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/*
* Copyright 2015 WebAssembly Community Group participants
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
//
// Simple WebAssembly interpreter. This operates directly on the AST,
// for simplicity and clarity. A goal is for it to be possible for
// people to read this code and understand WebAssembly semantics.
//
#ifndef wasm_wasm_interpreter_h
#define wasm_wasm_interpreter_h
#include <limits.h>
#include <sstream>
#include "support/bits.h"
#include "wasm.h"
#ifdef WASM_INTERPRETER_DEBUG
#include "wasm-printing.h"
#endif
namespace wasm {
using namespace cashew;
// Utilities
IString WASM("wasm"),
RETURN_FLOW("*return:)*");
enum {
maxCallDepth = 250
};
// Stuff that flows around during executing expressions: a literal, or a change in control flow
class Flow {
public:
Flow() {}
Flow(Literal value) : value(value) {}
Flow(IString breakTo) : breakTo(breakTo) {}
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();
}
}
friend std::ostream& operator<<(std::ostream& o, Flow& flow) {
o << "(flow " << (flow.breakTo.is() ? flow.breakTo.str : "-") << " : " << flow.value << ')';
return o;
}
};
//
// An instance of a WebAssembly module, which can execute it via AST interpretation.
//
// To embed this interpreter, you need to provide an ExternalInterface instance
// (see below) which provides the embedding-specific details, that is, how to
// connect to the embedding implementation.
//
// To call into the interpreter, use callExport.
//
class ModuleInstance {
public:
typedef std::vector<Literal> LiteralList;
//
// You need to implement one of these to create a concrete interpreter. The
// ExternalInterface provides embedding-specific functionality like calling
// an imported function or accessing memory.
//
struct ExternalInterface {
virtual void init(Module& wasm) {}
virtual Literal callImport(Import* import, LiteralList& arguments) = 0;
virtual Literal load(Load* load, size_t addr) = 0;
virtual void store(Store* store, size_t addr, Literal value) = 0;
virtual void growMemory(size_t oldSize, size_t newSize) = 0;
virtual void trap(const char* why) = 0;
};
Module& wasm;
ModuleInstance(Module& wasm, ExternalInterface* externalInterface) : wasm(wasm), externalInterface(externalInterface) {
memorySize = wasm.memory.initial;
externalInterface->init(wasm);
if (wasm.start.is()) {
LiteralList arguments;
callFunction(wasm.start, arguments);
}
}
Literal callExport(Name name, LiteralList& arguments) {
Export *export_ = wasm.checkExport(name);
if (!export_) externalInterface->trap("callExport not found");
return callFunction(export_->value, arguments);
}
std::string printFunctionStack() {
std::string ret = "/== (binaryen interpreter stack trace)\n";
for (int i = int(functionStack.size()) - 1; i >= 0; i--) {
ret += std::string("|: ") + functionStack[i].str + "\n";
}
ret += std::string("\\==\n");
return ret;
}
private:
size_t callDepth = 0;
#ifdef WASM_INTERPRETER_DEBUG
int indent = 0;
#endif
// Function stack. We maintain this explicitly to allow printing of
// stack traces.
std::vector<Name> functionStack;
//
// Calls a function. This can be used both internally (calls from
// the interpreter to another method), or when you want to call into
// the module.
