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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 <list>
#include <map>
#include <optional>
#include <utility>
#include <vector>
#include "common/check.h"
#include "executable_semantics/ast/expression.h"
#include "executable_semantics/ast/function_definition.h"
#include "executable_semantics/common/arena.h"
#include "executable_semantics/common/error.h"
#include "executable_semantics/common/tracing_flag.h"
#include "executable_semantics/interpreter/action.h"
#include "executable_semantics/interpreter/frame.h"
#include "executable_semantics/interpreter/stack.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/Casting.h"
using llvm::cast;
namespace Carbon {
State* state = nullptr;
auto PatternMatch(const Value* pat, const Value* val, Env,
std::list<std::string>*, int) -> std::optional<Env>;
void Step();
//
// Auxiliary Functions
//
void PrintEnv(Env values, llvm::raw_ostream& out) {
llvm::ListSeparator sep;
for (const auto& [name, address] : values) {
out << sep << name << ": ";
state->heap.PrintAddress(address, out);
}
}
//
// State Operations
//
void PrintStack(const Stack<Frame*>& ls, llvm::raw_ostream& out) {
llvm::ListSeparator sep(" :: ");
for (const auto& frame : ls) {
out << sep << *frame;
}
}
auto CurrentEnv(State* state) -> Env {
Frame* frame = state->stack.Top();
return frame->scopes.Top()->values;
}
void PrintState(llvm::raw_ostream& out) {
out << "{\nstack: ";
PrintStack(state->stack, out);
out << "\nheap: " << state->heap;
if (!state->stack.IsEmpty() && !state->stack.Top()->scopes.IsEmpty()) {
out << "\nvalues: ";
PrintEnv(CurrentEnv(state), out);
}
out << "\n}\n";
}
auto EvalPrim(Operator op, const std::vector<const Value*>& args, int line_num)
-> const Value* {
switch (op) {
case Operator::Neg:
return global_arena->New<IntValue>(-cast<IntValue>(*args[0]).Val());
case Operator::Add:
return global_arena->New<IntValue>(cast<IntValue>(*args[0]).Val() +
cast<IntValue>(*args[1]).Val());
case Operator::Sub:
return global_arena->New<IntValue>(cast<IntValue>(*args[0]).Val() -
cast<IntValue>(*args[1]).Val());
case Operator::Mul:
return global_arena->New<IntValue>(cast<IntValue>(*args[0]).Val() *
cast<IntValue>(*args[1]).Val());
case Operator::Not:
return global_arena->New<BoolValue>(!cast<BoolValue>(*args[0]).Val());
case Operator::And:
return global_arena->New<BoolValue>(cast<BoolValue>(*args[0]).Val() &&
cast<BoolValue>(*args[1]).Val());
case Operator::Or:
return global_arena->New<BoolValue>(cast<BoolValue>(*args[0]).Val() ||
cast<BoolValue>(*args[1]).Val());
case Operator::Eq:
return global_arena->New<BoolValue>(
ValueEqual(args[0], args[1], line_num));
case Operator::Ptr:
return global_arena->New<PointerType>(args[0]);
case Operator::Deref:
llvm::errs() << line_num << ": dereference not implemented yet\n";
exit(-1);
}
}
// Globally-defined entities, such as functions, structs, choices.
static Env globals;
void InitEnv(const Declaration& d, Env* env) {
switch (d.tag()) {
case DeclarationKind::FunctionDeclaration: {
const FunctionDefinition& func_def =
d.GetFunctionDeclaration().definition;
Env new_env = *env;
// Bring the deduced parameters into scope.
for (const auto& deduced : func_def.deduced_parameters) {
Address a = state->heap.AllocateValue(
global_arena->New<VariableType>(deduced.name));
new_env.Set(deduced.name, a);
}
auto pt = InterpPattern(new_env, func_def.param_pattern);
auto f =
global_arena->New<FunctionValue>(func_def.name, pt, func_def.body);
Address a = state->heap.AllocateValue(f);
env->Set(func_def.name, a);
break;
}
case DeclarationKind::StructDeclaration: {
const StructDefinition& struct_def = d.GetStructDeclaration().definition;
VarValues fields;
VarValues methods;
for (const Member* m : struct_def.members) {
switch (m->tag()) {
case MemberKind::FieldMember: {
const BindingPattern* binding = m->GetFieldMember().binding;
const Expression* type_expression =
cast<ExpressionPattern>(binding->Type())->Expression();
auto type = InterpExp(Env(), type_expression);
fields.push_back(make_pair(*binding->Name(), type));
break;
}
}
}
auto st = global_arena->New<StructType>(
struct_def.name, std::move(fields), std::move(methods));
auto a = state->heap.AllocateValue(st);
env->Set(struct_def.name, a);
break;
}
case DeclarationKind::ChoiceDeclaration: {
const auto& choice = d.GetChoiceDeclaration();
VarValues alts;
for (const auto& [name, signature] : choice.alternatives) {
auto t = InterpExp(Env(), signature);
alts.push_back(make_pair(name, t));
}
auto ct = global_arena->New<ChoiceType>(choice.name, std::move(alts));
auto a = state->heap.AllocateValue(ct);
env->Set(choice.name, a);
break;
}
case DeclarationKind::VariableDeclaration: {
const auto& var = d.GetVariableDeclaration();
// Adds an entry in `globals` mapping the variable's name to the
// result of evaluating the initializer.
