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carbon-lang/executable_semantics/interpreter/interpreter.cpp
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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::CurrentEnv() -> Env { return todo_.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: " << todo_;
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 DeclarationKind::FunctionDeclaration: {
const auto& func_def = cast<FunctionDeclaration>(d);
Env new_env = *env;
// Bring the deduced parameters into scope.
for (Nonnull<const GenericBinding*> 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 DeclarationKind::ClassDeclaration: {
const auto& class_decl = cast<ClassDeclaration>(d);
std::vector<NamedValue> fields;
std::vector<NamedValue> methods;
for (Nonnull<const Member*> m : class_decl.members()) {
switch (m->kind()) {
case MemberKind::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_decl.name(), std::move(fields), std::move(methods));
AllocationId a = heap_.AllocateValue(st);
env->Set(class_decl.name(), a);
break;
}
case DeclarationKind::ChoiceDeclaration: {
const auto& choice = cast<ChoiceDeclaration>(d);
std::vector<NamedValue> alts;
for (Nonnull<const AlternativeSignature*> 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 DeclarationKind::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_);
}
}
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";
}
}
void Interpreter::StepLvalue() {
Action& act = todo_.CurrentAction();
const Expression& exp = cast<LValAction>(act).expression();
if (trace_) {
llvm::outs() << "--- step lvalue " << exp << " (" << exp.source_loc()
<< ") --->\n";
}
switch (exp.kind()) {
case ExpressionKind::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 todo_.FinishAction(v);
}
case ExpressionKind::FieldAccessExpression: {
if (act.pos() == 0) {
// { {e.f :: C, E, F} :: S, H}
// -> { e :: [].f :: C, E, F} :: S, H}
return todo_.Spawn(std::make_unique<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 todo_.FinishAction(arena_->New<PointerValue>(field));
}
}
case ExpressionKind::IndexExpression: {
if (act.pos() == 0) {
// { {e[i] :: C, E, F} :: S, H}
// -> { e :: [][i] :: C, E, F} :: S, H}
return todo_.Spawn(std::make_unique<LValAction>(
&cast<IndexExpression>(exp).aggregate()));
} else if (act.pos() == 1) {
return todo_.Spawn(std::make_unique<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 todo_.FinishAction(arena_->New<PointerValue>(field));
}
}
case ExpressionKind::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 todo_.Spawn(std::make_unique<LValAction>(
cast<TupleLiteral>(exp).fields()[act.pos()]));
} else {
return todo_.FinishAction(arena_->New<TupleValue>(act.results()));
}
}
case ExpressionKind::StructLiteral:
case ExpressionKind::StructTypeLiteral:
case ExpressionKind::IntLiteral:
case ExpressionKind::BoolLiteral:
case ExpressionKind::CallExpression:
case ExpressionKind::PrimitiveOperatorExpression:
case ExpressionKind::IntTypeLiteral:
case ExpressionKind::BoolTypeLiteral:
case ExpressionKind::TypeTypeLiteral:
case ExpressionKind::FunctionTypeLiteral:
case ExpressionKind::ContinuationTypeLiteral:
case ExpressionKind::StringLiteral:
case ExpressionKind::StringTypeLiteral:
case ExpressionKind::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<NamedValue> 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));
}
}
}
void Interpreter::StepExp() {
Action& act = todo_.CurrentAction();
const Expression& exp = cast<ExpressionAction>(act).expression();
if (trace_) {
llvm::outs() << "--- step exp " << exp << " (" << exp.source_loc()
<< ") --->\n";
}
switch (exp.kind()) {
case ExpressionKind::IndexExpression: {
if (act.pos() == 0) {
// { { e[i] :: C, E, F} :: S, H}
// -> { { e :: [][i] :: C, E, F} :: S, H}
return todo_.Spawn(std::make_unique<ExpressionAction>(
&cast<IndexExpression>(exp).aggregate()));
} else if (act.pos() == 1) {
return todo_.Spawn(std::make_unique<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 todo_.FinishAction(tuple.elements()[i]);
}
}
case ExpressionKind::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 todo_.Spawn(std::make_unique<ExpressionAction>(
