[mypyc] Speed up equality with optional str/bytes types #19758
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Previously these used a generic comparison primitive. Now we special case these comparisons.
p-sawicki
approved these changes
Aug 29, 2025
mypyc/irbuild/ll_builder.py
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| else: | ||
| r_none = BasicBlock() | ||
| r_not_none = BasicBlock() | ||
| # Fast path: eight value is None? |
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| # Fast path: eight value is None? | |
| # Fast path: right value is None? |
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Specialize most equality (
==and!=) operations when one of the operands isstr | Noneorbytes | None. First check if the value isNone, and based on that branch into fast path operations. Previously we used a generic C API primitive for such comparisons, which was quite slow.This could be generalized to other optional types, but let's start with
str | Nonesince it's a very common type and it's often used in equality tests.bytes | Noneis also covered, since it's very similar to thestrcase.Also add support for unchecked
Castoperations in the IR. These don't perform a runtime type check -- they can be used to narrow the static type when it can be known statically that the cast is always safe.