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Check that the size optimisation is not redundant

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This commit is contained in:
varkor 2018-03-18 11:11:17 +00:00
parent 9896b38f01
commit 81edd1796b
1 changed files with 10 additions and 5 deletions
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15
src/liballoc/slice.rs
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@ -1384,8 +1384,8 @@ impl<T> [T] {
let mut indices: Vec<_> = let mut indices: Vec<_> =
$slice.iter().map($f).enumerate().map(|(i, k)| (k, i as $t)).collect(); $slice.iter().map($f).enumerate().map(|(i, k)| (k, i as $t)).collect();
// The elements of `indices` are unique, as they are indexed, so any sort will be // The elements of `indices` are unique, as they are indexed, so any sort will be
// stable with respect to the original slice. We use `sort_unstable` here because it // stable with respect to the original slice. We use `sort_unstable` here because
// requires less memory allocation. // it requires less memory allocation.
indices.sort_unstable(); indices.sort_unstable();
for i in 0..$slice.len() { for i in 0..$slice.len() {
let mut index = indices[i].1; let mut index = indices[i].1;
@ -1398,10 +1398,15 @@ impl<T> [T] {
}) })
} }
let sz_u8 = mem::size_of::<(K, u8)>();
let sz_u16 = mem::size_of::<(K, u16)>();
let sz_u32 = mem::size_of::<(K, u32)>();
let sz_usize = mem::size_of::<(K, usize)>();
let len = self.len(); let len = self.len();
if len <= ( u8::MAX as usize) { return sort_by_key!( u8, self, f) } if sz_u8 < sz_u16 && len <= ( u8::MAX as usize) { return sort_by_key!( u8, self, f) }
if len <= (u16::MAX as usize) { return sort_by_key!(u16, self, f) } if sz_u16 < sz_u32 && len <= (u16::MAX as usize) { return sort_by_key!(u16, self, f) }
if len <= (u32::MAX as usize) { return sort_by_key!(u32, self, f) } if sz_u32 < sz_usize && len <= (u32::MAX as usize) { return sort_by_key!(u32, self, f) }
sort_by_key!(usize, self, f) sort_by_key!(usize, self, f)
} }