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carbon-lang/executable_semantics/interpreter/interpreter.cpp
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Geoff Romer 0df9e8666c Factor AllocationId out of Address (#916) 
This lets us statically distinguish between code that works with arbitrary `Address`es and code that can only work with pointers to separately-allocated storage, and so we no longer need to worry about the latter code crashing at run-time (as `Heap::Deallocate` did) or silently doing the wrong thing (as `Heap::PrintAddress` did) if it's given the wrong kind of `Address`.
2021-10-27 16:40:17 -07:00

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// Part of the Carbon Language project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
#include "executable_semantics/interpreter/interpreter.h"
#include <iterator>
#include <map>
#include <optional>
#include <utility>
#include <variant>
#include <vector>
#include "common/check.h"
#include "executable_semantics/ast/declaration.h"
#include "executable_semantics/ast/expression.h"
#include "executable_semantics/common/arena.h"
#include "executable_semantics/common/error.h"
#include "executable_semantics/interpreter/action.h"
#include "executable_semantics/interpreter/stack.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/Casting.h"
using llvm::cast;
using llvm::dyn_cast;
namespace Carbon {
//
// Auxiliary Functions
//
void Interpreter::PrintEnv(Env values, llvm::raw_ostream& out) {
llvm::ListSeparator sep;
for (const auto& [name, allocation] : values) {
out << sep << name << ": ";
heap_.PrintAllocation(allocation, out);
}
}
//
// State Operations
//
auto Interpreter::CurrentScope() -> Scope& {
for (Nonnull<Action*> action : todo_) {
if (action->scope().has_value()) {
return *action->scope();
}
}
FATAL() << "No current scope";
}
auto Interpreter::CurrentEnv() -> Env { return CurrentScope().values; }
// Returns the given name from the environment, printing an error if not found.
auto Interpreter::GetFromEnv(SourceLocation source_loc, const std::string& name)
-> Address {
std::optional<AllocationId> pointer = CurrentEnv().Get(name);
if (!pointer) {
FATAL_RUNTIME_ERROR(source_loc) << "could not find `" << name << "`";
}
return Address(*pointer);
}
void Interpreter::PrintState(llvm::raw_ostream& out) {
out << "{\nstack: ";
llvm::ListSeparator sep(" :: ");
for (Nonnull<const Action*> action : todo_) {
out << sep << *action;
}
out << "\nheap: " << heap_;
if (!todo_.IsEmpty()) {
out << "\nvalues: ";
PrintEnv(CurrentEnv(), out);
}
out << "\n}\n";
}
auto Interpreter::EvalPrim(Operator op,
const std::vector<Nonnull<const Value*>>& args,
SourceLocation source_loc) -> Nonnull<const Value*> {
switch (op) {
case Operator::Neg:
return arena_->New<IntValue>(-cast<IntValue>(*args[0]).value());
case Operator::Add:
return arena_->New<IntValue>(cast<IntValue>(*args[0]).value() +
cast<IntValue>(*args[1]).value());
case Operator::Sub:
return arena_->New<IntValue>(cast<IntValue>(*args[0]).value() -
cast<IntValue>(*args[1]).value());
case Operator::Mul:
return arena_->New<IntValue>(cast<IntValue>(*args[0]).value() *
cast<IntValue>(*args[1]).value());
case Operator::Not:
return arena_->New<BoolValue>(!cast<BoolValue>(*args[0]).value());
case Operator::And:
return arena_->New<BoolValue>(cast<BoolValue>(*args[0]).value() &&
cast<BoolValue>(*args[1]).value());
case Operator::Or:
return arena_->New<BoolValue>(cast<BoolValue>(*args[0]).value() ||
cast<BoolValue>(*args[1]).value());
case Operator::Eq:
return arena_->New<BoolValue>(ValueEqual(args[0], args[1], source_loc));
case Operator::Ptr:
return arena_->New<PointerType>(args[0]);
case Operator::Deref:
FATAL() << "dereference not implemented yet";
}
}
void Interpreter::InitEnv(const Declaration& d, Env* env) {
switch (d.kind()) {
case Declaration::Kind::FunctionDeclaration: {
const auto& func_def = cast<FunctionDeclaration>(d);
Env new_env = *env;
// Bring the deduced parameters into scope.
for (const auto& deduced : func_def.deduced_parameters()) {
AllocationId a =
heap_.AllocateValue(arena_->New<VariableType>(deduced.name));
new_env.Set(deduced.name, a);
}
Nonnull<const FunctionValue*> f = arena_->New<FunctionValue>(&func_def);
AllocationId a = heap_.AllocateValue(f);
env->Set(func_def.name(), a);
break;
}
case Declaration::Kind::ClassDeclaration: {
const ClassDefinition& class_def = cast<ClassDeclaration>(d).definition();
std::vector<NamedValue> fields;
std::vector<NamedValue> methods;
for (Nonnull<const Member*> m : class_def.members()) {
switch (m->kind()) {
case Member::Kind::FieldMember: {
const BindingPattern& binding = cast<FieldMember>(*m).binding();
const Expression& type_expression =
cast<ExpressionPattern>(binding.type()).expression();
auto type = InterpExp(Env(arena_), &type_expression);
fields.push_back({.name = *binding.name(), .value = type});
break;
}
}
}
auto st = arena_->New<NominalClassType>(
class_def.name(), std::move(fields), std::move(methods));
AllocationId a = heap_.AllocateValue(st);
env->Set(class_def.name(), a);
break;
}
case Declaration::Kind::ChoiceDeclaration: {
const auto& choice = cast<ChoiceDeclaration>(d);
std::vector<NamedValue> alts;
for (const auto& alternative : choice.alternatives()) {
auto t = InterpExp(Env(arena_), &alternative.signature());
alts.push_back({.name = alternative.name(), .value = t});
}
auto ct = arena_->New<ChoiceType>(choice.name(), std::move(alts));
AllocationId a = heap_.AllocateValue(ct);
env->Set(choice.name(), a);
break;
}
case Declaration::Kind::VariableDeclaration: {
const auto& var = cast<VariableDeclaration>(d);
// Adds an entry in `globals` mapping the variable's name to the
// result of evaluating the initializer.
