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Inline and remove DroplessArena::alloc_raw_without_grow.

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It has a single call site. I find the code clearer with it gone.
This commit is contained in:
Nicholas Nethercote 2023-09-20 08:04:14 +10:00
parent 55a1a5223a
commit bb5344a1bf
1 changed files with 22 additions and 29 deletions
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51
compiler/rustc_arena/src/lib.rs
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@ -453,33 +453,6 @@ impl DroplessArena {
}
}
/// Allocates a byte slice with specified layout from the current memory
/// chunk. Returns `None` if there is no free space left to satisfy the
/// request.
#[inline]
fn alloc_raw_without_grow(&self, layout: Layout) -> Option<*mut u8> {
let start = self.start.get().addr();
let old_end = self.end.get();
let end = old_end.addr();
// Align allocated bytes so that `self.end` stays aligned to DROPLESS_ALIGNMENT
let bytes = align_up(layout.size(), DROPLESS_ALIGNMENT);
// Tell LLVM that `end` is aligned to DROPLESS_ALIGNMENT
unsafe { intrinsics::assume(end == align_down(end, DROPLESS_ALIGNMENT)) };
let new_end = align_down(end.checked_sub(bytes)?, layout.align());
if start <= new_end {
let new_end = old_end.with_addr(new_end);
// `new_end` is aligned to DROPLESS_ALIGNMENT as `align_down` preserves alignment
// as both `end` and `bytes` are already aligned to DROPLESS_ALIGNMENT.
self.end.set(new_end);
Some(new_end)
} else {
None
}
}
#[inline]
pub fn alloc_raw(&self, layout: Layout) -> *mut u8 {
assert!(layout.size() != 0);
@ -487,9 +460,29 @@ impl DroplessArena {
// This loop executes once or twice: if allocation fails the first
// time, the `grow` ensures it will succeed the second time.
loop {
if let Some(a) = self.alloc_raw_without_grow(layout) {
return a;
let start = self.start.get().addr();
let old_end = self.end.get();
let end = old_end.addr();
// Align allocated bytes so that `self.end` stays aligned to
// DROPLESS_ALIGNMENT.
let bytes = align_up(layout.size(), DROPLESS_ALIGNMENT);
// Tell LLVM that `end` is aligned to DROPLESS_ALIGNMENT.
unsafe { intrinsics::assume(end == align_down(end, DROPLESS_ALIGNMENT)) };
if let Some(sub) = end.checked_sub(bytes) {
let new_end = align_down(sub, layout.align());
if start <= new_end {
let new_end = old_end.with_addr(new_end);
// `new_end` is aligned to DROPLESS_ALIGNMENT as `align_down`
// preserves alignment as both `end` and `bytes` are already
// aligned to DROPLESS_ALIGNMENT.
self.end.set(new_end);
return new_end;
}
}
// No free space left. Allocate a new chunk to satisfy the request.
// On failure the grow will panic or abort.
self.grow(layout);