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Implement hashing tag discriminants in derivers, rather than using low-level
This makes it so we can decide the discriminant in the front-end. With this, we can also now revert the `LowLevel::TagDiscriminant` introductions.
This commit is contained in:
Ayaz Hafiz
parent
a308ebb38c
commit
cb96a64259
3 changed files with 75 additions and 81 deletions
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@ -3,11 +3,12 @@
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use std::iter::once;
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use roc_can::{
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def::Def,
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expr::{AnnotatedMark, ClosureData, Expr, Recursive, WhenBranch, WhenBranchPattern},
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expr::{AnnotatedMark, ClosureData, Expr, IntValue, Recursive, WhenBranch, WhenBranchPattern},
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num::{IntBound, IntLitWidth},
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pattern::Pattern,
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};
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use roc_derive_key::hash::FlatHashKey;
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use roc_error_macros::internal_error;
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use roc_module::{
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called_via::CalledVia,
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ident::{Lowercase, TagName},
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@ -15,6 +16,7 @@ use roc_module::{
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};
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use roc_region::all::{Loc, Region};
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use roc_types::{
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num::int_lit_width_to_variable,
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subs::{
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Content, ExhaustiveMark, FlatType, GetSubsSlice, LambdaSet, OptVariable, RecordFields,
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RedundantMark, SubsIndex, SubsSlice, UnionLambdas, UnionTags, Variable, VariableSubsSlice,
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@ -150,49 +152,40 @@ fn hash_tag_union(
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//
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// hash_union : hasher, [ A t11 .. t1n, ..., Q tq1 .. tqm ] -> hasher | hasher has Hasher
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// hash_union = \hasher, union ->
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// discrHasher = Hash.hash hasher (@tag_discriminant union)
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// when union is
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// A x11 .. x1n -> Hash.hash (... (Hash.hash discrHasher x11) ...) x1n
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// A x11 .. x1n -> Hash.hash (... (Hash.hash (Hash.uN hasher 0) x11) ...) x1n
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// ...
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// Q xq1 .. xqm -> Hash.hash (... (Hash.hash discrHasher xq1) ...) xqm
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// Q xq1 .. xqm -> Hash.hash (... (Hash.hash (Hash.uN hasher (q - 1)) xq1) ...) xqm
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//
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// where `Hash.uN` is the appropriate hasher for the discriminant value - typically a `u8`, but
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// if there are more than `u8::MAX` tags, we use `u16`, and so on.
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let union_sym = env.new_symbol("union");
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let hasher_sym = env.new_symbol("hasher");
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let hasher_var = synth_var(env.subs, Content::FlexAbleVar(None, Symbol::HASH_HASHER));
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let discr_hasher_sym = env.new_symbol("discrHasher");
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// discrHasher = ...
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let (discr_hasher_var, discr_hasher_def) = {
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let discr_expr = Expr::RunLowLevel {
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op: roc_module::low_level::LowLevel::TagDiscriminant,
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args: vec![(union_var, Expr::Var(union_sym))],
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ret_var: Variable::U16,
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};
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let discr_var = Variable::U16;
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let (discr_hasher_var, disc_hasher_expr) = call_hash_add_u16(
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env,
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(hasher_var, Expr::Var(hasher_sym)),
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(discr_var, discr_expr),
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);
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let discr_def = Def {
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loc_pattern: Loc::at_zero(Pattern::Identifier(discr_hasher_sym)),
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loc_expr: Loc::at_zero(disc_hasher_expr),
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expr_var: discr_hasher_var,
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pattern_vars: once((discr_hasher_sym, discr_hasher_var)).collect(),
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annotation: None,
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};
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(discr_hasher_var, discr_def)
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let (discr_width, discr_precision_var, hash_discr_member) = if union_tags.len() > u64::MAX as _
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{
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// Should never happen, `usize` isn't more than 64 bits on most machines, but who knows?
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// Maybe someday soon someone will try to compile a huge Roc program on a 128-bit one.