auto v = InterpExp(*env, var.initializer);
Address a = state->heap.AllocateValue(v);
env->Set(*var.binding->Name(), a);
break;
}
}
}
static void InitGlobals(std::list<Declaration>* fs) {
for (auto const& d : *fs) {
InitEnv(d, &globals);
}
}
// { S, H} -> { { C, E, F} :: S, H}
// where C is the body of the function,
// E is the environment (functions + parameters + locals)
// F is the function
void CallFunction(int line_num, std::vector<const Value*> operas,
State* state) {
switch (operas[0]->Tag()) {
case Value::Kind::FunctionValue: {
const auto& fn = cast<FunctionValue>(*operas[0]);
// Bind arguments to parameters
std::list<std::string> params;
std::optional<Env> matches =
PatternMatch(fn.Param(), operas[1], globals, &params, line_num);
CHECK(matches) << "internal error in call_function, pattern match failed";
// Create the new frame and push it on the stack
auto* scope = global_arena->New<Scope>(*matches, params);
auto* frame = global_arena->New<Frame>(
fn.Name(), Stack(scope),
Stack(Action::MakeStatementAction(fn.Body())));
state->stack.Push(frame);
break;
}
case Value::Kind::StructType: {
const Value* arg = CopyVal(operas[1], line_num);
const Value* sv = global_arena->New<StructValue>(operas[0], arg);
Frame* frame = state->stack.Top();
frame->todo.Push(Action::MakeValAction(sv));
break;
}
case Value::Kind::AlternativeConstructorValue: {
const auto& alt = cast<AlternativeConstructorValue>(*operas[0]);
const Value* arg = CopyVal(operas[1], line_num);
const Value* av = global_arena->New<AlternativeValue>(
alt.AltName(), alt.ChoiceName(), arg);
Frame* frame = state->stack.Top();
frame->todo.Push(Action::MakeValAction(av));
break;
}
default:
FATAL_RUNTIME_ERROR(line_num)
<< "in call, expected a function, not " << *operas[0];
}
}
void DeallocateScope(int line_num, Scope* scope) {
for (const auto& l : scope->locals) {
std::optional<Address> a = scope->values.Get(l);
CHECK(a);
state->heap.Deallocate(*a);
}
}
void DeallocateLocals(int line_num, Frame* frame) {
while (!frame->scopes.IsEmpty()) {
DeallocateScope(line_num, frame->scopes.Top());
frame->scopes.Pop();
}
}
void CreateTuple(Frame* frame, Action* act, const Expression* exp) {
// { { (v1,...,vn) :: C, E, F} :: S, H}
// -> { { `(v1,...,vn) :: C, E, F} :: S, H}
std::vector<TupleElement> elements;
auto f = exp->GetTupleLiteral().fields.begin();
for (auto i = act->results.begin(); i != act->results.end(); ++i, ++f) {
elements.push_back({.name = f->name, .value = *i});
}
const Value* tv = global_arena->New<TupleValue>(std::move(elements));
frame->todo.Pop(1);
frame->todo.Push(Action::MakeValAction(tv));
}
// Returns an updated environment that includes the bindings of
// pattern variables to their matched values, if matching succeeds.
//
// The names of the pattern variables are added to the vars parameter.
// Returns nullopt if the value doesn't match the pattern.
auto PatternMatch(const Value* p, const Value* v, Env values,
std::list<std::string>* vars, int line_num)
-> std::optional<Env> {
switch (p->Tag()) {
case Value::Kind::BindingPlaceholderValue: {
const auto& placeholder = cast<BindingPlaceholderValue>(*p);
if (placeholder.Name().has_value()) {
Address a = state->heap.AllocateValue(CopyVal(v, line_num));
vars->push_back(*placeholder.Name());
values.Set(*placeholder.Name(), a);
}
return values;
}
case Value::Kind::TupleValue:
switch (v->Tag()) {
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_RUNTIME_ERROR(line_num)
<< "arity mismatch in tuple pattern match:\n pattern: "
<< p_tup << "\n value: " << v_tup;
}
for (const TupleElement& pattern_element : p_tup.Elements()) {
const Value* value_field = v_tup.FindField(pattern_element.name);
if (value_field == nullptr) {
FATAL_RUNTIME_ERROR(line_num)
<< "field " << pattern_element.name << "not in " << *v;
}
std::optional<Env> matches = PatternMatch(
pattern_element.value, value_field, values, vars, line_num);
if (!matches) {
return std::nullopt;
}
values = *matches;
} // for
return values;
}
default:
llvm::errs()
<< "internal error, expected a tuple value in pattern, not " << *v
<< "\n";
exit(-1);
}
case Value::Kind::AlternativeValue:
switch (v->Tag()) {
case Value::Kind::AlternativeValue: {
const auto& p_alt = cast<AlternativeValue>(*p);
const auto& v_alt = cast<AlternativeValue>(*v);
if (p_alt.ChoiceName() != v_alt.ChoiceName() ||
p_alt.AltName() != v_alt.AltName()) {
return std::nullopt;
}
std::optional<Env> matches = PatternMatch(
p_alt.Argument(), v_alt.Argument(), values, vars, line_num);
if (!matches) {
return std::nullopt;
}
return *matches;
}
default:
llvm::errs()
<< "internal error, expected a choice alternative in pattern, "
"not "
<< *v << "\n";
exit(-1);
}
case Value::Kind::FunctionType:
switch (v->Tag()) {
case Value::Kind::FunctionType: {
