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convert enum tag unions to mono

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This commit is contained in:
Folkert 2020-03-09 23:40:18 +01:00
parent 9081b7f2d1
commit 2bad39e8b9
3 changed files with 124 additions and 9 deletions
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40
compiler/mono/src/layout.rs
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@ -19,6 +19,8 @@ pub enum Layout<'a> {
pub enum Builtin<'a> {
Int64,
Float64,
Bool(TagName, TagName),
Byte(MutMap<TagName, u8>),
Str,
Map(&'a Layout<'a>, &'a Layout<'a>),
Set(&'a Layout<'a>),
@ -81,6 +83,8 @@ impl<'a> Layout<'a> {
impl<'a> Builtin<'a> {
const I64_SIZE: u32 = std::mem::size_of::<i64>() as u32;
const F64_SIZE: u32 = std::mem::size_of::<f64>() as u32;
const BOOL_SIZE: u32 = std::mem::size_of::<bool>() as u32;
const BYTE_SIZE: u32 = std::mem::size_of::<u8>() as u32;
/// Number of machine words in an empty one of these
const STR_WORDS: u32 = 3;
@ -94,6 +98,8 @@ impl<'a> Builtin<'a> {
match self {
Int64 => Builtin::I64_SIZE,
Float64 => Builtin::F64_SIZE,
Bool(_, _) => Builtin::BOOL_SIZE,
Byte(_) => Builtin::BYTE_SIZE,
Str => Builtin::STR_WORDS * pointer_size,
Map(_, _) => Builtin::MAP_WORDS * pointer_size,
Set(_) => Builtin::SET_WORDS * pointer_size,
@ -243,7 +249,34 @@ fn layout_from_flat_type<'a>(
}
}
_ => {
panic!("TODO handle a tag union with mutliple tags: {:?}", tags);
// Check if we can turn this tag union into an enum
// TODO rather than the arguments being empty, check whether their layout has size 0.
if tags.len() <= 256 && tags.iter().all(|(_, args)| args.is_empty()) {
if tags.len() <= 2 {
// Up to 2 enum tags can be stored (in theory) in one bit
let mut it = tags.keys();
let a: TagName = it.next().unwrap().clone();
let b: TagName = it.next().unwrap().clone();
if a < b {
Ok(Layout::Builtin(Builtin::Bool(a, b)))
} else {
Ok(Layout::Builtin(Builtin::Bool(b, a)))
}
} else {
// up to 256 enum tags can be stored in a byte
let mut counter = 0u8;
let mut tag_to_u8 = MutMap::default();
for (name, _) in tags {
tag_to_u8.insert(name, counter);
counter += 1;
}
Ok(Layout::Builtin(Builtin::Byte(tag_to_u8)))
}
} else {
panic!("TODO handle a tag union with mutliple tags: {:?}", tags);
}
}
}
}
@ -301,13 +334,15 @@ fn flatten_union(
match subs.get_without_compacting(ext_var).content {
Structure(EmptyTagUnion) => (),
Structure(TagUnion(new_tags, new_ext_var)) => {
Structure(TagUnion(new_tags, new_ext_var))
| Structure(RecursiveTagUnion(_, new_tags, new_ext_var)) => {
for (tag_name, vars) in new_tags {
tags.insert(tag_name, vars);
}
flatten_union(tags, new_ext_var, subs)
}
Alias(_, _, actual) => flatten_union(tags, actual, subs),
invalid => {
panic!("Compiler error: flatten_union got an ext_var in a tag union that wasn't itself a tag union; instead, it was: {:?}", invalid);
}
@ -329,6 +364,7 @@ fn flatten_record(fields: &mut MutMap<Lowercase, Variable>, ext_var: Variable, s
flatten_record(fields, new_ext_var, subs)
}
Alias(_, _, actual) => flatten_record(fields, actual, subs),
invalid => {
panic!("Compiler error: flatten_record encountered an ext_var in a record that wasn't itself a record; instead, it was: {:?}", invalid);
}