Optimize reference counting overhead of LOAD_FAST variants
#130704
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interpreter-core
(Objects, Python, Grammar, and Parser dirs)
performance
Performance or resource usage
type-feature
A feature request or enhancement
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mpage
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type-feature
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this issue
Apr 1, 2025
Optimize `LOAD_FAST` opcodes into faster versions that load borrowed references onto the operand stack when we can prove that the lifetime of the local outlives the lifetime of the temporary that is loaded onto the stack.
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Feature or enhancement
Proposal:
LOAD_FASTand its super instruction form are the most frequently executed bytecode instructions in most Python programs (they represent ~20% of dynamic instruction frequency on the benchmark suite). While they are very cheap (they're just an incref and a push to the stack), they are not free. If we can prove that the reference in the frame outlives the reference that is loaded on the stack we can use a cheaper variant ofLOAD_FASTthat loads an appropriately tagged borrowed reference onto the operand stack, thereby avoiding the incref/decref.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:
faster-cpython/ideas#700
Linked PRs
LOAD_FAST{_LOAD_FAST}#130708The text was updated successfully, but these errors were encountered: