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| author | bors <bors@rust-lang.org> | 2024-06-02 00:05:32 +0000 |
|---|---|---|
| committer | bors <bors@rust-lang.org> | 2024-06-02 00:05:32 +0000 |
| commit | 12b5d3c29c221a4c61f9e6863f4bc1133f3e3403 (patch) | |
| tree | 0303b22359ad595b27095c4643cd3820ea20304f /compiler/rustc_interface/src | |
| parent | f67a1acc04c7ecbf05751b17592dd8d245b75256 (diff) | |
| parent | 245cc23a2f7d55c22437b2482f057fa44cce0624 (diff) | |
| download | rust-12b5d3c29c221a4c61f9e6863f4bc1133f3e3403.tar.gz rust-12b5d3c29c221a4c61f9e6863f4bc1133f3e3403.zip | |
Auto merge of #124294 - tspiteri:ilog-first-iter, r=the8472
Unroll first iteration of checked_ilog loop This follows the optimization of #115913. As shown in https://github.com/rust-lang/rust/pull/115913#issuecomment-2066788006, the performance was improved in all important cases, but some regressions were introduced for the benchmarks `u32_log_random_small`, `u8_log_random` and `u8_log_random_small`. Basically, #115913 changed the implementation from one division per iteration to one multiplication per iteration plus one division. When there are zero iterations, this is a regression from zero divisions to one division. This PR avoids this by avoiding the division if we need zero iterations by returning `Some(0)` early. It also reduces the number of multiplications by one in all other cases.
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