Support for existentials in Embedded Swift has been available for a
little while now and appears to be solid. Remove the ability to disable
them (via `-disable-experimental-feature EmbeddedExistentials`), both
because it simplifies the code and because it's an ABI break to
disable the feature.
We don't need to export the type metadata address point alias in clients that
lazily emit other module's type metadata. There will be an exported
metadata symbol in the originating module for that purpose.
Instead, satisfy any local uses of the metadata address point uses by its
underlying address computation.
This is to workaround a bug where LLVM generates the wrong assembly for
weak aliases that point to an offset of another symbol.
```
@"$e1C7MyClassCySiGN" = weak_odr hidden alias %swift.type, getelementptr
inbounds (<{ ptr, ptr, ptr, ptr, ptr, ptr, ptr, ptr, ptr, ptr, ptr }>,
ptr @"$e1C7MyClassCySiGMf", i32 0, i32 1)
```
Generates:
```
.weak_reference _$e1C7MyClassCySiGN
.private_extern _$e1C7MyClassCySiGN
.alt_entry _$e1C7MyClassCySiGN
_$e1C7MyClassCySiGN = _$e1C7MyClassCySiGMf+8
```
Instead of
```
.weak_definition _$e1C7MyClassCySiGN
.private_extern _$e1C7MyClassCySiGN
.alt_entry _$e1C7MyClassCySiGN
_$e1C7MyClassCySiGN = _$e1C7MyClassCySiGMf+8
```
Leading for "weak"ness to be ignored and duplicate type medata symbol linkage
errors.
rdar://169573918
Find all the usages of `--enable-experimental-feature` or
`--enable-upcoming-feature` in the tests and replace some of the
`REQUIRES: asserts` to use `REQUIRES: swift-feature-Foo` instead, which
should correctly apply to depending on the asserts/noasserts mode of the
toolchain for each feature.
Remove some comments that talked about enabling asserts since they don't
apply anymore (but I might had miss some).
All this was done with an automated script, so some formatting weirdness
might happen, but I hope I fixed most of those.
There might be some tests that were `REQUIRES: asserts` that might run
in `noasserts` toolchains now. This will normally be because their
feature went from experimental to upcoming/base and the tests were not
updated.
Doug Gregor
Arnold Schwaighofer
Erik Eckstein
Kuba Mracek
Daniel Rodríguez Troitiño