What are DialectRegistry and MLIRContext, and what is their connection/relation?

Beginners
1

What are DialectRegistry and MLIRContext, and what is their connection/relation?
I see, I can do registry.insert<toy::ToyDialect>(); or context.getOrLoadDialect<toy::ToyDialect>(); context.appendDialectRegistry(registry);.
However, if I load and appendDialectRegistry, it is not the same as insert. Got confused. Clarity will be helpful.

2

Hello,

Well, I am a newbie in MLIR. But, still, I will try to answer what I learned so far.

MLIRContext
It provides mechanisms to manage dialects and other components of the MLIR ecosystem. Think of it as a Manager :smile:

DialectRegistry
DialectRegistry is a helper class used to register multiple dialects at once. Think of it as a Registrar :smile:

Relationship and Usage

  • Registering Dialects with DialectRegistry
    – Main purpose:
    The main purpose of DialectRegistry is to aggregate and register multiple dialects within the MLIRContext.

    – When it is useful
    This is useful when you have multiple dialects to register and want to manage them collectively. It’s a cleaner approach when dealing with multiple dialects.

Here’s an example of how to use it:

mlir::DialectRegistry registry;
registry.insert<toy::ToyDialect>(); // Registers the type, not an instance
registry.insert<another::AnotherDialect>(); // Registers another type

mlir::MLIRContext context;
context.appendDialectRegistry(registry); // This creates instances of the dialects and registers them

  • Registering Dialects with MLIRContext

    – Main purpose:
    This is straightforward and useful for registering a single dialect directly within the MLIRContext.

    – When it is useful
    It’s simpler when dealing with only a few dialects or when you want immediate registration.

Here’s an example of how to use it:

mlir::MLIRContext context;
context.getOrLoadDialect<toy::ToyDialect>(); // Directly creates and registers an instance of ToyDialect
context.getOrLoadDialect<another::AnotherDialect>(); // Directly creates and registers an instance of AnotherDialect

In summary:
DialectRegistry is used to manage the registration of multiple dialects collectively.

While without DialectRegistry, MLIRContext can directly manage individual dialects.

Both approaches ensure that the necessary dialects are available within the context, but target to different needs depending on whether you are dealing with multiple dialects at once or just a few.

Use of DialectRegistry with insert and appendDialectRegistry for managing multiple dialects collectively.

Use of getOrLoadDialect with MLIRContext and does not involve DialectRegistry

Hope it helps… :blush:

3

There is a difference between registering a dialect and loading one, this is explained in this FAQ: FAQ - MLIR

getOrLoadDialect is not just “registering”: it is fundamentally different.

Let me know if it isn’t clear, we can improve it.

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