//
Literal callFunction(IString name, LiteralList& arguments) {
class FunctionScope {
public:
std::map<IString, Literal> locals;
Function* function;
FunctionScope(Function* function, LiteralList& arguments)
: function(function) {
if (function->params.size() != arguments.size()) {
std::cerr << "Function `" << function->name << "` expects "
<< function->params.size() << " parameters, got "
<< arguments.size() << " arguments." << std::endl;
abort();
}
for (size_t i = 0; i < function->getNumLocals(); i++) {
if (i < arguments.size()) {
assert(function->isParam(i));
if (function->params[i] != arguments[i].type) {
std::cerr << "Function `" << function->name << "` expects type "
<< printWasmType(function->params[i])
<< " for parameter " << i << ", got "
<< printWasmType(arguments[i].type) << "." << std::endl;
abort();
}
locals[function->getLocalName(i)] = arguments[i];
} else {
assert(function->isVar(i));
locals[function->getLocalName(i)].type = function->getLocalType(i);
}
}
}
};
#ifdef WASM_INTERPRETER_DEBUG
struct IndentHandler {
int& indent;
const char *name;
IndentHandler(int& indent, const char *name, Expression *expression) : indent(indent), name(name) {
doIndent(std::cout, indent);
std::cout << "visit " << name << " :\n";
indent++;
#if WASM_INTERPRETER_DEBUG == 2
doIndent(std::cout, indent);
std::cout << "\n" << expression << '\n';
indent++;
#endif
}
~IndentHandler() {
#if WASM_INTERPRETER_DEBUG == 2
indent--;
#endif
indent--;
doIndent(std::cout, indent);
std::cout << "exit " << name << '\n';
}
};
#define NOTE_ENTER(x) IndentHandler indentHandler(instance.indent, x, curr);
#define NOTE_NAME(p0) { doIndent(std::cout, instance.indent); std::cout << "name in " << indentHandler.name << '(' << Name(p0) << ")\n"; }
#define NOTE_EVAL1(p0) { doIndent(std::cout, instance.indent); std::cout << "eval in " << indentHandler.name << '(' << p0 << ")\n"; }
#define NOTE_EVAL2(p0, p1) { doIndent(std::cout, instance.indent); std::cout << "eval in " << indentHandler.name << '(' << p0 << ", " << p1 << ")\n"; }
#else
#define NOTE_ENTER(x)
#define NOTE_NAME(p0)
#define NOTE_EVAL1(p0)
#define NOTE_EVAL2(p0, p1)
#endif
// Execute a statement
class ExpressionRunner : public Visitor<ExpressionRunner, Flow> {
ModuleInstance& instance;
FunctionScope& scope;
public:
ExpressionRunner(ModuleInstance& instance, FunctionScope& scope) : instance(instance), scope(scope) {}
Flow visitBlock(Block *curr) {
NOTE_ENTER("Block");
// special-case Block, because Block nesting (in their first element) can be incredibly deep
std::vector<Block*> stack;
stack.push_back(curr);
while (curr->list.size() > 0 && curr->list[0]->is<Block>()) {
curr = curr->list[0]->cast<Block>();
stack.push_back(curr);
}
Flow flow;
auto* top = stack.back();
while (stack.size() > 0) {
curr = stack.back();
stack.pop_back();
if (flow.breaking()) {
flow.clearIf(curr->name);
continue;
}
auto& list = curr->list;
for (size_t i = 0; i < list.size(); i++) {
if (curr != top && i == 0) {
// one of the block recursions we already handled
continue;
}
flow = visit(list[i]);
if (flow.breaking()) {
flow.clearIf(curr->name);
break;
}
}
}
return flow;
}
Flow visitIf(If *curr) {
NOTE_ENTER("If");
Flow flow = visit(curr->condition);
if (flow.breaking()) return flow;
NOTE_EVAL1(flow.value);
if (flow.value.geti32()) {
Flow flow = visit(curr->ifTrue);
if (!flow.breaking() && !curr->ifFalse) flow.value = Literal(); // if_else returns a value, but if does not
return flow;
}
if (curr->ifFalse) return visit(curr->ifFalse);
return Flow();
}
Flow visitLoop(Loop *curr) {
NOTE_ENTER("Loop");
while (1) {
Flow flow = visit(curr->body);
