[mypyc] Use cached ASCII characters in CPyStr_GetItem#21035
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ilevkivskyi merged 1 commit intopython:masterfrom Mar 18, 2026
Merged
[mypyc] Use cached ASCII characters in CPyStr_GetItem#21035ilevkivskyi merged 1 commit intopython:masterfrom
CPyStr_GetItem#21035ilevkivskyi merged 1 commit intopython:masterfrom
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For characters < 256, use PyUnicode_FromOrdinal() which returns CPython's cached single-char Latin-1 string objects instead of allocating a new PyUnicode object on every str[i] access. This avoids allocation+deallocation overhead in character-scanning hot loops. Characters >= 256 (BMP, supplementary) keep the original PyUnicode_New allocation path unchanged.
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For characters < 256, use
PyUnicode_FromOrdinal()which returns CPython's cached single-char Latin-1 string objects instead of allocating a new PyUnicode object on everystr[i]access. This avoids allocation+deallocation overhead in character-scanning hot loops.Characters >= 256 (BMP, supplementary) keep the original
PyUnicode_Newallocation path unchanged.I ran the following micro-benchmark: Scan a 50k-character string with
s[i]in a loop (repeated the benchmark 5000 times):This was coauthored with @tobymao