[Unity] Implement R.macro for Relax macros

[kparzysz-quic]

In the same way as T.macro, R.macro support hygiene (via "hygienic" keyword), but unlike TIR macros, Relax macros produce expressions, and have to return a value: the last statement in R.macro must be "return".

[tvm-bot]

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• cc @quic-sanirudh _{See #10317 for details}

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[tvm-bot]

Thanks for contributing to TVM! Please refer to the contributing guidelines https://tvm.apache.org/docs/contribute/ for useful information and tips. Please request code reviews from Reviewers by @-ing them in a comment.

• cc @quic-sanirudh _{See #10317 for details}

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[tvm-bot]

Thanks for contributing to TVM! Please refer to the contributing guidelines https://tvm.apache.org/docs/contribute/ for useful information and tips. Please request code reviews from Reviewers by @-ing them in a comment.

• cc @quic-sanirudh _{See #10317 for details}

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[tvm-bot]

Thanks for contributing to TVM! Please refer to the contributing guidelines https://tvm.apache.org/docs/contribute/ for useful information and tips. Please request code reviews from Reviewers by @-ing them in a comment.

• cc @quic-sanirudh _{See #10317 for details}

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[kparzysz-quic]

cc: @cyx-6 @yzh119 @slyubomirsky @masahi

[junrushao]

CC @slyubomirsky if you’d love to review

[slyubomirsky]

I'll review, sorry I didn't see the pings.

[slyubomirsky]

Can macros take in Relax vars as arguments and define new Relax vars? That would be an important test case for hygienic macros. Otherwise, everything in this PR looks good to me.

edit: I think this case should simply work, but we should make sure of it. Relax var identity is determined by pointer, so creating new vars inside a macro should "just work."

[junrushao]

Any updates?

[kparzysz-quic]

Sorry, I was on vacation in the last two weeks.

Relax macros are technically SeqExprs, so they cannot define variables that are visible outside. The value of the macro is the last expression, which syntactically must be wrapped in a return expression.

[kparzysz-quic]

Rebased, and added a test for using (outside of a macro) a variable defined in a macro.

[junrushao]

Looking good to me! @slyubomirsky would you like to take a second look?