if (flow.breaking()) {
if (flow.breakTo == curr->in) continue; // lol
flow.clearIf(curr->out);
}
return flow; // loop does not loop automatically, only continue achieves that
}
}
Flow visitBreak(Break *curr) {
NOTE_ENTER("Break");
bool condition = true;
Flow flow(curr->name);
if (curr->value) {
flow = visit(curr->value);
if (flow.breaking()) return flow;
flow.breakTo = curr->name;
}
if (curr->condition) {
Flow conditionFlow = visit(curr->condition);
if (conditionFlow.breaking()) return conditionFlow;
condition = conditionFlow.value.getInteger() != 0;
}
return condition ? flow : Flow();
}
Flow visitSwitch(Switch *curr) {
NOTE_ENTER("Switch");
Flow flow;
Literal value;
if (curr->value) {
flow = visit(curr->value);
if (flow.breaking()) return flow;
value = flow.value;
NOTE_EVAL1(value);
}
flow = visit(curr->condition);
if (flow.breaking()) return flow;
int64_t index = flow.value.getInteger();
Name target = curr->default_;
if (index >= 0 && (size_t)index < curr->targets.size()) {
target = curr->targets[(size_t)index];
}
flow.breakTo = target;
flow.value = value;
return flow;
}
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) {
NOTE_ENTER("Call");
NOTE_NAME(curr->target);
LiteralList arguments;
Flow flow = generateArguments(curr->operands, arguments);
if (flow.breaking()) return flow;
Flow ret = instance.callFunction(curr->target, arguments);
#ifdef WASM_INTERPRETER_DEBUG
std::cout << "(returned to " << scope.function->name << ")\n";
#endif
return ret;
}
Flow visitCallImport(CallImport *curr) {
NOTE_ENTER("CallImport");
LiteralList arguments;
Flow flow = generateArguments(curr->operands, arguments);
if (flow.breaking()) return flow;
return instance.externalInterface->callImport(instance.wasm.getImport(curr->target), arguments);
}
Flow visitCallIndirect(CallIndirect *curr) {
NOTE_ENTER("CallIndirect");
Flow target = visit(curr->target);
if (target.breaking()) return target;
size_t index = target.value.geti32();
if (index >= instance.wasm.table.names.size()) trap("callIndirect: overflow");
Name name = instance.wasm.table.names[index];
Function *func = instance.wasm.getFunction(name);
if (func->type.is() && func->type != curr->fullType->name) trap("callIndirect: bad type");
LiteralList arguments;
Flow flow = generateArguments(curr->operands, arguments);
if (flow.breaking()) return flow;
return instance.callFunction(name, arguments);
}
Flow visitGetLocal(GetLocal *curr) {
NOTE_ENTER("GetLocal");
IString name = scope.function->getLocalName(curr->index);
NOTE_NAME(name);
NOTE_EVAL1(scope.locals[name]);
return scope.locals[name];
}
Flow visitSetLocal(SetLocal *curr) {
NOTE_ENTER("SetLocal");
IString name = scope.function->getLocalName(curr->index);
Flow flow = visit(curr->value);
if (flow.breaking()) return flow;
NOTE_NAME(name);
NOTE_EVAL1(flow.value);
assert(flow.value.type == curr->type);
scope.locals[name] = flow.value;
return flow;
}
Flow visitLoad(Load *curr) {
NOTE_ENTER("Load");
Flow flow = visit(curr->ptr);
if (flow.breaking()) return flow;
return instance.externalInterface->load(curr, instance.getFinalAddress(curr, flow.value));
}
Flow visitStore(Store *curr) {
NOTE_ENTER("Store");
Flow ptr = visit(curr->ptr);
if (ptr.breaking()) return ptr;
Flow value = visit(curr->value);
if (value.breaking()) return value;
instance.externalInterface->store(curr, instance.getFinalAddress(curr, ptr.value), value.value);
return value;
}
Flow visitConst(Const *curr) {
NOTE_ENTER("Const");
NOTE_EVAL1(curr->value);
return Flow(curr->value); // heh
}
Flow visitUnary(Unary *curr) {
NOTE_ENTER("Unary");
Flow flow = visit(curr->value);
if (flow.breaking()) return flow;
