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use a peekable iterator to check the first chunk

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This commit is contained in:
Erik Desjardins 2021-08-25 17:44:27 -04:00
parent c07a2eb5b4
commit adf3b013c8
1 changed files with 14 additions and 3 deletions
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17
compiler/rustc_middle/src/mir/interpret/allocation.rs
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@ -894,6 +894,14 @@ pub enum InitChunk {
}
impl InitChunk {
#[inline]
pub fn is_init(&self) -> bool {
match self {
Self::Init(_) => true,
Self::Uninit(_) => false,
}
}
#[inline]
pub fn range(&self) -> Range<Size> {
match self {
@ -1035,7 +1043,7 @@ impl InitMaskCompressed {
/// Transferring the initialization mask to other allocations.
impl<Tag, Extra> Allocation<Tag, Extra> {
/// Creates a run-length encoding of the initialization mask.
/// Creates a run-length encoding of the initialization mask; panics if range is empty.
///
/// This is essentially a more space-efficient version of
/// `InitMask::range_as_init_chunks(...).collect::<Vec<_>>()`.
@ -1053,10 +1061,13 @@ impl<Tag, Extra> Allocation<Tag, Extra> {
// where each element toggles the state.
let mut ranges = smallvec::SmallVec::<[u64; 1]>::new();
let initial = self.init_mask.get(range.start);
let mut chunks = self.init_mask.range_as_init_chunks(range.start, range.end()).peekable();
let initial = chunks.peek().expect("range should be nonempty").is_init();
// Here we rely on `range_as_init_chunks` to yield alternating init/uninit chunks.
for chunk in self.init_mask.range_as_init_chunks(range.start, range.end()) {
for chunk in chunks {
let len = chunk.range().end.bytes() - chunk.range().start.bytes();
ranges.push(len);
}