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gcc/libstdc++-v3/include/std/version
Jason Merrill 76b75018b3 c++: implement C++17 hardware interference size 
The last missing piece of the C++17 standard library is the hardware
intereference size constants.  Much of the delay in implementing these has
been due to uncertainty about what the right values are, and even whether
there is a single constant value that is suitable; the destructive
interference size is intended to be used in structure layout, so program
ABIs will depend on it.

In principle, both of these values should be the same as the target's L1
cache line size.  When compiling for a generic target that is intended to
support a range of target CPUs with different cache line sizes, the
constructive size should probably be the minimum size, and the destructive
size the maximum, unless you are constrained by ABI compatibility with
previous code.

From discussion on gcc-patches, I've come to the conclusion that the
solution to the difficulty of choosing stable values is to give up on it,
and instead encourage only uses where ABI stability is unimportant: in
particular, uses where the ABI is shared at most between translation units
built at the same time with the same flags.

To that end, I've added a warning for any use of the constant value of
std::hardware_destructive_interference_size in a header or module export.
Appropriate uses within a project can disable the warning.

A previous iteration of this patch included an -finterference-tune flag to
make the value vary with -mtune; this iteration makes that the default
behavior, which should be appropriate for all reasonable uses of the
variable.  The previous default of "stable-ish" seems to me likely to have
been more of an attractive nuisance; since we can't promise actual
stability, we should instead make proper uses more convenient.

JF Bastien's implementation proposal is summarized at
https://github.com/itanium-cxx-abi/cxx-abi/issues/74

I implement this by adding new --params for the two sizes.  Targets can
override these values in targetm.target_option.override() to support a range
of values for the generic target; otherwise, both will default to the L1
cache line size.

64 bytes still seems correct for all x86.

I'm not sure why he proposed 64/64 for generic 32-bit ARM, since the Cortex
A9 has a 32-byte cache line, so I'd think 32/64 would make more sense.

He proposed 64/128 for generic AArch64, but since the A64FX now has a 256B
cache line, I've changed that to 64/256.

Other arch maintainers are invited to set ranges for their generic targets
if that seems better than using the default cache line size for both values.

With the above choice to reject stability as a goal, getting these values
"right" is now just a matter of what we want the default optimization to be,
and we can feel free to adjust them as CPUs with different cache lines
become more and less common.

gcc/ChangeLog:

	* params.opt: Add destructive-interference-size and
	constructive-interference-size.
	* doc/invoke.texi: Document them.
	* config/aarch64/aarch64.c (aarch64_override_options_internal):
	Set them.
	* config/arm/arm.c (arm_option_override): Set them.
	* config/i386/i386-options.c (ix86_option_override_internal):
	Set them.

gcc/c-family/ChangeLog:

	* c.opt: Add -Winterference-size.
	* c-cppbuiltin.c (cpp_atomic_builtins): Add __GCC_DESTRUCTIVE_SIZE
	and __GCC_CONSTRUCTIVE_SIZE.

gcc/cp/ChangeLog:

	* constexpr.c (maybe_warn_about_constant_value):
	Complain about std::hardware_destructive_interference_size.
	(cxx_eval_constant_expression): Call it.
	* decl.c (cxx_init_decl_processing): Check
	--param *-interference-size values.

libstdc++-v3/ChangeLog:

	* include/std/version: Define __cpp_lib_hardware_interference_size.
	* libsupc++/new: Define hardware interference size variables.

gcc/testsuite/ChangeLog:

	* g++.dg/warn/Winterference.H: New file.
	* g++.dg/warn/Winterference.C: New test.
	* g++.target/aarch64/interference.C: New test.
	* g++.target/arm/interference.C: New test.
	* g++.target/i386/interference.C: New test.
2021-09-13 12:28:06 -04:00

