| @@ -45,7 +45,8 @@ impl IndexRange { |
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#[inline] |
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pub const fn len(&self) -> usize { |
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// SAFETY: By invariant, this cannot wrap |
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-unsafe { self.end.unchecked_sub(self.start) } |
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+// Using the intrinsic because a UB check here impedes LLVM optimization. (#131563) |
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+unsafe { crate::intrinsics::unchecked_sub(self.end, self.start) } |
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} |
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/// # Safety |
| @@ -82,7 +83,8 @@ impl IndexRange { |
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let mid = if n <= self.len() { |
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// SAFETY: We just checked that this will be between start and end, |
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// and thus the addition cannot overflow. |
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-unsafe { self.start.unchecked_add(n) } |
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+// Using the intrinsic avoids a superfluous UB check. |
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+unsafe { crate::intrinsics::unchecked_add(self.start, n) } |
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} else { |
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self.end |
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}; |
| @@ -100,8 +102,9 @@ impl IndexRange { |
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pub fn take_suffix(&mut self, n: usize) -> Self { |
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let mid = if n <= self.len() { |
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// SAFETY: We just checked that this will be between start and end, |
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-// and thus the addition cannot overflow. |
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-unsafe { self.end.unchecked_sub(n) } |
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+// and thus the subtraction cannot overflow. |
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+// Using the intrinsic avoids a superfluous UB check. |
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+unsafe { crate::intrinsics::unchecked_sub(self.end, n) } |
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} else { |
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self.start |
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}; |