[wasm] Instantiate the interpreter on demand

src/wasm/wasm-debug.cc

 // Copyright 2016 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+#include "src/assembler-inl.h"
 #include "src/assert-scope.h"
+#include "src/compiler/wasm-compiler.h"
 #include "src/debug/debug.h"
 #include "src/factory.h"
+#include "src/frames-inl.h"
 #include "src/isolate.h"
 #include "src/wasm/module-decoder.h"
+#include "src/wasm/wasm-interpreter.h"
 #include "src/wasm/wasm-module.h"
 #include "src/wasm/wasm-objects.h"
+#include "src/zone/accounting-allocator.h"
 
 using namespace v8::internal;
 using namespace v8::internal::wasm;
 
+namespace {
+
+class InterpreterHandle {
+  AccountingAllocator allocator_;
+  WasmInstance instance_;
+  WasmInterpreter interpreter_;
+
+ public:
+  // Initialize in the right order, using helper methods to make this possible.
+  // WasmInterpreter has to be allocated in place, since it is not movable.
+  InterpreterHandle(Isolate *isolate, WasmDebugInfo *debug_info)
+      : instance_(debug_info->wasm_instance()->compiled_module()->module()),
+        interpreter_(GetBytesEnv(&instance_, debug_info), &allocator_) {
+    Handle<JSArrayBuffer> mem_buffer =
+        handle(debug_info->wasm_instance()->memory_buffer(), isolate);
+    if (mem_buffer->IsUndefined(isolate)) {
+      DCHECK_EQ(0, instance_.module->min_mem_pages);
+      instance_.mem_start = nullptr;
+      instance_.mem_size = 0;
+    } else {
+      instance_.mem_start =
+          reinterpret_cast<byte *>(mem_buffer->backing_store());
+      CHECK(mem_buffer->byte_length()->ToUint32(&instance_.mem_size));
+    }
+  }
+
+  static ModuleBytesEnv GetBytesEnv(WasmInstance *instance,
+                                    WasmDebugInfo *debug_info) {
+    // Return raw pointer into heap. The WasmInterpreter will make its own copy
+    // of this data anyway, and there is no heap allocation in-between.
+    SeqOneByteString *bytes_str =
+        debug_info->wasm_instance()->compiled_module()->module_bytes();
+    Vector<const byte> bytes(bytes_str->GetChars(), bytes_str->length());
+    return ModuleBytesEnv(instance->module, instance, bytes);
+  }
+
+  WasmInterpreter *interpreter() { return &interpreter_; }
+  const WasmModule *module() { return instance_.module; }
+
+  void Execute(uint32_t func_index, uint8_t *arg_buffer) {
+    DCHECK_GE(module()->functions.size(), func_index);
+    FunctionSig *sig = module()->functions[func_index].sig;
+    DCHECK_GE(kMaxInt, sig->parameter_count());
+    int num_params = static_cast<int>(sig->parameter_count());
+    ScopedVector<WasmVal> wasm_args(num_params);
+    uint8_t *arg_buf_ptr = arg_buffer;
+    for (int i = 0; i < num_params; ++i) {
+      uint32_t param_size = 1 << ElementSizeLog2Of(sig->GetParam(i));
+#define CASE_ARG_TYPE(type, ctype)                                   \
+  case type:                                                         \
+    DCHECK_EQ(param_size, sizeof(ctype));                            \
+    wasm_args[i] = WasmVal(*reinterpret_cast<ctype *>(arg_buf_ptr)); \
+    break;
+      switch (sig->GetParam(i)) {
+        CASE_ARG_TYPE(kWasmI32, uint32_t)
+        CASE_ARG_TYPE(kWasmI64, uint64_t)
+        CASE_ARG_TYPE(kWasmF32, float)
+        CASE_ARG_TYPE(kWasmF64, double)
+#undef CASE_ARG_TYPE
+        default:
+          UNREACHABLE();
+      }
+      arg_buf_ptr += param_size;
+    }
+
+    WasmInterpreter::Thread *thread = interpreter_.GetThread(0);
+    // We do not support reentering an already running interpreter at the moment
+    // (like INTERPRETER -> JS -> WASM -> INTERPRETER).
+    DCHECK(thread->state() == WasmInterpreter::STOPPED ||
+           thread->state() == WasmInterpreter::FINISHED);
+    thread->Reset();
+    thread->PushFrame(&module()->functions[func_index], wasm_args.start());
+    WasmInterpreter::State state;
+    do {
+      state = thread->Run();
+      switch (state) {
+        case WasmInterpreter::State::PAUSED: {
+          // We hit a breakpoint.
+          // TODO(clemensh): Handle this.
+        } break;
+        case WasmInterpreter::State::FINISHED:
+          // Perfect, just break the switch and exit the loop.
+          break;
+        case WasmInterpreter::State::TRAPPED:
+          // TODO(clemensh): Generate appropriate JS exception.
+          UNIMPLEMENTED();
+          break;
+        // STOPPED and RUNNING should never occur here.
+        case WasmInterpreter::State::STOPPED:
+        case WasmInterpreter::State::RUNNING:
+        default:
+          UNREACHABLE();
+      }
+    } while (state != WasmInterpreter::State::FINISHED);
+
+    // Copy back the return value
+    DCHECK_GE(1, sig->return_count());

[titzer, 2017/01/12 15:32:05]

I think you should check against kV8MaxWasmFunctionReturns here, and a add a
TODO about multi-value returns.