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internal_error!("new record unlocked: you fit more than 18 billion, billion tags in a Roc program, and the compiler didn't fall over! But it will now. 🤯")
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} else if union_tags.len() > u32::MAX as _ {
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(IntLitWidth::U64, Variable::UNSIGNED64, Symbol::HASH_ADD_U64)
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} else if union_tags.len() > u16::MAX as _ {
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(IntLitWidth::U32, Variable::UNSIGNED32, Symbol::HASH_ADD_U32)
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} else if union_tags.len() > u8::MAX as _ {
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(IntLitWidth::U16, Variable::UNSIGNED16, Symbol::HASH_ADD_U16)
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} else {
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(IntLitWidth::U8, Variable::UNSIGNED8, Symbol::HASH_ADD_U8)
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};
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let discr_num_var = int_lit_width_to_variable(discr_width);
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// Build the branches of the body
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let whole_hasher_var = env.subs.fresh_unnamed_flex_var();
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let branches = union_tags
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.iter_all()
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.map(|(tag, payloads)| {
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.enumerate()
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.map(|(discr_n, (tag, payloads))| {
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// A
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let tag_name = env.subs[tag].clone();
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// t11 .. t1n
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@ -218,9 +211,26 @@ fn hash_tag_union(
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degenerate: false,
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};
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// discrHasher = (Hash.uN hasher n)
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let (discr_hasher_var, disc_hasher_expr) = call_hash_ability_member(
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env,
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hash_discr_member,
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(hasher_var, Expr::Var(hasher_sym)),
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(
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discr_num_var,
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Expr::Int(
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discr_num_var,
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discr_precision_var,
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format!("{}", discr_n).into_boxed_str(),
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IntValue::I128((discr_n as i128).to_ne_bytes()),
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IntBound::Exact(discr_width),
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),
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),
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);
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// Fold up `Hash.hash (... (Hash.hash discrHasher x11) ...) x1n`
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let (body_var, body_expr) = (payload_vars.into_iter()).zip(payload_syms).fold(
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(discr_hasher_var, Expr::Var(discr_hasher_sym)),
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(discr_hasher_var, disc_hasher_expr),
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|total_hasher, (payload_var, payload_sym)| {
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call_hash_hash(env, total_hasher, (payload_var, Expr::Var(payload_sym)))
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},
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@ -250,12 +260,6 @@ fn hash_tag_union(
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exhaustive: ExhaustiveMark::known_exhaustive(),
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};
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let body_var = when_var;
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let body_expr = Expr::LetNonRec(
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Box::new(discr_hasher_def),
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Box::new(Loc::at_zero(when_expr)),
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);
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// Finally, build the closure
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// \hasher, rcd -> body
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build_outer_derived_closure(
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@ -263,7 +267,7 @@ fn hash_tag_union(
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fn_name,
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(hasher_var, hasher_sym),
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(union_var, Pattern::Identifier(union_sym)),
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(body_var, body_expr),
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(when_var, when_expr),
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)
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}
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@ -351,14 +355,6 @@ fn hash_newtype_tag_union(
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)
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}
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fn call_hash_add_u16(
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env: &mut Env<'_>,
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hasher: (Variable, Expr),
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val: (Variable, Expr),
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) -> (Variable, Expr) {
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call_hash_ability_member(env, Symbol::HASH_ADD_U16, hasher, val)
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}
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fn call_hash_hash(
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env: &mut Env<'_>,
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hasher: (Variable, Expr),
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@ -400,7 +396,7 @@ fn call_hash_ability_member(
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env.unify(exposed_hash_fn_var, this_hash_fn_var);
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// Hash.hash : hasher, (typeof field) -[clos]-> hasher | hasher has Hasher, (typeof field) has Hash
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let hash_fn_head = Expr::AbilityMember(Symbol::HASH_HASH, None, this_hash_fn_var);
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let hash_fn_head = Expr::AbilityMember(member, None, this_hash_fn_var);
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let hash_fn_data = Box::new((
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this_hash_fn_var,
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Loc::at_zero(hash_fn_head),
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