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Add can::builtins
This commit is contained in:
Richard Feldman
parent
6b952e0c98
commit
07001131b2
5 changed files with 271 additions and 13 deletions
250
compiler/can/src/builtins.rs
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250
compiler/can/src/builtins.rs
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use crate::def::Def;
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use crate::expr::Recursive;
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use roc_collections::all::SendMap;
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use roc_module::ident::TagName;
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use roc_module::symbol::Symbol;
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use roc_parse::operator::CalledVia;
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use roc_region::all::{Located, Region};
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use roc_types::subs::VarStore;
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/// Some builtins cannot be constructed in code gen alone, and need to be defined
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/// as separate Roc defs. For example, List.get has this type:
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///
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/// List.get : List elem, Int -> Result elem [ OutOfBounds ]*
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///
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/// Because this returns an open tag union for its Err type, it's not possible
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/// for code gen to return a hardcoded value for OutOfBounds. For example,
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/// if this Result unifies to [ Foo, OutOfBounds ] then OutOfBOunds will
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/// get assigned the number 1 (because Foo got 0 alphabetically), whereas
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/// if it unifies to [ OutOfBounds, Qux ] then OutOfBounds will get the number 0.
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///
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/// Getting these numbers right requires having List.get participate in the
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/// normal type-checking and monomorphization processes. As such, this function
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/// returns a normal def for List.get, which performs a bounds check and then
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/// delegates to the compiler-internal List.getUnsafe function to do the actual
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/// lookup (if the bounds check passed). That internal function is hardcoded in code gen,
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/// which works fine because it doesn't involve any open tag unions.
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pub fn builtin_defs(var_store: &VarStore) -> Vec<Def> {
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vec![list_get(var_store), list_first(var_store)]
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}
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/// List.get : List elem, Int -> Result elem [ OutOfBounds ]*
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fn list_get(var_store: &VarStore) -> Def {
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use crate::expr::Expr::*;
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use crate::pattern::Pattern::*;
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let args = vec![
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(
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var_store.fresh(),
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no_region(Identifier(Symbol::LIST_GET_ARG_LIST)),
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),
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(
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var_store.fresh(),
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no_region(Identifier(Symbol::LIST_GET_ARG_INDEX)),
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),
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];
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// Perform a bounds check. If it passes, delegate to List.getUnsafe
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let body = If {
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cond_var: var_store.fresh(),
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branch_var: var_store.fresh(),
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branches: vec![(
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// if-condition
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Located {
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region: Region::zero(),
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value: Call(
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Box::new((
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var_store.fresh(),
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Located {
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region: Region::zero(),
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value: Var(Symbol::LIST_IS_EMPTY), // TODO actually check if (index < List.len list)
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},
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var_store.fresh(),
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)),
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vec![(
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var_store.fresh(),
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Located {
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region: Region::zero(),
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value: Var(Symbol::LIST_GET_ARG_LIST),
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},
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)],
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CalledVia::Space,
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),
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},
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// then-branch
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Located {
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region: Region::zero(),
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value:
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// Ok
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Tag {
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variant_var: var_store.fresh(),
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ext_var: var_store.fresh(),
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name: TagName::Global("Ok".into()),
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arguments: vec![(
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var_store.fresh(),
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no_region(
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// List.getUnsafe list index
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Call(
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Box::new((var_store.fresh(), no_region(Var(Symbol::LIST_GET_UNSAFE)), var_store.fresh())),
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vec![
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(var_store.fresh(), no_region(Var(Symbol::LIST_GET_ARG_LIST))),
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(var_store.fresh(), no_region(Var(Symbol::LIST_GET_ARG_INDEX))),
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],
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CalledVia::Space,
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)
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)
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)]
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},
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},
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)],
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final_else: Box::new(
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// else-branch
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no_region(
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// Err
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Tag {
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variant_var: var_store.fresh(),
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ext_var: var_store.fresh(),
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name: TagName::Global("Err".into()),
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arguments: vec![(
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var_store.fresh(),
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no_region(Tag {
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variant_var: var_store.fresh(),
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ext_var: var_store.fresh(),
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name: TagName::Global("OutOfBounds".into()),
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arguments: std::vec::Vec::new(),
