Support allocating iterators with arenas #59533
Conversation
rust-highfive
added
the
S-waiting-on-review
This comment has been minimized.
This comment has been minimized.
| @@ -161,21 +186,60 @@ impl<T> TypedArena<T> { | |||
| where | |||
| T: Copy, | |||
| { | |||
| unsafe { | |||
There was a problem hiding this comment.
A comment would be good here.
Zoxc
force-pushed
the
arena-slices
branch
2 times, most recently
from
29cef27 to
3c51be5
Compare
Zoxc
changed the title
Introduce an arena type which may be used to allocate a list of types with destructors You can also specify that you want deserializers for `&'tcx [T]` and `&'tcx T` for a type in the list, which will allocate those using the arena. Based on #59517 and #59533. Look at the last commit for the interesting changes. An alternative to #56448. cc @michaelwoerister @eddyb r? @oli-obk
src/libarena/lib.rs
Outdated
| assert!(len != 0); | ||
|
|
||
| if !self.can_allocate(len) { | ||
| self.grow(len); |
There was a problem hiding this comment.
Maybe add a debug_assert!(self.can_allocate(len)) here, just to be sure.
src/libarena/lib.rs
Outdated
| } | ||
| match size_hint { | ||
| (min, Some(max)) if min == max => { | ||
| if min == 0 { |
There was a problem hiding this comment.
Can you add a let len = min; binding here? I think that makes it more readable.
There was a problem hiding this comment.
@michaelwoerister that seems like an odd use of let bindings... perhaps a comment instead?
There was a problem hiding this comment.
I'd do both actually, as in:
// In this branch we know the exact length
let len = min;
src/libarena/lib.rs
Outdated
| let len = vec.len(); | ||
| let start_ptr = self.alloc_raw_slice(len); | ||
| vec.as_ptr().copy_to_nonoverlapping(start_ptr, len); | ||
| mem::forget(vec.drain()); |
There was a problem hiding this comment.
From looking at the implementation of SmallVec, it looks like this does the right thing, but I think it would be clearer to directly call vec.set_len(0) here.
| @@ -189,6 +257,7 @@ impl<T> TypedArena<T> { | |||
| if let Some(last_chunk) = chunks.last_mut() { | |||
| let used_bytes = self.ptr.get() as usize - last_chunk.start() as usize; | |||
| let currently_used_cap = used_bytes / mem::size_of::<T>(); | |||
| last_chunk.entries = currently_used_cap; | |||
There was a problem hiding this comment.
Looks like this was an existing bug, right? Good find!
There was a problem hiding this comment.
There previously wasn't a way to end up with unused memory at the end of a chunk for types with destructors, so not an existing bug.
There was a problem hiding this comment.
No? It looks like a similar case can also happen already in alloc_slice:
Line 170 in f694222
There was a problem hiding this comment.
That requires Copy types, so it can't trigger it.
|
📌 Commit 59ff059 has been approved by |
bors
added
S-waiting-on-bors
Support allocating iterators with arenas Split out from rust-lang#57173. r? @michaelwoerister
Rollup of 8 pull requests Successful merges: - #59262 (Remove duplicated code from Iterator::{ne, lt, le, gt, ge}) - #59286 (Refactor async fn return type lowering) - #59444 (Implement useful steps_between for all integers) - #59452 (Speed up rustdoc run a bit) - #59533 (Support allocating iterators with arenas) - #59585 (Fixes for shallow borrows) - #59607 (Renames `EvalErrorKind` to `InterpError`) - #59613 (SGX target: convert a bunch of panics to aborts) Failed merges: - #59630 (Shrink `mir::Statement`.) r? @ghost
Introduce an arena type which may be used to allocate a list of types with destructors You can also specify that you want deserializers for `&'tcx [T]` and `&'tcx T` for a type in the list, which will allocate those using the arena. Based on #59517 and #59533. Look at the last commit for the interesting changes. An alternative to #56448. cc @michaelwoerister @eddyb r? @oli-obk
Split out from #57173.
r? @michaelwoerister