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12b5d3c29c
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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| .. | ||
| alloc | ||
| backtrace@5e05efa879 | ||
| core | ||
| panic_abort | ||
| panic_unwind | ||
| portable-simd | ||
| proc_macro | ||
| profiler_builtins | ||
| rtstartup | ||
| rustc-std-workspace-alloc | ||
| rustc-std-workspace-core | ||
| rustc-std-workspace-std | ||
| std | ||
| stdarch@df3618d9f3 | ||
| sysroot | ||
| test | ||
| unwind | ||