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/*
* Copyright 2016 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.
*/
//
// Implementation of the shell interpreter execution environment
//
#include "asmjs/shared-constants.h"
#include "wasm.h"
#include "wasm-interpreter.h"
namespace wasm {
struct ExitException {};
struct TrapException {};
struct ParseException {};
struct ShellExternalInterface : ModuleInstance::ExternalInterface {
// The underlying memory can be accessed through unaligned pointers which
// isn't well-behaved in C++. WebAssembly nonetheless expects it to behave
// properly. Avoid emitting unaligned load/store by checking for alignment
// explicitly, and performing memcpy if unaligned.
//
// The allocated memory tries to have the same alignment as the memory being
// simulated.
class Memory {
// Use char because it doesn't run afoul of aliasing rules.
std::vector<char> memory;
template <typename T>
static bool aligned(const char* address) {
static_assert(!(sizeof(T) & (sizeof(T) - 1)), "must be a power of 2");
return 0 == (reinterpret_cast<uintptr_t>(address) & (sizeof(T) - 1));
}
Memory(Memory&) = delete;
Memory& operator=(const Memory&) = delete;
public:
Memory() {}
void resize(size_t newSize) {
// Ensure the smallest allocation is large enough that most allocators
// will provide page-aligned storage. This hopefully allows the
// interpreter's memory to be as aligned as the memory being simulated,
// ensuring that the performance doesn't needlessly degrade.
//
// The code is optimistic this will work until WG21's p0035r0 happens.
const size_t minSize = 1 << 12;
size_t oldSize = memory.size();
memory.resize(std::max(minSize, newSize));
if (newSize < oldSize && newSize < minSize) {
std::memset(&memory[newSize], 0, minSize - newSize);
}
}
template <typename T>
void set(size_t address, T value) {
if (aligned<T>(&memory[address])) {
*reinterpret_cast<T*>(&memory[address]) = value;
} else {
std::memcpy(&memory[address], &value, sizeof(T));
}
}
template <typename T>
T get(size_t address) {
if (aligned<T>(&memory[address])) {
return *reinterpret_cast<T*>(&memory[address]);
} else {
T loaded;
std::memcpy(&loaded, &memory[address], sizeof(T));
return loaded;
}
}
} memory;
ShellExternalInterface() : memory() {}
void init(Module& wasm) override {
memory.resize(wasm.memory.initial * wasm::Memory::kPageSize);
// apply memory segments
for (auto segment : wasm.memory.segments) {
assert(segment.offset + segment.size <= wasm.memory.initial * wasm::Memory::kPageSize);
for (size_t i = 0; i != segment.size; ++i) {
memory.set(segment.offset + i, segment.data[i]);
}
}
}
Literal callImport(Import *import, ModuleInstance::LiteralList& arguments) override {
if (import->module == SPECTEST && import->base == PRINT) {
for (auto argument : arguments) {
std::cout << argument << '\n';
}
return Literal();
} else if (import->module == ENV && import->base == EXIT) {
// XXX hack for torture tests
std::cout << "exit()\n";
throw ExitException();
}
std::cout << "callImport " << import->name.str << "\n";
abort();
}
Literal load(Load* load, size_t addr) override {
switch (load->type) {
case i32: {
switch (load->bytes) {
case 1: return load->signed_ ? Literal((int32_t)memory.get<int8_t>(addr)) : Literal((int32_t)memory.get<uint8_t>(addr));
case 2: return load->signed_ ? Literal((int32_t)memory.get<int16_t>(addr)) : Literal((int32_t)memory.get<uint16_t>(addr));
case 4: return load->signed_ ? Literal((int32_t)memory.get<int32_t>(addr)) : Literal((int32_t)memory.get<uint32_t>(addr));
default: abort();
}
break;
}
case i64: {
switch (load->bytes) {
case 1: return load->signed_ ? Literal((int64_t)memory.get<int8_t>(addr)) : Literal((int64_t)memory.get<uint8_t>(addr));
case 2: return load->signed_ ? Literal((int64_t)memory.get<int16_t>(addr)) : Literal((int64_t)memory.get<uint16_t>(addr));
case 4: return load->signed_ ? Literal((int64_t)memory.get<int32_t>(addr)) : Literal((int64_t)memory.get<uint32_t>(addr));
case 8: return load->signed_ ? Literal((int64_t)memory.get<int64_t>(addr)) : Literal((int64_t)memory.get<uint64_t>(addr));
default: abort();
}
break;
}
case f32: return Literal(memory.get<float>(addr));
case f64: return Literal(memory.get<double>(addr));
default: abort();
}
}
void store(Store* store, size_t addr, Literal value) override {
switch (store->type) {
case i32: {
switch (store->bytes) {
case 1: memory.set<int8_t>(addr, value.geti32()); break;
case 2: memory.set<int16_t>(addr, value.geti32()); break;
case 4: memory.set<int32_t>(addr, value.geti32()); break;
default: abort();
}
break;
}
case i64: {
switch (store->bytes) {
case 1: memory.set<int8_t>(addr, (int8_t)value.geti64()); break;
case 2: memory.set<int16_t>(addr, (int16_t)value.geti64()); break;
case 4: memory.set<int32_t>(addr, (int32_t)value.geti64()); break;
case 8: memory.set<int64_t>(addr, value.geti64()); break;
default: abort();
}
break;
}
// write floats carefully, ensuring all bits reach memory
case f32: memory.set<int32_t>(addr, value.reinterpreti32()); break;
case f64: memory.set<int64_t>(addr, value.reinterpreti64()); break;
default: abort();
}
}
void growMemory(size_t /*oldSize*/, size_t newSize) override {
memory.resize(newSize);
}
void trap(const char* why) override {
std::cerr << "[trap " << why << "]\n";
throw TrapException();
}
};
}
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