[wasm] Introduce NamesProvider

NamesProvider class:
This consolidates logic used so far for the debugger interface.
It also adds support for the "extended name section" proposal:
https://github.com/WebAssembly/extended-name-section

StringBuilder class:
Like std::ostringstream, but 4x faster for this use case.

This lays the groundwork for an updated Wasm disassembler.

Bug: v8:12917
Change-Id: I98aa258147834bc0e314ba98c5927b4cd6070b8f
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3720714Reviewed-by: Philip Pfaffe <pfaffe@chromium.org>
Commit-Queue: Jakob Kummerow <jkummerow@chromium.org>
Reviewed-by: Andreas Haas <ahaas@chromium.org>
Cr-Commit-Position: refs/heads/main@{#81446}

BUILD.bazel

@@ -2512,6 +2512,8 @@ filegroup(
             "src/wasm/module-decoder.h",
             "src/wasm/module-instantiate.cc",
             "src/wasm/module-instantiate.h",
+            "src/wasm/names-provider.cc",
+            "src/wasm/names-provider.h",
             "src/wasm/object-access.h",
             "src/wasm/signature-map.cc",
             "src/wasm/signature-map.h",
@@ -2520,6 +2522,7 @@ filegroup(
             "src/wasm/stacks.h",
             "src/wasm/streaming-decoder.cc",
             "src/wasm/streaming-decoder.h",
+            "src/wasm/string-builder.h",
             "src/wasm/struct-types.h",
             "src/wasm/sync-streaming-decoder.cc",
             "src/wasm/value-type.cc",

BUILD.gn

@@ -3610,15 +3610,18 @@ v8_header_set("v8_internal_headers") {
       "src/wasm/module-compiler.h",
       "src/wasm/module-decoder.h",
       "src/wasm/module-instantiate.h",
+      "src/wasm/names-provider.h",
       "src/wasm/object-access.h",
       "src/wasm/signature-map.h",
       "src/wasm/simd-shuffle.h",
       "src/wasm/stacks.h",
       "src/wasm/streaming-decoder.h",
+      "src/wasm/string-builder.h",
       "src/wasm/struct-types.h",
       "src/wasm/value-type.h",
       "src/wasm/wasm-arguments.h",
       "src/wasm/wasm-code-manager.h",
+      "src/wasm/wasm-debug.h",
       "src/wasm/wasm-engine.h",
       "src/wasm/wasm-external-refs.h",
       "src/wasm/wasm-feature-flags.h",
@@ -4694,6 +4697,7 @@ v8_source_set("v8_base_without_compiler") {
       "src/wasm/module-compiler.cc",
       "src/wasm/module-decoder.cc",
       "src/wasm/module-instantiate.cc",
+      "src/wasm/names-provider.cc",
       "src/wasm/signature-map.cc",
       "src/wasm/simd-shuffle.cc",
       "src/wasm/streaming-decoder.cc",
@@ -4701,7 +4705,6 @@ v8_source_set("v8_base_without_compiler") {
       "src/wasm/value-type.cc",
       "src/wasm/wasm-code-manager.cc",
       "src/wasm/wasm-debug.cc",
-      "src/wasm/wasm-debug.h",
       "src/wasm/wasm-engine.cc",
       "src/wasm/wasm-external-refs.cc",
       "src/wasm/wasm-features.cc",

src/debug/debug-wasm-objects.cc

@@ -10,6 +10,8 @@
 #include "src/debug/debug-wasm-objects-inl.h"
 #include "src/execution/frames-inl.h"
 #include "src/objects/property-descriptor.h"
+#include "src/wasm/names-provider.h"
+#include "src/wasm/string-builder.h"
 #include "src/wasm/wasm-debug.h"
 #include "src/wasm/wasm-objects-inl.h"
 #include "src/wasm/wasm-value.h"
@@ -18,53 +20,10 @@ namespace v8 {
 namespace internal {
 namespace {
 
