[mypyc] Call generator helper method directly in await expression #19376
+251
−70
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Also use generator class as the return type of generators.
JukkaL
commented
Jul 4, 2025
| # Give a more precise type for generators, so that we can optimize | ||
| # code that uses them. They return a generator object, which has a | ||
| # specific class. Without this, the type would have to be 'object'. | ||
| ret: RType = RInstance(self.fdef_to_generator[fdef]) |
There was a problem hiding this comment.
This is the first part of the optimization.
| and val.type.class_ir.has_method(helper_method) | ||
| ): | ||
| # This is a generated generator class, and we can use a fast path. | ||
| iter_val: Value = val |
There was a problem hiding this comment.
The changes in this function implemented the bulk of the optimization.
There was a problem hiding this comment.
Maybe add a bit more detailed comment (essentially summarizing the PR description) so we will not forget the motivation.
ilevkivskyi
approved these changes
Jul 7, 2025
| and val.type.class_ir.has_method(helper_method) | ||
| ): | ||
| # This is a generated generator class, and we can use a fast path. | ||
| iter_val: Value = val |
There was a problem hiding this comment.
Maybe add a bit more detailed comment (essentially summarizing the PR description) so we will not forget the motivation.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Previously calls like
await foo()were compiled to code that included code like this (in Python-like pseudocode):In the above code,
get_coro(a)just returnsaiffoois a native async function, so we now optimize this call away. Alsonext(b)callsb.__next__(), which calls the generated generator helper method__mypyc_generator_helper__. Now we call the helper method directly, which saves some unnecessary calls.More importantly, in a follow-up PR I can easily change the way
__mypyc_generator_helper__is called, since we now call it directly. This makes it possible to avoid raising aStopIterationexception in many await expressions. The goal of this PR is to prepare for the latter optimization. This PR doesn't help performance significantly by itself.In order to call the helper method directly, I had to generate the declaration of this method and the generated generator class before the main irbuild pass, since otherwise a call site could be processed before we have processed the called generator.
I also improved test coverage of related functionality. We don't have an IR test for async calls, since the IR is very verbose. I manually inspected the generated IR to verify that the new code path works both when calling a top-level function and when calling a method. I'll later add a mypyc benchmark to ensure that we will notice if the performance of async calls is degraded.