cast<TupleLiteral>(exp).fields()[act.pos()]));
} else {
return todo_.FinishAction(arena_->New<TupleValue>(act.results()));
}
}
case ExpressionKind::StructLiteral: {
const auto& literal = cast<StructLiteral>(exp);
if (act.pos() < static_cast<int>(literal.fields().size())) {
return todo_.Spawn(std::make_unique<ExpressionAction>(
&literal.fields()[act.pos()].expression()));
} else {
return todo_.FinishAction(
CreateStruct(literal.fields(), act.results()));
}
}
case ExpressionKind::StructTypeLiteral: {
const auto& struct_type = cast<StructTypeLiteral>(exp);
if (act.pos() < static_cast<int>(struct_type.fields().size())) {
return todo_.Spawn(std::make_unique<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 todo_.FinishAction(arena_->New<StructType>(std::move(fields)));
}
}
case ExpressionKind::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 todo_.Spawn(
std::make_unique<ExpressionAction>(&access.aggregate()));
} else {
// { { v :: [].f :: C, E, F} :: S, H}
// -> { { v_f :: C, E, F} : S, H}
return todo_.FinishAction(act.results()[0]->GetField(
arena_, FieldPath(access.field()), exp.source_loc()));
}
}
case ExpressionKind::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 todo_.FinishAction(heap_.Read(pointer, exp.source_loc()));
}
case ExpressionKind::IntLiteral:
CHECK(act.pos() == 0);
// { {n :: C, E, F} :: S, H} -> { {n' :: C, E, F} :: S, H}
return todo_.FinishAction(
arena_->New<IntValue>(cast<IntLiteral>(exp).value()));
case ExpressionKind::BoolLiteral:
CHECK(act.pos() == 0);
// { {n :: C, E, F} :: S, H} -> { {n' :: C, E, F} :: S, H}
return todo_.FinishAction(
arena_->New<BoolValue>(cast<BoolLiteral>(exp).value()));
case ExpressionKind::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 todo_.Spawn(std::make_unique<ExpressionAction>(arg));
} else {
// { {v :: op(vs,[]) :: C, E, F} :: S, H}
// -> { {eval_prim(op, (vs,v)) :: C, E, F} :: S, H}
return todo_.FinishAction(
EvalPrim(op.op(), act.results(), exp.source_loc()));
}
}
case ExpressionKind::CallExpression:
if (act.pos() == 0) {
// { {e1(e2) :: C, E, F} :: S, H}
// -> { {e1 :: [](e2) :: C, E, F} :: S, H}
return todo_.Spawn(std::make_unique<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 todo_.Spawn(std::make_unique<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 todo_.FinishAction(arena_->New<AlternativeValue>(
alt.alt_name(), alt.choice_name(), act.results()[1]));
}
case Value::Kind::FunctionValue: {
const FunctionDeclaration& function =
cast<FunctionValue>(*act.results()[0]).declaration();
Nonnull<const Value*> converted_args = Convert(
act.results()[1], &function.param_pattern().static_type());
std::optional<Env> matches =
PatternMatch(&function.param_pattern().value(), converted_args,
exp.source_loc());
CHECK(matches.has_value())
<< "internal error in call_function, pattern match failed";
Scope new_scope(globals_, &heap_);
for (const auto& [name, value] : *matches) {
new_scope.AddLocal(name, value);
}
CHECK(function.body().has_value())
<< "Calling a function that's missing a body";
return todo_.Spawn(
std::make_unique<StatementAction>(*function.body()),
std::move(new_scope));
}
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 todo_.FinishAction(TupleValue::Empty());
} else {
return todo_.FinishAction(act.results()[2]);
}
} else {
FATAL() << "in handle_value with Call pos " << act.pos();
}
case ExpressionKind::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 todo_.FinishAction(TupleValue::Empty());
}
case ExpressionKind::IntTypeLiteral: {
CHECK(act.pos() == 0);
return todo_.FinishAction(arena_->New<IntType>());
}
case ExpressionKind::BoolTypeLiteral: {
CHECK(act.pos() == 0);
return todo_.FinishAction(arena_->New<BoolType>());
}
case ExpressionKind::TypeTypeLiteral: {
CHECK(act.pos() == 0);
return todo_.FinishAction(arena_->New<TypeType>());
}
case ExpressionKind::FunctionTypeLiteral: {
if (act.pos() == 0) {
return todo_.Spawn(std::make_unique<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 todo_.Spawn(std::make_unique<ExpressionAction>(
&cast<FunctionTypeLiteral>(exp).return_type()));
} else {
// { { rt :: fn pt -> [] :: C, E, F} :: S, H}
// -> { fn pt -> rt :: {C, E, F} :: S, H}
