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13 daysDaily bump.GCC Administrator1-0/+67
14 dayslibstdc++: Conditionalize LWG 3569 changes to join_viewPatrick Palka1-12/+37
LWG 3569 adjusted join_view's iterator specification to handle non default-constructible iterators by wrapping the corresponding data member in std::optional, which we followed suit in r13-2649-g7aa80c82ecf3a3. But this wrapping is unnecessary for iterators that are already default-constructible. Rather than unconditionally using std::optional here, which introduces time/space overhead, this patch conditionalizes our LWG 3569 changes on the iterator in question being non-forward (and thus non default-constructible). We check forwardness instead of default-constructibility in order to accommodate input-only iterators that satisfy but do not model default_initializable, e.g. whose default constructor is underconstrained. libstdc++-v3/ChangeLog: * include/std/ranges (join_view::_Iterator::_M_satisfy): Adjust to handle non-std::optional _M_inner as per before LWG 3569. (join_view::_Iterator::_M_get_inner): New. (join_view::_Iterator::_M_inner): Don't wrap in std::optional if the iterator is forward. Initialize. (join_view::_Iterator::operator*): Use _M_get_inner instead of *_M_inner. (join_view::_Iterator::operator++): Likewise. (join_view::_Iterator::iter_move): Likewise. (join_view::_Iterator::iter_swap): Likewise. Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com> Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
14 dayslibstdc++: Reuse _Bind_back_t functor in ranges::_PartialTomasz Kamiński2-97/+17
This patch refactors ranges::_Partial to be implemented using _Bind_back_t. This allows it to benefit from the changes in r16-3398-g250dd5b5604fbc, specifically making the closure trivially copyable. Since _Bind_back_t already provides an optimized implementation for a single bound argument, specializations for _Partial with a single argument are now removed. We still preserve a specialization of _Partial for trivially copy-constructible arguments that define only a const overload of operator(). To avoid re-checking invocability constraints, this specialization calls the now-public, unconstrained _Binder::_S_call static method instead of the constrained _Binder::operator(). The primary specialization of _Partial retains its operator(), which uses a simpler __adaptor_invocable constraint that does not consider member pointers, as they are not relevant here. This implementation also calls _Binder::_S_call to avoid re-performing overload resolution and invocability checks for _Binder::operator(). Finally, the _M_binder member (_Bind_back_t) is now marked [[no_unique_address]]. This is beneficial as ranges::_Partial is used with ranges::to, which commonly has zero or empty bound arguments (e.g., stateless allocators, comparators, or hash functions). libstdc++-v3/ChangeLog: * include/bits/binders.h (_Binder::_S_call): Make public. * include/std/ranges (ranges::_Partial<_Adaptor, _Args...>): Replace tuple<_Args...> with _Bind_back_t<_Adaptor, _Args...>. (ranges::_Partial<_Adaptor, _Arg>): Remove. Reviewed-by: Patrick Palka <ppalka@redhat.com> Reviewed-by: Jonathan Wakely <jwakely@redhat.com> Signed-off-by: Tomasz Kamiński <tkaminsk@redhat.com>
14 dayslibstdc++: Move _Binder and related aliases to separate file.Tomasz Kamiński4-186/+237
bits/binders.h is already mapped in libstdc++-v3/doc/doxygen/stdheader.cc. libstdc++-v3/ChangeLog: * include/Makefile.am: Add bits/binders.h * include/Makefile.in: Add bits/binders.h * include/std/functional (std::_Indexed_bound_arg, std::_Binder) (std::__make_bound_args, std::_Bind_front_t, std::_Bind_back_t): Moved to bits/binders.h file, that is now included. * include/bits/binders.h: New file. Reviewed-by: Patrick Palka <ppalka@redhat.com> Reviewed-by: Jonathan Wakely <jwakely@redhat.com> Signed-off-by: Tomasz Kamiński <tkaminsk@redhat.com>
14 dayslibstdc++: Merge bind_front and bind_back bindersTomasz Kamiński5-105/+103
The _Bind_front and _Bind_back class templates are now merged into a single _Binder implementation that accepts _Back as a template parameter. This makes the bind_back implementation available in C++20 mode, allowing it to be used for range adaptor closures. With zero bound arguments, bind_back and bind_front have equivalent functionality. Consequently, _Bind_back_t now produces the same type as bind_front (_Binder<false, _Fd>). A simple copy of the functor cannot be returned in this case, as it would visibly affect overload resolution (see included test cases). We also replace std::invoke in internal functions, with std::__invoke. libstdc++-v3/ChangeLog: * include/std/functional: (std::_Indexed_bound_arg): Fixed indentation. (__Bound_arg_storage::_S_apply_front) (__Bound_arg_storage::_S_apply_front): Merged into _S_apply. (__Bound_arg_storage::_S_apply): Merged above, add _Back template parameter, replace std::invoke with std::__invoke. (std::_Bind_front): Renamed to std::_Binder and add _Back template parameter. (std::_Binder): Renamed from std::_Bind_front. (_Binder::_Result_t, _Binder::_S_noexcept_invoke): Define. (_Binder::operator()): Use _Result_t and _S_noexcept_invoke. (_Binder::_S_call): Handle zero args specially, replace std::invoke with std::__invoke. (std::_Bind_front_t, std::_Bind_back_t): Defined in terms of _Binder. (std::_Bind_back): Merged into _Binder. * testsuite/20_util/function_objects/bind_back/1.cc: New tests. * testsuite/20_util/function_objects/bind_back/111327.cc: Updated error messages. * testsuite/20_util/function_objects/bind_front/1.cc: New tests. * testsuite/20_util/function_objects/bind_front/111327.cc: Updated error messages. Reviewed-by: Patrick Palka <ppalka@redhat.com> Reviewed-by: Jonathan Wakely <jwakely@redhat.com> Signed-off-by: Tomasz Kamiński <tkaminsk@redhat.com>
14 dayslibstdc++: Add _GLIBCXX_RESOLVE_LIB_DEFECTS for 4314 in <mdspan>.Luc Grosheintz1-1/+7
