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gh-124951: Optimize base64 encode & decode for an easy 2-3x speedup [no SIMD] #143262

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Merged
gpshead merged 13 commits into from
Jan 2, 2026
+134 −23
Merged

gh-124951: Optimize base64 encode & decode for an easy 2-3x speedup [no SIMD] #143262

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2d2be30
Add base64 benchmark tool and optimize encoding/decoding
gpshead Dec 28, 2025
573eaf3
Fix MSVC build: move table_b2a_base64 before inline functions
gpshead Dec 29, 2025
eaac671
NEWS entry
gpshead Dec 29, 2025
060dbf5
Add a whatsnew entry
gpshead Dec 29, 2025
1e12273
expose the benchmark defaults in the help text.
gpshead Dec 29, 2025
ef38895
Align base64 tables to 64-byte cache line boundaries
gpshead Dec 29, 2025
7458c99
Use BASE64_PAD macro instead of literal '=' in fast path
gpshead Dec 29, 2025
1f8ff74
Simplify block comment for base64 helpers
gpshead Dec 29, 2025
4b1245b
Remove binasciibench in favor of pyperformance bm_base64 addition PR.
gpshead Dec 29, 2025
4b50c73
reword L1 cache line comment
gpshead Jan 2, 2026
f7b27ee
doc Contributed by
gpshead Jan 2, 2026
2b13b81
Remove redundant PAD check in base64 decode fast path
gpshead Jan 2, 2026
30976a9
Use pointer increment in base64_encode_fast
gpshead Jan 2, 2026
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reword L1 cache line comment
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@gpshead
gpshead committed Jan 2, 2026
commit 4b50c736df0c434f313d0a956e9e97921433e179
4 changes: 2 additions & 2 deletions Modules/binascii.c
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Original file line number Diff line number Diff line change
Expand Up @@ -76,7 +76,7 @@ get_binascii_state(PyObject *module)
}


/* Align to 64 bytes to ensure table fits in a single L1 cache line */
/* Align to 64 bytes for L1 cache line friendliness */
static const unsigned char table_a2b_base64[] Py_ALIGNED(64) = {
-1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
-1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1, -1,-1,-1,-1,
Expand Down Expand Up @@ -108,7 +108,7 @@ static const unsigned char table_a2b_base64[] Py_ALIGNED(64) = {
* Process complete groups without loop-carried dependencies.
*/

/* Align to 64 bytes to ensure table fits in a single L1 cache line */
/* Align to 64 bytes for L1 cache line friendliness */
static const unsigned char table_b2a_base64[] Py_ALIGNED(64) =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

Expand Down