Nonnull<const Value*> v =
Convert(InterpExp(*env, &var.initializer()), &var.static_type());
AllocationId a = heap_.AllocateValue(v);
env->Set(*var.binding().name(), a);
break;
}
}
}
void Interpreter::InitGlobals(llvm::ArrayRef<Nonnull<Declaration*>> fs) {
for (const auto d : fs) {
InitEnv(*d, &globals_);
}
}
void Interpreter::DeallocateScope(Scope& scope) {
CHECK(!scope.deallocated);
for (const auto& l : scope.locals) {
std::optional<AllocationId> a = scope.values.Get(l);
CHECK(a);
heap_.Deallocate(*a);
}
scope.deallocated = true;
}
auto Interpreter::CreateTuple(Nonnull<Action*> act,
Nonnull<const Expression*> exp)
-> Nonnull<const Value*> {
// { { (v1,...,vn) :: C, E, F} :: S, H}
// -> { { `(v1,...,vn) :: C, E, F} :: S, H}
const auto& tup_lit = cast<TupleLiteral>(*exp);
CHECK(act->results().size() == tup_lit.fields().size());
return arena_->New<TupleValue>(act->results());
}
auto Interpreter::CreateStruct(const std::vector<FieldInitializer>& fields,
const std::vector<Nonnull<const Value*>>& values)
-> Nonnull<const Value*> {
CHECK(fields.size() == values.size());
std::vector<NamedValue> elements;
for (size_t i = 0; i < fields.size(); ++i) {
elements.push_back({.name = fields[i].name(), .value = values[i]});
}
return arena_->New<StructValue>(std::move(elements));
}
auto Interpreter::PatternMatch(Nonnull<const Value*> p, Nonnull<const Value*> v,
SourceLocation source_loc)
-> std::optional<Env> {
switch (p->kind()) {
case Value::Kind::BindingPlaceholderValue: {
const auto& placeholder = cast<BindingPlaceholderValue>(*p);
Env values(arena_);
if (placeholder.name().has_value()) {
AllocationId a = heap_.AllocateValue(v);
values.Set(*placeholder.name(), a);
}
return values;
}
case Value::Kind::TupleValue:
switch (v->kind()) {
case Value::Kind::TupleValue: {
const auto& p_tup = cast<TupleValue>(*p);
const auto& v_tup = cast<TupleValue>(*v);
if (p_tup.elements().size() != v_tup.elements().size()) {
FATAL_PROGRAM_ERROR(source_loc)
<< "arity mismatch in tuple pattern match:\n pattern: "
<< p_tup << "\n value: " << v_tup;
}
Env values(arena_);
for (size_t i = 0; i < p_tup.elements().size(); ++i) {
std::optional<Env> matches = PatternMatch(
p_tup.elements()[i], v_tup.elements()[i], source_loc);
if (!matches) {
return std::nullopt;
}
for (const auto& [name, value] : *matches) {
values.Set(name, value);
}
} // for
return values;
}
default:
FATAL() << "expected a tuple value in pattern, not " << *v;
}
case Value::Kind::StructValue: {
const auto& p_struct = cast<StructValue>(*p);
const auto& v_struct = cast<StructValue>(*v);
CHECK(p_struct.elements().size() == v_struct.elements().size());
Env values(arena_);
for (size_t i = 0; i < p_struct.elements().size(); ++i) {
CHECK(p_struct.elements()[i].name == v_struct.elements()[i].name);
std::optional<Env> matches =
PatternMatch(p_struct.elements()[i].value,
v_struct.elements()[i].value, source_loc);
if (!matches) {
return std::nullopt;
}
for (const auto& [name, value] : *matches) {
values.Set(name, value);
}
}
return values;
}
case Value::Kind::AlternativeValue:
switch (v->kind()) {
case Value::Kind::AlternativeValue: {
const auto& p_alt = cast<AlternativeValue>(*p);
const auto& v_alt = cast<AlternativeValue>(*v);
if (p_alt.choice_name() != v_alt.choice_name() ||
p_alt.alt_name() != v_alt.alt_name()) {
return std::nullopt;
}
return PatternMatch(&p_alt.argument(), &v_alt.argument(), source_loc);
}
default:
FATAL() << "expected a choice alternative in pattern, not " << *v;
}
case Value::Kind::FunctionType:
switch (v->kind()) {
case Value::Kind::FunctionType: {
const auto& p_fn = cast<FunctionType>(*p);
const auto& v_fn = cast<FunctionType>(*v);
std::optional<Env> param_matches =
PatternMatch(&p_fn.parameters(), &v_fn.parameters(), source_loc);
if (!param_matches) {
return std::nullopt;
}
std::optional<Env> ret_matches = PatternMatch(
&p_fn.return_type(), &v_fn.return_type(), source_loc);
if (!ret_matches) {
return std::nullopt;
}
Env values = *param_matches;
for (const auto& [name, value] : *ret_matches) {
values.Set(name, value);
}
return values;
}
default:
return std::nullopt;
}
case Value::Kind::AutoType:
// `auto` matches any type, without binding any new names. We rely
// on the typechecker to ensure that `v` is a type.
