clang emit wrong code sequence for `int16`(`short`) to `__fp16` conversion,
and that should fix the code gen directly is the right way I think,
but I found there is a FIXME comment in clang/Basic/TargetInfo.h say
that's should be removed in future so I think just let swich to using
generic LLVM IR rather than llvm.convert.to.fp16 intrinsics code gen
path is enough.
```
/// Check whether llvm intrinsics such as llvm.convert.to.fp16 should be used
/// to convert to and from __fp16.
/// FIXME: This function should be removed once all targets stop using the
/// conversion intrinsics.
virtual bool useFP16ConversionIntrinsics() const {
return true;
}
```
Reviewed By: craig.topper
Differential Revision: https://reviews.llvm.org/D124509
Test case to show the wrong code gen for `int16` -> `__fp16` conversion,
clang just emit a load and store without did conversion in the case,
and another case used for demonstrate the code gen change of `__fp16`
-> `int16`.
Reviewed By: khchen
Differential Revision: https://reviews.llvm.org/D124510
Kito Cheng