mypy

c591c891 - [mypyc] Implement lowering pass and add primitives for int (in)equality (#17027)

[mypyc] Implement lowering pass and add primitives for int (in)equality (#17027) Add a new `PrimitiveOp` op which can be transformed into lower-level ops in a lowering pass after reference counting op insertion pass. Higher-level ops in IR make it easier to implement various optimizations, and the output of irbuild test cases will be more compact and readable. Implement the lowering pass. Currently it's pretty minimal, and I will add additional primitives and the direct transformation of various primitives to `CallC` ops in follow-up PRs. Currently primitives that map to C calls generate `CallC` ops in the main irbuild pass, but the long-term goal is to only/mostly generate `PrimitiveOp`s instead of `CallC` ops during the main irbuild pass. Also implement primitives for tagged integer equality and inequality as examples. Lowering of primitives is implemented using decorated handler functions in `mypyc.lower` that are found based on the name of the primitive. The name has no other significance, though it's also used in pretty-printed IR output. Work on mypyc/mypyc#854. The issue describes the motivation in more detail.