return todo_.FinishAction(arena_->New<FunctionType>(
std::vector<Nonnull<const GenericBinding*>>(), act.results()[0],
act.results()[1]));
}
}
case ExpressionKind::ContinuationTypeLiteral: {
CHECK(act.pos() == 0);
return todo_.FinishAction(arena_->New<ContinuationType>());
}
case ExpressionKind::StringLiteral:
CHECK(act.pos() == 0);
// { {n :: C, E, F} :: S, H} -> { {n' :: C, E, F} :: S, H}
return todo_.FinishAction(
arena_->New<StringValue>(cast<StringLiteral>(exp).value()));
case ExpressionKind::StringTypeLiteral: {
CHECK(act.pos() == 0);
return todo_.FinishAction(arena_->New<StringType>());
}
} // switch (exp->kind)
}
void Interpreter::StepPattern() {
Action& act = todo_.CurrentAction();
const Pattern& pattern = cast<PatternAction>(act).pattern();
if (trace_) {
llvm::outs() << "--- step pattern " << pattern << " ("
<< pattern.source_loc() << ") --->\n";
}
switch (pattern.kind()) {
case PatternKind::AutoPattern: {
CHECK(act.pos() == 0);
return todo_.FinishAction(arena_->New<AutoType>());
}
case PatternKind::BindingPattern: {
const auto& binding = cast<BindingPattern>(pattern);
if (act.pos() == 0) {
return todo_.Spawn(std::make_unique<PatternAction>(&binding.type()));
} else {
return todo_.FinishAction(arena_->New<BindingPlaceholderValue>(
binding.name(), act.results()[0]));
}
}
case PatternKind::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 todo_.Spawn(
std::make_unique<PatternAction>(tuple.fields()[act.pos()]));
} else {
return todo_.FinishAction(arena_->New<TupleValue>(act.results()));
}
}
case PatternKind::AlternativePattern: {
const auto& alternative = cast<AlternativePattern>(pattern);
if (act.pos() == 0) {
return todo_.Spawn(
std::make_unique<ExpressionAction>(&alternative.choice_type()));
} else if (act.pos() == 1) {
return todo_.Spawn(
std::make_unique<PatternAction>(&alternative.arguments()));
} else {
CHECK(act.pos() == 2);
const auto& choice_type = cast<ChoiceType>(*act.results()[0]);
return todo_.FinishAction(arena_->New<AlternativeValue>(
alternative.alternative_name(), choice_type.name(),
act.results()[1]));
}
}
case PatternKind::ExpressionPattern:
if (act.pos() == 0) {
return todo_.Spawn(std::make_unique<ExpressionAction>(
&cast<ExpressionPattern>(pattern).expression()));
} else {
return todo_.FinishAction(act.results()[0]);
}
}
}
void Interpreter::StepStmt() {
Action& act = todo_.CurrentAction();
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 StatementKind::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(), &heap_));
return todo_.Spawn(
std::make_unique<ExpressionAction>(&match_stmt.expression()));
} else {
int clause_num = act.pos() - 1;
if (clause_num >= static_cast<int>(match_stmt.clauses().size())) {
return todo_.FinishAction();
}
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()->AddLocal(name, value);
}
return todo_.Spawn(std::make_unique<StatementAction>(&c.statement()));
} else {
return todo_.RunAgain();
}
}
}
case StatementKind::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 todo_.Spawn(
std::make_unique<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 todo_.Spawn(
std::make_unique<StatementAction>(&cast<While>(stmt).body()));
} else {
// { {false :: (while ([]) s) :: C, E, F} :: S, H}
// -> { { C, E, F } :: S, H}
return todo_.FinishAction();
}
}
case StatementKind::Break: {
CHECK(act.pos() == 0);
// { { break; :: ... :: (while (e) s) :: C, E, F} :: S, H}
// -> { { C, E', F} :: S, H}
return todo_.UnwindPast(&cast<Break>(stmt).loop());
}
case StatementKind::Continue: {
CHECK(act.pos() == 0);
// { { continue; :: ... :: (while (e) s) :: C, E, F} :: S, H}
// -> { { (while (e) s) :: C, E', F} :: S, H}
return todo_.UnwindTo(&cast<Continue>(stmt).loop());
}
case StatementKind::Block: {
const auto& block = cast<Block>(stmt);
if (act.pos() >= static_cast<int>(block.statements().size())) {
// If the position is past the end of the block, end processing. Note
// that empty blocks immediately end.
return todo_.FinishAction();
}
// Initialize a scope when starting a block.
if (act.pos() == 0) {
act.StartScope(Scope(CurrentEnv(), &heap_));
}
// Process the next statement in the block. The position will be
// incremented as part of Spawn.
