a, RARRAY_EMBED_FLAG)) {
return FIX_CONST_VALUE_PTR(RARRAY(a)->as.ary);
}
else {
return FIX_CONST_VALUE_PTR(RARRAY(a)->as.heap.ptr);
}
}
#if ! USE_TRANSIENT_HEAP
RBIMPL_ATTR_PURE_UNLESS_DEBUG()
#endif
/**
* @private
*
* This is an implementation detail of RARRAY_PTR(). People do not use it
* directly.
*
* @param[in] a An object of ::RArray.
* @return Its backend storage.
* @post `a` is not a transient array.
*/
static inline const VALUE *
rb_array_const_ptr(VALUE a)
{
RBIMPL_ASSERT_TYPE(a, RUBY_T_ARRAY);
#if USE_TRANSIENT_HEAP
if (RARRAY_TRANSIENT_P(a)) {
rb_ary_detransient(a);
}
#endif
return rb_array_const_ptr_transient(a);
}
/**
* @private
*
* This is an implementation detail of #RARRAY_PTR_USE. People do not use it
* directly.
*
* @param[in] a An object of ::RArray.
* @param[in] allow_transient Whether `a` can be transient or not.
* @return Its backend storage.
* @post `a` is not a transient array unless `allow_transient`.
*/
static inline VALUE *
rb_array_ptr_use_start(VALUE a,
RBIMPL_ATTR_MAYBE_UNUSED()
int allow_transient)
{
RBIMPL_ASSERT_TYPE(a, RUBY_T_ARRAY);
#if USE_TRANSIENT_HEAP
if (!allow_transient) {
if (RARRAY_TRANSIENT_P(a)) {
rb_ary_detransient(a);
}
}
#endif
return rb_ary_ptr_use_start(a);
}
/**
* @private
*
* This is an implementation detail of #RARRAY_PTR_USE. People do not use it
* directly.
*
* @param[in] a An object of ::RArray.
* @param[in] allow_transient Whether `a` can be transient or not.
*/
static inline void
rb_array_ptr_use_end(VALUE a,
RBIMPL_ATTR_MAYBE_UNUSED()
int allow_transient)
{
RBIMPL_ASSERT_TYPE(a, RUBY_T_ARRAY);
rb_ary_ptr_use_end(a);
}
/**
* @private
*
* This is an implementation detail of #RARRAY_PTR_USE. People do not use it
* directly.
*/
#define RBIMPL_RARRAY_STMT(flag, ary, var, expr) do { \
RBIMPL_ASSERT_TYPE((ary), RUBY_T_ARRAY); \
const VALUE rbimpl_ary = (ary); \
VALUE *var = rb_array_ptr_use_start(rbimpl_ary, (flag)); \
expr; \
rb_array_ptr_use_end(rbimpl_ary, (flag)); \
} while (0)
/**
* @private
*
* This is an implementation detail of #RARRAY_PTR_USE. People do not use it
* directly.
*/
#define RARRAY_PTR_USE_START(a) rb_array_ptr_use_start(a, 0)
/**
* @private
*
* This is an implementation detail of #RARRAY_PTR_USE. People do not use it
* directly.
*/
#define RARRAY_PTR_USE_END(a) rb_array_ptr_use_end(a, 0)
/**
* Declares a section of code where raw pointers are used. In case you need to
* touch the raw C array instead of polite CAPIs, then that operation shall be
* wrapped using this macro.
*
* ```CXX
* const auto ary = rb_eval_string("[...]");
* const auto len = RARRAY_LENINT(ary);
* const auto symwrite = rb_intern("write");
*
* RARRAY_PTR_USE(ary, ptr, {
* rb_funcallv(rb_stdout, symwrite, len, ptr);
* });
* ```
*
* @param ary An object of ::RArray.
* @param ptr_name A variable name which points the C array in `expr`.
* @param expr The expression that touches `ptr_name`.
*
* @internal
*
* For historical reasons use of this macro is not enforced. There are
* extension libraries in the wild which call RARRAY_PTR() without it. We want
* them use it... Maybe some transition path can be implemented later.
*/
#define RARRAY_PTR_USE(ary, ptr_name, expr) \
RBIMPL_RARRAY_STMT(0, ary, ptr_name, expr)
/**
* @private
*
* This is an implementation detail of #RARRAY_PTR_USE_TRANSIENT. People do
* not use it directly.
*/
#define RARRAY_PTR_USE_START_TRANSIENT(a) rb_array_ptr_use_start(a, 1)
/**
* @private
*
* This is an implementation detail of #RARRAY_PTR_USE_TRANSIENT. People do
* not use it directly.
*/
#define RARRAY_PTR_USE_END_TRANSIENT(a) rb_array_ptr_use_end(a, 1)
/**
* Identical to #RARRAY_PTR_USE, except the pointer can be a transient one.
*
* @param ary An object of ::RArray.
* @param ptr_name A variable name which points the C array in `expr`.
* @param expr The expression that touches `ptr_name`.
*/
#define RARRAY_PTR_USE_TRANSIENT(ary, ptr_name, expr) \
RBIMPL_RARRAY_STMT(1, ary, ptr_name, expr)
/**
* Wild use of a C pointer. This function accesses the backend storage
* directly. This is slower than #RARRAY_PTR_USE_TRANSIENT. It exercises
* extra manoeuvres to protect our generational GC. Use of this function is
* considered archaic. Use a modern way instead.
*
* @param[in] ary An object of ::RArray.
* @return The backend C array.
*
* @internal
*
* That said... there are extension libraries in the wild who uses it. We
* cannot but continue supporting.
*/
static inline VALUE *
RARRAY_PTR(VALUE ary)
{
RBIMPL_ASSERT_TYPE(ary, RUBY_T_ARRAY);
VALUE tmp = RB_OBJ_WB_UNPROTECT_FOR(ARRAY, ary);
return RBIMPL_CAST((VALUE *)RARRAY_CONST_PTR(tmp));
}
/**
* Assigns an object in an array.
*
* @param[out] ary Destination array object.
* @param[in] i Index of `ary`.
* @param[in] v Arbitrary ruby object.
* @pre `ary` must be an instance of ::RArray.
* @pre `ary`'s length must be longer than or equal to `i`.
* @pre `i` must be greater than or equal to zero.
* @post `ary`'s `i`th element is set to `v`.
*/
static inline void
RARRAY_ASET(VALUE ary, long i, VALUE v)
{
RARRAY_PTR_USE_TRANSIENT(ary, ptr,
RB_OBJ_WRITE(ary, &ptr[i], v));
}
/**
* @deprecated
*
* :FIXME: we want to convert RARRAY_AREF into an inline function (to add rooms
* for more sanity checks). However there were situations where the address of
* this macro is taken i.e. &RARRAY_AREF(...). They cannot be possible if this
* is not a macro. Such usages are abuse, and we eliminated them internally.
* However we are afraid of similar things to remain in the wild. This macro
* remains as it is due to that. If we could warn such usages we can set a
* transition path, but currently no way is found to do so.
*/
#define RARRAY_AREF(a, i) RARRAY_CONST_PTR_TRANSIENT(a)[i]
#endif /* RBIMPL_RARRAY_H */
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