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check can_reuse on reuse

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J.Teeuwissen 2023-04-12 10:05:02 +02:00
parent 13ee3cac6c
commit 584024f230
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1 changed files with 64 additions and 45 deletions
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109
crates/compiler/mono/src/reset_reuse.rs
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@ -129,23 +129,31 @@ fn insert_reset_reuse_operations_stmt<'a, 'i>(
// But for completeness we add every kind of union to the layout_tags.
environment.add_layout_tag(layout, *tag_id);
// See if we have a reuse token
match environment.pop_reuse_token(layout) {
// We have a reuse token for this layout, use it.
Some(reuse_token) => {
Expr::Reuse {
symbol: reuse_token.symbol,
update_mode: reuse_token.update_mode_id,
// for now, always overwrite the tag ID just to be sure
update_tag_id: true,
tag_layout: *tag_layout,
tag_id: *tag_id,
arguments,
// Check if the tag id for this layout can be reused at all.
match can_reuse_union_layout_tag(tag_layout, Option::Some(*tag_id)) {
// The tag is reusable.
Reuse::Reusable => {
// See if we have a token.
match environment.pop_reuse_token(layout) {
// We have a reuse token for this layout, use it.
Some(reuse_token) => {
Expr::Reuse {
symbol: reuse_token.symbol,
update_mode: reuse_token.update_mode_id,
// for now, always overwrite the tag ID just to be sure
update_tag_id: true,
tag_layout: *tag_layout,
tag_id: *tag_id,
arguments,
}
}
// We have no reuse token available, keep the old expression with a fresh allocation.
None => expr.clone(),
}
}
// We have no reuse token available, keep the old expression with a fresh allocation.
None => expr.clone(),
// We cannot reuse this tag id because it's a null pointer.
Reuse::Nonreusable => expr.clone(),
}
}
_ => expr.clone(),
@ -339,7 +347,7 @@ fn insert_reset_reuse_operations_stmt<'a, 'i>(
match layout_option.clone() {
LayoutOption::Layout(layout)
if matches!(
can_reuse_layout_tag(layout_interner, environment, layout),
can_reuse_layout(layout_interner, environment, layout),
Reuse::Reusable
) =>
{
@ -1110,46 +1118,57 @@ impl<'a> ReuseEnvironment<'a> {
}
}
fn can_reuse_layout_tag<'a, 'i>(
/**
Check if a layout can be reused. by verifying if the layout is a union and if the tag is not nullable.
*/
fn can_reuse_layout<'a, 'i>(
layout_interner: &'i STLayoutInterner<'a>,
environment: &ReuseEnvironment<'a>,
layout: &InLayout<'a>,
) -> Reuse {
match layout_interner.get(*layout) {
Layout::Union(union_layout) => match union_layout {
UnionLayout::NonRecursive(_) => Reuse::Nonreusable,
// Non nullable union layouts
UnionLayout::Recursive(_) | UnionLayout::NonNullableUnwrapped(_) => {
// Non nullable union layouts can always be reused.
Reuse::Reusable
}
// Nullable union layouts
UnionLayout::NullableWrapped { .. } | UnionLayout::NullableUnwrapped { .. } => {
// Nullable union layouts can only be reused if the tag is not null.
match environment.get_layout_tag(layout) {
Some(tag_id) => {
if union_layout.tag_is_null(tag_id) {
// Variable of layout is always null, so it can't ever be reused.
Reuse::Nonreusable
} else {
// Variable of layout is not null, so it can be reused.
Reuse::Reusable
}
}
None => {
// Variable of layout might be null, so it might be reused.
// If null will cause null pointer and fresh allocation.
Reuse::Reusable
}
}
}
},
Layout::Union(union_layout) => {
can_reuse_union_layout_tag(&union_layout, environment.get_layout_tag(layout))
}
// Strings literals are constants.
// Arrays are probably given to functions and reused there. Little use to reuse them here.
_ => Reuse::Nonreusable,
}
}
/**
Check if a union layout can be reused. by verifying if the tag is not nullable.
*/
fn can_reuse_union_layout_tag(union_layout: &UnionLayout<'_>, tag_id_option: Option<Tag>) -> Reuse {
match union_layout {
UnionLayout::NonRecursive(_) => Reuse::Nonreusable,
// Non nullable union layouts
UnionLayout::Recursive(_) | UnionLayout::NonNullableUnwrapped(_) => {
// Non nullable union layouts can always be reused.
Reuse::Reusable
}
// Nullable union layouts
UnionLayout::NullableWrapped { .. } | UnionLayout::NullableUnwrapped { .. } => {
match tag_id_option {
Some(tag_id) => {
if union_layout.tag_is_null(tag_id) {
// Variable of layout is always null, so it can't ever be reused.
Reuse::Nonreusable
} else {
// Variable of layout is not null, so it can be reused.
Reuse::Reusable
}
}
None => {
// Variable of layout might be null, so it might be reused.
// If null will cause null pointer and fresh allocation.
Reuse::Reusable
}
}
}
}
}
/**
Drop the reuse tokens that are not used anymore.
Useful when reuse tokens are used in a branch, and thus should be created.