const auto& p_fn = cast<FunctionType>(*p);
const auto& v_fn = cast<FunctionType>(*v);
std::optional<Env> matches =
PatternMatch(p_fn.Param(), v_fn.Param(), values, vars, line_num);
if (!matches) {
return std::nullopt;
}
return PatternMatch(p_fn.Ret(), v_fn.Ret(), *matches, vars, line_num);
}
default:
return std::nullopt;
}
default:
if (ValueEqual(p, v, line_num)) {
return values;
} else {
return std::nullopt;
}
}
}
void PatternAssignment(const Value* pat, const Value* val, int line_num) {
switch (pat->Tag()) {
case Value::Kind::PointerValue:
state->heap.Write(cast<PointerValue>(*pat).Val(), CopyVal(val, line_num),
line_num);
break;
case Value::Kind::TupleValue: {
switch (val->Tag()) {
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(line_num)
<< "arity mismatch in tuple pattern assignment:\n pattern: "
<< pat_tup << "\n value: " << val_tup;
}
for (const TupleElement& pattern_element : pat_tup.Elements()) {
const Value* value_field = val_tup.FindField(pattern_element.name);
if (value_field == nullptr) {
FATAL_RUNTIME_ERROR(line_num)
<< "field " << pattern_element.name << "not in " << *val;
}
PatternAssignment(pattern_element.value, value_field, line_num);
}
break;
}
default:
llvm::errs()
<< "internal error, expected a tuple value on right-hand-side, "
"not "
<< *val << "\n";
exit(-1);
}
break;
}
case Value::Kind::AlternativeValue: {
switch (val->Tag()) {
case Value::Kind::AlternativeValue: {
const auto& pat_alt = cast<AlternativeValue>(*pat);
const auto& val_alt = cast<AlternativeValue>(*val);
CHECK(val_alt.ChoiceName() == pat_alt.ChoiceName() &&
val_alt.AltName() == pat_alt.AltName())
<< "internal error in pattern assignment";
PatternAssignment(pat_alt.Argument(), val_alt.Argument(), line_num);
break;
}
default:
llvm::errs()
<< "internal error, expected an alternative in left-hand-side, "
"not "
<< *val << "\n";
exit(-1);
}
break;
}
default:
CHECK(ValueEqual(pat, val, line_num))
<< "internal error in pattern assignment";
}
}
// State transitions for lvalues.
void StepLvalue() {
Frame* frame = state->stack.Top();
Action* act = frame->todo.Top();
const Expression* exp = act->GetLValAction().exp;
if (tracing_output) {
llvm::outs() << "--- step lvalue " << *exp << " --->\n";
}
switch (exp->tag()) {
case ExpressionKind::IdentifierExpression: {
// { {x :: C, E, F} :: S, H}
// -> { {E(x) :: C, E, F} :: S, H}
std::optional<Address> pointer =
CurrentEnv(state).Get(exp->GetIdentifierExpression().name);
if (!pointer) {
FATAL_RUNTIME_ERROR(exp->line_num)
<< ": could not find `" << exp->GetIdentifierExpression().name
<< "`";
}
const Value* v = global_arena->New<PointerValue>(*pointer);
frame->todo.Pop();
frame->todo.Push(Action::MakeValAction(v));
break;
}
case ExpressionKind::FieldAccessExpression: {
if (act->pos == 0) {
// { {e.f :: C, E, F} :: S, H}
// -> { e :: [].f :: C, E, F} :: S, H}
frame->todo.Push(
Action::MakeLValAction(exp->GetFieldAccessExpression().aggregate));
act->pos++;
} else {
// { v :: [].f :: C, E, F} :: S, H}
// -> { { &v.f :: C, E, F} :: S, H }
Address aggregate = cast<PointerValue>(*act->results[0]).Val();
Address field =
aggregate.SubobjectAddress(exp->GetFieldAccessExpression().field);
frame->todo.Pop(1);
frame->todo.Push(
Action::MakeValAction(global_arena->New<PointerValue>(field)));
}
break;
}
case ExpressionKind::IndexExpression: {
if (act->pos == 0) {
// { {e[i] :: C, E, F} :: S, H}
// -> { e :: [][i] :: C, E, F} :: S, H}
frame->todo.Push(
Action::MakeLValAction(exp->GetIndexExpression().aggregate));
act->pos++;
} else if (act->pos == 1) {
frame->todo.Push(
Action::MakeExpressionAction(exp->GetIndexExpression().offset));
act->pos++;
} else if (act->pos == 2) {
// { v :: [][i] :: C, E, F} :: S, H}
// -> { { &v[i] :: C, E, F} :: S, H }
Address aggregate = cast<PointerValue>(*act->results[0]).Val();
std::string f = std::to_string(cast<IntValue>(*act->results[1]).Val());
Address field = aggregate.SubobjectAddress(f);
frame->todo.Pop(1);
frame->todo.Push(
Action::MakeValAction(global_arena->New<PointerValue>(field)));
}
break;
}
case ExpressionKind::TupleLiteral: {
if (act->pos == 0) {
// { {(f1=e1,...) :: C, E, F} :: S, H}
// -> { {e1 :: (f1=[],...) :: C, E, F} :: S, H}
const Expression* e1 = exp->GetTupleLiteral().fields[0].expression;
frame->todo.Push(Action::MakeLValAction(e1));
act->pos++;
} else if (act->pos !=
static_cast<int>(exp->GetTupleLiteral().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}
const Expression* elt =
exp->GetTupleLiteral().fields[act->pos].expression;
frame->todo.Push(Action::MakeLValAction(elt));
act->pos++;
} else {
CreateTuple(frame, act, exp);
}
break;
}
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: {
FATAL_RUNTIME_ERROR_NO_LINE()
<< "Can't treat expression as lvalue: " << *exp;
}
}
}
// State transitions for expressions.