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// -*- C++ -*- Libstdc++ version details header.
// Copyright (C) 2018-2021 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library. This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.
/** @file version
* This is a Standard C++ Library file. You should @c \#include this file
* in your programs, rather than any of the @a *.h implementation files.
*/
#ifndef _GLIBCXX_VERSION_INCLUDED
#define _GLIBCXX_VERSION_INCLUDED
#pragma GCC system_header
#include <bits/c++config.h>
// c++03
#if _GLIBCXX_HOSTED
# define __cpp_lib_incomplete_container_elements 201505
#endif
#if !defined(__STRICT_ANSI__)
// gnu++03
# define __cpp_lib_uncaught_exceptions 201411L
#endif
#if __cplusplus >= 201103L
// c++11
#define __cpp_lib_is_null_pointer 201309
#define __cpp_lib_result_of_sfinae 201210
#if _GLIBCXX_HOSTED
# define __cpp_lib_allocator_traits_is_always_equal 201411
# define __cpp_lib_shared_ptr_arrays 201611L
#endif
#if !defined(__STRICT_ANSI__)
// gnu++11
# define __cpp_lib_is_swappable 201603
# define __cpp_lib_void_t 201411
# if _GLIBCXX_HOSTED
# define __cpp_lib_enable_shared_from_this 201603
# endif
#endif
// For C++11 and later we support ISO/IEC 29124 Mathematical Special Functions
#define __STDCPP_MATH_SPEC_FUNCS__ 201003L
#if __cplusplus >= 201402L
// c++14
#if __cpp_impl_coroutine
# define __cpp_lib_coroutine 201902L
#endif
#define __cpp_lib_integral_constant_callable 201304
#define __cpp_lib_is_final 201402L
#define __cpp_lib_transformation_trait_aliases 201304
#if _GLIBCXX_HOSTED
# define __cpp_lib_chrono_udls 201304
# define __cpp_lib_complex_udls 201309
# define __cpp_lib_exchange_function 201304
# define __cpp_lib_generic_associative_lookup 201304
# define __cpp_lib_integer_sequence 201304
# define __cpp_lib_make_reverse_iterator 201402
# define __cpp_lib_make_unique 201304
# ifndef _GLIBCXX_DEBUG // PR libstdc++/70303
# define __cpp_lib_null_iterators 201304L
# endif
# define __cpp_lib_quoted_string_io 201304
# define __cpp_lib_robust_nonmodifying_seq_ops 201304
# ifdef _GLIBCXX_HAS_GTHREADS
# define __cpp_lib_shared_timed_mutex 201402L
# endif
# define __cpp_lib_string_udls 201304
# define __cpp_lib_transparent_operators 201510
# define __cpp_lib_tuple_element_t 201402L
# define __cpp_lib_tuples_by_type 201304L
#endif
#if __cplusplus >= 201703L
// c++17
#define __cpp_lib_addressof_constexpr 201603
#define __cpp_lib_atomic_is_always_lock_free 201603
#define __cpp_lib_bool_constant 201505
#define __cpp_lib_byte 201603
#ifdef _GLIBCXX_HAVE_BUILTIN_HAS_UNIQ_OBJ_REP
# define __cpp_lib_has_unique_object_representations 201606
#endif
#ifdef _GLIBCXX_HAVE_BUILTIN_IS_AGGREGATE
# define __cpp_lib_is_aggregate 201703
#endif
#define __cpp_lib_is_invocable 201703
#define __cpp_lib_is_swappable 201603
#ifdef _GLIBCXX_HAVE_BUILTIN_LAUNDER
# define __cpp_lib_launder 201606
#endif
#define __cpp_lib_logical_traits 201510
#define __cpp_lib_type_trait_variable_templates 201510L
#define __cpp_lib_uncaught_exceptions 201411L
#define __cpp_lib_void_t 201411
#if _GLIBCXX_HOSTED
#define __cpp_lib_any 201606L
#define __cpp_lib_apply 201603
#if __cplusplus == 201703L // N.B. updated value in C++20
# define __cpp_lib_array_constexpr 201803L
#endif
#define __cpp_lib_as_const 201510
#define __cpp_lib_boyer_moore_searcher 201603
#define __cpp_lib_chrono 201611
#define __cpp_lib_clamp 201603
#if __cplusplus == 201703L // N.B. updated value in C++20
# if _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
# define __cpp_lib_constexpr_char_traits 201611L
# define __cpp_lib_constexpr_string 201611L
# endif
#endif
#define __cpp_lib_enable_shared_from_this 201603
#define __cpp_lib_execution 201902L // FIXME: should be 201603L
#define __cpp_lib_filesystem 201703
#define __cpp_lib_gcd 201606
#define __cpp_lib_gcd_lcm 201606
#ifdef __GCC_DESTRUCTIVE_SIZE
# define __cpp_lib_hardware_interference_size 201703L
#endif
#define __cpp_lib_hypot 201603
#define __cpp_lib_invoke 201411L
#define __cpp_lib_lcm 201606
#define __cpp_lib_make_from_tuple 201606
#define __cpp_lib_map_try_emplace 201411
#define __cpp_lib_math_special_functions 201603L
#ifdef _GLIBCXX_HAS_GTHREADS
# define __cpp_lib_memory_resource 201603L
#else
# define __cpp_lib_memory_resource 1
#endif
#define __cpp_lib_node_extract 201606
#define __cpp_lib_nonmember_container_access 201411
#define __cpp_lib_not_fn 201603
#define __cpp_lib_optional 201606L
