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A clarity around disabling list drop specialization

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Brendan Hansknecht 2024-07-15 17:12:22 -07:00
parent 50ba3071e1
commit ae0f445d86
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1 changed files with 13 additions and 5 deletions
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18
crates/compiler/mono/src/drop_specialization.rs
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@ -17,8 +17,8 @@ use roc_module::low_level::LowLevel;
use roc_module::symbol::{IdentIds, ModuleId, Symbol};
use crate::ir::{
BranchInfo, Call, CallType, ErasedField, Expr, JoinPointId, ListLiteralElement, Literal,
ModifyRc, Proc, ProcLayout, Stmt, UpdateModeId,
BranchInfo, Call, CallType, ErasedField, Expr, JoinPointId, ListLiteralElement, ModifyRc, Proc,
ProcLayout, Stmt, UpdateModeId,
};
use crate::layout::{
Builtin, InLayout, Layout, LayoutInterner, LayoutRepr, STLayoutInterner, UnionLayout,
@ -1080,8 +1080,6 @@ fn specialize_list<'a, 'i>(
_item_layout: InLayout<'a>,
continuation: &'a Stmt<'a>,
) -> &'a Stmt<'a> {
// let current_length = environment.list_length.get(symbol).copied();
macro_rules! keep_original_decrement {
() => {{
let new_continuation =
@ -1090,6 +1088,17 @@ fn specialize_list<'a, 'i>(
}};
}
// TODO: Investigate if there is still any utility in List drop specialization.
// Fundamentally, an allocation for a list holds onto exactly one reference to all elements in the allocation.
// So even if there are 100 references to the list, the list will hold only 1 reference to each element.
// On top of that, the list now holds onto a reference to dead elements.
// A single slice to 10 elements of a 100 element list will hold 1 reference to each to the 100 elements.
// The whole allocation will get freed in a unit.
// This makes it much closer to the lifetime of the underlying vector for a reference slice in rust.
// If this specialization does not make sense anymore delete it as a whole.
keep_original_decrement!()
// let current_length = environment.list_length.get(symbol).copied();
// match (
// layout_interner.contains_refcounted(item_layout),
// current_length,
@ -1198,7 +1207,6 @@ fn specialize_list<'a, 'i>(
// keep_original_decrement!()
// }
// }
keep_original_decrement!()
}
/**