Literal value = flow.value;
NOTE_EVAL1(value);
if (value.type == i32) {
switch (curr->op) {
case Clz: return value.countLeadingZeroes();
case Ctz: return value.countTrailingZeroes();
case Popcnt: return value.popCount();
case EqZ: return Literal(int32_t(value == Literal(int32_t(0))));
case ReinterpretInt: return value.castToF32();
case ExtendSInt32: return value.extendToSI64();
case ExtendUInt32: return value.extendToUI64();
case ConvertUInt32: return curr->type == f32 ? value.convertUToF32() : value.convertUToF64();
case ConvertSInt32: return curr->type == f32 ? value.convertSToF32() : value.convertSToF64();
default: abort();
}
}
if (value.type == i64) {
switch (curr->op) {
case Clz: return value.countLeadingZeroes();
case Ctz: return value.countTrailingZeroes();
case Popcnt: return value.popCount();
case EqZ: return Literal(int32_t(value == Literal(int64_t(0))));
case WrapInt64: return value.truncateToI32();
case ReinterpretInt: return value.castToF64();
case ConvertUInt64: return curr->type == f32 ? value.convertUToF32() : value.convertUToF64();
case ConvertSInt64: return curr->type == f32 ? value.convertSToF32() : value.convertSToF64();
default: abort();
}
}
if (value.type == f32) {
switch (curr->op) {
case Neg: return value.neg();
case Abs: return value.abs();
case Ceil: return value.ceil();
case Floor: return value.floor();
case Trunc: return value.trunc();
case Nearest: return value.nearbyint();
case Sqrt: return value.sqrt();
case TruncSFloat32: return truncSFloat(curr, value);
case TruncUFloat32: return truncUFloat(curr, value);
case ReinterpretFloat: return value.castToI32();
case PromoteFloat32: return value.extendToF64();
default: abort();
}
}
if (value.type == f64) {
switch (curr->op) {
case Neg: return value.neg();
case Abs: return value.abs();
case Ceil: return value.ceil();
case Floor: return value.floor();
case Trunc: return value.trunc();
case Nearest: return value.nearbyint();
case Sqrt: return value.sqrt();
case TruncSFloat64: return truncSFloat(curr, value);
case TruncUFloat64: return truncUFloat(curr, value);
case ReinterpretFloat: return value.castToI64();
case DemoteFloat64: return value.truncateToF32();
default: abort();
}
}
abort();
}
Flow visitBinary(Binary *curr) {
NOTE_ENTER("Binary");
Flow flow = visit(curr->left);
if (flow.breaking()) return flow;
Literal left = flow.value;
flow = visit(curr->right);
if (flow.breaking()) return flow;
Literal right = flow.value;
NOTE_EVAL2(left, right);
assert(isConcreteWasmType(curr->left->type) ? left.type == curr->left->type : true);
assert(isConcreteWasmType(curr->right->type) ? right.type == curr->right->type : true);
if (left.type == i32) {
switch (curr->op) {
case Add: return left.add(right);
case Sub: return left.sub(right);
case Mul: return left.mul(right);
case DivS: {
if (right.getInteger() == 0) trap("i32.div_s by 0");
if (left.getInteger() == std::numeric_limits<int32_t>::min() && right.getInteger() == -1) trap("i32.div_s overflow"); // signed division overflow
return left.divS(right);
}
case DivU: {
if (right.getInteger() == 0) trap("i32.div_u by 0");
return left.divU(right);
}
case RemS: {
if (right.getInteger() == 0) trap("i32.rem_s by 0");
if (left.getInteger() == std::numeric_limits<int32_t>::min() && right.getInteger() == -1) return Literal(int32_t(0));
return left.remS(right);
}
case RemU: {
if (right.getInteger() == 0) trap("i32.rem_u by 0");
return left.remU(right);
}
case And: return left.and_(right);
case Or: return left.or_(right);
case Xor: return left.xor_(right);
case Shl: return left.shl(right.and_(Literal(int32_t(31))));