-// Helper for unpacking a maybe name that makes a default with an index if
-// the name is empty. If the name is not empty, it's prefixed with a $.
-Handle<String> GetNameOrDefault(Isolate* isolate,
-                                MaybeHandle<String> maybe_name,
-                                const char* default_name_prefix,
-                                uint32_t index) {
-  Handle<String> name;
-  if (maybe_name.ToHandle(&name)) {
-    name = isolate->factory()
-               ->NewConsString(
-                   isolate->factory()->NewStringFromAsciiChecked("$"), name)
-               .ToHandleChecked();
-    return isolate->factory()->InternalizeString(name);
-  }
-  base::EmbeddedVector<char, 64> value;
-  int len = SNPrintF(value, "%s%u", default_name_prefix, index);
-  return isolate->factory()->InternalizeString(value.SubVector(0, len));
-}
-
-MaybeHandle<String> GetNameFromImportsAndExportsOrNull(
-    Isolate* isolate, Handle<WasmInstanceObject> instance,
-    wasm::ImportExportKindCode kind, uint32_t index) {
-  auto debug_info = instance->module_object().native_module()->GetDebugInfo();
-  wasm::ModuleWireBytes wire_bytes(
-      instance->module_object().native_module()->wire_bytes());
-
-  auto import_name_ref = debug_info->GetImportName(kind, index);
-  if (!import_name_ref.first.is_empty()) {
-    base::ScopedVector<char> name(import_name_ref.first.length() + 1 +
-                                  import_name_ref.second.length());
-    auto name_begin = &name.first(), name_end = name_begin;
-    auto module_name = wire_bytes.GetNameOrNull(import_name_ref.first);
-    name_end = std::copy(module_name.begin(), module_name.end(), name_end);
-    *name_end++ = '.';
-    auto field_name = wire_bytes.GetNameOrNull(import_name_ref.second);
-    name_end = std::copy(field_name.begin(), field_name.end(), name_end);
-    return isolate->factory()->NewStringFromUtf8(
-        base::VectorOf(name_begin, name_end - name_begin));
-  }
-
-  auto export_name_ref = debug_info->GetExportName(kind, index);
-  if (!export_name_ref.is_empty()) {
-    auto name = wire_bytes.GetNameOrNull(export_name_ref);
-    return isolate->factory()->NewStringFromUtf8(name);
-  }
-
-  return {};
+using StringBuilder = wasm::StringBuilder;
+Handle<String> ToInternalString(StringBuilder& sb, Isolate* isolate) {
+  return isolate->factory()->InternalizeString(
+      base::VectorOf(sb.start(), sb.length()));
 }
 
 enum DebugProxyId {
@@ -352,12 +311,11 @@ struct GlobalsProxy : NamedDebugProxy<GlobalsProxy, kGlobalsProxy> {
   static Handle<String> GetName(Isolate* isolate,
                                 Handle<WasmInstanceObject> instance,
                                 uint32_t index) {
-    return GetNameOrDefault(
-        isolate,
-        GetNameFromImportsAndExportsOrNull(
-            isolate, instance, wasm::ImportExportKindCode::kExternalGlobal,
-            index),
-        "$global", index);
+    wasm::NamesProvider* names =
+        instance->module_object().native_module()->GetNamesProvider();
+    StringBuilder sb;
+    names->PrintGlobalName(sb, index);
+    return ToInternalString(sb, isolate);
   }
 };
 
@@ -378,12 +336,11 @@ struct MemoriesProxy : NamedDebugProxy<MemoriesProxy, kMemoriesProxy> {
   static Handle<String> GetName(Isolate* isolate,
                                 Handle<WasmInstanceObject> instance,
                                 uint32_t index) {
-    return GetNameOrDefault(
-        isolate,
-        GetNameFromImportsAndExportsOrNull(
-            isolate, instance, wasm::ImportExportKindCode::kExternalMemory,
-            index),
-        "$memory", index);
+    wasm::NamesProvider* names =
+        instance->module_object().native_module()->GetNamesProvider();
+    StringBuilder sb;
+    names->PrintMemoryName(sb, index);
+    return ToInternalString(sb, isolate);
   }
 };
 
@@ -404,12 +361,11 @@ struct TablesProxy : NamedDebugProxy<TablesProxy, kTablesProxy> {
   static Handle<String> GetName(Isolate* isolate,
                                 Handle<WasmInstanceObject> instance,
                                 uint32_t index) {
-    return GetNameOrDefault(
-        isolate,
-        GetNameFromImportsAndExportsOrNull(
-            isolate, instance, wasm::ImportExportKindCode::kExternalTable,
-            index),
-        "$table", index);
+    wasm::NamesProvider* names =
+        instance->module_object().native_module()->GetNamesProvider();
+    StringBuilder sb;
+    names->PrintTableName(sb, index);
+    return ToInternalString(sb, isolate);
   }
 };
 