Come to think of it, you should also add this in the wasm-compiler.cc where it
compiles the stubs.

[Clemens Hammacher, 2017/01/12 19:19:54]

Done.

+    if (sig->return_count()) {
+      WasmVal ret_val = thread->GetReturnValue(0);
+#define CASE_RET_TYPE(type, ctype)                                       \
+  case type:                                                             \
+    DCHECK_EQ(1 << ElementSizeLog2Of(sig->GetReturn(0)), sizeof(ctype)); \
+    *reinterpret_cast<ctype *>(arg_buffer) = ret_val.to<ctype>();        \
+    break;
+      switch (sig->GetReturn(0)) {
+        CASE_RET_TYPE(kWasmI32, uint32_t)
+        CASE_RET_TYPE(kWasmI64, uint64_t)
+        CASE_RET_TYPE(kWasmF32, float)
+        CASE_RET_TYPE(kWasmF64, double)
+#undef CASE_RET_TYPE
+        default:
+          UNREACHABLE();
+      }
+    }
+  }
+};
+
+InterpreterHandle *GetOrCreateInterpreterHandle(
+    Isolate *isolate, Handle<WasmDebugInfo> debug_info) {
+  Handle<Object> handle(debug_info->get(WasmDebugInfo::kInterpreterHandle),
+                        isolate);
+  if (handle->IsUndefined(isolate)) {
+    InterpreterHandle *cpp_handle = new InterpreterHandle(isolate, *debug_info);
+    handle = Managed<InterpreterHandle>::New(isolate, cpp_handle);
+    debug_info->set(WasmDebugInfo::kInterpreterHandle, *handle);
+  }
+
+  return Handle<Managed<InterpreterHandle>>::cast(handle)->get();
+}
+
+int GetNumFunctions(WasmInstanceObject *instance) {
+  size_t num_functions =
+      instance->compiled_module()->module()->functions.size();
+  DCHECK_GE(kMaxInt, num_functions);
+  return static_cast<int>(num_functions);
+}
+
+Handle<FixedArray> GetOrCreateInterpretedFunctions(
+    Isolate *isolate, Handle<WasmDebugInfo> debug_info) {
+  Handle<Object> obj(debug_info->get(WasmDebugInfo::kInterpretedFunctions),
+                     isolate);
+  if (!obj->IsUndefined(isolate)) return Handle<FixedArray>::cast(obj);
+
+  Handle<FixedArray> new_arr = isolate->factory()->NewFixedArray(
+      GetNumFunctions(debug_info->wasm_instance()));
+  debug_info->set(WasmDebugInfo::kInterpretedFunctions, *new_arr);
+  return new_arr;
+}
+
+void RedirectCallsitesInCode(Code *code, Code *old_target, Code *new_target) {
+  DisallowHeapAllocation no_gc;
+  for (RelocIterator it(code, RelocInfo::kCodeTargetMask); !it.done();
+       it.next()) {
+    DCHECK(RelocInfo::IsCodeTarget(it.rinfo()->rmode()));
+    Code *target = Code::GetCodeFromTargetAddress(it.rinfo()->target_address());
+    if (target != old_target) continue;
+    it.rinfo()->set_target_address(new_target->instruction_start());
+  }
+}
+
+void RedirectCallsitesInInstance(Isolate *isolate, WasmInstanceObject *instance,
+                                 Code *old_target, Code *new_target) {
+  DisallowHeapAllocation no_gc;
+  // Redirect in all wasm functions.
+  FixedArray *code_table = instance->compiled_module()->ptr_to_code_table();
+  for (int i = 0, e = GetNumFunctions(instance); i < e; ++i)

[titzer, 2017/01/12 15:32:05]

Please add brackets.

[Clemens Hammacher, 2017/01/12 19:19:54]

Done.

+    RedirectCallsitesInCode(Code::cast(code_table->get(i)), old_target,
+                            new_target);
+
+  // Redirect in all exported functions.

[titzer, 2017/01/12 15:32:05]

"Redirect all calls in exported functions"? and move a line down.

[Clemens Hammacher, 2017/01/12 19:19:54]

Done, and removed the DCHECK which does not really serve a purpose here...

