checked_ilog: improve performance by FedericoStra · Pull Request #115913

checked_ilog: improve performance by FedericoStra · Pull Request #115913 · rust-lang/rust

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Sep 17, 2023

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Sep 17, 2023

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Feb 29, 2024

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Apr 21, 2024

bors added a commit to rust-lang-ci/rust that referenced this pull request

Apr 22, 2024

checked_ilog: improve performance

Addresses rust-lang#115874.

(This PR replicates the original rust-lang#115875, which I accidentally closed by deleting my forked repository...)

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Apr 22, 2024

bors added a commit to rust-lang-ci/rust that referenced this pull request

Apr 22, 2024

…llaumeGomez

Rollup of 7 pull requests

Successful merges:

 - rust-lang#115913 (checked_ilog: improve performance)
 - rust-lang#124178 ([cleanup] [llvm backend] Prevent creating the same `Instance::mono` multiple times)
 - rust-lang#124183 (Stop taking `ParamTy`/`ParamConst`/`EarlyParamRegion`/`AliasTy` by ref)
 - rust-lang#124217 (coverage: Prepare for improved branch coverage)
 - rust-lang#124230 (Stabilize generic `NonZero`.)
 - rust-lang#124252 (Improve ICE message for forbidden dep-graph reads.)
 - rust-lang#124268 (Update books)

r? `@ghost`
`@rustbot` modify labels: rollup

bors added a commit to rust-lang-ci/rust that referenced this pull request

Apr 23, 2024

…llaumeGomez

Rollup of 7 pull requests

Successful merges:

 - rust-lang#115913 (checked_ilog: improve performance)
 - rust-lang#124178 ([cleanup] [llvm backend] Prevent creating the same `Instance::mono` multiple times)
 - rust-lang#124183 (Stop taking `ParamTy`/`ParamConst`/`EarlyParamRegion`/`AliasTy` by ref)
 - rust-lang#124217 (coverage: Prepare for improved branch coverage)
 - rust-lang#124230 (Stabilize generic `NonZero`.)
 - rust-lang#124252 (Improve ICE message for forbidden dep-graph reads.)
 - rust-lang#124268 (Update books)

r? `@ghost`
`@rustbot` modify labels: rollup

rust-timer added a commit to rust-lang-ci/rust that referenced this pull request

Apr 23, 2024

Rollup merge of rust-lang#115913 - FedericoStra:checked_ilog, r=the8472

checked_ilog: improve performance

Addresses rust-lang#115874.

(This PR replicates the original rust-lang#115875, which I accidentally closed by deleting my forked repository...)

matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request

Jun 1, 2024

Unroll first iteration of checked_ilog loop

This follows the optimization of rust-lang#115913. As shown in rust-lang#115913 (comment), 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, rust-lang#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.

matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request

Jun 1, 2024

Unroll first iteration of checked_ilog loop

This follows the optimization of rust-lang#115913. As shown in rust-lang#115913 (comment), 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, rust-lang#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.

matthiaskrgr added a commit to matthiaskrgr/rust that referenced this pull request

Jun 1, 2024

Unroll first iteration of checked_ilog loop

This follows the optimization of rust-lang#115913. As shown in rust-lang#115913 (comment), 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, rust-lang#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.

fmease added a commit to fmease/rust that referenced this pull request

Jun 1, 2024

Unroll first iteration of checked_ilog loop

This follows the optimization of rust-lang#115913. As shown in rust-lang#115913 (comment), 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, rust-lang#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.

bors added a commit to rust-lang-ci/rust that referenced this pull request

Jun 2, 2024

Unroll first iteration of checked_ilog loop

This follows the optimization of rust-lang#115913. As shown in rust-lang#115913 (comment), 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, rust-lang#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.

github-actions bot pushed a commit to rust-lang/miri that referenced this pull request

Jun 5, 2024

Unroll first iteration of checked_ilog loop

This follows the optimization of #115913. As shown in rust-lang/rust#115913 (comment), 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.

bors added a commit to rust-lang/rust-analyzer that referenced this pull request

Jun 20, 2024

Unroll first iteration of checked_ilog loop

This follows the optimization of #115913. As shown in rust-lang/rust#115913 (comment), 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.

flip1995 pushed a commit to flip1995/rust-clippy that referenced this pull request

Jun 28, 2024

Unroll first iteration of checked_ilog loop

This follows the optimization of #115913. As shown in rust-lang/rust#115913 (comment), 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.

Kobzol pushed a commit to Kobzol/portable-simd that referenced this pull request

Feb 3, 2026

Unroll first iteration of checked_ilog loop

This follows the optimization of #115913. As shown in rust-lang/rust#115913 (comment), 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.