[mypyc] Generate efficient code for (some) conversions i64(x) and i32(x) #13621
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These are now optimized for i32, i64 and int arguments. I'll add optimized conversions from float in another PR once we support unboxed floats. Conversions from other types could also be improved in the future. Work on mypyc/mypyc#837.
ilevkivskyi
approved these changes
Sep 8, 2022
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These are now optimized for i32, i64 and int arguments.
i32(x)truncates fromi64, but does a range check when converting fromint. The rationale is that implicit conversions fromintperform range checks to avoid silently corrupting data, and explicit coercions use the same semantics. However, conversions fromi64toi32must be explicit and thus there is no implicit corruption possible. Truncation is also a very fast operation, which we generally prefer when working purely on native integers. A range check would introduce some overhead. I'm not sure if this is the best approach, however, and this feels a bit inconsistent.I'll add optimized conversions from float in another PR once we support unboxed floats. Conversions from other types could also be improved in the future.
Work on mypyc/mypyc#837.