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Decrease generated code compilation time
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It seems that many closures slow down compilation tremendously. This change provides a 10x speed-up or more depending on the number of variants.
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@stephaneyfx
stephaneyfx committed Feb 27, 2023
1 parent e47ea9f commit 35cd31e
Showing 1 changed file with 57 additions and 32 deletions.
89 changes: 57 additions & 32 deletions enum-iterator-derive/src/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -58,8 +58,8 @@ fn derive_for_struct(
fields: &Fields,
) -> Result<TokenStream, syn::Error> {
let cardinality = tuple_cardinality(fields);
let first = init_fields(fields, Direction::Forward);
let last = init_fields(fields, Direction::Backward);
let first = init_value(ty, None, fields, Direction::Forward);
let last = init_value(ty, None, fields, Direction::Backward);
let next_body = advance_struct(ty, fields, Direction::Forward);
let previous_body = advance_struct(ty, fields, Direction::Backward);
let (impl_generics, ty_generics, where_clause) = generics.split_for_impl();
Expand Down Expand Up @@ -92,11 +92,11 @@ fn derive_for_struct(
}

fn first() -> ::core::option::Option<Self> {
::core::option::Option::Some(#ty { #first })
#first
}

fn last() -> ::core::option::Option<Self> {
::core::option::Option::Some(#ty { #last })
#last
}
}
};
Expand Down Expand Up @@ -209,18 +209,25 @@ fn field_id(field: &Field, index: usize) -> Member {
.map_or_else(|| Member::from(index), Member::from)
}

fn init_fields(fields: &Fields, direction: Direction) -> TokenStream {
fn init_value(
ty: &Ident,
variant: Option<&Ident>,
fields: &Fields,
direction: Direction,
) -> TokenStream {
let reset = direction.reset();
fields
.iter()
.enumerate()
.map(|(i, field)| {
let id = field_id(field, i);
quote! {
#id: ::enum_iterator::Sequence::#reset()?,
let initialization = repeat(quote! { ::enum_iterator::Sequence::#reset() }).take(fields.len());
let assignments = field_assignments(fields);
let bindings = bindings().take(fields.len());
let id = variant.map_or_else(|| quote! { #ty }, |v| quote! { #ty::#v });
quote! {{
match (#(#initialization,)*) {
(#(::core::option::Option::Some(#bindings),)*) => {
::core::option::Option::Some(#id { #assignments })
}
})
.collect::<TokenStream>()
_ => ::core::option::Option::None,
}
}}
}

fn next_variant(
Expand All @@ -241,17 +248,17 @@ fn next_variant(
};
let arms = variants.iter().enumerate().map(|(i, v)| {
let id = &v.ident;
let init = init_fields(&v.fields, direction);
let init = init_value(ty, Some(id), &v.fields, direction);
quote! {
#i => ::core::option::Option::Some(#ty::#id { #init })
#i => #init
}
});
quote! {
loop {
let next = (|| match i {
let next = match i {
#(#arms,)*
_ => ::core::option::Option::None,
})();
};
match next {
::core::option::Option::Some(_) => break next,
::core::option::Option::None => #advance,
Expand Down Expand Up @@ -299,12 +306,12 @@ fn advance_enum(
fn advance_enum_arm(ty: &Ident, direction: Direction, i: usize, variant: &Variant) -> TokenStream {
let next = match direction {
Direction::Forward => match i.checked_add(1) {
Some(next_i) => quote! { .or_else(|| next_variant(#next_i)) },
None => quote! {},
Some(next_i) => quote! { next_variant(#next_i) },
None => quote! { ::core::option::Option::None },
},
Direction::Backward => match i.checked_sub(1) {
Some(prev_i) => quote! { .or_else(|| previous_variant(#prev_i)) },
None => quote! {},
Some(prev_i) => quote! { previous_variant(#prev_i) },
None => quote! { ::core::option::Option::None },
},
};
let id = &variant.ident;
Expand All @@ -314,9 +321,13 @@ fn advance_enum_arm(ty: &Ident, direction: Direction, i: usize, variant: &Varian
let tuple = advance_tuple(&bindings, direction);
quote! {
#ty::#id { #destructuring } => {
#tuple
.map(|(#(#bindings,)*)| #ty::#id { #assignments })
#next
let y = #tuple;
match y {
::core::option::Option::Some((#(#bindings,)*)) => {
::core::option::Option::Some(#ty::#id { #assignments })
}
::core::option::Option::None => #next,
}
}
}
}
Expand All @@ -332,8 +343,8 @@ fn advance_tuple(bindings: &[Ident], direction: Direction) -> TokenStream {
let rev_binding_head = match rev_binding_head {
Some(head) => quote! {
let (#head, carry) = match ::enum_iterator::Sequence::#advance(#head) {
::core::option::Option::Some(#head) => (#head, false),
::core::option::Option::None => (::enum_iterator::Sequence::#reset()?, true),
::core::option::Option::Some(#head) => (::core::option::Option::Some(#head), false),
::core::option::Option::None => (::enum_iterator::Sequence::#reset(), true),
};
},
None => quote! {
Expand All @@ -345,17 +356,31 @@ fn advance_tuple(bindings: &[Ident], direction: Direction) -> TokenStream {
#(
let (#rev_binding_tail, carry) = if carry {
match ::enum_iterator::Sequence::#advance(#rev_binding_tail) {
::core::option::Option::Some(#rev_binding_tail) => (#rev_binding_tail, false),
::core::option::Option::None => (::enum_iterator::Sequence::#reset()?, true),
::core::option::Option::Some(#rev_binding_tail) => {
(::core::option::Option::Some(#rev_binding_tail), false)
}
::core::option::Option::None => (::enum_iterator::Sequence::#reset(), true),
}
} else {
(::core::clone::Clone::clone(#rev_binding_tail), false)
(
::core::option::Option::Some(::core::clone::Clone::clone(#rev_binding_tail)),
false,
)
};
)*
::core::option::Option::Some((#(#bindings,)*)).filter(|_| !carry)
if carry {
::core::option::Option::None
} else {
match (#(#bindings,)*) {
(#(::core::option::Option::Some(#bindings),)*) => {
::core::option::Option::Some((#(#bindings,)*))
}
_ => ::core::option::Option::None,
}
}
};
quote! {
(|| { #body })()
{ #body }
}
}

Expand Down

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