@@ -454,14 +410,10 @@ struct LocalsProxy : NamedDebugProxy<LocalsProxy, kLocalsProxy, FixedArray> {
     auto native_module =
         WasmModuleObject::cast(values->get(count + 0)).native_module();
     auto function_index = Smi::ToInt(Smi::cast(values->get(count + 1)));
-    wasm::ModuleWireBytes module_wire_bytes(native_module->wire_bytes());
-    auto name_vec = module_wire_bytes.GetNameOrNull(
-        native_module->GetDebugInfo()->GetLocalName(function_index, index));
-    return GetNameOrDefault(
-        isolate,
-        name_vec.empty() ? MaybeHandle<String>()
-                         : isolate->factory()->NewStringFromUtf8(name_vec),
-        "$var", index);
+    wasm::NamesProvider* names = native_module->GetNamesProvider();
+    StringBuilder sb;
+    names->PrintLocalName(sb, function_index, index);
+    return ToInternalString(sb, isolate);
   }
 };
 
@@ -772,22 +724,9 @@ Handle<String> WasmSimd128ToString(Isolate* isolate, wasm::Simd128 s128) {
 Handle<String> GetRefTypeName(Isolate* isolate, wasm::ValueType type,
                               wasm::NativeModule* module) {
   DCHECK(type.is_object_reference());
-  std::ostringstream name;
-  if (type.heap_type().is_generic()) {
-    name << type.name();
-  } else {
-    name << "(ref " << (type.is_nullable() ? "null " : "") << "$";
-    wasm::ModuleWireBytes module_wire_bytes(module->wire_bytes());
-    base::Vector<const char> module_name = module_wire_bytes.GetNameOrNull(
-        module->GetDebugInfo()->GetTypeName(type.ref_index()));
-    if (module_name.empty()) {
-      name << "type" << type.ref_index();
-    } else {
-      name.write(module_name.begin(), module_name.size());
-    }
-    name << ")";
-  }
-  return isolate->factory()->InternalizeString(base::VectorOf(name.str()));
+  StringBuilder name;
+  module->GetNamesProvider()->PrintValueType(name, type);
+  return ToInternalString(name, isolate);
 }
 
 }  // namespace
@@ -866,14 +805,10 @@ struct StructProxy : NamedDebugProxy<StructProxy, kStructProxy, FixedArray> {
     wasm::NativeModule* native_module =
         WasmModuleObject::cast(data->get(kModuleIndex)).native_module();
     int struct_type_index = Smi::ToInt(Smi::cast(data->get(kTypeIndexIndex)));
-    wasm::ModuleWireBytes module_wire_bytes(native_module->wire_bytes());
-    base::Vector<const char> name_vec = module_wire_bytes.GetNameOrNull(
-        native_module->GetDebugInfo()->GetFieldName(struct_type_index, index));
-    return GetNameOrDefault(
-        isolate,
-        name_vec.empty() ? MaybeHandle<String>()
-                         : isolate->factory()->NewStringFromUtf8(name_vec),
-        "$field", index);
+    wasm::NamesProvider* names = native_module->GetNamesProvider();
+    StringBuilder sb;
+    names->PrintFieldName(sb, struct_type_index, index);
+    return ToInternalString(sb, isolate);
   }
 };
 
@@ -1017,18 +952,14 @@ Handle<String> GetWasmFunctionDebugName(Isolate* isolate,
                                         Handle<WasmInstanceObject> instance,
                                         uint32_t func_index) {
   Handle<WasmModuleObject> module_object(instance->module_object(), isolate);
-  MaybeHandle<String> maybe_name = WasmModuleObject::GetFunctionNameOrNull(
-      isolate, module_object, func_index);
-  if (module_object->is_asm_js()) {
-    // In case of asm.js, we use the names from the function declarations.
-    return maybe_name.ToHandleChecked();
-  }
-  if (maybe_name.is_null()) {
-    maybe_name = GetNameFromImportsAndExportsOrNull(
-        isolate, instance, wasm::ImportExportKindCode::kExternalFunction,
-        func_index);
-  }
-  return GetNameOrDefault(isolate, maybe_name, "$func", func_index);
+  wasm::NamesProvider* names =
+      module_object->native_module()->GetNamesProvider();
+  StringBuilder sb;
+  wasm::NamesProvider::FunctionNamesBehavior behavior =
+      module_object->is_asm_js() ? wasm::NamesProvider::kWasmInternal
+                                 : wasm::NamesProvider::kDevTools;
+  names->PrintFunctionName(sb, func_index, behavior);
+  return ToInternalString(sb, isolate);
 }
 
