38 lines
1001 B
Markdown
38 lines
1001 B
Markdown
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# Crunchy
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The crunchy unroller - deterministically unroll constant loops. For number
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"crunching".
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The Rust optimizer will unroll constant loops that don't use the loop variable,
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like this:
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```rust
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for _ in 0..100 {
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println!("Hello!");
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}
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```
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However, using the loop variable will cause it to never unroll the loop. This is
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unfortunate because it means that you can't constant-fold the loop variable, and
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if you end up stomping on the registers it will have to do a load for each
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iteration. This crate ensures that your code is unrolled and const-folded. It
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only works on literals, unfortunately, but there's a work-around:
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```rust
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debug_assert_eq!(MY_CONSTANT, 100);
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unroll! {
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for i in 0..100 {
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println!("Iteration {}", i);
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}
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}
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```
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This means that your tests will catch if you redefine the constant.
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To default maximum number of loops to unroll is `64`, but that can be easily increased using the cargo features:
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* `limit_128`
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* `limit_256`
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* `limit_512`
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* `limit_1024`
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* `limit_2048`
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