#define __cpp_lib_parallel_algorithm 201603L
#define __cpp_lib_raw_memory_algorithms 201606L
#define __cpp_lib_sample 201603
#ifdef _GLIBCXX_HAS_GTHREADS
# define __cpp_lib_scoped_lock 201703
# define __cpp_lib_shared_mutex 201505L
#endif
#define __cpp_lib_shared_ptr_weak_type 201606
#define __cpp_lib_string_view 201803L
#if _GLIBCXX_HAVE_USELOCALE
# define __cpp_lib_to_chars 201611L
#endif
#define __cpp_lib_unordered_map_try_emplace 201411
#define __cpp_lib_variant 201606L
#endif
#if __cplusplus >= 202002L
// c++20
#define __cpp_lib_atomic_flag_test 201907L
#define __cpp_lib_atomic_float 201711L
#define __cpp_lib_atomic_ref 201806L
#define __cpp_lib_atomic_value_initialization 201911L
#define __cpp_lib_bitops 201907L
#define __cpp_lib_bounded_array_traits 201902L
// __cpp_lib_char8_t is defined in <bits/c++config.h>
#if __cpp_concepts >= 201907L
# define __cpp_lib_concepts 202002L
#endif
#if __cpp_impl_destroying_delete
# define __cpp_lib_destroying_delete 201806L
#endif
#define __cpp_lib_endian 201907L
#define __cpp_lib_int_pow2 202002L
#ifdef _GLIBCXX_HAVE_BUILTIN_IS_CONSTANT_EVALUATED
# define __cpp_lib_is_constant_evaluated 201811L
#endif
#define __cpp_lib_is_nothrow_convertible 201806L
#define __cpp_lib_remove_cvref 201711L
#if __cpp_impl_three_way_comparison >= 201907L && __cpp_lib_concepts
# define __cpp_lib_three_way_comparison 201907L
#endif
#define __cpp_lib_type_identity 201806L
#define __cpp_lib_unwrap_ref 201811L
#if _GLIBCXX_HOSTED
#define __cpp_lib_array_constexpr 201811L
#define __cpp_lib_assume_aligned 201811L
#if defined _GLIBCXX_HAS_GTHREADS || defined _GLIBCXX_HAVE_LINUX_FUTEX
# define __cpp_lib_atomic_wait 201907L
# if __cpp_aligned_new
# define __cpp_lib_barrier 201907L
# endif
#endif
#define __cpp_lib_bind_front 201907L
#if __has_builtin(__builtin_bit_cast)
# define __cpp_lib_bit_cast 201806L
#endif
// FIXME: #define __cpp_lib_execution 201902L
#define __cpp_lib_integer_comparison_functions 202002L
#define __cpp_lib_constexpr_algorithms 201806L
#ifdef __cpp_lib_is_constant_evaluated
# define __cpp_lib_constexpr_char_traits 201811L
#endif
#define __cpp_lib_constexpr_complex 201711L
#define __cpp_lib_constexpr_dynamic_alloc 201907L
#define __cpp_lib_constexpr_functional 201907L
#define __cpp_lib_constexpr_iterator 201811L
#define __cpp_lib_constexpr_memory 201811L
#define __cpp_lib_constexpr_numeric 201911L
#ifdef __cpp_lib_is_constant_evaluated
# define __cpp_lib_constexpr_string 201811L
#endif
#define __cpp_lib_constexpr_string_view 201811L
#define __cpp_lib_constexpr_tuple 201811L
#define __cpp_lib_constexpr_utility 201811L
#define __cpp_lib_erase_if 202002L
#define __cpp_lib_generic_unordered_lookup 201811L
#define __cpp_lib_interpolate 201902L
#ifdef _GLIBCXX_HAS_GTHREADS
# define __cpp_lib_jthread 201911L
#endif
#if __has_builtin(__is_layout_compatible) \
&& __has_builtin(__builtin_is_corresponding_member)
# define __cpp_lib_is_layout_compatible 201907L
#endif
#if __has_builtin(__is_pointer_interconvertible_base_of) \
&& __has_builtin(__builtin_is_pointer_interconvertible_with_class)
# define __cpp_lib_is_pointer_interconvertible 201907L
#endif
#if __cpp_lib_atomic_wait
# define __cpp_lib_latch 201907L
#endif
#define __cpp_lib_list_remove_return_type 201806L
#if __cpp_lib_concepts
# define __cpp_lib_make_obj_using_allocator 201811L
#endif
#define __cpp_lib_math_constants 201907L
#define __cpp_lib_polymorphic_allocator 201902L
#if __cpp_lib_concepts
# define __cpp_lib_ranges 202106L
#endif
#if __cpp_lib_atomic_wait || _GLIBCXX_HAVE_POSIX_SEMAPHORE
# define __cpp_lib_semaphore 201907L
#endif
#define __cpp_lib_shift 201806L
#if __has_builtin(__builtin_source_location)
# define __cpp_lib_source_location 201907L
#endif
#if __cpp_lib_concepts
# define __cpp_lib_span 202002L
#endif
#define __cpp_lib_ssize 201902L
#define __cpp_lib_starts_ends_with 201711L
# if _GLIBCXX_USE_CXX11_ABI
// Only supported with cxx11-abi
# define __cpp_lib_syncbuf 201803L
# endif
#define __cpp_lib_to_address 201711L
#define __cpp_lib_to_array 201907L
#endif
#if __cplusplus > 202002L
// c++2b
#define __cpp_lib_invoke_r 202106L
#define __cpp_lib_is_scoped_enum 202011L
#define __cpp_lib_string_contains 202011L
#define __cpp_lib_to_underlying 202102L
#endif // C++2b
#endif // C++20
#endif // C++17
#endif // C++14
#endif // C++11
#endif // _GLIBCXX_VERSION_INCLUDED
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