In r16-2328-g29d53f6213e0a1 we fixed a bug related to user-defined objects that can convert to an integers only via an rvalue reference. The same commit also implemented LWG 4314 [1], but didn't mark it with _GLIBCXX_RESOLVE_LIB_DEFECTS. This commit adds the missing markers. [1]: https://cplusplus.github.io/LWG/issue4314 It also fixes one cases of trailing white-space near a ctor for aligned_accessor. libstdc++-v3/ChangeLog: * include/std/mdspan (layout_left::mapping::operator()): Add _GLIBCXX_RESOLVE_LIB_DEFECTS marker for 4314. (layout_left::mapping::operator()): Ditto. (layout_stride::mapping::operator()): Ditto. Reviewed-by: Jonathan Wakely <jwakely@redhat.com> Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
14 dayslibstdc++: Add stable names to C++98 implementation-defined docs.Tomasz Kamiński2-98/+108
Stable names are based on C++03 standard document, and some of then were changed since then. libstdc++-v3/ChangeLog: * doc/html/manual/status.html: Regenerated the file. * doc/xml/manual/status_cxx1998.xml: Add stable name to each entry. Reviewed-by: Jonathan Wakely <jwakely@redhat.com> Signed-off-by: Tomasz Kamiński <tkaminsk@redhat.com>
2025-09-04Daily bump.GCC Administrator1-0/+30
2025-09-03libstdc++: Implement LWG4222 'expected' constructor from a single value ↵Yihan Wang2-0/+40
missing a constraint libstdc++-v3/ChangeLog: * include/std/expected (expected(U&&)): Add missing constraint as per LWG 4222. * testsuite/20_util/expected/lwg4222.cc: New test. Signed-off-by: Yihan Wang <yronglin777@gmail.com>
2025-09-03libstdc++: Fix std::get<T> for std::pair with reference members [PR121745]Jonathan Wakely2-4/+56
Make the std::get<T> overloads for rvalues use std::forward<T>(p.first) not std::move(p.first), so that lvalue reference members are not incorrectly converted to rvalues. It might appear that std::move(p).first would also work, but the language rules say that for std::pair<T&&, U> that would produce T& rather than the expected T&& (see the discussion in P2445R1 §8.2). Additional tests are added to verify all combinations of reference members, value categories, and const-qualification. libstdc++-v3/ChangeLog: PR libstdc++/121745 * include/bits/stl_pair.h (get): Use forward instead of move in std::get<T> overloads for rvalue pairs. * testsuite/20_util/pair/astuple/get_by_type.cc: Check all value categories and cv-qualification. Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
2025-09-03libstdc++: Make CTAD ignore pair(const T1&, const T2&) constructor [PR110853]Jonathan Wakely2-1/+11
For the pair(T1, T2) explicit deduction type to decay its arguments as intended, we need the pair(const T1&, const T2&) constructor to not be used for CTAD. Otherwise we try to instantiate pair<T1, T2> without decaying, which is ill-formed for function lvalues. Use std::type_identity_t<T1> to make the constructor unusable for an implicit deduction guide. libstdc++-v3/ChangeLog: PR libstdc++/110853 * include/bits/stl_pair.h [C++20] (pair(const T1&, const T2&)): Use std::type_identity_t<T1> for first parameter. * testsuite/20_util/pair/cons/110853.cc: New test. Reviewed-by: Patrick Palka <ppalka@redhat.com> Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
2025-09-03libstdc++: Restore C++20 <chrono> support for old std::string ABIJonathan Wakely4-6/+28
The r16-3416-g806de30f51c8b9 change to use __cpp_lib_chrono in preprocessor conditions broke support for <chrono> for freestanding and the COW std::string ABI. That happened because __cpp_lib_chrono is only defined to the C++20 value for hosted and for the new ABI, because the full set of C++20 features are not defined for freestanding and tzdb is not defined for the old ABI. This introduces a new internal feature test macro that corresponds to the features that are always supported (e.g. chrono::local_time, chrono::year, chrono::weekday). libstdc++-v3/ChangeLog: * include/bits/version.def (chrono_cxx20): Define. * include/bits/version.h: Regenerate. * include/std/chrono: Check __glibcxx_chrono_cxx20 instead of __cpp_lib_chrono for C++20 features that don't require the new std::string ABI and/or can be used for freestanding. * src/c++20/clock.cc: Adjust preprocessor condition. Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
2025-09-03Daily bump.GCC Administrator1-0/+15
2025-09-02libstdc++: Move _Index_tuple, _Build_index_tuple to <type_traits>.Luc Grosheintz2-20/+22
As preparation for implementing std::constant_wrapper that's part of the C++26 version of the <type_traits> header, the two classes _Index_tuple and _Build_index_tuple are moved to <type_traits>. These two helpers are needed by std::constant_wrapper to initialize the elements of one C array with another. Since, <bits/utility.h> already includes <type_traits> this solution avoids creating a very small header file for just these two internal classes. This approach doesn't move std::index_sequence and related code to <type_traits> and therefore doesn't change which headers provide user-facing features. libstdc++-v3/ChangeLog: * include/bits/utility.h (_Index_tuple): Move to <type_traits>. (_Build_index_tuple): Ditto. * include/std/type_traits (_Index_tuple): Ditto. (_Build_index_tuple): Ditto. Reviewed-by: Jonathan Wakely <jwakely@redhat.com> Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
2025-09-02libstdc++: Rename __cmp_cat::__unspec to __cmp_cat::__literal_zero.Tomasz Kamiński1-35/+35
This slightly improve the readability of error message, by suggesting that 0 (literal) is expected as argument: invalid conversion from 'int' to 'std::__cmp_cat::__literal_zero*' libstdc++-v3/ChangeLog: * libsupc++/compare (__cmp_cat::__literal_zero): Rename from __unspec. (__cmp_cat::__unspec): Rename to __literal_zero. (operator==, operator<, operator>, operator<=, operator>=): Replace __cmp_cat::__unspec to __cmp_cat::__literal_zero.
2025-09-01Daily bump.GCC Administrator1-0/+13
2025-08-31libstdc++: Update link to Boost "Exception-Safety"Gerald Pfeifer2-2/+2
libstdc++-v3: * doc/xml/manual/using_exceptions.xml: Update link to Boost's "Exception-Safety" * doc/html/manual/using_exceptions.html: Rebuild.
