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replace if with match in binary_search #106969

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replace if with match in binary_search #106969

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c76ee15
replace 'if' with 'match'
a1393323447 Jan 17, 2023
b5155ee
add `Ordering`
a1393323447 Jan 17, 2023
aa2a968
remove extra whitespace
a1393323447 Jan 17, 2023
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23 changes: 10 additions & 13 deletions library/core/src/slice/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -2480,20 +2480,17 @@ impl<T> [T] {
// coupled with the `left + size <= self.len()` invariant means
// we have `left + size/2 < self.len()`, and this is in-bounds.
let cmp = f(unsafe { self.get_unchecked(mid) });

// The reason why we use if/else control flow rather than match
// is because match reorders comparison operations, which is perf sensitive.
// This is x86 asm for u8: https://rust.godbolt.org/z/8Y8Pra.
if cmp == Less {
left = mid + 1;
} else if cmp == Greater {
right = mid;
} else {
// SAFETY: same as the `get_unchecked` above
unsafe { crate::intrinsics::assume(mid < self.len()) };
return Ok(mid);

match cmp {
Less => left = mid + 1,
Greater => right = mid,
Equal => {
// SAFETY: same as the `get_unchecked` above
unsafe { crate::intrinsics::assume(mid < self.len()) };
return Ok(mid);
}
}

size = right - left;
}

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