return Env(arena_);
default:
if (ValueEqual(p, v, source_loc)) {
return Env(arena_);
} else {
return std::nullopt;
}
}
}
void Interpreter::PatternAssignment(Nonnull<const Value*> pat,
Nonnull<const Value*> val,
SourceLocation source_loc) {
switch (pat->kind()) {
case Value::Kind::PointerValue:
heap_.Write(cast<PointerValue>(*pat).value(), val, source_loc);
break;
case Value::Kind::TupleValue: {
switch (val->kind()) {
case Value::Kind::TupleValue: {
const auto& pat_tup = cast<TupleValue>(*pat);
const auto& val_tup = cast<TupleValue>(*val);
if (pat_tup.elements().size() != val_tup.elements().size()) {
FATAL_RUNTIME_ERROR(source_loc)
<< "arity mismatch in tuple pattern assignment:\n pattern: "
<< pat_tup << "\n value: " << val_tup;
}
for (size_t i = 0; i < pat_tup.elements().size(); ++i) {
PatternAssignment(pat_tup.elements()[i], val_tup.elements()[i],
source_loc);
}
break;
}
default:
FATAL() << "expected a tuple value on right-hand-side, not " << *val;
}
break;
}
case Value::Kind::AlternativeValue: {
switch (val->kind()) {
case Value::Kind::AlternativeValue: {
const auto& pat_alt = cast<AlternativeValue>(*pat);
const auto& val_alt = cast<AlternativeValue>(*val);
CHECK(val_alt.choice_name() == pat_alt.choice_name() &&
val_alt.alt_name() == pat_alt.alt_name())
<< "internal error in pattern assignment";
PatternAssignment(&pat_alt.argument(), &val_alt.argument(),
source_loc);
break;
}
default:
FATAL() << "expected an alternative in left-hand-side, not " << *val;
}
break;
}
default:
CHECK(ValueEqual(pat, val, source_loc))
<< "internal error in pattern assignment";
}
}
auto Interpreter::StepLvalue() -> Transition {
Nonnull<Action*> act = todo_.Top();
const Expression& exp = cast<LValAction>(*act).expression();
if (trace_) {
llvm::outs() << "--- step lvalue " << exp << " (" << exp.source_loc()
<< ") --->\n";
}
switch (exp.kind()) {
case Expression::Kind::IdentifierExpression: {
// { {x :: C, E, F} :: S, H}
// -> { {E(x) :: C, E, F} :: S, H}
Address pointer =
GetFromEnv(exp.source_loc(), cast<IdentifierExpression>(exp).name());
Nonnull<const Value*> v = arena_->New<PointerValue>(pointer);
return Done{v};
}
case Expression::Kind::FieldAccessExpression: {
if (act->pos() == 0) {
// { {e.f :: C, E, F} :: S, H}
// -> { e :: [].f :: C, E, F} :: S, H}
return Spawn{arena_->New<LValAction>(
&cast<FieldAccessExpression>(exp).aggregate())};
} else {
// { v :: [].f :: C, E, F} :: S, H}
// -> { { &v.f :: C, E, F} :: S, H }
Address aggregate = cast<PointerValue>(*act->results()[0]).value();
Address field = aggregate.SubobjectAddress(
cast<FieldAccessExpression>(exp).field());
return Done{arena_->New<PointerValue>(field)};
}
}
case Expression::Kind::IndexExpression: {
if (act->pos() == 0) {
// { {e[i] :: C, E, F} :: S, H}
// -> { e :: [][i] :: C, E, F} :: S, H}
return Spawn{
arena_->New<LValAction>(&cast<IndexExpression>(exp).aggregate())};
} else if (act->pos() == 1) {
return Spawn{arena_->New<ExpressionAction>(
&cast<IndexExpression>(exp).offset())};
} else {
// { v :: [][i] :: C, E, F} :: S, H}
// -> { { &v[i] :: C, E, F} :: S, H }
Address aggregate = cast<PointerValue>(*act->results()[0]).value();
std::string f =
std::to_string(cast<IntValue>(*act->results()[1]).value());
Address field = aggregate.SubobjectAddress(f);
return Done{arena_->New<PointerValue>(field)};
}
}
case Expression::Kind::TupleLiteral: {
if (act->pos() <
static_cast<int>(cast<TupleLiteral>(exp).fields().size())) {
// { { vk :: (f1=v1,..., fk=[],fk+1=ek+1,...) :: C, E, F} :: S,
// H}
// -> { { ek+1 :: (f1=v1,..., fk=vk, fk+1=[],...) :: C, E, F} :: S,
// H}
return Spawn{arena_->New<LValAction>(
cast<TupleLiteral>(exp).fields()[act->pos()])};
} else {
return Done{CreateTuple(act, &exp)};
}
}
case Expression::Kind::StructLiteral:
case Expression::Kind::StructTypeLiteral:
case Expression::Kind::IntLiteral:
case Expression::Kind::BoolLiteral:
case Expression::Kind::CallExpression:
case Expression::Kind::PrimitiveOperatorExpression:
case Expression::Kind::IntTypeLiteral:
case Expression::Kind::BoolTypeLiteral:
case Expression::Kind::TypeTypeLiteral:
case Expression::Kind::FunctionTypeLiteral:
case Expression::Kind::ContinuationTypeLiteral:
case Expression::Kind::StringLiteral:
case Expression::Kind::StringTypeLiteral:
case Expression::Kind::IntrinsicExpression:
FATAL_RUNTIME_ERROR_NO_LINE()
<< "Can't treat expression as lvalue: " << exp;
}
}
auto Interpreter::Convert(Nonnull<const Value*> value,
Nonnull<const Value*> destination_type) const
-> Nonnull<const Value*> {
switch (value->kind()) {
case Value::Kind::IntValue:
case Value::Kind::FunctionValue:
case Value::Kind::PointerValue:
case Value::Kind::BoolValue:
case Value::Kind::NominalClassValue:
case Value::Kind::AlternativeValue:
case Value::Kind::IntType:
case Value::Kind::BoolType:
case Value::Kind::TypeType:
case Value::Kind::FunctionType:
case Value::Kind::PointerType:
case Value::Kind::AutoType:
case Value::Kind::StructType:
case Value::Kind::NominalClassType:
case Value::Kind::ChoiceType:
case Value::Kind::ContinuationType:
case Value::Kind::VariableType:
case Value::Kind::BindingPlaceholderValue:
case Value::Kind::AlternativeConstructorValue:
case Value::Kind::ContinuationValue:
case Value::Kind::StringType:
case Value::Kind::StringValue:
// TODO: add `CHECK(TypeEqual(type, value->dynamic_type()))`, once we
// have Value::dynamic_type.
