[Mlir-commits] [mlir] [mlir][emitc] Restrict types in EmitC (PR #88391)

[Tina Jung]

TinaAMD wrote:

Assuming you would expect a bfloat16 represented as follows in your C code:

```
reprOfYourBf16Type myVar; // Variable declaration of myVar with the bfloat16 type
```
When you convert from some dialect that uses bfloat16 to EmitC, you can add a [type converter](https://mlir.llvm.org/docs/DialectConversion/#type-conversion) that describes what your type will look like in EmitC.
Converting bfloat16 could look similar to this:

```
TypeConverter typeConverter;
typeConverter.addConversion([this](Type type) -> std::optional<Type> {
  // Convert bfloat16 to emitc.opaque
  if (type.isBF16()) {
    return emitc::OpaqueType::get(this->getContext(), "reprOfYourBf16Type");
  }
  // ...possibly more conversions....
  return type;  // default for all types which are allowed in EmitC
});
```

https://github.com/llvm/llvm-project/pull/88391