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Improve documentation around allocation accessors

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This commit is contained in:
Andreas Molzer 2019-08-31 17:01:56 +02:00
parent 7388cb4cf8
commit 823c3b9845
1 changed files with 13 additions and 8 deletions
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21
src/librustc/mir/interpret/allocation.rs
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@ -581,8 +581,10 @@ impl<'tcx, Tag, Extra> Allocation<Tag, Extra> {
/// Run-length encoding of the undef mask.
/// Used to copy parts of a mask multiple times to another allocation.
pub struct AllocationDefinedness {
/// The lengths of ranges that are run-length encoded.
ranges: smallvec::SmallVec::<[u64; 1]>,
first: bool,
/// The definedness of the first range.
initial: bool,
}
/// Transferring the definedness mask to other allocations.
@ -606,9 +608,9 @@ impl<Tag, Extra> Allocation<Tag, Extra> {
// where each element toggles the state
let mut ranges = smallvec::SmallVec::<[u64; 1]>::new();
let first = self.undef_mask.get(src.offset);
let initial = self.undef_mask.get(src.offset);
let mut cur_len = 1;
let mut cur = first;
let mut cur = initial;
for i in 1..size.bytes() {
// FIXME: optimize to bitshift the current undef block's bits and read the top bit
@ -623,7 +625,7 @@ impl<Tag, Extra> Allocation<Tag, Extra> {
ranges.push(cur_len);
AllocationDefinedness { ranges, first, }
AllocationDefinedness { ranges, initial, }
}
/// Apply multiple instances of the run-length encoding to the undef_mask.
@ -640,7 +642,7 @@ impl<Tag, Extra> Allocation<Tag, Extra> {
self.undef_mask.set_range_inbounds(
dest.offset,
dest.offset + size * repeat,
defined.first,
defined.initial,
);
return;
}
@ -648,7 +650,7 @@ impl<Tag, Extra> Allocation<Tag, Extra> {
for mut j in 0..repeat {
j *= size.bytes();
j += dest.offset.bytes();
let mut cur = defined.first;
let mut cur = defined.initial;
for range in &defined.ranges {
let old_j = j;
j += range;
@ -725,9 +727,9 @@ impl<Tag: Copy, Extra> Allocation<Tag, Extra> {
// shift offsets from source allocation to destination allocation
offset + dest_offset - src.offset,
reloc,
)
)
})
);
);
}
AllocationRelocations {
@ -735,6 +737,9 @@ impl<Tag: Copy, Extra> Allocation<Tag, Extra> {
}
}
/// Apply a relocation copy.
/// The affected range, as defined in the parameters to `prepare_relocation_copy` is expected
/// to be clear of relocations.
pub fn mark_relocation_range(
&mut self,
relocations: AllocationRelocations<Tag>,