void StepExp() {
Frame* frame = state->stack.Top();
Action* act = frame->todo.Top();
const Expression* exp = act->GetExpressionAction().exp;
if (tracing_output) {
llvm::outs() << "--- step exp " << *exp << " --->\n";
}
switch (exp->tag()) {
case ExpressionKind::IndexExpression: {
if (act->pos == 0) {
// { { e[i] :: C, E, F} :: S, H}
// -> { { e :: [][i] :: C, E, F} :: S, H}
frame->todo.Push(
Action::MakeExpressionAction(exp->GetIndexExpression().aggregate));
act->pos++;
} else if (act->pos == 1) {
frame->todo.Push(
Action::MakeExpressionAction(exp->GetIndexExpression().offset));
act->pos++;
} else if (act->pos == 2) {
auto tuple = act->results[0];
switch (tuple->Tag()) {
case Value::Kind::TupleValue: {
// { { v :: [][i] :: C, E, F} :: S, H}
// -> { { v_i :: C, E, F} : S, H}
std::string f =
std::to_string(cast<IntValue>(*act->results[1]).Val());
const Value* field = cast<TupleValue>(*tuple).FindField(f);
if (field == nullptr) {
FATAL_RUNTIME_ERROR_NO_LINE()
<< "field " << f << " not in " << *tuple;
}
frame->todo.Pop(1);
frame->todo.Push(Action::MakeValAction(field));
break;
}
default:
FATAL_RUNTIME_ERROR_NO_LINE()
<< "expected a tuple in field access, not " << *tuple;
}
}
break;
}
case ExpressionKind::TupleLiteral: {
if (act->pos == 0) {
if (exp->GetTupleLiteral().fields.size() > 0) {
// { {(f1=e1,...) :: C, E, F} :: S, H}
// -> { {e1 :: (f1=[],...) :: C, E, F} :: S, H}
const Expression* e1 = exp->GetTupleLiteral().fields[0].expression;
frame->todo.Push(Action::MakeExpressionAction(e1));
act->pos++;
} else {
CreateTuple(frame, act, exp);
}
} else if (act->pos !=
static_cast<int>(exp->GetTupleLiteral().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}
const Expression* elt =
exp->GetTupleLiteral().fields[act->pos].expression;
frame->todo.Push(Action::MakeExpressionAction(elt));
act->pos++;
} else {
CreateTuple(frame, act, exp);
}
break;
}
case ExpressionKind::FieldAccessExpression: {
if (act->pos == 0) {
// { { e.f :: C, E, F} :: S, H}
// -> { { e :: [].f :: C, E, F} :: S, H}
frame->todo.Push(Action::MakeExpressionAction(
exp->GetFieldAccessExpression().aggregate));
act->pos++;
} else {
// { { v :: [].f :: C, E, F} :: S, H}
// -> { { v_f :: C, E, F} : S, H}
const Value* element = act->results[0]->GetField(
FieldPath(exp->GetFieldAccessExpression().field), exp->line_num);
frame->todo.Pop(1);
frame->todo.Push(Action::MakeValAction(element));
}
break;
}
case ExpressionKind::IdentifierExpression: {
CHECK(act->pos == 0);
// { {x :: C, E, F} :: S, H} -> { {H(E(x)) :: C, E, F} :: S, H}
std::optional<Address> pointer =
CurrentEnv(state).Get(exp->GetIdentifierExpression().name);
if (!pointer) {
FATAL_RUNTIME_ERROR(exp->line_num)
<< ": could not find `" << exp->GetIdentifierExpression().name
<< "`";
}
const Value* pointee = state->heap.Read(*pointer, exp->line_num);
frame->todo.Pop(1);
frame->todo.Push(Action::MakeValAction(pointee));
break;
}
case ExpressionKind::IntLiteral:
CHECK(act->pos == 0);
// { {n :: C, E, F} :: S, H} -> { {n' :: C, E, F} :: S, H}
frame->todo.Pop(1);
frame->todo.Push(Action::MakeValAction(
global_arena->New<IntValue>(exp->GetIntLiteral())));
break;
case ExpressionKind::BoolLiteral:
CHECK(act->pos == 0);
// { {n :: C, E, F} :: S, H} -> { {n' :: C, E, F} :: S, H}
frame->todo.Pop(1);
frame->todo.Push(Action::MakeValAction(
global_arena->New<BoolValue>(exp->GetBoolLiteral())));
break;
case ExpressionKind::PrimitiveOperatorExpression:
if (act->pos !=
static_cast<int>(
exp->GetPrimitiveOperatorExpression().arguments.size())) {
// { {v :: op(vs,[],e,es) :: C, E, F} :: S, H}
// -> { {e :: op(vs,v,[],es) :: C, E, F} :: S, H}
const Expression* arg =
exp->GetPrimitiveOperatorExpression().arguments[act->pos];
frame->todo.Push(Action::MakeExpressionAction(arg));
act->pos++;
} else {
// { {v :: op(vs,[]) :: C, E, F} :: S, H}
// -> { {eval_prim(op, (vs,v)) :: C, E, F} :: S, H}
const Value* v = EvalPrim(exp->GetPrimitiveOperatorExpression().op,
act->results, exp->line_num);
frame->todo.Pop(1);
frame->todo.Push(Action::MakeValAction(v));
}
break;
case ExpressionKind::CallExpression:
if (act->pos == 0) {
// { {e1(e2) :: C, E, F} :: S, H}
// -> { {e1 :: [](e2) :: C, E, F} :: S, H}
frame->todo.Push(
Action::MakeExpressionAction(exp->GetCallExpression().function));
act->pos++;
} else if (act->pos == 1) {
// { { v :: [](e) :: C, E, F} :: S, H}
// -> { { e :: v([]) :: C, E, F} :: S, H}
frame->todo.Push(
Action::MakeExpressionAction(exp->GetCallExpression().argument));
act->pos++;
} else if (act->pos == 2) {
// { { v2 :: v1([]) :: C, E, F} :: S, H}
// -> { {C',E',F'} :: {C, E, F} :: S, H}
