Many uses of std::numeric_limits in C++17 and C++20 features only really
need the min(), max() and digits constants for integral types. By adding
__detail::__int_limits we can avoid including the whole <limits> header.
The <limits> header isn't especially large, but avoiding it still gives
small savings in compilation time and memory usage for the compiler.
There are also C++11 features that could benefit from this change (e.g.
<bits/hashtable_policy.h> and <bits/uniform_int_dist.h>) but I won't
change those until stage 1.
The implementation of __int_limits assumes two's complement integers,
which is true for all targets supported by GCC.
PR libstdc++/92546 (partial)
* include/Makefile.am: Add new header.
* include/Makefile.in: Regenerate.
* include/bits/int_limits.h: New header.
* include/bits/parse_numbers.h (__select_int::_Select_int): Replace
numeric_limits with __detail::__int_limits.
* include/std/bit (__rotl, __rotr, __countl_zero, __countl_one)
(__countr_zero, __countr_one, __popcount, __ceil2, __floor2, __log2p1):
Likewise.
* include/std/charconv (__to_chars_8, __from_chars_binary)
(__from_chars_alpha_to_num, from_chars): Likewise.
* include/std/memory_resource (polymorphic_allocator::allocate)
(polymorphic_allocator::allocate_object): Likewise.
* include/std/string_view (basic_string_view::_S_compare): Likewise.
* include/std/utility (in_range): Likewise.
* testsuite/20_util/integer_comparisons/in_range_neg.cc: Adjust for
extra error about incomplete type __int_limits<bool>.
* testsuite/26_numerics/bit/bit.count/countl_one.cc: Include <limits>.
* testsuite/26_numerics/bit/bit.count/countl_zero.cc: Likewise.
* testsuite/26_numerics/bit/bit.count/countr_one.cc: Likewise.
* testsuite/26_numerics/bit/bit.count/countr_zero.cc: Likewise.
* testsuite/26_numerics/bit/bit.count/popcount.cc: Likewise.
* testsuite/26_numerics/bit/bit.pow.two/ceil2_neg.cc: Likewise.
* testsuite/26_numerics/bit/bit.pow.two/ceil2.cc: Likewise.
* testsuite/26_numerics/bit/bit.pow.two/floor2.cc: Likewise.
* testsuite/26_numerics/bit/bit.pow.two/ispow2.cc: Likewise.
* testsuite/26_numerics/bit/bit.pow.two/log2p1.cc: Likewise.
* testsuite/26_numerics/bit/bit.rotate/rotl.cc: Likewise.
* testsuite/26_numerics/bit/bit.rotate/rotr.cc: Likewise.
* include/std/type_traits (__is_standard_integer): New helper trait.
* include/std/utility (cmp_equal, cmp_not_equal, cmp_less, cmp_greater)
(cmp_less_equal, cmp_greater_equal, in_range): Define for C++20.
* include/std/version (__cpp_lib_integer_comparison_functions): Define.
* testsuite/20_util/integer_comparisons/1.cc: New test.
* testsuite/20_util/integer_comparisons/2.cc: New test.
* testsuite/20_util/integer_comparisons/equal.cc: New test.
* testsuite/20_util/integer_comparisons/equal_neg.cc: New test.
* testsuite/20_util/integer_comparisons/greater_equal.cc: New test.
* testsuite/20_util/integer_comparisons/greater_equal_neg.cc: New test.
* testsuite/20_util/integer_comparisons/greater_neg.cc: New test.
* testsuite/20_util/integer_comparisons/in_range.cc: New test.
* testsuite/20_util/integer_comparisons/in_range_neg.cc: New test.
* testsuite/20_util/integer_comparisons/less.cc: New test.
* testsuite/20_util/integer_comparisons/less_equal.cc: New test.
* testsuite/20_util/integer_comparisons/less_equal_neg.cc: New test.
* testsuite/20_util/integer_comparisons/less_neg.cc: New test.
* testsuite/20_util/integer_comparisons/not_equal.cc: New test.
* testsuite/20_util/integer_comparisons/not_equal_neg.cc: New test.
