Use unchecked_sub in split_at
#124699
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Use unchecked_sub in split_at
#124699
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| @@ -2035,7 +2035,12 @@ impl<T> [T] { | |||
| // | |||
| // `[ptr; mid]` and `[mid; len]` are not overlapping, so returning a mutable reference | |||
| // is fine. | |||
| unsafe { (from_raw_parts_mut(ptr, mid), from_raw_parts_mut(ptr.add(mid), len - mid)) } | |||
| unsafe { | |||
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two local variables for the left and right sides would have been nice here to reduce the lines from 6 to 3 :3, things like this are certainly formative of your opinions about rustfmt 😆 (though i can't really complain, it's doing its best)
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Yeah, my preferred philosophical underpinnings for a formatter are pretty different from those that rustfmt picked :(
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@bors r+ rollup |
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r? Nilstrieb |
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…_use_unchecked, r=Nilstrieb Use `unchecked_sub` in `split_at` LLVM currently isn't figuring it out on its own, even in the checked version where it hypothetically could. Before: <https://rust.godbolt.org/z/PEY38YrKs> ```llvm bb1: ; preds = %start %4 = getelementptr inbounds float, ptr %x.0, i64 %n %5 = sub i64 %x.1, %n ``` After: ```llvm bb1: ; preds = %start %4 = getelementptr inbounds float, ptr %x.0, i64 %n %5 = sub nuw i64 %x.1, %n ``` This is not using the wrapper because there's already a ubcheck covering it, so I don't want this to get a second one once rust-lang#121571 lands. --- This is basically the same as rust-lang#108763, since `split_at` is essentially doing two `get_unchecked`s.
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…iaskrgr Rollup of 5 pull requests Successful merges: - rust-lang#122441 (Improve several `Read` implementations) - rust-lang#124584 (Various improvements to entrypoint code) - rust-lang#124699 (Use `unchecked_sub` in `split_at`) - rust-lang#124704 (Fix ignored tests for formatting) - rust-lang#124709 (Miri subtree update) r? `@ghost` `@rustbot` modify labels: rollup
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…iaskrgr Rollup of 5 pull requests Successful merges: - rust-lang#122441 (Improve several `Read` implementations) - rust-lang#124584 (Various improvements to entrypoint code) - rust-lang#124699 (Use `unchecked_sub` in `split_at`) - rust-lang#124704 (Fix ignored tests for formatting) - rust-lang#124709 (Miri subtree update) r? `@ghost` `@rustbot` modify labels: rollup
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…iaskrgr Rollup of 4 pull requests Successful merges: - rust-lang#122441 (Improve several `Read` implementations) - rust-lang#124584 (Various improvements to entrypoint code) - rust-lang#124699 (Use `unchecked_sub` in `split_at`) - rust-lang#124715 (interpret, miri: uniform treatments of intrinsics/functions with and without return block) r? `@ghost` `@rustbot` modify labels: rollup
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Rollup merge of rust-lang#124699 - scottmcm:split_at_unchecked_should_use_unchecked, r=Nilstrieb Use `unchecked_sub` in `split_at` LLVM currently isn't figuring it out on its own, even in the checked version where it hypothetically could. Before: <https://rust.godbolt.org/z/PEY38YrKs> ```llvm bb1: ; preds = %start %4 = getelementptr inbounds float, ptr %x.0, i64 %n %5 = sub i64 %x.1, %n ``` After: ```llvm bb1: ; preds = %start %4 = getelementptr inbounds float, ptr %x.0, i64 %n %5 = sub nuw i64 %x.1, %n ``` This is not using the wrapper because there's already a ubcheck covering it, so I don't want this to get a second one once rust-lang#121571 lands. --- This is basically the same as rust-lang#108763, since `split_at` is essentially doing two `get_unchecked`s.
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LLVM currently isn't figuring it out on its own, even in the checked version where it hypothetically could.
Before: https://rust.godbolt.org/z/PEY38YrKs
After:
This is not using the wrapper because there's already a ubcheck covering it, so I don't want this to get a second one once #121571 lands.
This is basically the same as #108763, since
split_atis essentially doing twoget_uncheckeds.