2025-08-31libstdc++: Fix bootstrap failures in src/c++26/debugging.ccJonathan Wakely1-1/+2
ptrace on Darwin requires <sys/types.h>. The inline x86 asm doesn't work with the Solaris assembler. libstdc++-v3/ChangeLog: * src/c++26/debugging.cc [_GLIBCXX_HAVE_SYS_PTRACE_H]: Include <sys/types.h>. (breakpoint) [__i386__ || __x86_64__]: Use "int 0x03" instead of "int3".
2025-08-29Daily bump.GCC Administrator1-0/+56
2025-08-28libstdc++: Implement C++26 <debugging> features [PR119670]Jonathan Wakely17-3/+464
This implements P2546R5 (Debugging Support), including the P2810R4 (is_debugger_present is_replaceable) changes, allowing std::is_debugger_present to be replaced by the program. It would be good to provide a macOS definition of is_debugger_present as per https://developer.apple.com/library/archive/qa/qa1361/_index.html but that isn't included in this change. The src/c++26/debugging.cc file defines a global volatile int which can be set by debuggers to indicate when they are attached and detached from a running process. This allows std::is_debugger_present() to give a reliable answer, and additionally allows a debugger to choose how std::breakpoint() should behave. Setting the global to a positive value will cause std::breakpoint() to use that value as an argument to std::raise, so debuggers that prefer SIGABRT for breakpoints can select that. By default std::breakpoint() will use a platform-specific action such as the INT3 instruction on x86, or GCC's __builtin_trap(). On Linux the std::is_debugger_present() function checks whether the process is being traced by a process named "gdb", "gdbserver" or "lldb-server", to try to avoid interpreting other tracing processes (such as strace) as a debugger. There have been comments suggesting this isn't desirable and that std::is_debugger_present() should just return true for any tracing process (which is the case for non-Linux targets that support the ptrace system call). libstdc++-v3/ChangeLog: PR libstdc++/119670 * acinclude.m4 (GLIBCXX_CHECK_DEBUGGING): Check for facilities needed by <debugging>. * config.h.in: Regenerate. * configure: Regenerate. * configure.ac: Use GLIBCXX_CHECK_DEBUGGING. * include/Makefile.am: Add new header. * include/Makefile.in: Regenerate. * include/bits/version.def (debugging): Add. * include/bits/version.h: Regenerate. * include/precompiled/stdc++.h: Add new header. * src/c++26/Makefile.am: Add new file. * src/c++26/Makefile.in: Regenerate. * include/std/debugging: New file. * src/c++26/debugging.cc: New file. * testsuite/19_diagnostics/debugging/breakpoint.cc: New test. * testsuite/19_diagnostics/debugging/breakpoint_if_debugging.cc: New test. * testsuite/19_diagnostics/debugging/is_debugger_present.cc: New test. * testsuite/19_diagnostics/debugging/is_debugger_present-2.cc: New test. Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
2025-08-28libstdc++: Test comparing ordering with type convertible to any pointer.Tomasz Kamiński1-0/+16
libstdc++-v3/ChangeLog: * testsuite/18_support/comparisons/categories/zero_neg.cc: New test. Reviewed-by: Jonathan Wakely <jwakely@redhat.com> Signed-off-by: Tomasz Kamiński <tkaminsk@redhat.com>
2025-08-28libstdc++: Remove implicit type conversions in std::complexWeslley da Silva Pereira1-7/+8
The current implementation of `complex<_Tp>` assumes that int `int` is implicitly convertible to `_Tp`, e.g., when using `complex<_Tp>(1)`. This patch transforms the implicit conversions into explicit type casts. As a result, `std::complex` is now able to support more types. One example is the type `Eigen::Half` from https://eigen.tuxfamily.org/dox-devel/Half_8h_source.html which does not implement implicit type conversions. libstdc++-v3/ChangeLog: * include/std/complex (polar, __complex_sqrt, pow) (__complex_pow_unsigned): Use explicit conversions from int to the complex value_type.
2025-08-28libstdc++: Constrain bitset(const CharT*) constructor [PR121046]Jonathan Wakely2-1/+18
Asking std::is_constructible_v<std::bitset<1>, NonTrivial*> gives an error, rather than answering the query. The problem is that the constructor for std::bitset("010101") is not constrained to only accept pointers to char-like types, and for the second parameter (which has a default argument) std::basic_string_view<CharT> gets instantiated. If the type is not char-like then that has undefined behaviour, and might trigger a static_assert to fail in the body of std::basic_string_view. We can fix it by constraining that constructor using the requirements for char-like types from [strings.general] p1. I've submitted LWG 4294 and proposed making this change in the standard. libstdc++-v3/ChangeLog: PR libstdc++/121046 * include/std/bitset (bitset(const CharT*, ...)): Add constraints on CharT type. * testsuite/23_containers/bitset/lwg4294.cc: New test.
