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// Simple WebAssembly interpreter, designed to be embeddable in JavaScript, so it
// can function as a polyfill.
#include "wasm.h"
using namespace cashew;
using namespace wasm;
namespace wasm {
// An instance of a WebAssembly module
class ModuleInstance {
public:
ModuleInstance(Module& wasm) : wasm(wasm) {
for (auto function : wasm.functions) {
functions[function->name] = function;
}
}
typedef std::vector<Literal> LiteralList;
Literal callFunction(IString name) {
LiteralList empty;
return callFunction(name, empty);
}
Literal callFunction(IString name, LiteralList& arguments) {
class FunctionScope {
public:
std::map<IString, Literal> locals;
FunctionScope(Function* function, LiteralList& arguments) {
assert(function->params.size() == arguments.size());
for (size_t i = 0; i < arguments.size(); i++) {
assert(function->params[i].type == arguments[i].type);
locals[function->params[i].name] = arguments[i];
}
for (auto& local : function->locals) {
locals[local.name].type = local.type;
}
}
};
// Stuff that flows around during executing expressions: a literal, or a change in control flow
class Flow {
public:
Flow() {}
Flow(Literal value) : value(value) {}
Literal value;
IString breakTo; // if non-null, a break is going on
bool breaking() { return breakTo.is(); }
void clearIf(IString target) {
if (breakTo == target) {
breakTo.clear();
}
}
};
// Execute a statement
class ExpressionRunner : public WasmVisitor<Flow> {
FunctionScope& scope;
public:
ExpressionRunner(FunctionScope& scope) : scope(scope) {}
Flow visitBlock(Block *curr) override {
Flow flow;
for (auto expression : curr->list) {
flow = visit(expression);
if (flow.breaking()) {
flow.clearIf(curr->name);
return flow;
}
}
return flow;
}
Flow visitIf(If *curr) override {
Flow flow = visit(curr->condition);
if (flow.breaking()) return flow;
if (flow.value.geti32()) return visit(curr->ifTrue);
if (curr->ifFalse) return visit(curr->ifFalse);
return Flow();
}
Flow visitLoop(Loop *curr) override {
while (1) {
Flow flow = visit(curr->body);
if (flow.breaking()) {
if (flow.breakTo == curr->in) continue; // lol
flow.clearIf(curr->out);
return flow;
}
}
}
Flow visitLabel(Label *curr) override {
Flow flow = visit(curr->body);
flow.clearIf(curr->name);
return flow;
}
Flow visitBreak(Break *curr) override {
if (curr->condition) {
Flow flow = visit(curr->condition);
if (flow.breaking()) return flow;
if (!flow.value.geti32()) return Flow();
}
Flow flow = visit(curr->value);
if (!flow.breaking()) {
flow.breakTo = curr->name;
}
return flow;
}
Flow visitSwitch(Switch *curr) override {
abort();
}
Flow visitCall(Call *curr) override {
LiteralList arguments;
arguments.reserve(curr->operands.size());
for (auto expression : curr->operands) {
Flow flow = visit(expression);
if (flow.breaking()) return flow;
arguments.push_back(flow.value);
}
return callFunction(curr->target, arguments);
}
Flow visitCallImport(CallImport *curr) override {
}
Flow visitCallIndirect(CallIndirect *curr) override {
}
Flow visitGetLocal(GetLocal *curr) override {
}
Flow visitSetLocal(SetLocal *curr) override {
}
Flow visitLoad(Load *curr) override {
}
Flow visitStore(Store *curr) override {
}
Flow visitConst(Const *curr) override {
return Flow(curr->value); // heh
}
Flow visitUnary(Unary *curr) override {
}
Flow visitBinary(Binary *curr) override {
}
Flow visitCompare(Compare *curr) override {
}
Flow visitConvert(Convert *curr) override {
}
Flow visitHost(Host *curr) override {
}
Flow visitNop(Nop *curr) override {
}
};
Function *function = functions[name];
FunctionScope scope(function, arguments);
return ExpressionRunner(scope).visit(function->body).value;
}
private:
Module& wasm;
std::map<IString, Function*> functions;
};
} // namespace wasm
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