return value;
case Value::Kind::StructValue: {
const auto& struct_val = cast<StructValue>(*value);
switch (destination_type->kind()) {
case Value::Kind::StructType: {
const auto& destination_struct_type =
cast<StructType>(*destination_type);
std::vector<StructElement> new_elements;
for (const auto& [field_name, field_type] :
destination_struct_type.fields()) {
std::optional<Nonnull<const Value*>> old_value =
struct_val.FindField(field_name);
new_elements.push_back(
{.name = field_name, .value = Convert(*old_value, field_type)});
}
return arena_->New<StructValue>(std::move(new_elements));
}
case Value::Kind::NominalClassType:
return arena_->New<NominalClassValue>(destination_type, value);
default:
FATAL() << "Can't convert value " << *value << " to type "
<< *destination_type;
}
}
case Value::Kind::TupleValue: {
const auto& tuple = cast<TupleValue>(value);
const auto& destination_tuple_type = cast<TupleValue>(destination_type);
CHECK(tuple->elements().size() ==
destination_tuple_type->elements().size());
std::vector<Nonnull<const Value*>> new_elements;
for (size_t i = 0; i < tuple->elements().size(); ++i) {
new_elements.push_back(Convert(tuple->elements()[i],
destination_tuple_type->elements()[i]));
}
return arena_->New<TupleValue>(std::move(new_elements));
}
}
}
auto Interpreter::StepExp() -> Transition {
Nonnull<Action*> act = todo_.Top();
const Expression& exp = cast<ExpressionAction>(*act).expression();
if (trace_) {
llvm::outs() << "--- step exp " << exp << " (" << exp.source_loc()
<< ") --->\n";
}
switch (exp.kind()) {
case Expression::Kind::IndexExpression: {
if (act->pos() == 0) {
// { { e[i] :: C, E, F} :: S, H}
// -> { { e :: [][i] :: C, E, F} :: S, H}
return Spawn{arena_->New<ExpressionAction>(
&cast<IndexExpression>(exp).aggregate())};
} else if (act->pos() == 1) {
return Spawn{arena_->New<ExpressionAction>(
&cast<IndexExpression>(exp).offset())};
} else {
// { { v :: [][i] :: C, E, F} :: S, H}
// -> { { v_i :: C, E, F} : S, H}
const auto& tuple = cast<TupleValue>(*act->results()[0]);
int i = cast<IntValue>(*act->results()[1]).value();
if (i < 0 || i >= static_cast<int>(tuple.elements().size())) {
FATAL_RUNTIME_ERROR_NO_LINE()
<< "index " << i << " out of range in " << tuple;
}
return Done{tuple.elements()[i]};
}
}
case Expression::Kind::TupleLiteral: {
if (act->pos() <
static_cast<int>(cast<TupleLiteral>(exp).fields().size())) {
// { { vk :: (f1=v1,..., fk=[],fk+1=ek+1,...) :: C, E, F} :: S,
// H}
// -> { { ek+1 :: (f1=v1,..., fk=vk, fk+1=[],...) :: C, E, F} :: S,
// H}
return Spawn{arena_->New<ExpressionAction>(
cast<TupleLiteral>(exp).fields()[act->pos()])};
} else {
return Done{CreateTuple(act, &exp)};
}
}
case Expression::Kind::StructLiteral: {
const auto& literal = cast<StructLiteral>(exp);
if (act->pos() < static_cast<int>(literal.fields().size())) {
return Spawn{arena_->New<ExpressionAction>(
&literal.fields()[act->pos()].expression())};
} else {
return Done{CreateStruct(literal.fields(), act->results())};
}
}
case Expression::Kind::StructTypeLiteral: {
const auto& struct_type = cast<StructTypeLiteral>(exp);
if (act->pos() < static_cast<int>(struct_type.fields().size())) {
return Spawn{arena_->New<ExpressionAction>(
&struct_type.fields()[act->pos()].expression())};
} else {
std::vector<NamedValue> fields;
for (size_t i = 0; i < struct_type.fields().size(); ++i) {
fields.push_back({struct_type.fields()[i].name(), act->results()[i]});
}
return Done{arena_->New<StructType>(std::move(fields))};
}
}
case Expression::Kind::FieldAccessExpression: {
const auto& access = cast<FieldAccessExpression>(exp);
if (act->pos() == 0) {
// { { e.f :: C, E, F} :: S, H}
// -> { { e :: [].f :: C, E, F} :: S, H}
return Spawn{arena_->New<ExpressionAction>(&access.aggregate())};
} else {
// { { v :: [].f :: C, E, F} :: S, H}
// -> { { v_f :: C, E, F} : S, H}
return Done{act->results()[0]->GetField(
arena_, FieldPath(access.field()), exp.source_loc())};
}
}
case Expression::Kind::IdentifierExpression: {
CHECK(act->pos() == 0);
const auto& ident = cast<IdentifierExpression>(exp);
// { {x :: C, E, F} :: S, H} -> { {H(E(x)) :: C, E, F} :: S, H}
Address pointer = GetFromEnv(exp.source_loc(), ident.name());
return Done{heap_.Read(pointer, exp.source_loc())};
}
case Expression::Kind::IntLiteral:
CHECK(act->pos() == 0);
// { {n :: C, E, F} :: S, H} -> { {n' :: C, E, F} :: S, H}
return Done{arena_->New<IntValue>(cast<IntLiteral>(exp).value())};
case Expression::Kind::BoolLiteral:
CHECK(act->pos() == 0);
// { {n :: C, E, F} :: S, H} -> { {n' :: C, E, F} :: S, H}
return Done{arena_->New<BoolValue>(cast<BoolLiteral>(exp).value())};