+  DCHECK(!instance->compiled_module()->is_asm_js());
+
+  FixedArray *weak_exported_functions =
+      instance->compiled_module()->ptr_to_weak_exported_functions();
+  for (int i = 0, e = weak_exported_functions->length(); i != e; ++i) {
+    WeakCell *weak_function = WeakCell::cast(weak_exported_functions->get(i));
+    if (weak_function->cleared()) continue;
+    Code *code = JSFunction::cast(weak_function->value())->code();
+    RedirectCallsitesInCode(code, old_target, new_target);
+  }
+}
+
+void EnsureRedirectToInterpreter(Isolate *isolate,
+                                 Handle<WasmDebugInfo> debug_info,
+                                 int func_index) {
+  DCHECK_LE(0, func_index);
+  Handle<FixedArray> interpreted_functions =
+      GetOrCreateInterpretedFunctions(isolate, debug_info);
+  DCHECK_GT(interpreted_functions->length(), func_index);

[titzer, 2017/01/12 15:32:05]

The FixedArray should do this bounds check for you.

[Clemens Hammacher, 2017/01/12 19:19:54]

Yeah, but it's only SLOW_DCHECK.
I removed it for now, but I feel more comfortable with these early checks.

+  if (!interpreted_functions->get(func_index)->IsUndefined(isolate)) return;
+
+  Handle<WasmInstanceObject> instance(debug_info->wasm_instance(), isolate);
+  Handle<Code> new_code = compiler::CompileWasmInterpreterEntry(
+      isolate, func_index,
+      instance->compiled_module()->module()->functions[func_index].sig,
+      instance);
+
+  Handle<FixedArray> code_table = instance->compiled_module()->code_table();
+  DCHECK_GT(code_table->length(), func_index);

[titzer, 2017/01/12 15:32:05]

Same here. The FixedArray will bounds check for you.

[Clemens Hammacher, 2017/01/12 19:19:54]

Done.

+  Handle<Code> old_code =
+      code_table->GetValueChecked<Code>(isolate, func_index);
+  interpreted_functions->set(func_index, *new_code);
+
+  RedirectCallsitesInInstance(isolate, *instance, *old_code, *new_code);
+}
+
+}  // namespace
+
 Handle<WasmDebugInfo> WasmDebugInfo::New(Handle<WasmInstanceObject> instance) {
   Isolate *isolate = instance->GetIsolate();
   Factory *factory = isolate->factory();
   Handle<FixedArray> arr = factory->NewFixedArray(kFieldCount, TENURED);
   arr->set(kInstance, *instance);
-
   return Handle<WasmDebugInfo>::cast(arr);
 }
 
 bool WasmDebugInfo::IsDebugInfo(Object *object) {
   if (!object->IsFixedArray()) return false;
   FixedArray *arr = FixedArray::cast(object);
-  return arr->length() == kFieldCount && IsWasmInstance(arr->get(kInstance));
+  if (arr->length() != kFieldCount) return false;
+  if (!IsWasmInstance(arr->get(kInstance))) return false;
+  Isolate *isolate = arr->GetIsolate();
+  if (!arr->get(kInterpreterHandle)->IsUndefined(isolate) &&
+      !arr->get(kInterpreterHandle)->IsForeign())
+    return false;
+  return true;
 }
 
 WasmDebugInfo *WasmDebugInfo::cast(Object *object) {
   DCHECK(IsDebugInfo(object));
   return reinterpret_cast<WasmDebugInfo *>(object);
 }
 
 WasmInstanceObject *WasmDebugInfo::wasm_instance() {
   return WasmInstanceObject::cast(get(kInstance));
 }
 
+void WasmDebugInfo::SetBreakpoint(Handle<WasmDebugInfo> debug_info,
+                                  int func_index, int offset) {
+  Isolate *isolate = debug_info->GetIsolate();
+  InterpreterHandle *handle = GetOrCreateInterpreterHandle(isolate, debug_info);
+  WasmInterpreter *interpreter = handle->interpreter();
+  DCHECK_LE(0, func_index);
+  DCHECK_GT(handle->module()->functions.size(), func_index);
+  const WasmFunction *func = &handle->module()->functions[func_index];
+  interpreter->SetBreakpoint(func, offset, true);
+  EnsureRedirectToInterpreter(isolate, debug_info, func_index);
+}
+
 void WasmDebugInfo::RunInterpreter(Handle<WasmDebugInfo> debug_info,
                                    int func_index, uint8_t *arg_buffer) {
-  // TODO(clemensh): Implement this.
-  UNIMPLEMENTED();
+  DCHECK_LE(0, func_index);
+  InterpreterHandle *interp_handle =
+      GetOrCreateInterpreterHandle(debug_info->GetIsolate(), debug_info);
+  interp_handle->Execute(static_cast<uint32_t>(func_index), arg_buffer);
 }