return todo_.Spawn(
std::make_unique<StatementAction>(block.statements()[act.pos()]));
}
case StatementKind::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 todo_.Spawn(
std::make_unique<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 = todo_.CurrentScope();
current_scope.AddLocal(name, value);
}
return todo_.FinishAction();
}
}
case StatementKind::ExpressionStatement:
if (act.pos() == 0) {
// { {e :: C, E, F} :: S, H}
// -> { {e :: C, E, F} :: S, H}
return todo_.Spawn(std::make_unique<ExpressionAction>(
&cast<ExpressionStatement>(stmt).expression()));
} else {
return todo_.FinishAction();
}
case StatementKind::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 todo_.Spawn(std::make_unique<LValAction>(&assign.lhs()));
} else if (act.pos() == 1) {
// { { a :: ([] = e) :: C, E, F} :: S, H}
// -> { { e :: (a = []) :: C, E, F} :: S, H}
return todo_.Spawn(std::make_unique<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 todo_.FinishAction();
}
}
case StatementKind::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 todo_.Spawn(
std::make_unique<ExpressionAction>(&cast<If>(stmt).condition()));
} else if (act.pos() == 1) {
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 todo_.Spawn(
std::make_unique<StatementAction>(&cast<If>(stmt).then_block()));
} else if (cast<If>(stmt).else_block()) {
// { {false :: if ([]) then_stmt else else_stmt :: C, E, F} ::
// S, H}
// -> { { else_stmt :: C, E, F } :: S, H}
return todo_.Spawn(
std::make_unique<StatementAction>(*cast<If>(stmt).else_block()));
} else {
return todo_.FinishAction();
}
} else {
return todo_.FinishAction();
}
case StatementKind::Return:
if (act.pos() == 0) {
// { {return e :: C, E, F} :: S, H}
// -> { {e :: return [] :: C, E, F} :: S, H}
return todo_.Spawn(std::make_unique<ExpressionAction>(
&cast<Return>(stmt).expression()));
} else {
// { {v :: return [] :: C, E, F} :: {C', E', F'} :: S, H}
// -> { {v :: C', E', F'} :: S, H}
const FunctionDeclaration& function = cast<Return>(stmt).function();
return todo_.UnwindPast(
*function.body(),
Convert(act.results()[0], &function.return_term().static_type()));
}
case StatementKind::Continuation: {
CHECK(act.pos() == 0);
// Create a continuation object by creating a frame similar the
// way one is created in a function call.
auto fragment = arena_->New<ContinuationValue::StackFragment>();
stack_fragments_.push_back(fragment);
std::vector<std::unique_ptr<Action>> reversed_todo;
reversed_todo.push_back(
std::make_unique<StatementAction>(&cast<Continuation>(stmt).body()));
reversed_todo.push_back(
std::make_unique<ScopeAction>(Scope(CurrentEnv(), &heap_)));
fragment->StoreReversed(std::move(reversed_todo));
AllocationId continuation_address =
heap_.AllocateValue(arena_->New<ContinuationValue>(fragment));
// Bind the continuation object to the continuation variable
todo_.CurrentScope().AddLocal(
cast<Continuation>(stmt).continuation_variable(),
continuation_address);
return todo_.FinishAction();
}
case StatementKind::Run: {
auto& run = cast<Run>(stmt);
if (act.pos() == 0) {
// Evaluate the argument of the run statement.
return todo_.Spawn(std::make_unique<ExpressionAction>(&run.argument()));
} else if (act.pos() == 1) {
// Push the continuation onto the current stack.
return todo_.Resume(cast<const ContinuationValue>(act.results()[0]));
} else {
return todo_.FinishAction();
}
}
case StatementKind::Await:
CHECK(act.pos() == 0);
return todo_.Suspend();
}
}
// State transition.
void Interpreter::Step() {
Action& act = todo_.CurrentAction();
switch (act.kind()) {
case Action::Kind::LValAction:
StepLvalue();
break;
case Action::Kind::ExpressionAction:
StepExp();
break;
case Action::Kind::PatternAction:
StepPattern();
break;
case Action::Kind::StatementAction:
StepStmt();
break;
case Action::Kind::ScopeAction:
FATAL() << "ScopeAction escaped ActionStack";
} // switch
}
auto Interpreter::ExecuteAction(std::unique_ptr<Action> action, Env values,
bool trace_steps) -> Nonnull<const Value*> {
todo_.Start(std::move(action), Scope(values, &heap_));
while (!todo_.IsEmpty()) {
Step();
if (trace_steps) {
PrintState(llvm::outs());
}
}
// Clean up any remaining suspended continuations.
for (Nonnull<ContinuationValue::StackFragment*> fragment : stack_fragments_) {
fragment->Clear();
}
return todo_.result();
}
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(std::make_unique<ExpressionAction>(call_main),
globals_, trace_))
.value();
}
auto Interpreter::InterpExp(Env values, Nonnull<const Expression*> e)
-> Nonnull<const Value*> {
return ExecuteAction(std::make_unique<ExpressionAction>(e), values,
/*trace_steps=*/false);
}
auto Interpreter::InterpPattern(Env values, Nonnull<const Pattern*> p)
-> Nonnull<const Value*> {
return ExecuteAction(std::make_unique<PatternAction>(p), values,
/*trace_steps=*/false);
}
} // namespace Carbon
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