Convert variadic argument opcodes to leave their argument on the stack for JIT optimization

[Fidget-Spinner]

Feature or enhancement

Proposal:

This expands on #134584. Please read that first to get an idea.

We want to expand this to things with variadic (oparg) arguments too.

The key is to reserve an extra slot in the compiler, then swap the first and last+1 argument slots in the args array. This will allow us to insert a single result at the bottom of everything, like what we did previously.

The following call opcodes need converting, after I land the initial PR

• CALL_BUILTIN_FAST @Fidget-Spinner
• CALL_BUILTIN_FAST_WITH_KEYWORDS @Sacul0457
• CALL_METHOD_DESCRIPTOR_FAST_WITH_KEYWORDS @kumaraditya303
• CALL_METHOD_DESCRIPTOR_FAST @kumaraditya303
• CALL_BUILTIN_CLASS @corona10

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

No response

Linked PRs

• gh-148171: Convert CALL_BUILTIN_FAST to leave inputs on the stack for refcount elimination in JIT #148172
• gh-148171: convert more variadic uops to leave input on stack  #148361
• gh-148171: Convert variadic argument opcodes to leave their arguments on the stack (CALL_BUILTIN_FAST_WITH_KEYWORDS) #148366

[Fidget-Spinner]

@Sacul0457 would you like to try this out for CALL_BUILTIN_FAST_WITH_KEYWORDS or the others? Should be similar to my first PR. The idea is to:

1. Swap the first output slot (callable) with the result, and discard the callable.
2. Change the helper function to not close the arguments on failure.
3. Do the usual _POP_TOP_OPARG (for args[oparg]), _POP_TOP, _POP_TOP (however many times needed) etc.
4. Add tests.

[Sacul0457]

Yeah sure, I'll look into this!

[Sacul0457]

Hi @Fidget-Spinner,

Do the usual _POP_TOP_OPARG (for args[oparg]), _POP_TOP, _POP_TOP (however many times needed) etc.

I was looking at #148172 and I wanted to check if the extra POP_TOP was for self_or_null? Because args is handled by _POP_TOP_OPARG and callable has to be left on the stack since it is the result.

[Fidget-Spinner]

@Sacul0457

I was looking at #148172 and I wanted to check if the extra POP_TOP was for self_or_null? Because args is handled by _POP_TOP_OPARG and callable has to be left on the stack since it is the result.

Yes your understanding is correct.