 Handle<ArrayList> AddWasmInstanceObjectInternalProperties(

src/wasm/module-decoder.cc

@@ -1274,6 +1274,8 @@ class ModuleDecoderImpl : public Decoder {
     // Ignore all but the first occurrence of name section.
     if (!has_seen_unordered_section(kNameSectionCode)) {
       set_seen_unordered_section(kNameSectionCode);
+      module_->name_section = {buffer_offset_,
+                               static_cast<uint32_t>(end_ - start_)};
       // Use an inner decoder so that errors don't fail the outer decoder.
       Decoder inner(start_, pc_, end_, buffer_offset_);
       // Decode all name subsections.
@@ -1744,9 +1746,9 @@ class ModuleDecoderImpl : public Decoder {
   void VerifyFunctionBody(AccountingAllocator* allocator, uint32_t func_num,
                           const ModuleWireBytes& wire_bytes,
                           const WasmModule* module, WasmFunction* function) {
-    WasmFunctionName func_name(function,
-                               wire_bytes.GetNameOrNull(function, module));
     if (FLAG_trace_wasm_decoder) {
+      WasmFunctionName func_name(function,
+                                 wire_bytes.GetNameOrNull(function, module));
       StdoutStream{} << "Verifying wasm function " << func_name << std::endl;
     }
     FunctionBody body = {
@@ -1762,6 +1764,8 @@ class ModuleDecoderImpl : public Decoder {
     // location.
     if (result.failed() && intermediate_error_.empty()) {
       // Wrap the error message from the function decoder.
+      WasmFunctionName func_name(function,
+                                 wire_bytes.GetNameOrNull(function, module));
       std::ostringstream error_msg;
       error_msg << "in function " << func_name << ": "
                 << result.error().message();
@@ -2561,10 +2565,7 @@ bool FindNameSection(Decoder* decoder) {
 }  // namespace
 
 void DecodeFunctionNames(const byte* module_start, const byte* module_end,
-                         std::unordered_map<uint32_t, WireBytesRef>* names) {
-  DCHECK_NOT_NULL(names);
-  DCHECK(names->empty());
-
+                         std::unordered_map<uint32_t, WireBytesRef>& names) {
   Decoder decoder(module_start, module_end);
   if (FindNameSection(&decoder)) {
     while (decoder.ok() && decoder.more()) {
@@ -2589,52 +2590,71 @@ void DecodeFunctionNames(const byte* module_start, const byte* module_end,
         // You can even assign to the same function multiple times (last valid
         // one wins).
         if (decoder.ok() && validate_utf8(&decoder, name)) {
-          names->insert(std::make_pair(function_index, name));
+          names.insert(std::make_pair(function_index, name));
         }
       }
     }
   }
 }
 
-NameMap DecodeNameMap(base::Vector<const uint8_t> module_bytes,
-                      uint8_t name_section_kind) {
-  Decoder decoder(module_bytes);
-  if (!FindNameSection(&decoder)) return NameMap{{}};
+namespace {
 
+void DecodeNameMap(NameMap& target, Decoder& decoder) {
   std::vector<NameAssoc> names;
-  while (decoder.ok() && decoder.more()) {
-    uint8_t name_type = decoder.consume_u8("name type");
-    if (name_type & 0x80) break;  // no varuint7
-
-    uint32_t name_payload_len = decoder.consume_u32v("name payload length");
-    if (!decoder.checkAvailable(name_payload_len)) break;
-
-    if (name_type != name_section_kind) {
-      decoder.consume_bytes(name_payload_len, "name subsection payload");
-      continue;
-    }
+  uint32_t count = decoder.consume_u32v("names count");
+  names.reserve(count);
+  for (uint32_t i = 0; i < count; i++) {
+    uint32_t index = decoder.consume_u32v("index");
+    WireBytesRef name =
+        consume_string(&decoder, StringValidation::kNone, "name");
+    if (!decoder.ok()) break;
+    if (index > kMaxInt) continue;
+    if (name.is_empty()) continue;  // Empty names are useless.
+    if (!validate_utf8(&decoder, name)) continue;
+    names.emplace_back(static_cast<int>(index), name);
+  }
+  std::stable_sort(names.begin(), names.end(), NameAssoc::IndexLess{});
+  target = NameMap{std::move(names)};
+}
 