2025-08-28libstdc++: Provide helpers to interoperate between __cmp_cat::_Ord and ↵Tomasz Kamiński1-44/+41
ordering types. This patch adds two new internal helpers for ordering types: * __cmp_cat::__ord to retrieve an internal _Ord value, * __cmp_cat::__make<Ordering> to create an ordering from an _Ord value. Conversions between ordering types are now handled by __cmp_cat::__make. As a result, ordering types no longer need to befriend each other, only the new helpers. The __fp_weak_ordering implementation has also been simplified by: * using the new helpers to convert partial_ordering to weak_ordering, * using strong_ordering to weak_ordering conversion operator, for the __isnan_sign comparison, * removing the unused __cat local variable. Finally, the _Ncmp enum is removed, and the unordered enumerator is added to the existing _Ord enum. libstdc++-v3/ChangeLog: * libsupc++/compare (__cmp_cat::_Ord): Add unordered enumerator. (__cmp_cat::_Ncmp): Remove. (__cmp_cat::__ord, __cmp_cat::__make): Define. (partial_ordering::partial_ordering(__cmp_cat::_Ncmp)): Remove. (operator<=>(__cmp_cat::__unspec, partial_ordering)) (partial_ordering::unordered): Replace _Ncmp with _Ord. (std::partial_ordering, std::weak_ordering, std::strong_ordering): Befriend __ord and __make helpers, remove friend declartions for other orderings. (__compare::__fp_weak_ordering): Remove unused __cat variable. Simplify ordering conversions. Reviewed-by: Jonathan Wakely <jwakely@redhat.com> Signed-off-by: Tomasz Kamiński <tkaminsk@redhat.com>
2025-08-28Daily bump.GCC Administrator1-0/+42
2025-08-27libstdc++: Use _M_reverse to reverse partial_ordering using operator<=>Tomasz Kamiński1-6/+1
The patch r16-3414-gfcb3009a32dc33 changed the representation of unordered to optimize reversing of order, but it did not update implementation of reversing operator<=>(0, partial_order). libstdc++-v3/ChangeLog: * libsupc++/compare (operator<=>(__cmp_cat::__unspec, partial_ordering)): Implement using _M_reverse. Reviewed-by: Jonathan Wakely <jwakely@redhat.com> Signed-off-by: Tomasz Kamiński <tkaminsk@redhat.com>
2025-08-27libstdc++: Move tai_- and gps_clock::now impls out of ABINathan Myers5-20/+74
This patch moves std::tai_clock::now() and std::tai_clock::now() definitions from header inlines to static members invoked via a normal function call, in service of stabilizing the C++20 ABI. It also changes #if guards to mention the actual __cpp_lib_* feature gated, not just the language version, for clarity. New global function symbols std::chrono::tai_clock::now and std::chrono::gps_clock::now are exported. libstdc++-v3/ChangeLog: * include/std/chrono (gps_clock::now, tai_clock::now): Remove inline definitions. * src/c++20/clock.cc (gps_clock::now, tai_clock::now): New file for out-of-line now() impls. * src/c++20/Makefile.am: Mention clock.cc. * src/c++20/Makefile.in: Regenerate. * config/abi/pre/gnu.ver: add mangled now() symbols.
2025-08-27libsupc++: Change _Unordered comparison value to minimum value of signed char.Tomasz Kamiński2-8/+20
For any minimum value of a signed type, its negation (with wraparound) results in the same value, behaving like zero. Representing the unordered result with this minimum value, along with 0 for equal, 1 for greater, and -1 for less in partial_ordering, allows its value to be reversed using unary negation. The operator<=(partial_order, 0) now checks if the reversed value is positive. This works correctly because the unordered value remains unchanged and thus negative. libstdc++-v3/ChangeLog: * libsupc++/compare (_Ncmp::_Unordered): Rename and change the value to minimum value of signed char. (_Ncomp::unordered): Renamed from _Unordered, the name is reserved by partial_ordered::unordered. (partial_ordering::_M_reverse()): Define. (operator<=(partial_ordering, __cmp_cat::__unspec)) (operator>=(__cmp_cat::__unspec, partial_ordering)): Implemented in terms of negated _M_value. (operator>=(partial_ordering, __cmp_cat::__unspec)) (operator<=(__cmp_cat::__unspec, partial_ordering)): Directly compare _M_value, as unordered value is negative. (partial_ordering::unordered): Handle _Ncmp::unoredred rename. * python/libstdcxx/v6/printers.py: Add -128 as integer value for unordered, keeping 2 to preserve backward compatibility. Reviewed-by: Jonathan Wakely <jwakely@redhat.com> Signed-off-by: Tomasz Kamiński <tkaminsk@redhat.com>
2025-08-27libstdc++: Reduce chances of object aliasing for function wrapper.Tomasz Kamiński3-10/+50
Previously, an empty functor (EmptyIdFunc) stored inside a std::move_only_function being first member of a Composite class could have the same address as the base of the EmptyIdFunc type (see included test cases), resulting in two objects of the same type at the same address. This commit addresses the issue by moving the internal buffer from the start of the wrapper object to a position after the manager function pointer. This minimizes aliasing with the stored buffer but doesn't completely eliminate it, especially when multiple empty base objects are involved (PR121180). To facilitate this member reordering, the private section of _Mo_base was eliminated, and the corresponding _M_manager and _M_destroy members were made protected. They remain inaccessible to users, as user-facing wrappers derive from _Mo_base privately. libstdc++-v3/ChangeLog: * include/bits/funcwrap.h (__polyfunc::_Mo_base): Reorder _M_manage and _M_storage members. Make _M_destroy protected and remove friend declaration. * testsuite/20_util/copyable_function/call.cc: Add test for aliasing base class. * testsuite/20_util/move_only_function/call.cc: Likewise. Reviewed-by: Jonathan Wakely <jwakely@redhat.com> Reviewed-by: Patrick Palka <ppalka@redhat.com> Signed-off-by: Tomasz Kamiński <tkaminsk@redhat.com>
2025-08-27Daily bump.GCC Administrator1-0/+42
2025-08-26libstdc++/ranges: Prefer using offset-based _CachedPositionPatrick Palka1-2/+0
The offset-based partial specialization of _CachedPosition for random-access iterators is currently only selected if the offset type is smaller than the iterator type. Before r12-1018-g46ed811bcb4b86 this made sense since the main partial specialization only stored the iterator (incorrectly). After that bugfix, the main partial specialization now effectively stores a std::optional<iter> so the size constraint is inaccurate. And this main partial specialization must invalidate itself upon copy/move unlike the offset-based partial specialization. So I think we should just always prefer the offset-based _CachedPosition for a random-access iterator, even if the offset type happens to be larger than the iterator type. libstdc++-v3/ChangeLog: * include/std/ranges (__detail::_CachedPosition): Remove additional size constraint on the offset-based partial specialization. Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com> Reviewed-by: Jonathan Wakely <jwakely@redhat.com>
2025-08-26libstdc++: Do not require assignment for vector::resize(n, v) [PR90192]Tomasz Kamiński5-21/+148