case ShrU: return left.shrU(right.and_(Literal(int32_t(31))));
case ShrS: return left.shrS(right.and_(Literal(int32_t(31))));
case RotL: return left.rotL(right);
case RotR: return left.rotR(right);
case Eq: return left.eq(right);
case Ne: return left.ne(right);
case LtS: return left.ltS(right);
case LtU: return left.ltU(right);
case LeS: return left.leS(right);
case LeU: return left.leU(right);
case GtS: return left.gtS(right);
case GtU: return left.gtU(right);
case GeS: return left.geS(right);
case GeU: return left.geU(right);
default: abort();
}
} else if (left.type == i64) {
switch (curr->op) {
case Add: return left.add(right);
case Sub: return left.sub(right);
case Mul: return left.mul(right);
case DivS: {
if (right.getInteger() == 0) trap("i64.div_s by 0");
if (left.getInteger() == LLONG_MIN && right.getInteger() == -1LL) trap("i64.div_s overflow"); // signed division overflow
return left.divS(right);
}
case DivU: {
if (right.getInteger() == 0) trap("i64.div_u by 0");
return left.divU(right);
}
case RemS: {
if (right.getInteger() == 0) trap("i64.rem_s by 0");
if (left.getInteger() == LLONG_MIN && right.getInteger() == -1LL) return Literal(int64_t(0));
return left.remS(right);
}
case RemU: {
if (right.getInteger() == 0) trap("i64.rem_u by 0");
return left.remU(right);
}
case And: return left.and_(right);
case Or: return left.or_(right);
case Xor: return left.xor_(right);
case Shl: return left.shl(right.and_(Literal(int64_t(63))));
case ShrU: return left.shrU(right.and_(Literal(int64_t(63))));
case ShrS: return left.shrS(right.and_(Literal(int64_t(63))));
case RotL: return left.rotL(right);
case RotR: return left.rotR(right);
case Eq: return left.eq(right);
case Ne: return left.ne(right);
case LtS: return left.ltS(right);
case LtU: return left.ltU(right);
case LeS: return left.leS(right);
case LeU: return left.leU(right);
case GtS: return left.gtS(right);
case GtU: return left.gtU(right);
case GeS: return left.geS(right);
case GeU: return left.geU(right);
default: abort();
}
} else if (left.type == f32 || left.type == f64) {
switch (curr->op) {
case Add: return left.add(right);
case Sub: return left.sub(right);
case Mul: return left.mul(right);
case Div: return left.div(right);
case CopySign: return left.copysign(right);
case Min: return left.min(right);
case Max: return left.max(right);
case Eq: return left.eq(right);
case Ne: return left.ne(right);
case Lt: return left.lt(right);
case Le: return left.le(right);
case Gt: return left.gt(right);
case Ge: return left.ge(right);
default: abort();
}
}
abort();
}
Flow visitSelect(Select *curr) {
NOTE_ENTER("Select");
Flow ifTrue = visit(curr->ifTrue);
if (ifTrue.breaking()) return ifTrue;
Flow ifFalse = visit(curr->ifFalse);
if (ifFalse.breaking()) return ifFalse;
Flow condition = visit(curr->condition);
if (condition.breaking()) return condition;
NOTE_EVAL1(condition.value);
return condition.value.geti32() ? ifTrue : ifFalse; // ;-)
}
Flow visitReturn(Return *curr) {
NOTE_ENTER("Return");
Flow flow;
if (curr->value) {
flow = visit(curr->value);
if (flow.breaking()) return flow;
NOTE_EVAL1(flow.value);
}
flow.breakTo = RETURN_FLOW;
return flow;
}
Flow visitHost(Host *curr) {
NOTE_ENTER("Host");
switch (curr->op) {
case PageSize: return Literal((int32_t)Memory::kPageSize);
case CurrentMemory: return Literal(int32_t(instance.memorySize));
case GrowMemory: {
Flow flow = visit(curr->operands[0]);
if (flow.breaking()) return flow;
int32_t ret = instance.memorySize;
uint32_t delta = flow.value.geti32();
if (delta > uint32_t(-1) /Memory::kPageSize) trap("growMemory: delta relatively too big");