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}),
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)],
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},
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),
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),
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};
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let expr = Closure(
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var_store.fresh(),
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Symbol::LIST_GET,
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Recursive::NotRecursive,
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args,
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Box::new((no_region(body), var_store.fresh())),
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);
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Def {
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loc_pattern: no_region(Identifier(Symbol::LIST_GET)),
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loc_expr: no_region(expr),
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expr_var: var_store.fresh(),
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pattern_vars: SendMap::default(),
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annotation: None,
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}
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}
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/// List.first : List elem -> Result elem [ OutOfBounds ]*
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fn list_first(var_store: &VarStore) -> Def {
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use crate::expr::Expr::*;
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use crate::pattern::Pattern::*;
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let args = vec![(
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var_store.fresh(),
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no_region(Identifier(Symbol::LIST_FIRST_ARG)),
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)];
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// Perform a bounds check. If it passes, delegate to List.getUnsafe.
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let body =
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// Use "when" instead of "if" so that we can have False be the first branch.
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// We want that for branch prediction; usually we expect the list to be nonempty.
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If {
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cond_var: var_store.fresh(),
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branch_var: var_store.fresh(),
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branches: vec![(
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// if-condition
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Located {
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region: Region::zero(),
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value: Call(
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Box::new((
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var_store.fresh(),
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Located {
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region: Region::zero(),
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value: Var(Symbol::LIST_IS_EMPTY),
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},
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var_store.fresh(),
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)),
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vec![(
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var_store.fresh(),
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Located {
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region: Region::zero(),
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value: Var(Symbol::LIST_GET_ARG_LIST),
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},
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)],
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CalledVia::Space,
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),
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},
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// then-branch
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Located {
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region: Region::zero(),
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value:
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// Ok
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Tag {
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variant_var: var_store.fresh(),
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ext_var: var_store.fresh(),
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name: TagName::Global("Ok".into()),
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arguments: vec![(
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var_store.fresh(),
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no_region(
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// List.getUnsafe list index
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Call(
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Box::new((var_store.fresh(), no_region(Var(Symbol::LIST_GET_UNSAFE)), var_store.fresh())),
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vec![
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(var_store.fresh(), no_region(Var(Symbol::LIST_GET_ARG_LIST))),
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(var_store.fresh(), no_region(Var(Symbol::LIST_GET_ARG_INDEX))),
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],
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CalledVia::Space,
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)
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)
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)]
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},
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},
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)],
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final_else: Box::new(
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// default branch
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no_region(
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// Err
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Tag {
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variant_var: var_store.fresh(),
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ext_var: var_store.fresh(),
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name: TagName::Global("Err".into()),
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arguments: vec![(
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var_store.fresh(),
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no_region(Tag {
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variant_var: var_store.fresh(),
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ext_var: var_store.fresh(),
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name: TagName::Global("OutOfBounds".into()),
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arguments: std::vec::Vec::new(),
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}),
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)],
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},
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),
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),
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};
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let expr = Closure(
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var_store.fresh(),
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Symbol::LIST_GET,
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Recursive::NotRecursive,
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args,
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Box::new((no_region(body), var_store.fresh())),
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);
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Def {
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loc_pattern: no_region(Identifier(Symbol::LIST_GET)),
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loc_expr: no_region(expr),
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expr_var: var_store.fresh(),
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pattern_vars: SendMap::default(),
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annotation: None,
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}
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}
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#[inline(always)]
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fn no_region<T>(value: T) -> Located<T> {
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Located {
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region: Region::zero(),
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value,
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}
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}
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