This patch introduces a new function, _M_fill_append, which is invoked when copies of the same value are appended to the end of a vector. Unlike _M_fill_insert(end(), n, v), _M_fill_append never permute elements in place, so it does not require: * vector element type to be assignable; * a copy of the inserted value, in the case where it points to an element of the vector. vector::resize(n, v) now uses _M_fill_append, fixing the non-conformance where element types were required to be assignable. In addition, _M_fill_insert(end(), n, v) now delegates to _M_fill_append, which eliminates an unnecessary copy of v when the existing capacity is used. PR libstdc++/90192 libstdc++-v3/ChangeLog: * include/bits/stl_vector.h (vector<T>::_M_fill_append): Declare. (vector<T>::fill): Use _M_fill_append instead of _M_fill_insert. * include/bits/vector.tcc (vector<T>::_M_fill_append): Define (vector<T>::_M_fill_insert): Delegate to _M_fill_append when elements are appended. * testsuite/23_containers/vector/modifiers/moveable.cc: Updated copycount for inserting at the end (appending). * testsuite/23_containers/vector/modifiers/resize.cc: New test. * testsuite/backward/hash_set/check_construct_destroy.cc: Updated copycount, the hash_set constructor uses insert to fill buckets with nullptrs. Reviewed-by: Jonathan Wakely <jwakely@redhat.com> Signed-off-by: Tomasz Kamiński <tkaminsk@redhat.com>
2025-08-26libstdc++: Refactor bound arguments storage for bind_front/backTomasz Kamiński6-49/+418
This patch refactors the implementation of bind_front and bind_back to avoid using std::tuple for argument storage. Instead, bound arguments are now: * stored directly if there is only one, * within a dedicated _Bound_arg_storage otherwise. _Bound_arg_storage is less expensive to instantiate and access than std::tuple. It can also be trivially copyable, as it doesn't require a non-trivial assignment operator for reference types. Storing a single argument directly provides similar benefits compared to both one element tuple or _Bound_arg_storage. _Bound_arg_storage holds each argument in an _Indexed_bound_arg base object. The base class is parameterized by both type and index to allow storing multiple arguments of the same type. Invocations are handled by _S_apply_front amd _S_apply_back static functions, which simulate explicit object parameters. To facilitate this, the __like_t alias template is now unconditionally available since C++11 in bits/move.h. libstdc++-v3/ChangeLog: * include/bits/move.h (std::__like_impl, std::__like_t): Make available in c++11. * include/std/functional (std::_Indexed_bound_arg) (std::_Bound_arg_storage, std::__make_bound_args): Define. (std::_Bind_front, std::_Bind_back): Use _Bound_arg_storage. * testsuite/20_util/function_objects/bind_back/1.cc: Expand test to cover cases of 0, 1, many bound args. * testsuite/20_util/function_objects/bind_back/111327.cc: Likewise. * testsuite/20_util/function_objects/bind_front/1.cc: Likewise. * testsuite/20_util/function_objects/bind_front/111327.cc: Likewise. Reviewed-by: Jonathan Wakely <jwakely@redhat.com> Reviewed-by: Patrick Palka <ppalka@redhat.com> Signed-off-by: Tomasz Kamiński <tkaminsk@redhat.com>
2025-08-26libstdc++: Specialize _Never_valueless_alt for jthread, stop_token and ↵Tomasz Kamiński2-0/+33
stop_source The move constructors for stop_source and stop_token are equivalent to copying and clearing the raw pointer, as they are wrappers for a counted-shared state. For jthread, the move constructor performs a member-wise move of stop_source and thread. While std::thread could also have a _Never_valueless_alt specialization due to its inexpensive move (only moving a handle), doing so now would change the ABI. This patch takes the opportunity to correct this behavior for jthread, before C++20 API is marked stable. libstdc++-v3/ChangeLog: * include/std/stop_token (__variant::_Never_valueless_alt): Declare. (__variant::_Never_valueless_alt<std::stop_token>) (__variant::_Never_valueless_alt<std::stop_source>): Define. * include/std/thread: (__variant::_Never_valueless_alt): Declare. (__variant::_Never_valueless_alt<std::jthread>): Define.
2025-08-22Daily bump.GCC Administrator1-0/+151
2025-08-21libstdc++: Use pthread_mutex_clocklock when TSan is active [PR121496]Jonathan Wakely2-2/+2
This reverts r14-905-g3b7cb33033fbe6 which disabled the use of pthread_mutex_clocklock when TSan is active. That's no longer needed, because GCC has TSan interceptors for pthread_mutex_clocklock since GCC 15.1 and Clang has them since 18.1.0 (released March 2024). The interceptor was added by https://github.com/llvm/llvm-project/pull/75713 libstdc++-v3/ChangeLog: PR libstdc++/121496 * acinclude.m4 (GLIBCXX_CHECK_PTHREAD_MUTEX_CLOCKLOCK): Do not use _GLIBCXX_TSAN in _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK macro. * configure: Regenerate. Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
2025-08-21libstdc++: Check _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK with #if [PR121496]Jonathan Wakely2-2/+16
The change in r14-905-g3b7cb33033fbe6 to disable the use of pthread_mutex_clocklock when TSan is active assumed that the _GLIBCXX_USE_PTHREAD_MUTEX_CLOCKLOCK macro was always checked with #if rather than #ifdef, which was not true. This makes the checks use #if consistently. libstdc++-v3/ChangeLog: PR libstdc++/121496 * include/std/mutex (__timed_mutex_impl::_M_try_wait_until): Change preprocessor condition to use #if instead of #ifdef. (recursive_timed_mutex::_M_clocklock): Likewise. * testsuite/30_threads/timed_mutex/121496.cc: New test. Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com>
2025-08-21libstdc++: Implement aligned_accessor from mdspan [PR120994]Luc Grosheintz9-3/+197
This commit completes the implementation of P2897R7 by implementing and testing the template class aligned_accessor. PR libstdc++/120994 libstdc++-v3/ChangeLog: * include/bits/version.def (aligned_accessor): Add. * include/bits/version.h: Regenerate. * include/std/mdspan (aligned_accessor): New class. * src/c++23/std.cc.in (aligned_accessor): Add. * testsuite/23_containers/mdspan/accessors/generic.cc: Add tests for aligned_accessor. * testsuite/23_containers/mdspan/accessors/aligned_neg.cc: New test. * testsuite/23_containers/mdspan/version.cc: Add test for __cpp_lib_aligned_accessor. Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com> Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
2025-08-21libstdc++: Implement is_sufficiently_aligned [PR120994]Luc Grosheintz7-0/+74
This commit implements and tests the function is_sufficiently_aligned from P2897R7. PR libstdc++/120994 libstdc++-v3/ChangeLog: * include/bits/align.h (is_sufficiently_aligned): New function. * include/bits/version.def (is_sufficiently_aligned): Add. * include/bits/version.h: Regenerate. * include/std/memory: Add __glibcxx_want_is_sufficiently_aligned. * src/c++23/std.cc.in (is_sufficiently_aligned): Add. * testsuite/20_util/headers/memory/version.cc: Add test for __cpp_lib_is_sufficiently_aligned. * testsuite/20_util/is_sufficiently_aligned/1.cc: New test. Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com> Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
2025-08-21libstdc++: Fix std::numeric_limits<__float128>::max_digits10 [PR121374]Jonathan Wakely2-1/+6
When I added this explicit specialization in r14-1433-gf150a084e25eaa I used the wrong value for the number of mantissa digits (I used 112 instead of 113). Then when I refactored it in r14-1582-g6261d10521f9fd I used the value calculated from the incorrect value (35 instead of 36). libstdc++-v3/ChangeLog: PR libstdc++/121374 * include/std/limits (numeric_limits<__float128>::max_digits10): Fix value. * testsuite/18_support/numeric_limits/128bit.cc: Check value.