if (instance.memorySize >= uint32_t(-1) - delta) trap("growMemory: delta objectively too big");
uint32_t newSize = instance.memorySize + delta;
if (newSize > instance.wasm.memory.max) trap("growMemory: exceeds max");
instance.externalInterface->growMemory(instance.memorySize * Memory::kPageSize, newSize * Memory::kPageSize);
instance.memorySize = newSize;
return Literal(int32_t(ret));
}
case HasFeature: {
IString id = curr->nameOperand;
if (id == WASM) return Literal(1);
return Literal((int32_t)0);
}
default: abort();
}
}
Flow visitNop(Nop *curr) {
NOTE_ENTER("Nop");
return Flow();
}
Flow visitUnreachable(Unreachable *curr) {
NOTE_ENTER("Unreachable");
trap("unreachable");
return Flow();
}
Literal truncSFloat(Unary* curr, Literal value) {
double val = value.getFloat();
if (std::isnan(val)) trap("truncSFloat of nan");
if (curr->type == i32) {
if (value.type == f32) {
if (!isInRangeI32TruncS(value.reinterpreti32())) trap("i32.truncSFloat overflow");
} else {
if (!isInRangeI32TruncS(value.reinterpreti64())) trap("i32.truncSFloat overflow");
}
return Literal(int32_t(val));
} else {
if (value.type == f32) {
if (!isInRangeI64TruncS(value.reinterpreti32())) trap("i64.truncSFloat overflow");
} else {
if (!isInRangeI64TruncS(value.reinterpreti64())) trap("i64.truncSFloat overflow");
}
return Literal(int64_t(val));
}
}
Literal truncUFloat(Unary* curr, Literal value) {
double val = value.getFloat();
if (std::isnan(val)) trap("truncUFloat of nan");
if (curr->type == i32) {
if (value.type == f32) {
if (!isInRangeI32TruncU(value.reinterpreti32())) trap("i32.truncUFloat overflow");
} else {
if (!isInRangeI32TruncU(value.reinterpreti64())) trap("i32.truncUFloat overflow");
}
return Literal(uint32_t(val));
} else {
if (value.type == f32) {
if (!isInRangeI64TruncU(value.reinterpreti32())) trap("i64.truncUFloat overflow");
} else {
if (!isInRangeI64TruncU(value.reinterpreti64())) trap("i64.truncUFloat overflow");
}
return Literal(uint64_t(val));
}
}
void trap(const char* why) {
instance.externalInterface->trap(why);
}
};
if (callDepth > maxCallDepth) externalInterface->trap("stack limit");
callDepth++;
functionStack.push_back(name);
Function *function = wasm.getFunction(name);
assert(function);
FunctionScope scope(function, arguments);
#ifdef WASM_INTERPRETER_DEBUG
std::cout << "entering " << function->name << '\n';
#endif
Flow flow = ExpressionRunner(*this, scope).visit(function->body);
assert(!flow.breaking() || flow.breakTo == RETURN_FLOW); // cannot still be breaking, it means we missed our stop
Literal ret = flow.value;
if (function->result == none) ret = Literal();
assert(function->result == ret.type);
callDepth--;
assert(functionStack.back() == name);
functionStack.pop_back();
#ifdef WASM_INTERPRETER_DEBUG
std::cout << "exiting " << function->name << " with " << ret << '\n';
#endif
return ret;
}
size_t memorySize; // in pages
template <class LS>
size_t getFinalAddress(LS* curr, Literal ptr) {
auto trapIfGt = [this](uint64_t lhs, uint64_t rhs, const char* msg) {
if (lhs > rhs) {
std::stringstream ss;
ss << msg << ": " << lhs << " > " << rhs;
externalInterface->trap(ss.str().c_str());
}
};
uint32_t memorySizeBytes = memorySize * Memory::kPageSize;
uint64_t addr = ptr.type == i32 ? ptr.geti32() : ptr.geti64();
trapIfGt(curr->offset, memorySizeBytes, "offset > memory");
trapIfGt(addr, memorySizeBytes - curr->offset, "final > memory");
addr += curr->offset;
trapIfGt(curr->bytes, memorySizeBytes, "bytes > memory");
trapIfGt(addr, memorySizeBytes - curr->bytes, "highest > memory");
return addr;
}
ExternalInterface* externalInterface;
};
} // namespace wasm
#endif // wasm_wasm_interpreter_h