case Expression::Kind::PrimitiveOperatorExpression: {
const auto& op = cast<PrimitiveOperatorExpression>(exp);
if (act->pos() != static_cast<int>(op.arguments().size())) {
// { {v :: op(vs,[],e,es) :: C, E, F} :: S, H}
// -> { {e :: op(vs,v,[],es) :: C, E, F} :: S, H}
Nonnull<const Expression*> arg = op.arguments()[act->pos()];
return Spawn{arena_->New<ExpressionAction>(arg)};
} else {
// { {v :: op(vs,[]) :: C, E, F} :: S, H}
// -> { {eval_prim(op, (vs,v)) :: C, E, F} :: S, H}
return Done{EvalPrim(op.op(), act->results(), exp.source_loc())};
}
}
case Expression::Kind::CallExpression:
if (act->pos() == 0) {
// { {e1(e2) :: C, E, F} :: S, H}
// -> { {e1 :: [](e2) :: C, E, F} :: S, H}
return Spawn{arena_->New<ExpressionAction>(
&cast<CallExpression>(exp).function())};
} else if (act->pos() == 1) {
// { { v :: [](e) :: C, E, F} :: S, H}
// -> { { e :: v([]) :: C, E, F} :: S, H}
return Spawn{arena_->New<ExpressionAction>(
&cast<CallExpression>(exp).argument())};
} else if (act->pos() == 2) {
// { { v2 :: v1([]) :: C, E, F} :: S, H}
// -> { {C',E',F'} :: {C, E, F} :: S, H}
switch (act->results()[0]->kind()) {
case Value::Kind::AlternativeConstructorValue: {
const auto& alt =
cast<AlternativeConstructorValue>(*act->results()[0]);
return Done{arena_->New<AlternativeValue>(
alt.alt_name(), alt.choice_name(), act->results()[1])};
}
case Value::Kind::FunctionValue:
return CallFunction{
.function =
&cast<FunctionValue>(*act->results()[0]).declaration(),
.args = act->results()[1],
.source_loc = exp.source_loc()};
default:
FATAL_RUNTIME_ERROR(exp.source_loc())
<< "in call, expected a function, not " << *act->results()[0];
}
} else if (act->pos() == 3) {
if (act->results().size() < 3) {
// Control fell through without explicit return.
return Done{TupleValue::Empty()};
} else {
return Done{act->results()[2]};
}
} else {
FATAL() << "in handle_value with Call pos " << act->pos();
}
case Expression::Kind::IntrinsicExpression:
CHECK(act->pos() == 0);
// { {n :: C, E, F} :: S, H} -> { {n' :: C, E, F} :: S, H}
switch (cast<IntrinsicExpression>(exp).intrinsic()) {
case IntrinsicExpression::Intrinsic::Print:
Address pointer = GetFromEnv(exp.source_loc(), "format_str");
Nonnull<const Value*> pointee = heap_.Read(pointer, exp.source_loc());
CHECK(pointee->kind() == Value::Kind::StringValue);
// TODO: This could eventually use something like llvm::formatv.
llvm::outs() << cast<StringValue>(*pointee).value();
return Done{TupleValue::Empty()};
}
case Expression::Kind::IntTypeLiteral: {
CHECK(act->pos() == 0);
return Done{arena_->New<IntType>()};
}
case Expression::Kind::BoolTypeLiteral: {
CHECK(act->pos() == 0);
return Done{arena_->New<BoolType>()};
}
case Expression::Kind::TypeTypeLiteral: {
CHECK(act->pos() == 0);
return Done{arena_->New<TypeType>()};
}
case Expression::Kind::FunctionTypeLiteral: {
if (act->pos() == 0) {
return Spawn{arena_->New<ExpressionAction>(
&cast<FunctionTypeLiteral>(exp).parameter())};
} else if (act->pos() == 1) {
// { { pt :: fn [] -> e :: C, E, F} :: S, H}
// -> { { e :: fn pt -> []) :: C, E, F} :: S, H}
return Spawn{arena_->New<ExpressionAction>(
&cast<FunctionTypeLiteral>(exp).return_type())};
} else {
// { { rt :: fn pt -> [] :: C, E, F} :: S, H}
// -> { fn pt -> rt :: {C, E, F} :: S, H}
return Done{arena_->New<FunctionType>(std::vector<GenericBinding>(),
act->results()[0],
act->results()[1])};
}
}
case Expression::Kind::ContinuationTypeLiteral: {
CHECK(act->pos() == 0);
return Done{arena_->New<ContinuationType>()};
}
case Expression::Kind::StringLiteral:
CHECK(act->pos() == 0);
// { {n :: C, E, F} :: S, H} -> { {n' :: C, E, F} :: S, H}
return Done{arena_->New<StringValue>(cast<StringLiteral>(exp).value())};
case Expression::Kind::StringTypeLiteral: {
CHECK(act->pos() == 0);
return Done{arena_->New<StringType>()};
}
} // switch (exp->kind)
}
auto Interpreter::StepPattern() -> Transition {
Nonnull<Action*> act = todo_.Top();
const Pattern& pattern = cast<PatternAction>(*act).pattern();
if (trace_) {
llvm::outs() << "--- step pattern " << pattern << " ("
<< pattern.source_loc() << ") --->\n";
}
switch (pattern.kind()) {
case Pattern::Kind::AutoPattern: {
CHECK(act->pos() == 0);
return Done{arena_->New<AutoType>()};
}
case Pattern::Kind::BindingPattern: {
const auto& binding = cast<BindingPattern>(pattern);
if (act->pos() == 0) {
return Spawn{arena_->New<PatternAction>(&binding.type())};
} else {
return Done{arena_->New<BindingPlaceholderValue>(binding.name(),
act->results()[0])};
}
}
case Pattern::Kind::TuplePattern: {
const auto& tuple = cast<TuplePattern>(pattern);
