How to add a relay pass

Questions
#1

From the tvm docs, there are two ways to implement a pass: Using Python Decorator or Use C++. I found most relay passes are implemented by C++, such as fold_constant, etc,. Only one pass named ChangeBatch(https://github.com/apache/tvm/blob/main/python/tvm/relay/transform/transform.py#L1062) is impled using Python Decorator.

So if I want to add a custom relay pass, is it better to implemented it by C++?

#2

both implementions is ok. in most condition, writing python pass is enough.

#3

But there are few examples of passes writing by python. Only one pass named ChangeBatch is writen by python. So it may be hard for pass beginers.

BTY, if I want to insert a op to the relay graph ir, I should use module-level pass?

#4

Hi, @zhaoyang-star.

I believe that is because Python interface is more recommended for the quick tryout, rather than the formal integration. If you are planning to push your pass to the main branch, I think C++ implementation is generally recommended.

You can either use a module-level pass or a relay function-level pass. But since a function-level pass applies transformation for each relay function independently, you would need to use a module-level pass if you want to make change across functions.

#5

Thanks for your kind reply.