2025-08-21libstdc++: Suppress some more additional diagnostics [PR117294]Jonathan Wakely2-0/+3
libstdc++-v3/ChangeLog: PR c++/117294 * testsuite/20_util/optional/cons/value_neg.cc: Prune additional output for C++20 and later. * testsuite/20_util/scoped_allocator/69293_neg.cc: Match additional error for C++20 and later.
2025-08-21libstdc++: Implement std::dims from <mdspan>.Luc Grosheintz6-5/+32
This commit implements the C++26 feature std::dims described in P2389R2. It sets the feature testing macro to 202406 and adds tests. Also fixes the test mdspan/version.cc libstdc++-v3/ChangeLog: * include/bits/version.def (mdspan): Set value for C++26. * include/bits/version.h: Regenerate. * include/std/mdspan (dims): Add. * src/c++23/std.cc.in (dims): Add. * testsuite/23_containers/mdspan/extents/misc.cc: Add tests. * testsuite/23_containers/mdspan/version.cc: Update test. Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com> Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
2025-08-21libstdc++: Simplify precomputed partial products in <mdspan>.Luc Grosheintz1-21/+23
Prior to this commit, the partial products of static extents in <mdspan> was done in a loop that calls a function that computes the partial product. The complexity is quadratic in the rank. This commit removes the quadratic complexity. libstdc++-v3/ChangeLog: * include/std/mdspan (__static_prod): Delete. (__fwd_partial_prods): Compute at compile-time in O(rank), not O(rank**2). (__rev_partial_prods): Ditto. (__size): Inline __static_prod. Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com> Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
2025-08-21libstdc++: Reduce size static storage for __fwd_prod in mdspan.Luc Grosheintz1-2/+2
This fixes an oversight in a previous commit that improved mdspan related code. Because __size doesn't use __fwd_prod, __fwd_prod(__rank) is not needed anymore. Hence, one can shrink the size of __fwd_partial_prods. libstdc++-v3/ChangeLog: * include/std/mdspan (__fwd_partial_prods): Reduce size of the array by 1 element. Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com> Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
2025-08-21libstdc++: Replace numeric_limit with __int_traits in mdspan.Luc Grosheintz2-12/+17
Using __int_traits avoids the need to include <limits> from <mdspan>. This in turn should reduce the size of the pre-compiled <mdspan>. Similar refactoring was carried out for PR92546. Unfortunately, ./gcc/xgcc -std=c++23 -P -E -x c++ - -include mdspan | wc -l shows a decrease by 1(!) line. This is due to bits/max_size_type.h which includes <limits>. libstdc++-v3/ChangeLog: * include/std/mdspan (__valid_static_extent): Replace numeric_limits with __int_traits. (extents::_S_ctor_explicit): Ditto. (extents::__static_quotient): Ditto. (layout_stride::mapping::mapping): Ditto. (mdspan::size): Ditto. * testsuite/23_containers/mdspan/extents/class_mandates_neg.cc: Update test with additional diagnostics. Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com> Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
2025-08-21libstdc++: Improve extents::operator==.Luc Grosheintz1-4/+5
An interesting case to consider is: bool same11(const std::extents<int, dyn, 2, 3>& e1, const std::extents<int, dyn, dyn, 3>& e2) { return e1 == e2; } Which has the following properties: - There's no mismatching static extents, preventing any short-circuiting. - There's a comparison between dynamic and static extents. - There's one trivial comparison: ... && 3 == 3. Let E[i] denote the array of static extents, D[k] denote the array of dynamic extents and k[i] be the index of the i-th extent in D. (Naturally, k[i] is only meaningful if i is a dynamic extent). The previous implementation results in assembly that's more or less a literal translation of: for (i = 0; i < 3; ++i) e1 = E1[i] == -1 ? D1[k1[i]] : E1[i]; e2 = E2[i] == -1 ? D2[k2[i]] : E2[i]; if e1 != e2: return false return true; While the proposed method results in assembly for if(D1[0] == D2[0]) return false; return 2 == D2[1]; i.e. 110: 8b 17 mov edx,DWORD PTR [rdi] 112: 31 c0 xor eax,eax 114: 39 16 cmp DWORD PTR [rsi],edx 116: 74 08 je 120 <same11+0x10> 118: c3 ret 119: 0f 1f 80 00 00 00 00 nop DWORD PTR [rax+0x0] 120: 83 7e 04 02 cmp DWORD PTR [rsi+0x4],0x2 124: 0f 94 c0 sete al 127: c3 ret It has the following nice properties: - It eliminated the indirection D[k[i]], because k[i] is known at compile time. Saving us a comparison E[i] == -1 and conditionally loading k[i]. - It eliminated the trivial condition 3 == 3. The result is code that only loads the required values and performs exactly the number of comparisons needed by the algorithm. It also results in smaller object files. Therefore, this seems like a sensible change. We've check several other examples, including fully statically determined cases and high-rank examples. The example given above illustrates the other cases well. The constexpr condition: if constexpr (!_S_is_compatible_extents<...>) return false; is no longer needed, because the optimizer correctly handles this case. However, it's retained for clarity/certainty. libstdc++-v3/ChangeLog: * include/std/mdspan (extents::operator==): Replace loop with pack expansion. Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com> Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
