[mypyc] Add lowered primitive for unsafe list get item op #18136
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This inlines the list get item op in loops like `for x in <list>`. I estimated the impact using two microbenchmarks that iterate over `list[int]` objects. One of them was 1.3x faster, while the other was 1.09x faster. Since we now generate detailed IR for the op, instead of using a C primitive function, this also opens up further IR optimization opportunities in the future.
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This seems broken on 32-bit platforms. I may need to tweak some integer sizes. |
svalentin
approved these changes
Dec 9, 2024
mypyc/lower/list_ops.py
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| def list_item_ptr(builder: LowLevelIRBuilder, obj: Value, index: Value, line: int) -> Value: | ||
| """Get a pointer to a list item (index must be valid and non-negative). | ||
| Type of index must be c_pyssize_t_rprimitive. |
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Might be useful to add a doc/comment about the internal representation of lists.
I assume it's a just a list of pointers, and that's why we assume it's pyssize_t per element. And we translate &list[index] to list + size_t*index. (or something similar to this)
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This inlines the list get item op in loops like
for x in <list>.I estimated the impact using two microbenchmarks that iterate over
list[int]objects. One of them was 1.3x faster, while the other was 1.09x faster.Since we now generate detailed IR for the op, instead of using a C primitive function, this also opens up further IR optimization opportunities in the future.