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.
* Implement Builtin.freeze for integer and integer-vector types.
https://llvm.org/docs/LangRef.html#freeze-instruction
> If the argument is undef or poison, ‘freeze’ returns an arbitrary, but fixed, value of type ‘ty’. Otherwise, this instruction is a no-op and returns the input argument. All uses of a value returned by the same ‘freeze’ instruction are guaranteed to always observe the same value, while different ‘freeze’ instructions may yield different values.
It's most importation for integer and integer-vector types because floating-point results are generally not poison (except in the case of conversion from poison integer values).
However, we might want to implement this for other types as well in the future.
* Make builtin.freeze TrivialUse
Also fix filecheck patterns for its test to work with asserts build.