2025-08-21libstdc++: Reduce indirection in extents::extent.Luc Grosheintz1-10/+25
In both fully static and dynamic extents the comparison static_extent(i) == dynamic_extent is known at compile time. As a result, extents::extent doesn't need to perform the check at runtime. An illustrative example is: using E = std::extents<int, 3, 5, 7, 11, 13, 17>; int required_span_size(const typename Layout::mapping<E>& m) { return m.required_span_size(); } Prior to this commit the generated code (on -O2) is: 2a0: b9 01 00 00 00 mov ecx,0x1 2a5: 31 d2 xor edx,edx 2a7: 66 66 2e 0f 1f 84 00 data16 cs nop WORD PTR [rax+rax*1+0x0] 2ae: 00 00 00 00 2b2: 66 66 2e 0f 1f 84 00 data16 cs nop WORD PTR [rax+rax*1+0x0] 2b9: 00 00 00 00 2bd: 0f 1f 00 nop DWORD PTR [rax] 2c0: 48 8b 04 d5 00 00 00 mov rax,QWORD PTR [rdx*8+0x0] 2c7: 00 2c8: 48 83 f8 ff cmp rax,0xffffffffffffffff 2cc: 0f 84 00 00 00 00 je 2d2 <required_span_size_6d_static+0x32> 2d2: 83 e8 01 sub eax,0x1 2d5: 0f af 04 97 imul eax,DWORD PTR [rdi+rdx*4] 2d9: 48 83 c2 01 add rdx,0x1 2dd: 01 c1 add ecx,eax 2df: 48 83 fa 06 cmp rdx,0x6 2e3: 75 db jne 2c0 <required_span_size_6d_static+0x20> 2e5: 89 c8 mov eax,ecx 2e7: c3 ret which is a scalar loop, and notably includes the check 308: 48 83 f8 ff cmp rax,0xffffffffffffffff to assert that the static extent is indeed not -1. Note, that on -O3 the optimizer eliminates the comparison; and generates a sequence of scalar operations: lea, shl, add and mov. The aim of this commit is to eliminate this comparison also for -O2. With the optimization applied we get: 2e0: f3 0f 6f 0f movdqu xmm1,XMMWORD PTR [rdi] 2e4: 66 0f 6f 15 00 00 00 movdqa xmm2,XMMWORD PTR [rip+0x0] 2eb: 00 2ec: 8b 57 10 mov edx,DWORD PTR [rdi+0x10] 2ef: 66 0f 6f c1 movdqa xmm0,xmm1 2f3: 66 0f 73 d1 20 psrlq xmm1,0x20 2f8: 66 0f f4 c2 pmuludq xmm0,xmm2 2fc: 66 0f 73 d2 20 psrlq xmm2,0x20 301: 8d 14 52 lea edx,[rdx+rdx*2] 304: 66 0f f4 ca pmuludq xmm1,xmm2 308: 66 0f 70 c0 08 pshufd xmm0,xmm0,0x8 30d: 66 0f 70 c9 08 pshufd xmm1,xmm1,0x8 312: 66 0f 62 c1 punpckldq xmm0,xmm1 316: 66 0f 6f c8 movdqa xmm1,xmm0 31a: 66 0f 73 d9 08 psrldq xmm1,0x8 31f: 66 0f fe c1 paddd xmm0,xmm1 323: 66 0f 6f c8 movdqa xmm1,xmm0 327: 66 0f 73 d9 04 psrldq xmm1,0x4 32c: 66 0f fe c1 paddd xmm0,xmm1 330: 66 0f 7e c0 movd eax,xmm0 334: 8d 54 90 01 lea edx,[rax+rdx*4+0x1] 338: 8b 47 14 mov eax,DWORD PTR [rdi+0x14] 33b: c1 e0 04 shl eax,0x4 33e: 01 d0 add eax,edx 340: c3 ret Which shows eliminating the trivial comparison, unlocks a new set of optimizations, i.e. SIMD-vectorization. In particular, the loop has been vectorized by loading the first four constants from aligned memory; the first four strides from non-aligned memory, then computes the product and reduction. It interleaves the above with computing 1 + 12*S[4] + 16*S[5] (as scalar operations) and then finishes the reduction. A similar effect can be observed for fully dynamic extents. libstdc++-v3/ChangeLog: * include/std/mdspan (__mdspan::__all_static): New function. (__mdspan::_StaticExtents::_S_is_dyn): Inline and eliminate. (__mdspan::_ExtentsStorage::_S_is_dynamic): New method. (__mdspan::_ExtentsStorage::_M_extent): Use _S_is_dynamic. Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com> Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
2025-08-21libstdc++: Improve nearly fully dynamic extents in mdspan.Luc Grosheintz1-2/+2
One previous commit optimized fully dynamic extents; and another refactored __size such that __fwd_prod is valid for __r = 0, ..., rank (exclusive). Therefore, by noticing that __rev_prod (and __fwd_prod) never accesses the first (or last) extent, one can avoid pre-computing partial products of static extents in those cases, if all other extents are dynamic. We check that the size of the reference object file decreases further and the .rodata sections for __fwd_prod<dyn, ..., dyn, 11> __rev_prod<3, dyn, ..., dyn> are absent. libstdc++-v3/ChangeLog: * include/std/mdspan (__fwd_prods): Relax condition for fully-dynamic extents to cover (dyn, ..., dyn, X). (__rev_partial_prods): Analogous for (X, dyn, ..., dyn). Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com> Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
2025-08-21libstdc++: Improve fully dynamic extents in mdspan.Luc Grosheintz1-10/+53