frame->todo.Pop(1);
CallFunction(exp->line_num, act->results, state);
} else {
llvm::errs() << "internal error in handle_value with Call\n";
exit(-1);
}
break;
case ExpressionKind::IntTypeLiteral: {
CHECK(act->pos == 0);
const Value* v = global_arena->New<IntType>();
frame->todo.Pop(1);
frame->todo.Push(Action::MakeValAction(v));
break;
}
case ExpressionKind::BoolTypeLiteral: {
CHECK(act->pos == 0);
const Value* v = global_arena->New<BoolType>();
frame->todo.Pop(1);
frame->todo.Push(Action::MakeValAction(v));
break;
}
case ExpressionKind::TypeTypeLiteral: {
CHECK(act->pos == 0);
const Value* v = global_arena->New<TypeType>();
frame->todo.Pop(1);
frame->todo.Push(Action::MakeValAction(v));
break;
}
case ExpressionKind::FunctionTypeLiteral: {
if (act->pos == 0) {
frame->todo.Push(Action::MakeExpressionAction(
exp->GetFunctionTypeLiteral().parameter));
act->pos++;
} else if (act->pos == 1) {
// { { pt :: fn [] -> e :: C, E, F} :: S, H}
// -> { { e :: fn pt -> []) :: C, E, F} :: S, H}
frame->todo.Push(Action::MakeExpressionAction(
exp->GetFunctionTypeLiteral().return_type));
act->pos++;
} else if (act->pos == 2) {
// { { rt :: fn pt -> [] :: C, E, F} :: S, H}
// -> { fn pt -> rt :: {C, E, F} :: S, H}
const Value* v = global_arena->New<FunctionType>(
std::vector<GenericBinding>(), act->results[0], act->results[1]);
frame->todo.Pop(1);
frame->todo.Push(Action::MakeValAction(v));
}
break;
}
case ExpressionKind::ContinuationTypeLiteral: {
CHECK(act->pos == 0);
const Value* v = global_arena->New<ContinuationType>();
frame->todo.Pop(1);
frame->todo.Push(Action::MakeValAction(v));
break;
}
} // switch (exp->tag)
}
void StepPattern() {
Frame* frame = state->stack.Top();
Action* act = frame->todo.Top();
const Pattern* pattern = act->GetPatternAction().pattern;
if (tracing_output) {
llvm::outs() << "--- step pattern " << *pattern << " --->\n";
}
switch (pattern->Tag()) {
case Pattern::Kind::AutoPattern: {
CHECK(act->pos == 0);
const Value* v = global_arena->New<AutoType>();
frame->todo.Pop(1);
frame->todo.Push(Action::MakeValAction(v));
break;
}
case Pattern::Kind::BindingPattern: {
const auto& binding = cast<BindingPattern>(*pattern);
if (act->pos == 0) {
frame->todo.Push(Action::MakePatternAction(binding.Type()));
act->pos++;
} else {
auto v = global_arena->New<BindingPlaceholderValue>(binding.Name(),
act->results[0]);
frame->todo.Pop(1);
frame->todo.Push(Action::MakeValAction(v));
}
break;
}
case Pattern::Kind::TuplePattern: {
const auto& tuple = cast<TuplePattern>(*pattern);
if (act->pos == 0) {
if (tuple.Fields().empty()) {
frame->todo.Pop(1);
frame->todo.Push(Action::MakeValAction(&TupleValue::Empty()));
} else {
const Pattern* p1 = tuple.Fields()[0].pattern;
frame->todo.Push(Action::MakePatternAction(p1));
act->pos++;
}
} else 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}
const Pattern* elt = tuple.Fields()[act->pos].pattern;
frame->todo.Push(Action::MakePatternAction(elt));
act->pos++;
} else {
std::vector<TupleElement> elements;
for (size_t i = 0; i < tuple.Fields().size(); ++i) {
elements.push_back(
{.name = tuple.Fields()[i].name, .value = act->results[i]});
}
const Value* tuple_value =
global_arena->New<TupleValue>(std::move(elements));
frame->todo.Pop(1);
frame->todo.Push(Action::MakeValAction(tuple_value));
}
break;
}
case Pattern::Kind::AlternativePattern: {
const auto& alternative = cast<AlternativePattern>(*pattern);
if (act->pos == 0) {
frame->todo.Push(
Action::MakeExpressionAction(alternative.ChoiceType()));
act->pos++;
} else if (act->pos == 1) {
frame->todo.Push(Action::MakePatternAction(alternative.Arguments()));
act->pos++;
} else {
CHECK(act->pos == 2);
const auto& choice_type = cast<ChoiceType>(*act->results[0]);
frame->todo.Pop(1);
frame->todo.Push(
Action::MakeValAction(global_arena->New<AlternativeValue>(
alternative.AlternativeName(), choice_type.Name(),
act->results[1])));
}
break;
}
case Pattern::Kind::ExpressionPattern:
frame->todo.Pop(1);
frame->todo.Push(Action::MakeExpressionAction(
cast<ExpressionPattern>(pattern)->Expression()));
break;
}
}
auto IsWhileAct(Action* act) -> bool {
switch (act->tag()) {
case ActionKind::StatementAction:
switch (act->GetStatementAction().stmt->tag()) {
case StatementKind::While:
return true;
default:
return false;
}
default:
return false;
}
}
auto IsBlockAct(Action* act) -> bool {
switch (act->tag()) {
case ActionKind::StatementAction:
switch (act->GetStatementAction().stmt->tag()) {
case StatementKind::Block:
return true;
default:
return false;
}
default:
return false;
}
}
// State transitions for statements.
