58708151ec
This is part of https://discourse.llvm.org/t/rfc-introduce-opasm-type-attr-interface-for-pretty-print-in-asmprinter/83792. Verbose printing of commonly used type/attribute that is long could severely reduce the readablity of the resulting assembly, and it has been asked several times in the LLVM discourse how to generate alias. Cc @ftynse ### Discussion * I am not sure where to put the markdown, so I put it in `mlir/docs/`. * Documentation on `OpAsmOpInterface` (controlling `AsmResultName`/`BlockArgName`/etc) could also be added in this markdown, so I used the title `Customizing AsmPrinter Behavior` and let further PR to update the content.
51 lines
2.0 KiB
Markdown
51 lines
2.0 KiB
Markdown
# Customizing Assembly Behavior
|
|
|
|
[TOC]
|
|
|
|
## Generating Aliases
|
|
|
|
To reduce verbosity in the resulting assembly, `AsmPrinter` can generate aliases for frequently used types and attributes.
|
|
|
|
For example, `!my_dialect.type<a=3,b=4,c=5,d=tuple,e=another_type>` and `#my_dialect.attr<a=3>` can be aliased to `!my_dialect_type` and `#my_dialect_attr`, simplifying further references.
|
|
|
|
To enable this, the owning dialect of these types/attributes can define an interface to hook into the `AsmPrinter`. This is effective only when the assembly is not printed in generic form.
|
|
|
|
```cpp
|
|
// OpAsmDialectInterface is defined in
|
|
// https://github.com/llvm/llvm-project/blob/91ab10e8d6c256d841da1a1a1b47c334e08d95b9/mlir/include/mlir/IR/OpImplementation.h#L1738
|
|
struct MyDialectOpAsmDialectInterface : public OpAsmDialectInterface {
|
|
public:
|
|
using OpAsmDialectInterface::OpAsmDialectInterface;
|
|
|
|
AliasResult getAlias(Type type, raw_ostream& os) const override {
|
|
if (mlir::isa<MyType>(type)) {
|
|
os << "my_dialect_type";
|
|
// Could return OverridableAlias when
|
|
// allowing other dialect to override the alias.
|
|
//
|
|
// Other dialects are allowed to provide alias for
|
|
// type/attribute not owned by them
|
|
// but the final result would depend on the registration order
|
|
// of these dialects in the MLIRContext
|
|
return AliasResult::FinalAlias;
|
|
}
|
|
return AliasResult::NoAlias;
|
|
}
|
|
|
|
AliasResult getAlias(Attribute attr, raw_ostream& os) const override {
|
|
if (mlir::isa<MyAttribute>(attr)) {
|
|
os << "my_dialect_attr";
|
|
return AliasResult::FinalAlias;
|
|
}
|
|
return AliasResult::NoAlias;
|
|
}
|
|
};
|
|
|
|
void MyDialect::initialize() {
|
|
// register the interface to the dialect
|
|
addInterface<MyDialectOpAsmDialectInterface>();
|
|
}
|
|
```
|
|
|
|
* If `getAlias` provides an alias with a trailing digit, `AsmPrinter` appends an underscore to avoid conflicts with autogenerated IDs.
|
|
* If multiple types/attributes have the same alias from `getAlias`, a number is appended to the alias to avoid conflicts. |