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rustc_arena: tweak some comments.

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This commit is contained in:
Nicholas Nethercote
2023-09-19 17:08:13 +10:00
parent 2ba4eb2d49
commit 79b11f0802
1 changed files with 4 additions and 2 deletions
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6
compiler/rustc_arena/src/lib.rs
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@@ -407,6 +407,8 @@ impl Default for DroplessArena {
#[inline] #[inline]
fn default() -> DroplessArena { fn default() -> DroplessArena {
DroplessArena { DroplessArena {
// We set both `start` and `end` to 0 so that the first call to
// alloc() will trigger a grow().
start: Cell::new(ptr::null_mut()), start: Cell::new(ptr::null_mut()),
end: Cell::new(ptr::null_mut()), end: Cell::new(ptr::null_mut()),
chunks: Default::default(), chunks: Default::default(),
@@ -417,7 +419,7 @@ impl Default for DroplessArena {
impl DroplessArena { impl DroplessArena {
fn grow(&self, layout: Layout) { fn grow(&self, layout: Layout) {
// Add some padding so we can align `self.end` while // Add some padding so we can align `self.end` while
// stilling fitting in a `layout` allocation. // still fitting in a `layout` allocation.
let additional = layout.size() + cmp::max(DROPLESS_ALIGNMENT, layout.align()) - 1; let additional = layout.size() + cmp::max(DROPLESS_ALIGNMENT, layout.align()) - 1;
unsafe { unsafe {
@@ -441,7 +443,7 @@ impl DroplessArena {
let mut chunk = ArenaChunk::new(align_up(new_cap, PAGE)); let mut chunk = ArenaChunk::new(align_up(new_cap, PAGE));
self.start.set(chunk.start()); self.start.set(chunk.start());
// Align the end to DROPLESS_ALIGNMENT // Align the end to DROPLESS_ALIGNMENT.
let end = align_down(chunk.end().addr(), DROPLESS_ALIGNMENT); let end = align_down(chunk.end().addr(), DROPLESS_ALIGNMENT);
// Make sure we don't go past `start`. This should not happen since the allocation // Make sure we don't go past `start`. This should not happen since the allocation