This enables the use of reference-counted foreign reference types on Windows. As it turns out, the assertion that was failing on Windows previously was unnecessary. This also enabled many of the tests on Windows.
rdar://154694125 / resolves https://github.com/swiftlang/swift/issues/82643
Most of the logic for C++ foreign reference types can be applied to C types as well. Swift had a compiler flag `-Xfrontend -experimental-c-foreign-reference-types` for awhile now which enables foreign reference types without having to enable C++ interop. This change makes it the default behavior.
Since we don't expect anyone to pass `experimental-c-foreign-reference-types` currently, this also removes the frontend flag.
rdar://150308819
PredictableMemoryAccessOptimizations has become unmaintainable as-is.
RedundantLoadElimination does (almost) the same thing as PredictableMemoryAccessOptimizations.
It's not as powerful but good enough because PredictableMemoryAccessOptimizations is actually only needed for promoting integer values for mandatory constant propagation.
And most importantly: RedundantLoadElimination does not insert additional copies which was a big problem in PredictableMemoryAccessOptimizations.
Fixes rdar://142814676
This test has been disabled since 2022.
This re-enables the test in order to have some test coverage of the `-experimental-c-foreign-reference-types` compiler flag.
See `test/Interop/Cxx/foreign-reference/reference-counted.swift` for a very similar test that enables C++ interop.
rdar://101790203
