Extend memcpy, memmove and memcmp optimizations

[Adam Bucior (AdamBucior)]

Fixes #431.

Product code changes

• Extended memcpy and memmove optimizations to not require is_trivially_copyable and is_trivial but just is_trivially_copy_constructible, is_trivially_move_constructible, is_trivially_copy_assignable or is_trivially_move_assignable depending on operation.
• Renamed _Ptr_copy_cat and _Ptr_move_cat to _Iter_copy_cat and _Iter_move_cat because they no longer work only on pointers.
• Fixed move_iterator handling in memcpy/memmove optimizations by specializing _To_address for it so that it doesn't warn about deprecated move_iterator::operator->.
• Extended memcpy, memmove and memcmp optimization to handle pointers to pointer-interconvertible types.
• Special cased nullptr_t in _Is_all_bits_zero.
• Refactored _Lex_compare_memcmp_classify and extended it to bools.
• Extended memcmp in lexicographical_compare_three_way to handle comparators like strong_order, weak_order and partial_order.
• Extended memcmp optimization to handle non-transparent functors (ex. to enable optimization in equal when using int, unsigned int and equal_to<int>. This also enables memcmp optimization with enums when using functor that converts them to their underlying type).
• Disabled memcpy and memmove optimization for volatile.
• Enabled memcpy optimization for const destination in (ranges::)unitialized_(copy|move)(_n) algorithms (see <memory>: uninitialized_meow should handle voidify's wording #1780).

Test changes

• Removed VSO_0180469_ptr_cat in favor of more detailed GH_000431_iter_copy_move_cat, GH_000431_equal_memcmp_is_safe and GH_000431_lex_compare_memcmp_classify.
• Inspired by VSO_0180469_fill_family added GH_000431_copy_move_family, GH_000431_equal_family and GH_000431_lex_compare_family to test that all of the optimizations work well (also the Some StdLib algorithms fail /std:c++latest compilation with custom contiguous iterators (Visual Studio 2019 16.8) #1523 test from VSO_0180469_ptr_cat was moved to GH_000431_equal_family).
• Fix P0202R3_constexpr_algorithm_and_exchange to define all necessary typedefs in output_pointer.

[Adam Bucior (AdamBucior)]

WOW, how is it possible that is_trivially_constructible_v<float, int> is true? That seems ridiculous. What's the real point of this trait?

[Alex Guteniev (AlexGuteniev)]

While having separate tests is more modular, and gives a better idea what failed when a test fails, they contribute to test execution time. Not sure what is more important.

[Adam Bucior (AdamBucior)]

Having them separate is better for development because you only run one of them and not all of them which would take much more time. Also I already had problems with GH_000431_lex_compare_memcmp_classify test failing on x86 due to compiler running out of memory.

[Stephan T. Lavavej (StephanTLavavej)]

I agree with both of you! 😸 There is definitely a test throughput concern with having lots of small test directories, but in this case I believe that it's reasonable to have separate directories for the reasons that Adam Bucior (@AdamBucior) stated.

[Stephan T. Lavavej (StephanTLavavej)]

Thanks - looking good so far, I've partially reviewed the product code (leaving a note to myself where I paused) in a video review. Will continue reviewing this later. 😸

[Stephan T. Lavavej (StephanTLavavej)]

Thanks - reviewed this in part 2 of the video review. Looked at the rest of <xutility>, still need to review the test code.

[Stephan T. Lavavej (StephanTLavavej)]

Finished reviewing the tests! Looks good, should need just one more round of minor changes. Thanks again for this major PR.

[Stephan T. Lavavej (StephanTLavavej)]

Thanks! I pushed two small commits, one to use if constexpr (promoted) for all compilers as Clang was correctly enforcing the Standard rule, and another to use dual-range equal() when a predicate is being passed.

[Stephan T. Lavavej (StephanTLavavej)]

I'm mirroring this to an MSVC-internal PR. Please notify me if any further changes are pushed.

[Stephan T. Lavavej (StephanTLavavej)]

I pushed workarounds for VSO-1409786 "/clr:pure BE assertion !tupLength || TU_SIZE(tup) == TU_IVAL(tupLength) in src\vctools\Compiler\Utc\src\p2\tuple.c line 6189" and VSO-1409862 "/clr and /clr:pure emit fatal error C1060: compiler is out of heap space for a not-very-pathological test".

[Stephan T. Lavavej (StephanTLavavej)]

Thanks to Jonathan Emmett (@joemmett), I've pushed a mechanical refactoring of the GH_000431_equal_memcmp_is_safe test that dramatically improves compiler memory consumption. This performs STATIC_ASSERTs at every level, guards the lambda with _HAS_CXX17 as we need constexpr lambdas now, and (importantly) removes the top-level function, so the top-level STATIC_ASSERTs are at namespace scope. This allows the compiler to free more memory between each STATIC_ASSERT. (Jonathan has also fixed the compiler to improve its behavior, but this refactoring is helpful both before and after his fix.) For x86 native, this improves compiler memory consumption as reported by /d1reportMemorySummary peak working set size from 807.7 MB to 283.3 MB.

Jonathan also confirmed that /clr:pure still needs to emit dynamic initializers for 150,000 variable template specializations (because /clr:pure lacks static initialization), which is why compilation still takes forever - so I am skipping it with the impure_matrix.lst. This is a perma-workaround so it isn't marked TRANSITION.

[Stephan T. Lavavej (StephanTLavavej)]

Thanks for this major optimization overhaul! 🚀 😻 ⚡