if (act->pos() < static_cast<int>(tuple.fields().size())) {
// { { vk :: (f1=v1,..., fk=[],fk+1=ek+1,...) :: C, E, F} :: S,
// H}
// -> { { ek+1 :: (f1=v1,..., fk=vk, fk+1=[],...) :: C, E, F} :: S,
// H}
return Spawn{arena_->New<PatternAction>(tuple.fields()[act->pos()])};
} else {
return Done{arena_->New<TupleValue>(act->results())};
}
}
case Pattern::Kind::AlternativePattern: {
const auto& alternative = cast<AlternativePattern>(pattern);
if (act->pos() == 0) {
return Spawn{arena_->New<ExpressionAction>(&alternative.choice_type())};
} else if (act->pos() == 1) {
return Spawn{arena_->New<PatternAction>(&alternative.arguments())};
} else {
CHECK(act->pos() == 2);
const auto& choice_type = cast<ChoiceType>(*act->results()[0]);
return Done{arena_->New<AlternativeValue>(
alternative.alternative_name(), choice_type.name(),
act->results()[1])};
}
}
case Pattern::Kind::ExpressionPattern:
return Delegate{arena_->New<ExpressionAction>(
&cast<ExpressionPattern>(pattern).expression())};
}
}
static auto IsRunAction(Nonnull<Action*> action) -> bool {
const auto* statement = dyn_cast<StatementAction>(action);
return statement != nullptr && llvm::isa<Run>(statement->statement());
}
auto Interpreter::StepStmt() -> Transition {
Nonnull<Action*> act = todo_.Top();
const Statement& stmt = cast<StatementAction>(*act).statement();
if (trace_) {
llvm::outs() << "--- step stmt ";
stmt.PrintDepth(1, llvm::outs());
llvm::outs() << " (" << stmt.source_loc() << ") --->\n";
}
switch (stmt.kind()) {
case Statement::Kind::Match: {
const auto& match_stmt = cast<Match>(stmt);
if (act->pos() == 0) {
// { { (match (e) ...) :: C, E, F} :: S, H}
// -> { { e :: (match ([]) ...) :: C, E, F} :: S, H}
act->StartScope(Scope(CurrentEnv()));
return Spawn{arena_->New<ExpressionAction>(&match_stmt.expression())};
} else {
int clause_num = act->pos() - 1;
if (clause_num >= static_cast<int>(match_stmt.clauses().size())) {
return Done{};
}
auto c = match_stmt.clauses()[clause_num];
std::optional<Env> matches =
PatternMatch(&c.pattern().value(),
Convert(act->results()[0], &c.pattern().static_type()),
stmt.source_loc());
if (matches) { // We have a match, start the body.
// Ensure we don't process any more clauses.
act->set_pos(match_stmt.clauses().size() + 1);
for (const auto& [name, value] : *matches) {
act->scope()->values.Set(name, value);
act->scope()->locals.push_back(name);
}
return Spawn{arena_->New<StatementAction>(&c.statement())};
} else {
return RunAgain{};
}
}
}
case Statement::Kind::While:
if (act->pos() % 2 == 0) {
// { { (while (e) s) :: C, E, F} :: S, H}
// -> { { e :: (while ([]) s) :: C, E, F} :: S, H}
act->Clear();
return Spawn{
arena_->New<ExpressionAction>(&cast<While>(stmt).condition())};
} else {
Nonnull<const Value*> condition =
Convert(act->results().back(), arena_->New<BoolType>());
if (cast<BoolValue>(*condition).value()) {
// { {true :: (while ([]) s) :: C, E, F} :: S, H}
// -> { { s :: (while (e) s) :: C, E, F } :: S, H}
return Spawn{arena_->New<StatementAction>(&cast<While>(stmt).body())};
} else {
// { {false :: (while ([]) s) :: C, E, F} :: S, H}
// -> { { C, E, F } :: S, H}
return Done{};
}
}
case Statement::Kind::Break: {
CHECK(act->pos() == 0);
// { { break; :: ... :: (while (e) s) :: C, E, F} :: S, H}
// -> { { C, E', F} :: S, H}
return UnwindPast{&cast<Break>(stmt).loop()};
}
case Statement::Kind::Continue: {
CHECK(act->pos() == 0);
// { { continue; :: ... :: (while (e) s) :: C, E, F} :: S, H}
// -> { { (while (e) s) :: C, E', F} :: S, H}
return UnwindTo{&cast<Continue>(stmt).loop()};
}
case Statement::Kind::Block: {
if (act->pos() == 0) {
const Block& block = cast<Block>(stmt);
if (block.statement()) {
act->StartScope(Scope(CurrentEnv()));
return Spawn{arena_->New<StatementAction>(*block.statement())};
} else {
return Done{};
}
} else {
return Done{};
}
}
case Statement::Kind::VariableDefinition: {
const auto& definition = cast<VariableDefinition>(stmt);
if (act->pos() == 0) {
// { {(var x = e) :: C, E, F} :: S, H}
// -> { {e :: (var x = []) :: C, E, F} :: S, H}
return Spawn{arena_->New<ExpressionAction>(&definition.init())};
} else {
// { { v :: (x = []) :: C, E, F} :: S, H}
// -> { { C, E(x := a), F} :: S, H(a := copy(v))}
Nonnull<const Value*> v =
Convert(act->results()[0], &definition.pattern().static_type());
Nonnull<const Value*> p =
&cast<VariableDefinition>(stmt).pattern().value();
std::optional<Env> matches = PatternMatch(p, v, stmt.source_loc());
CHECK(matches)
<< stmt.source_loc()
<< ": internal error in variable definition, match failed";
for (const auto& [name, value] : *matches) {
Scope& current_scope = CurrentScope();
