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Simplify bits_for_tags impl

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This commit is contained in:
Maybe Waffle 2023-04-20 19:24:04 +00:00
parent 7cfecf26f7
commit ad8c7b6705
1 changed files with 3 additions and 13 deletions
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16
compiler/rustc_data_structures/src/tagged_ptr.rs
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@ -155,7 +155,9 @@ pub const fn bits_for_tags(mut tags: &[usize]) -> u32 {
while let &[tag, ref rest @ ..] = tags {
tags = rest;
let b = bits_for_tag(tag);
// bits required to represent `tag`,
// position of the most significant 1
let b = usize::BITS - tag.leading_zeros();
if b > bits {
bits = b;
}
@ -164,18 +166,6 @@ pub const fn bits_for_tags(mut tags: &[usize]) -> u32 {
bits
}
/// Returns `(size_of::<usize>() * 8) - tag.leading_zeros()`
const fn bits_for_tag(mut tag: usize) -> u32 {
let mut bits = 0;
while tag > 0 {
bits += 1;
tag >>= 1;
}
bits
}
unsafe impl<T: ?Sized + Aligned> Pointer for Box<T> {
const BITS: u32 = bits_for::<Self::Target>();