void StepStmt() {
Frame* frame = state->stack.Top();
Action* act = frame->todo.Top();
const Statement* stmt = act->GetStatementAction().stmt;
CHECK(stmt != nullptr) << "null statement!";
if (tracing_output) {
llvm::outs() << "--- step stmt ";
stmt->PrintDepth(1, llvm::outs());
llvm::outs() << " --->\n";
}
switch (stmt->tag()) {
case StatementKind::Match:
if (act->pos == 0) {
// { { (match (e) ...) :: C, E, F} :: S, H}
// -> { { e :: (match ([]) ...) :: C, E, F} :: S, H}
frame->todo.Push(Action::MakeExpressionAction(stmt->GetMatch().exp));
act->pos++;
} else {
// Regarding act->pos:
// * odd: start interpreting the pattern of a clause
// * even: finished interpreting the pattern, now try to match
//
// Regarding act->results:
// * 0: the value that we're matching
// * 1: the pattern for clause 0
// * 2: the pattern for clause 1
// * ...
auto clause_num = (act->pos - 1) / 2;
if (clause_num >= static_cast<int>(stmt->GetMatch().clauses->size())) {
frame->todo.Pop(1);
break;
}
auto c = stmt->GetMatch().clauses->begin();
std::advance(c, clause_num);
if (act->pos % 2 == 1) {
// start interpreting the pattern of the clause
// { {v :: (match ([]) ...) :: C, E, F} :: S, H}
// -> { {pi :: (match ([]) ...) :: C, E, F} :: S, H}
frame->todo.Push(Action::MakePatternAction(c->first));
act->pos++;
} else { // try to match
auto v = act->results[0];
auto pat = act->results[clause_num + 1];
auto values = CurrentEnv(state);
std::list<std::string> vars;
std::optional<Env> matches =
PatternMatch(pat, v, values, &vars, stmt->line_num);
if (matches) { // we have a match, start the body
auto* new_scope = global_arena->New<Scope>(*matches, vars);
frame->scopes.Push(new_scope);
const Statement* body_block =
Statement::MakeBlock(stmt->line_num, c->second);
Action* body_act = Action::MakeStatementAction(body_block);
body_act->pos = 1;
frame->todo.Pop(1);
frame->todo.Push(body_act);
frame->todo.Push(Action::MakeStatementAction(c->second));
} else {
// this case did not match, moving on
act->pos++;
clause_num = (act->pos - 1) / 2;
if (clause_num ==
static_cast<int>(stmt->GetMatch().clauses->size())) {
frame->todo.Pop(1);
}
}
}
}
break;
case StatementKind::While:
if (act->pos == 0) {
// { { (while (e) s) :: C, E, F} :: S, H}
// -> { { e :: (while ([]) s) :: C, E, F} :: S, H}
frame->todo.Push(Action::MakeExpressionAction(stmt->GetWhile().cond));
act->pos++;
} else if (cast<BoolValue>(*act->results[0]).Val()) {
// { {true :: (while ([]) s) :: C, E, F} :: S, H}
// -> { { s :: (while (e) s) :: C, E, F } :: S, H}
frame->todo.Top()->pos = 0;
frame->todo.Top()->results.clear();
frame->todo.Push(Action::MakeStatementAction(stmt->GetWhile().body));
} else {
// { {false :: (while ([]) s) :: C, E, F} :: S, H}
// -> { { C, E, F } :: S, H}
frame->todo.Top()->pos = 0;
frame->todo.Top()->results.clear();
frame->todo.Pop(1);
}
break;
case StatementKind::Break:
CHECK(act->pos == 0);
// { { break; :: ... :: (while (e) s) :: C, E, F} :: S, H}
// -> { { C, E', F} :: S, H}
frame->todo.Pop(1);
while (!frame->todo.IsEmpty() && !IsWhileAct(frame->todo.Top())) {
if (IsBlockAct(frame->todo.Top())) {
DeallocateScope(stmt->line_num, frame->scopes.Top());
frame->scopes.Pop(1);
}
frame->todo.Pop(1);
}
frame->todo.Pop(1);
break;
case StatementKind::Continue:
CHECK(act->pos == 0);
// { { continue; :: ... :: (while (e) s) :: C, E, F} :: S, H}
// -> { { (while (e) s) :: C, E', F} :: S, H}
frame->todo.Pop(1);
while (!frame->todo.IsEmpty() && !IsWhileAct(frame->todo.Top())) {
if (IsBlockAct(frame->todo.Top())) {
DeallocateScope(stmt->line_num, frame->scopes.Top());
frame->scopes.Pop(1);
}
frame->todo.Pop(1);
}
break;
case StatementKind::Block: {
if (act->pos == 0) {
if (stmt->GetBlock().stmt) {
