[wasm] Implement frame printing for debug

This makes wasm frames show up nicely in stack traces generated e.g. by
Isolate::PrintStack() and Isolate::PrintCurrentStackTrace().
With this CL, we print the script name, function index, function name,
pc and source position.

R=titzer@chromium.org, ahaas@chromium.org

Review-Url: https://codereview.chromium.org/2509323002
Cr-Commit-Position: refs/heads/master@{#41102}

src/frames.cc

@@ -1487,7 +1487,28 @@ void StackFrame::PrintIndex(StringStream* accumulator,
 
 void WasmFrame::Print(StringStream* accumulator, PrintMode mode,
                       int index) const {
-  accumulator->Add("wasm frame");
+  PrintIndex(accumulator, mode, index);
+  accumulator->Add("WASM [");
+  Script* script = this->script();
+  accumulator->PrintName(script->name());
+  int pc = static_cast<int>(this->pc() - LookupCode()->instruction_start());
+  Vector<const uint8_t> raw_func_name;
+  Object* instance_or_undef = this->wasm_instance();
+  if (instance_or_undef->IsUndefined(this->isolate())) {
+    raw_func_name = STATIC_CHAR_VECTOR("<undefined>");
+  } else {
+    raw_func_name = WasmInstanceObject::cast(instance_or_undef)
+                        ->get_compiled_module()
+                        ->GetRawFunctionName(this->function_index());
+  }
+  const int kMaxPrintedFunctionName = 64;
+  char func_name[kMaxPrintedFunctionName + 1];
+  int func_name_len = std::min(kMaxPrintedFunctionName, raw_func_name.length());
+  memcpy(func_name, raw_func_name.start(), func_name_len);
+  func_name[func_name_len] = '\0';
+  accumulator->Add("], function #%u ('%s'), pc=%p, pos=%d\n",
+                   this->function_index(), func_name, pc, this->position());
+  if (mode != OVERVIEW) accumulator->Add("\n");
 }
 
 Code* WasmFrame::unchecked_code() const {

src/wasm/wasm-objects.cc

@@ -312,7 +312,7 @@ Handle<WasmCompiledModule> WasmCompiledModule::New(
 }
 
 wasm::WasmModule* WasmCompiledModule::module() const {
-  return reinterpret_cast<WasmModuleWrapper*>(*module_wrapper())->get();
+  return reinterpret_cast<WasmModuleWrapper*>(ptr_to_module_wrapper())->get();
 }
 
 void WasmCompiledModule::InitId() {
@@ -365,3 +365,15 @@ uint32_t WasmCompiledModule::mem_size() const {
 uint32_t WasmCompiledModule::default_mem_size() const {
   return min_mem_pages() * WasmModule::kPageSize;
 }
+
+Vector<const uint8_t> WasmCompiledModule::GetRawFunctionName(
+    uint32_t func_index) {
+  DCHECK_GT(module()->functions.size(), func_index);
+  WasmFunction& function = module()->functions[func_index];
+  SeqOneByteString* bytes = ptr_to_module_bytes();
+  DCHECK_GE(static_cast<size_t>(bytes->length()), function.name_offset);
+  DCHECK_GE(static_cast<size_t>(bytes->length() - function.name_offset),
+            function.name_length);
+  return Vector<const uint8_t>(bytes->GetCharsAddress() + function.name_offset,
+                               function.name_length);
+}

src/wasm/wasm-objects.h

@@ -259,12 +259,18 @@ class WasmCompiledModule : public FixedArray {
   static void RecreateModuleWrapper(Isolate* isolate,
                                     Handle<FixedArray> compiled_module);
 
-  // Extract a function name from the given wasm instance.
+  // Get the function name of the function identified by the given index.
   // Returns a null handle if the function is unnamed or the name is not a valid
   // UTF-8 string.
   static MaybeHandle<String> GetFunctionName(
       Handle<WasmCompiledModule> compiled_module, uint32_t func_index);
 
+  // Get the raw bytes of the function name of the function identified by the
+  // given index.
+  // Meant to be used for debugging or frame printing.
+  // Does not allocate, hence gc-safe.
+  Vector<const uint8_t> GetRawFunctionName(uint32_t func_index);
+
  private:
   void InitId();