current_scope.values.Set(name, value);
current_scope.locals.push_back(name);
}
return Done{};
}
}
case Statement::Kind::ExpressionStatement:
if (act->pos() == 0) {
// { {e :: C, E, F} :: S, H}
// -> { {e :: C, E, F} :: S, H}
return Spawn{arena_->New<ExpressionAction>(
&cast<ExpressionStatement>(stmt).expression())};
} else {
return Done{};
}
case Statement::Kind::Assign: {
const auto& assign = cast<Assign>(stmt);
if (act->pos() == 0) {
// { {(lv = e) :: C, E, F} :: S, H}
// -> { {lv :: ([] = e) :: C, E, F} :: S, H}
return Spawn{arena_->New<LValAction>(&assign.lhs())};
} else if (act->pos() == 1) {
// { { a :: ([] = e) :: C, E, F} :: S, H}
// -> { { e :: (a = []) :: C, E, F} :: S, H}
return Spawn{arena_->New<ExpressionAction>(&assign.rhs())};
} else {
// { { v :: (a = []) :: C, E, F} :: S, H}
// -> { { C, E, F} :: S, H(a := v)}
auto pat = act->results()[0];
auto val = Convert(act->results()[1], &assign.lhs().static_type());
PatternAssignment(pat, val, stmt.source_loc());
return Done{};
}
}
case Statement::Kind::If:
if (act->pos() == 0) {
// { {(if (e) then_stmt else else_stmt) :: C, E, F} :: S, H}
// -> { { e :: (if ([]) then_stmt else else_stmt) :: C, E, F} :: S, H}
return Spawn{
arena_->New<ExpressionAction>(&cast<If>(stmt).condition())};
} else {
Nonnull<const Value*> condition =
Convert(act->results()[0], arena_->New<BoolType>());
if (cast<BoolValue>(*condition).value()) {
// { {true :: if ([]) then_stmt else else_stmt :: C, E, F} ::
// S, H}
// -> { { then_stmt :: C, E, F } :: S, H}
return Delegate{
arena_->New<StatementAction>(&cast<If>(stmt).then_statement())};
} else if (cast<If>(stmt).else_statement()) {
// { {false :: if ([]) then_stmt else else_stmt :: C, E, F} ::
// S, H}
// -> { { else_stmt :: C, E, F } :: S, H}
return Delegate{
arena_->New<StatementAction>(*cast<If>(stmt).else_statement())};
} else {
return Done{};
}
}
case Statement::Kind::Return:
if (act->pos() == 0) {
// { {return e :: C, E, F} :: S, H}
// -> { {e :: return [] :: C, E, F} :: S, H}
return Spawn{
arena_->New<ExpressionAction>(&cast<Return>(stmt).expression())};
} else {
// { {v :: return [] :: C, E, F} :: {C', E', F'} :: S, H}
// -> { {v :: C', E', F'} :: S, H}
// TODO(geoffromer): convert the result to the function's return type,
// once #880 gives us a way to find that type.
const FunctionDeclaration& function = cast<Return>(stmt).function();
return UnwindPast{*function.body(), act->results()[0]};
}
case Statement::Kind::Sequence: {
// { { (s1,s2) :: C, E, F} :: S, H}
// -> { { s1 :: s2 :: C, E, F} :: S, H}
const auto& seq = cast<Sequence>(stmt);
if (act->pos() == 0) {
return Spawn{arena_->New<StatementAction>(&seq.statement())};
} else {
if (seq.next()) {
return Delegate{
arena_->New<StatementAction>(*cast<Sequence>(stmt).next())};
} else {
return Done{};
}
}
}
case Statement::Kind::Continuation: {
CHECK(act->pos() == 0);
// Create a continuation object by creating a frame similar the
// way one is created in a function call.
auto continuation_stack = arena_->New<std::vector<Nonnull<Action*>>>();
continuation_stack->push_back(
arena_->New<StatementAction>(&cast<Continuation>(stmt).body()));
continuation_stack->push_back(
arena_->New<ScopeAction>(Scope(CurrentEnv())));
AllocationId continuation_address = heap_.AllocateValue(
arena_->New<ContinuationValue>(continuation_stack));
// Bind the continuation object to the continuation variable
CurrentScope().values.Set(
cast<Continuation>(stmt).continuation_variable(),
continuation_address);
return Done{};
}
case Statement::Kind::Run: {
auto& run = cast<Run>(stmt);
if (act->pos() == 0) {
// Evaluate the argument of the run statement.
return Spawn{arena_->New<ExpressionAction>(&run.argument())};
} else if (act->pos() == 1) {
// Push the continuation onto the current stack.
std::vector<Nonnull<Action*>>& continuation_vector =
cast<const ContinuationValue>(*act->results()[0]).stack();
while (!continuation_vector.empty()) {
todo_.Push(continuation_vector.back());
continuation_vector.pop_back();
}
act->set_pos(2);
return ManualTransition{};
} else {
return Done{};
}
}
case Statement::Kind::Await:
CHECK(act->pos() == 0);
// Pause the current continuation
todo_.Pop();
std::vector<Nonnull<Action*>> paused;
while (!IsRunAction(todo_.Top())) {
paused.push_back(todo_.Pop());
}
const auto& continuation =
cast<const ContinuationValue>(*todo_.Top()->results()[0]);
CHECK(continuation.stack().empty());
// Update the continuation with the paused stack.
continuation.stack() = std::move(paused);
return ManualTransition{};
}
}
class Interpreter::DoTransition {
public:
// Does not take ownership of interpreter.
