Part 0/3 is D50119: it adds __has_extension(__is_trivially_relocatable) to the compiler.
Part 1/3 is D61761: it implements the library traits and algorithms mandated by P1144.
Part 2/3 is D63620: it implements Quality-of-Implementation features to warrant certain std library types as "trivially relocatable."
Part 3/3 is D67524: it implements Quality-of-Implementation features to optimize certain std library functions for better performance on types that have been warranted "trivially relocatable."
This patch has no ABI implications (or if it does, that's a bug, please tell me about it).
Notes on optimizations that I've made for https://p1144.godbolt.org/z/q2N_Ln but which are not part of this patch:
- std::any can be made trivially relocatable, by changing _IsSmallObject to be false for non-trivially-relocatable types. However, that would break ABI.