Joe Groff 57a56e5804 IRGen: Set a "not bitwise borrowable" bit in value witnesses for @_rawLayout types. ...

For types like `Atomic` and `Mutex`, we want to know that even though they are
technically bitwise-takable, they differ from other bitwise-takable types until
this point because they are not also "bitwise-borrowable"; while borrowed,
they are pinned in memory, so they cannot be passed by value as a borrowed
parameter, unlike copyable bitwise-takable types. Add a bit to the value witness
table flags to record this.

Note that this patch does not include any accompanying runtime support for
propagating the flag into runtime-instantiated type metadata. There isn't yet
any runtime functionality that varies based on this flag, so that can
be implemented separately.

rdar://136396806

2024-09-24 19:08:50 -07:00

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