auto* scope = global_arena->New<Scope>(CurrentEnv(state),
std::list<std::string>());
frame->scopes.Push(scope);
frame->todo.Push(Action::MakeStatementAction(stmt->GetBlock().stmt));
act->pos++;
act->pos++;
} else {
frame->todo.Pop();
}
} else {
Scope* scope = frame->scopes.Top();
DeallocateScope(stmt->line_num, scope);
frame->scopes.Pop(1);
frame->todo.Pop(1);
}
break;
}
case StatementKind::VariableDefinition:
if (act->pos == 0) {
// { {(var x = e) :: C, E, F} :: S, H}
// -> { {e :: (var x = []) :: C, E, F} :: S, H}
frame->todo.Push(
Action::MakeExpressionAction(stmt->GetVariableDefinition().init));
act->pos++;
} else if (act->pos == 1) {
frame->todo.Push(
Action::MakePatternAction(stmt->GetVariableDefinition().pat));
act->pos++;
} else if (act->pos == 2) {
// { { v :: (x = []) :: C, E, F} :: S, H}
// -> { { C, E(x := a), F} :: S, H(a := copy(v))}
const Value* v = act->results[0];
const Value* p = act->results[1];
std::optional<Env> matches =
PatternMatch(p, v, frame->scopes.Top()->values,
&frame->scopes.Top()->locals, stmt->line_num);
CHECK(matches)
<< stmt->line_num
<< ": internal error in variable definition, match failed";
frame->scopes.Top()->values = *matches;
frame->todo.Pop(1);
}
break;
case StatementKind::ExpressionStatement:
if (act->pos == 0) {
// { {e :: C, E, F} :: S, H}
// -> { {e :: C, E, F} :: S, H}
frame->todo.Push(
Action::MakeExpressionAction(stmt->GetExpressionStatement().exp));
act->pos++;
} else {
frame->todo.Pop(1);
}
break;
case StatementKind::Assign:
if (act->pos == 0) {
// { {(lv = e) :: C, E, F} :: S, H}
// -> { {lv :: ([] = e) :: C, E, F} :: S, H}
frame->todo.Push(Action::MakeLValAction(stmt->GetAssign().lhs));
act->pos++;
} else if (act->pos == 1) {
// { { a :: ([] = e) :: C, E, F} :: S, H}
// -> { { e :: (a = []) :: C, E, F} :: S, H}
frame->todo.Push(Action::MakeExpressionAction(stmt->GetAssign().rhs));
act->pos++;
} else if (act->pos == 2) {
// { { v :: (a = []) :: C, E, F} :: S, H}
// -> { { C, E, F} :: S, H(a := v)}
auto pat = act->results[0];
auto val = act->results[1];
PatternAssignment(pat, val, stmt->line_num);
frame->todo.Pop(1);
}
break;
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}
frame->todo.Push(Action::MakeExpressionAction(stmt->GetIf().cond));
act->pos++;
} else if (cast<BoolValue>(*act->results[0]).Val()) {
// { {true :: if ([]) then_stmt else else_stmt :: C, E, F} ::
// S, H}
// -> { { then_stmt :: C, E, F } :: S, H}
frame->todo.Pop(1);
frame->todo.Push(Action::MakeStatementAction(stmt->GetIf().then_stmt));
} else if (stmt->GetIf().else_stmt) {
// { {false :: if ([]) then_stmt else else_stmt :: C, E, F} ::
// S, H}
// -> { { else_stmt :: C, E, F } :: S, H}
frame->todo.Pop(1);
frame->todo.Push(Action::MakeStatementAction(stmt->GetIf().else_stmt));
} else {
frame->todo.Pop(1);
}
break;
case StatementKind::Return:
if (act->pos == 0) {
// { {return e :: C, E, F} :: S, H}
// -> { {e :: return [] :: C, E, F} :: S, H}
frame->todo.Push(Action::MakeExpressionAction(stmt->GetReturn().exp));
act->pos++;
} else {
// { {v :: return [] :: C, E, F} :: {C', E', F'} :: S, H}
// -> { {v :: C', E', F'} :: S, H}
const Value* ret_val = CopyVal(act->results[0], stmt->line_num);
DeallocateLocals(stmt->line_num, frame);
state->stack.Pop(1);
frame = state->stack.Top();
frame->todo.Push(Action::MakeValAction(ret_val));
}
break;
case StatementKind::Sequence:
CHECK(act->pos == 0);
// { { (s1,s2) :: C, E, F} :: S, H}
// -> { { s1 :: s2 :: C, E, F} :: S, H}
frame->todo.Pop(1);
if (stmt->GetSequence().next) {
frame->todo.Push(Action::MakeStatementAction(stmt->GetSequence().next));
}
frame->todo.Push(Action::MakeStatementAction(stmt->GetSequence().stmt));
break;
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.
