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Track element count only for types that need drop

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This commit is contained in:
Dániel Buga 2020-10-20 11:32:10 +02:00
parent a85e949276
commit 2705caed8a
1 changed files with 6 additions and 2 deletions
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8
compiler/rustc_arena/src/lib.rs
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@ -217,8 +217,12 @@ impl<T> TypedArena<T> {
let mut chunks = self.chunks.borrow_mut(); let mut chunks = self.chunks.borrow_mut();
let mut new_cap; let mut new_cap;
if let Some(last_chunk) = chunks.last_mut() { if let Some(last_chunk) = chunks.last_mut() {
let used_bytes = self.ptr.get() as usize - last_chunk.start() as usize; // If a type is `!needs_drop`, we don't need to keep track of how many elements
last_chunk.entries = used_bytes / mem::size_of::<T>(); // the chunk stores - the field will be ignored anyway.
if mem::needs_drop::<T>() {
let used_bytes = self.ptr.get() as usize - last_chunk.start() as usize;
last_chunk.entries = used_bytes / mem::size_of::<T>();
}
// If the previous chunk's len is less than HUGE_PAGE // If the previous chunk's len is less than HUGE_PAGE
// bytes, then this chunk will be least double the previous // bytes, then this chunk will be least double the previous