Auto merge of #125720 - folkertdev:optimize_for_size-ptr-rotate, r=Am… · model-checking/verify-rust-std@4aa43c7 (original) (raw)

`@@ -71,7 +71,9 @@ pub unsafe fn ptr_rotate(mut left: usize, mut mid: *mut T, mut right: usize)

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`if (right == 0) || (left == 0) {

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`return;

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if (left + right < 24) || (mem::size_of::() > mem::size_of::<[usize; 4]>()) {

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if !cfg!(feature = "optimize_for_size")

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&& ((left + right < 24) || (mem::size_of::() > mem::size_of::<[usize; 4]>()))

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{

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`// Algorithm 1

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`// Microbenchmarks indicate that the average performance for random shifts is better all

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`` // the way until about left + right == 32, but the worst case performance breaks even

`@@ -158,7 +160,9 @@ pub unsafe fn ptr_rotate(mut left: usize, mut mid: *mut T, mut right: usize)

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`return;

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`` // T is not a zero-sized type, so it's okay to divide by its size.

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} else if cmp::min(left, right) <= mem::size_of::() / mem::size_of::() {

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} else if !cfg!(feature = "optimize_for_size")

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&& cmp::min(left, right) <= mem::size_of::() / mem::size_of::()

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{

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`// Algorithm 2

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`` // The [T; 0] here is to ensure this is appropriately aligned for T

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`let mut rawarray = MaybeUninit::<(BufType, [T; 0])>::uninit();