explicit DoTransition(Interpreter* interpreter) : interpreter(interpreter) {}
void operator()(const Done& done) {
Nonnull<Action*> act = interpreter->todo_.Pop();
if (act->scope().has_value()) {
interpreter->DeallocateScope(*act->scope());
}
switch (act->kind()) {
case Action::Kind::ExpressionAction:
case Action::Kind::LValAction:
case Action::Kind::PatternAction:
CHECK(done.result.has_value());
interpreter->todo_.Top()->AddResult(*done.result);
break;
case Action::Kind::StatementAction:
CHECK(!done.result.has_value());
break;
case Action::Kind::ScopeAction:
if (done.result.has_value()) {
interpreter->todo_.Top()->AddResult(*done.result);
}
break;
}
}
void operator()(const Spawn& spawn) {
Nonnull<Action*> action = interpreter->todo_.Top();
action->set_pos(action->pos() + 1);
interpreter->todo_.Push(spawn.child);
}
void operator()(const Delegate& delegate) {
Nonnull<Action*> act = interpreter->todo_.Pop();
if (act->scope().has_value()) {
delegate.delegate->StartScope(*act->scope());
}
interpreter->todo_.Push(delegate.delegate);
}
void operator()(const RunAgain&) {
Nonnull<Action*> action = interpreter->todo_.Top();
action->set_pos(action->pos() + 1);
}
void operator()(const UnwindTo& unwind_to) {
while (true) {
if (const auto* statement_action =
dyn_cast<StatementAction>(interpreter->todo_.Top());
statement_action != nullptr &&
&statement_action->statement() == unwind_to.ast_node) {
break;
}
Nonnull<Action*> action = interpreter->todo_.Pop();
if (action->scope().has_value()) {
interpreter->DeallocateScope(*action->scope());
}
}
}
void operator()(const UnwindPast& unwind_past) {
while (true) {
Nonnull<Action*> action = interpreter->todo_.Pop();
if (action->scope().has_value()) {
interpreter->DeallocateScope(*action->scope());
}
if (const auto* statement_action = dyn_cast<StatementAction>(action);
statement_action != nullptr &&
&statement_action->statement() == unwind_past.ast_node) {
break;
}
}
if (unwind_past.result.has_value()) {
interpreter->todo_.Top()->AddResult(*unwind_past.result);
}
}
void operator()(const CallFunction& call) {
Nonnull<Action*> action = interpreter->todo_.Top();
action->set_pos(action->pos() + 1);
Nonnull<const Value*> converted_args = interpreter->Convert(
call.args, &call.function->param_pattern().static_type());
std::optional<Env> matches =
interpreter->PatternMatch(&call.function->param_pattern().value(),
converted_args, call.source_loc);
CHECK(matches.has_value())
<< "internal error in call_function, pattern match failed";
// Create the new frame and push it on the stack
Scope new_scope(interpreter->globals_);
for (const auto& [name, value] : *matches) {
new_scope.values.Set(name, value);
new_scope.locals.push_back(name);
}
interpreter->todo_.Push(
interpreter->arena_->New<ScopeAction>(std::move(new_scope)));
CHECK(call.function->body()) << "Calling a function that's missing a body";
interpreter->todo_.Push(
interpreter->arena_->New<StatementAction>(*call.function->body()));
}
void operator()(const ManualTransition&) {}
private:
Nonnull<Interpreter*> interpreter;
};
// State transition.
void Interpreter::Step() {
Nonnull<Action*> act = todo_.Top();
switch (act->kind()) {
case Action::Kind::LValAction:
std::visit(DoTransition(this), StepLvalue());
break;
case Action::Kind::ExpressionAction:
std::visit(DoTransition(this), StepExp());
break;
case Action::Kind::PatternAction:
std::visit(DoTransition(this), StepPattern());
break;
case Action::Kind::StatementAction:
std::visit(DoTransition(this), StepStmt());
break;
case Action::Kind::ScopeAction:
if (act->results().empty()) {
std::visit(DoTransition(this), Transition{Done{}});
} else {
CHECK(act->results().size() == 1);
std::visit(DoTransition(this), Transition{Done{act->results()[0]}});
}
} // switch
}
auto Interpreter::ExecuteAction(Nonnull<Action*> action, Env values,
bool trace_steps) -> Nonnull<const Value*> {
todo_ = {};
todo_.Push(arena_->New<ScopeAction>(Scope(values)));
todo_.Push(action);
while (todo_.Count() > 1) {
Step();
if (trace_steps) {
PrintState(llvm::outs());
}
}
CHECK(todo_.Top()->results().size() == 1);
return todo_.Top()->results()[0];
}
auto Interpreter::InterpProgram(llvm::ArrayRef<Nonnull<Declaration*>> fs,
Nonnull<const Expression*> call_main) -> int {
// Check that the interpreter is in a clean state.
CHECK(globals_.IsEmpty());
CHECK(todo_.IsEmpty());
if (trace_) {
llvm::outs() << "********** initializing globals **********\n";
}
InitGlobals(fs);
if (trace_) {
llvm::outs() << "********** calling main function **********\n";
PrintState(llvm::outs());
}
return cast<IntValue>(*ExecuteAction(arena_->New<ExpressionAction>(call_main),
globals_, trace_))
.value();
}
auto Interpreter::InterpExp(Env values, Nonnull<const Expression*> e)
-> Nonnull<const Value*> {
return ExecuteAction(arena_->New<ExpressionAction>(e), values,
/*trace_steps=*/false);
}
auto Interpreter::InterpPattern(Env values, Nonnull<const Pattern*> p)
-> Nonnull<const Value*> {
return ExecuteAction(arena_->New<PatternAction>(p), values,
/*trace_steps=*/false);
}
} // namespace Carbon
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