Clarify zero-value behavior of ctlz/cttz intrinsics.
#38310
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Hold off on reviewing. Going to discuss this at this week's docs team meeting. |
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@frewsxcv Ok, let me know when you're ready. |
| @@ -1156,10 +1156,44 @@ extern "rust-intrinsic" { | |||
| /// Returns the number of bits set in an integer type `T` | |||
| pub fn ctpop<T>(x: T) -> T; | |||
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| /// Returns the number of leading bits unset in an integer type `T` | |||
| /// Returns the number of leading unset bits (zeroes) in an integer type `T`. Unlike the | |||
| /// underlying LLVM intrinsic, an `x` with value `0` will always return the bit width of `T`. | |||
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First of all, underlying LLVM intrinsic has a prototype that looks like this:
declare iXYZ @llvm.ctlz.iXYZ(iXYZ <src>, i1 <is_zero_undef>)
so comparing it to the underlying LLVM intrinsic is not quite right :)
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I could just ditch this sentence and not talk about LLVM but leave the x = 0 example.
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Removed that sentence in the latest force push.
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@bors r+ rollup |
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📌 Commit a99f70b has been approved by |
Clarify zero-value behavior of `ctlz`/`cttz` intrinsics. Fixes rust-lang#34381.
Clarify zero-value behavior of `ctlz`/`cttz` intrinsics. Fixes rust-lang#34381.
Clarify zero-value behavior of `ctlz`/`cttz` intrinsics. Fixes #34381.
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☀️ Test successful - status-appveyor, status-travis |
Fixes #34381.