Auto merge of #130223 - LaihoE:faster_str_replace, r=thomcc

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optimize str.replace

Adds a fast path for str.replace for the ascii to ascii case. This allows for autovectorizing the code. Also should this instead be done with specialization? This way we could remove one branch. I think it is the kind of branch that is easy to predict though.

Benchmark for the fast path (replace all "a" with "b" in the rust wikipedia article, using criterion) :
| N        | Speedup | Time New (ns) | Time Old (ns) |
|----------|---------|---------------|---------------|
| 2        | 2.03    | 13.567        | 27.576        |
| 8        | 1.73    | 17.478        | 30.259        |
| 11       | 2.46    | 18.296        | 45.055        |
| 16       | 2.71    | 17.181        | 46.526        |
| 37       | 4.43    | 18.526        | 81.997        |
| 64       | 8.54    | 18.670        | 159.470       |
| 200      | 9.82    | 29.634        | 291.010       |
| 2000     | 24.34   | 81.114        | 1974.300      |
| 20000    | 30.61   | 598.520       | 18318.000     |
| 1000000  | 29.31   | 33458.000     | 980540.000    |

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This commit is contained in:

bors 2024-10-17 16:20:02 +00:00

parent 6cbfed8ee6 00037a0d67

commit d74d828457

Show all changes Ignore whitespace when comparing lines Ignore changes in amount of whitespace Ignore changes in whitespace at EOL

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