Scope* scope =
global_arena->New<Scope>(CurrentEnv(state), std::list<std::string>());
Stack<Scope*> scopes;
scopes.Push(scope);
Stack<Action*> todo;
todo.Push(Action::MakeStatementAction(
Statement::MakeReturn(stmt->line_num, nullptr,
/*is_omitted_exp=*/true)));
todo.Push(Action::MakeStatementAction(stmt->GetContinuation().body));
Frame* continuation_frame =
global_arena->New<Frame>("__continuation", scopes, todo);
Address continuation_address =
state->heap.AllocateValue(global_arena->New<ContinuationValue>(
std::vector<Frame*>({continuation_frame})));
// Store the continuation's address in the frame.
continuation_frame->continuation = continuation_address;
// Bind the continuation object to the continuation variable
frame->scopes.Top()->values.Set(
stmt->GetContinuation().continuation_variable, continuation_address);
// Pop the continuation statement.
frame->todo.Pop();
break;
}
case StatementKind::Run:
if (act->pos == 0) {
// Evaluate the argument of the run statement.
frame->todo.Push(Action::MakeExpressionAction(stmt->GetRun().argument));
act->pos++;
} else {
frame->todo.Pop(1);
// Push an expression statement action to ignore the result
// value from the continuation.
Action* ignore_result =
Action::MakeStatementAction(Statement::MakeExpressionStatement(
stmt->line_num,
Expression::MakeTupleLiteral(stmt->line_num, {})));
ignore_result->pos = 0;
frame->todo.Push(ignore_result);
// Push the continuation onto the current stack.
const std::vector<Frame*>& continuation_vector =
cast<ContinuationValue>(*act->results[0]).Stack();
for (auto frame_iter = continuation_vector.rbegin();
frame_iter != continuation_vector.rend(); ++frame_iter) {
state->stack.Push(*frame_iter);
}
}
break;
case StatementKind::Await:
CHECK(act->pos == 0);
// Pause the current continuation
frame->todo.Pop();
std::vector<Frame*> paused;
do {
paused.push_back(state->stack.Pop());
} while (paused.back()->continuation == std::nullopt);
// Update the continuation with the paused stack.
state->heap.Write(*paused.back()->continuation,
global_arena->New<ContinuationValue>(paused),
stmt->line_num);
break;
}
}
// State transition.
void Step() {
Frame* frame = state->stack.Top();
if (frame->todo.IsEmpty()) {
FATAL_RUNTIME_ERROR_NO_LINE()
<< "fell off end of function " << frame->name << " without `return`";
}
Action* act = frame->todo.Top();
switch (act->tag()) {
case ActionKind::ValAction: {
Action* val_act = frame->todo.Pop();
Action* act = frame->todo.Top();
act->results.push_back(val_act->GetValAction().val);
break;
}
case ActionKind::LValAction:
StepLvalue();
break;
case ActionKind::ExpressionAction:
StepExp();
break;
case ActionKind::PatternAction:
StepPattern();
break;
case ActionKind::StatementAction:
StepStmt();
break;
} // switch
}
// Interpret the whole porogram.
auto InterpProgram(std::list<Declaration>* fs) -> int {
state = global_arena->New<State>(); // Runtime state.
if (tracing_output) {
llvm::outs() << "********** initializing globals **********\n";
}
InitGlobals(fs);
const Expression* arg = Expression::MakeTupleLiteral(0, {});
const Expression* call_main = Expression::MakeCallExpression(
0, Expression::MakeIdentifierExpression(0, "main"), arg);
auto todo = Stack(Action::MakeExpressionAction(call_main));
auto* scope = global_arena->New<Scope>(globals, std::list<std::string>());
auto* frame = global_arena->New<Frame>("top", Stack(scope), todo);
state->stack = Stack(frame);
if (tracing_output) {
llvm::outs() << "********** calling main function **********\n";
PrintState(llvm::outs());
}
while (state->stack.Count() > 1 || state->stack.Top()->todo.Count() > 1 ||
state->stack.Top()->todo.Top()->tag() != ActionKind::ValAction) {
Step();
if (tracing_output) {
PrintState(llvm::outs());
}
}
const Value* v = state->stack.Top()->todo.Top()->GetValAction().val;
return cast<IntValue>(*v).Val();
}
// Interpret an expression at compile-time.
auto InterpExp(Env values, const Expression* e) -> const Value* {
auto todo = Stack(Action::MakeExpressionAction(e));
auto* scope = global_arena->New<Scope>(values, std::list<std::string>());
auto* frame = global_arena->New<Frame>("InterpExp", Stack(scope), todo);
state->stack = Stack(frame);
while (state->stack.Count() > 1 || state->stack.Top()->todo.Count() > 1 ||
state->stack.Top()->todo.Top()->tag() != ActionKind::ValAction) {
Step();
}
const Value* v = state->stack.Top()->todo.Top()->GetValAction().val;
return v;
}
// Interpret a pattern at compile-time.
auto InterpPattern(Env values, const Pattern* p) -> const Value* {
auto todo = Stack(Action::MakePatternAction(p));
auto* scope = global_arena->New<Scope>(values, std::list<std::string>());
auto* frame = global_arena->New<Frame>("InterpPattern", Stack(scope), todo);
state->stack = Stack(frame);
while (state->stack.Count() > 1 || state->stack.Top()->todo.Count() > 1 ||
state->stack.Top()->todo.Top()->tag() != ActionKind::ValAction) {
Step();
}
const Value* v = state->stack.Top()->todo.Top()->GetValAction().val;
return v;
}
} // namespace Carbon
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