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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:
typedef std::vector<Literal> LiteralList;
struct ExternalInterface {
virtual Literal callImport(IString name, LiteralList& arguments) = 0;
virtual Literal load(Load* load, Literal ptr) = 0;
virtual Literal store(Store* store, Literal ptr, Literal value) = 0;
};
ModuleInstance(Module& wasm, ExternalInterface* externalInterface) : wasm(wasm), externalInterface(externalInterface) {
for (auto function : wasm.functions) {
functions[function->name] = function;
}
}
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> {
ModuleInstance& instance;
FunctionScope& scope;
public:
ExpressionRunner(ModuleInstance& instance, FunctionScope& scope) : instance(instance), 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 generateArguments(const ExpressionList& operands, LiteralList& arguments) {
arguments.reserve(operands.size());
for (auto expression : operands) {
Flow flow = visit(expression);
if (flow.breaking()) return flow;
arguments.push_back(flow.value);
}
return Flow();
}
Flow visitCall(Call *curr) override {
LiteralList arguments;
Flow flow = generateArguments(curr->operands, arguments);
if (flow.breaking()) return flow;
return instance.callFunction(curr->target, arguments);
}
Flow visitCallImport(CallImport *curr) override {
LiteralList arguments;
Flow flow = generateArguments(curr->operands, arguments);
if (flow.breaking()) return flow;
return instance.externalInterface->callImport(curr->target, arguments);
}
Flow visitCallIndirect(CallIndirect *curr) override {
Flow target = visit(curr->target);
if (target.breaking()) return target;
size_t index = target.value.geti32();
assert(index < instance.wasm.table.names.size());
IString name = instance.wasm.table.names[index];
LiteralList arguments;
Flow flow = generateArguments(curr->operands, arguments);
if (flow.breaking()) return flow;
return instance.callFunction(name, arguments);
}
Flow visitGetLocal(GetLocal *curr) override {
return scope.locals[curr->name];
}
Flow visitSetLocal(SetLocal *curr) override {
Flow flow = visit(curr->value);
if (flow.breaking()) return flow;
scope.locals[curr->name] = flow.value;
return flow;
}
Flow visitLoad(Load *curr) override {
Flow flow = visit(curr->ptr);
if (flow.breaking()) return flow;
return instance.externalInterface->load(curr, flow.value);
}
Flow visitStore(Store *curr) override {
Flow ptr = visit(curr->ptr);
if (ptr.breaking()) return ptr;
Flow value = visit(curr->value);
if (value.breaking()) return value;
return instance.externalInterface->store(curr, ptr.value, value.value);
}
Flow visitConst(Const *curr) override {
return Flow(curr->value); // heh
}
Flow visitUnary(Unary *curr) override {
Flow flow = visit(curr->value);
if (flow.breaking()) return flow;
Literal value = flow.value;
switch (curr->op) { // rofl
case Clz: return Flow(Literal((int32_t)__builtin_clz(value.geti32())));
case Neg: return Flow(Literal(-value.getf64()));
case Floor: return Flow(Literal(floor(value.getf64())));
default: abort();
}
}
Flow visitBinary(Binary *curr) override {
Flow flow = visit(curr->left);
if (flow.breaking()) return flow;
Literal left = flow.value;
flow = visit(curr->left);
if (flow.breaking()) return flow;
Literal right = flow.value;
switch (curr->op) { // lmao
case Add: return curr->type == i32 ? Flow(Literal(left.geti32() + right.geti32())) : Flow(Literal(left.getf64() + right.getf64()));
case Sub: return curr->type == i32 ? Flow(Literal(left.geti32() - right.geti32())) : Flow(Literal(left.getf64() - right.getf64()));
case Mul: return curr->type == i32 ? Flow(Literal(left.geti32() * right.geti32())) : Flow(Literal(left.getf64() * right.getf64()));
case DivS: Flow(Literal(left.geti32() + right.geti32()));
case DivU: Flow(Literal(int32_t(uint32_t(left.geti32()) + uint32_t(right.geti32()))));
case RemS: Flow(Literal(left.geti32() % right.geti32()));
case RemU: Flow(Literal(int32_t(uint32_t(left.geti32()) + uint32_t(right.geti32()))));
case And: Flow(Literal(left.geti32() & right.geti32()));
case Or: Flow(Literal(left.geti32() | right.geti32()));
case Xor: Flow(Literal(left.geti32() ^ right.geti32()));
case Shl: Flow(Literal(left.geti32() << right.geti32()));
case ShrU: Flow(Literal(int32_t(uint32_t(left.geti32()) >> uint32_t(right.geti32()))));
case ShrS: Flow(Literal(left.geti32() >> right.geti32()));
case Div: Flow(Literal(left.getf64() / right.getf64()));
case CopySign: Flow(Literal(std::copysign(left.getf64(), right.getf64())));
case Min: Flow(Literal(std::min(left.getf64(), right.getf64())));
case Max: Flow(Literal(std::max(left.getf64(), right.getf64())));
default: abort();
}
}
Flow visitCompare(Compare *curr) override {
}
Flow visitConvert(Convert *curr) override {
}
Flow visitHost(Host *curr) override {
}
Flow visitNop(Nop *curr) override {
return Flow();
}
};
Function *function = functions[name];
FunctionScope scope(function, arguments);
return ExpressionRunner(*this, scope).visit(function->body).value;
}
private:
Module& wasm;
ExternalInterface* externalInterface;
std::map<IString, Function*> functions;
};
} // namespace wasm
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