[mypyc] feat: new primitive for int.bit_length
#19673
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BobTheBuidler
commented
Aug 16, 2025
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| // int.bit_length() | ||
| CPyTagged CPyTagged_BitLength(CPyTagged self) { | ||
| PyObject *pyint = CPyTagged_StealAsObject(self); |
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do we need this PyLong_Check?
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No, it's always an instance of int.
BobTheBuidler
commented
Aug 16, 2025
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JukkaL
reviewed
Aug 18, 2025
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| // int.bit_length() | ||
| CPyTagged CPyTagged_BitLength(CPyTagged self) { | ||
| PyObject *pyint = CPyTagged_StealAsObject(self); |
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No, it's always an instance of int.
| #if defined(__GNUC__) || defined(__clang__) | ||
| bits = (int)(CPY_BITS - CPY_CLZ(absval)); | ||
| #else | ||
| // Fallback to loop if no builtin |
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What about using _BitScanReverse[64] on MSVC (https://learn.microsoft.com/en-us/cpp/intrinsics/bitscanreverse-bitscanreverse64?view=msvc-170)?
| def bit_length(n: int) -> int: | ||
| return n.bit_length() | ||
| def test_bit_length() -> None: | ||
| assert bit_length(0) == 0 |
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Minor: This would be a bit more robust if you'd have say bit_length_python function that does return getattr(n, "bit_length")() and you can assert that bit_length(n) == bit_length_python(n).
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This PR adds a new primitive for
int.bit_lengthand is already ready for review.