bjoernager/rust
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Remove DropArena.

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Most arena-allocate types that impl `Drop` get their own `TypedArena`, but a
few infrequently used ones share a `DropArena`. This sharing adds complexity
but doesn't help performance or memory usage. Perhaps it was more effective in
the past prior to some other improvements to arenas.

This commit removes `DropArena` and the sharing of arenas via the `few`
attribute of the `arena_types` macro. This change removes over 100 lines of
code and nine uses of `unsafe` (one of which affects the parallel compiler) and
makes the remaining code easier to read.
This commit is contained in:
Nicholas Nethercote 2021-11-15 17:15:42 +11:00
parent ad44239975
commit fb80c73fb3
3 changed files with 17 additions and 154 deletions
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15
compiler/rustc_hir/src/arena.rs
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@ -1,10 +1,5 @@
/// This declares a list of types which can be allocated by `Arena`.
///
/// The `few` modifier will cause allocation to use the shared arena and recording the destructor.
/// This is faster and more memory efficient if there's only a few allocations of the type.
/// Leaving `few` out will cause the type to get its own dedicated `TypedArena` which is
/// faster and more memory efficient if there is lots of allocations.
///
/// Specifying the `decode` modifier will add decode impls for `&T` and `&[T]`,
/// where `T` is the type listed. These impls will appear in the implement_ty_decoder! macro.
#[macro_export]
@ -12,7 +7,7 @@ macro_rules! arena_types {
($macro:path, $tcx:lifetime) => (
$macro!([
// HIR types
[few] hir_krate: rustc_hir::Crate<$tcx>,
[] hir_krate: rustc_hir::Crate<$tcx>,
[] arm: rustc_hir::Arm<$tcx>,
[] asm_operand: (rustc_hir::InlineAsmOperand<$tcx>, Span),
[] asm_template: rustc_ast::InlineAsmTemplatePiece,
@ -29,14 +24,14 @@ macro_rules! arena_types {
[] pat_field: rustc_hir::PatField<$tcx>,
[] fn_decl: rustc_hir::FnDecl<$tcx>,
[] foreign_item: rustc_hir::ForeignItem<$tcx>,
[few] foreign_item_ref: rustc_hir::ForeignItemRef,
[] foreign_item_ref: rustc_hir::ForeignItemRef,
[] impl_item: rustc_hir::ImplItem<$tcx>,
[] impl_item_ref: rustc_hir::ImplItemRef,
[] item: rustc_hir::Item<$tcx>,
[few] inline_asm: rustc_hir::InlineAsm<$tcx>,
[few] llvm_inline_asm: rustc_hir::LlvmInlineAsm<$tcx>,
[] inline_asm: rustc_hir::InlineAsm<$tcx>,
[] llvm_inline_asm: rustc_hir::LlvmInlineAsm<$tcx>,
[] local: rustc_hir::Local<$tcx>,
[few] mod_: rustc_hir::Mod<$tcx>,
[] mod_: rustc_hir::Mod<$tcx>,
[] owner_info: rustc_hir::OwnerInfo<$tcx>,
[] param: rustc_hir::Param<$tcx>,
[] pat: rustc_hir::Pat<$tcx>,