[MetaSchedule] Use current pass context in compile_relay, extract_tasks

[tkonolige]

Adds the pass config information necessary for tuning and compiling relay with metaschedule to the existing pass context instead of overriding the existing one. Allows users to pass in their own pass instruments, required passes, and disabled passes. This also keeps the same API used to compile relay with autotvm and auto_scheduler.

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• cc @Hzfengsy, @elvin-n, @junrushao, @quic-sanirudh _{See #10317 for details}

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[tkonolige]

@junrushao @masahi This is a change to the API for compiling relay with metaschedule tuning. I believe it to be an improvement as it keeps the same passcontext api that is used in the rest of the codebase.

[tkonolige]

@junrushao @masahi any thoughts on this? The change is from

ms.compile_relay(mod, opt_level=3)

to

with transform.PassContext(opt_level=3):
  ms.compile_relay(mod)

Although more verbose this mirrors the compilation process for non-metascheduled relay:

with transform.PassContext(opt_level=3):
  vm.compile(mod)

[junrushao]

They are intentionally designed this way to keep the primary APIs as simple as possible, for advanced usecases like you mentioned in this PR, please do not use compile_relay and extract_tasks directly, but assemble those APIs call yourself. That is being said, I am not in favor of this change

[masahi]

@junrushao Isn't it actually simplifying the API? Also considering that this changes makes the MS API consistent with other tuner APIs, I think it is a good change.

[masahi]

This also makes PRs like #13688 and #13659 unnecessary.

If we want to make the tuning API as simple as possible, we should remove all those default arguments (builder / runner / db etc, and even random seeds) that never get used in practice as well.

[masahi]

To prevent breaking user's script after this change, how about setting a default ctx with opt_level = 3 if there is no current ctx?

[tkonolige]

Right now there is no way to determine whether or not if the current pass context is the default or not. It might be possible to add though.

It is not consistent with the rest of TVM to default the opt_level to 3 in meta schedule. Everywhere else defaults to 2. This does mean that we might break some user scripts.