In mdspan related code, for extents with no static extents, i.e. only dynamic extents, the following simplifications can be made: - The array of dynamic extents has size rank. - The two arrays dynamic-index and dynamic-index-inv become trivial, e.g. k[i] == i. - All elements of the arrays __{fwd,rev}_partial_prods are 1. This commits eliminates the arrays for dynamic-index, dynamic-index-inv and __{fwd,rev}_partial_prods. It also removes the indirection k[i] == i from the source code, which isn't as relevant because the optimizer is (often) capable of eliminating the indirection. To check if it's working we look at: using E2 = std::extents<int, dyn, dyn, dyn, dyn>; int stride_left_E2(const std::layout_left::mapping<E2>& m, size_t r) { return m.stride(r); } which generates the following 0000000000000190 <stride_left_E2>: 190: 48 c1 e6 02 shl rsi,0x2 194: 74 22 je 1b8 <stride_left_E2+0x28> 196: 48 01 fe add rsi,rdi 199: b8 01 00 00 00 mov eax,0x1 19e: 66 90 xchg ax,ax 1a0: 48 63 17 movsxd rdx,DWORD PTR [rdi] 1a3: 48 83 c7 04 add rdi,0x4 1a7: 48 0f af c2 imul rax,rdx 1ab: 48 39 fe cmp rsi,rdi 1ae: 75 f0 jne 1a0 <stride_left_E2+0x10> 1b0: c3 ret 1b1: 0f 1f 80 00 00 00 00 nop DWORD PTR [rax+0x0] 1b8: b8 01 00 00 00 mov eax,0x1 1bd: c3 ret We see that: - There's no code to load the partial product of static extents. - There's no indirection D[k[i]], it's just D[i] (as before). On a test file which computes both mapping::stride(r) and mapping::required_span_size, we check for static storage with objdump -h we don't see the NTTP _Extents, anything (anymore) related to _StaticExtents, __fwd_partial_prods or __rev_partial_prods. We also check that the size of the reference object file (described three commits prior) reduced by a few percent from 41.9kB to 39.4kB. libstdc++-v3/ChangeLog: * include/std/mdspan (__mdspan::__all_dynamic): New function. (__mdspan::_StaticExtents::_S_dynamic_index): Convert to method. (__mdspan::_StaticExtents::_S_dynamic_index_inv): Ditto. (__mdspan::_StaticExtents): New specialization for fully dynamic extents. (__mdspan::__fwd_prod): New constexpr if branch to avoid instantiating __fwd_partial_prods. (__mdspan::__rev_prod): Ditto. Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com> Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>
2025-08-21libstdc++: Improve low-rank layout_{left,right}::stride.Luc Grosheintz1-6/+28
The methods layout_{left,right}::mapping::stride are defined as \prod_{i = 0}^r E[i] \prod_{i = r+1}^n E[i] This is computed as the product of a precomputed static product and the product of the required dynamic extents. Disassembly shows that even for low-rank extents, i.e. rank == 1 and rank == 2, with at least one dynamic extent, the generated code loads two values; and then runs the loop over at most one element, e.g. for stride_left_d5 defined below the generated code is: 220: 48 8b 04 f5 00 00 00 mov rax,QWORD PTR [rsi*8+0x0] 227: 00 228: 31 d2 xor edx,edx 22a: 48 85 c0 test rax,rax 22d: 74 23 je 252 <stride_left_d5+0x32> 22f: 48 8b 0c f5 00 00 00 mov rcx,QWORD PTR [rsi*8+0x0] 236: 00 237: 48 c1 e1 02 shl rcx,0x2 23b: 74 13 je 250 <stride_left_d5+0x30> 23d: 48 01 f9 add rcx,rdi 240: 48 63 17 movsxd rdx,DWORD PTR [rdi] 243: 48 83 c7 04 add rdi,0x4 247: 48 0f af c2 imul rax,rdx 24b: 48 39 f9 cmp rcx,rdi 24e: 75 f0 jne 240 <stride_left_d5+0x20> 250: 89 c2 mov edx,eax 252: 89 d0 mov eax,edx 254: c3 ret If there's no dynamic extents, it simply loads the precomputed product of static extents. For rank == 1 the answer is the constant `1`; for rank == 2 it's either 1 or extents.extent(k), with k == 0 for layout_left and k == 1 for layout_right. Consider, using Ed = std::extents<int, dyn>; int stride_left_d(const std::layout_left::mapping<Ed>& m, size_t r) { return m.stride(r); } using E3d = std::extents<int, 3, dyn>; int stride_left_3d(const std::layout_left::mapping<E3d>& m, size_t r) { return m.stride(r); } using Ed5 = std::extents<int, dyn, 5>; int stride_left_d5(const std::layout_left::mapping<Ed5>& m, size_t r) { return m.stride(r); } The optimized code for these three cases is: 0000000000000060 <stride_left_d>: 60: b8 01 00 00 00 mov eax,0x1 65: c3 ret 0000000000000090 <stride_left_3d>: 90: 48 83 fe 01 cmp rsi,0x1 94: 19 c0 sbb eax,eax 96: 83 e0 fe and eax,0xfffffffe 99: 83 c0 03 add eax,0x3 9c: c3 ret 00000000000000a0 <stride_left_d5>: a0: b8 01 00 00 00 mov eax,0x1 a5: 48 85 f6 test rsi,rsi a8: 74 02 je ac <stride_left_d5+0xc> aa: 8b 07 mov eax,DWORD PTR [rdi] ac: c3 ret For rank == 1 it simply returns 1 (as expected). For rank == 2, it either implements a branchless formula, or conditionally loads one value. In all cases involving a dynamic extent this seems like it's always doing clearly less work, both in terms of computation and loads. In cases not involving a dynamic extent, it replaces loading one value with a branchless sequence of four instructions. This commit also refactors __size to no use any of the precomputed arrays. This prevents instantiating __{fwd,rev}_partial_prods for low-rank extents. This results in a further size reduction of a reference object file (described two commits prior) by 9% from 46.0kB to 41.9kB. In a prior commit we optimized __size to produce better object code by precomputing the static products. This refactor enables the optimizer to generate the same optimized code. libstdc++-v3/ChangeLog: * include/std/mdspan (__mdspan::__fwd_prod): Optimize for rank <= 2. (__mdspan::__rev_prod): Ditto. (__mdspan::__size): Refactor to use a pre-computed product, not a partial product. Reviewed-by: Tomasz Kamiński <tkaminsk@redhat.com> Signed-off-by: Luc Grosheintz <luc.grosheintz@gmail.com>