-    uint32_t count = decoder.consume_u32v("names count");
-    for (uint32_t i = 0; i < count; i++) {
-      uint32_t index = decoder.consume_u32v("index");
+void DecodeIndirectNameMap(IndirectNameMap& target, Decoder& decoder) {
+  std::vector<IndirectNameMapEntry> entries;
+  uint32_t outer_count = decoder.consume_u32v("outer count");
+  entries.reserve(outer_count);
+  for (uint32_t i = 0; i < outer_count; ++i) {
+    uint32_t outer_index = decoder.consume_u32v("outer index");
+    if (outer_index > kMaxInt) continue;
+    std::vector<NameAssoc> names;
+    uint32_t inner_count = decoder.consume_u32v("inner count");
+    names.reserve(inner_count);
+    for (uint32_t k = 0; k < inner_count; ++k) {
+      uint32_t inner_index = decoder.consume_u32v("inner index");
       WireBytesRef name =
           consume_string(&decoder, StringValidation::kNone, "name");
       if (!decoder.ok()) break;
-      if (index > kMaxInt) continue;
+      if (inner_index > kMaxInt) continue;
+      if (name.is_empty()) continue;  // Empty names are useless.
       if (!validate_utf8(&decoder, name)) continue;
-      names.emplace_back(static_cast<int>(index), name);
+      names.emplace_back(static_cast<int>(inner_index), name);
     }
+    // Use stable sort to get deterministic names (the first one declared)
+    // even in the presence of duplicates.
+    std::stable_sort(names.begin(), names.end(), NameAssoc::IndexLess{});
+    entries.emplace_back(static_cast<int>(outer_index), std::move(names));
   }
-  std::stable_sort(names.begin(), names.end(), NameAssoc::IndexLess{});
-  return NameMap{std::move(names)};
+  std::stable_sort(entries.begin(), entries.end(),
+                   IndirectNameMapEntry::IndexLess{});
+  target = IndirectNameMap{std::move(entries)};
 }
 
-IndirectNameMap DecodeIndirectNameMap(base::Vector<const uint8_t> module_bytes,
-                                      uint8_t name_section_kind) {
-  Decoder decoder(module_bytes);
-  if (!FindNameSection(&decoder)) return IndirectNameMap{{}};
+}  // namespace
 
-  std::vector<IndirectNameMapEntry> entries;
+DecodedNameSection::DecodedNameSection(base::Vector<const uint8_t> wire_bytes,
+                                       WireBytesRef name_section) {
+  if (name_section.is_empty()) return;  // No name section.
+  Decoder decoder(wire_bytes.begin() + name_section.offset(),
+                  wire_bytes.begin() + name_section.end_offset(),
+                  name_section.offset());
   while (decoder.ok() && decoder.more()) {
     uint8_t name_type = decoder.consume_u8("name type");
     if (name_type & 0x80) break;  // no varuint7
@@ -2642,36 +2662,44 @@ IndirectNameMap DecodeIndirectNameMap(base::Vector<const uint8_t> module_bytes,
     uint32_t name_payload_len = decoder.consume_u32v("name payload length");
     if (!decoder.checkAvailable(name_payload_len)) break;
 
-    if (name_type != name_section_kind) {
-      decoder.consume_bytes(name_payload_len, "name subsection payload");
-      continue;
-    }
-
-    uint32_t outer_count = decoder.consume_u32v("outer count");
-    for (uint32_t i = 0; i < outer_count; ++i) {
-      uint32_t outer_index = decoder.consume_u32v("outer index");
-      if (outer_index > kMaxInt) continue;
-      std::vector<NameAssoc> names;
-      uint32_t inner_count = decoder.consume_u32v("inner count");
-      for (uint32_t k = 0; k < inner_count; ++k) {
-        uint32_t inner_index = decoder.consume_u32v("inner index");
-        WireBytesRef name =
-            consume_string(&decoder, StringValidation::kNone, "name");
-        if (!decoder.ok()) break;
-        if (inner_index > kMaxInt) continue;
-        // Ignore non-utf8 names.
-        if (!validate_utf8(&decoder, name)) continue;
-        names.emplace_back(static_cast<int>(inner_index), name);
-      }
-      // Use stable sort to get deterministic names (the first one declared)
-      // even in the presence of duplicates.
-      std::stable_sort(names.begin(), names.end(), NameAssoc::IndexLess{});
-      entries.emplace_back(static_cast<int>(outer_index), std::move(names));
+    switch (name_type) {
+      case kModuleCode:
+      case kFunctionCode:
+        // Already handled elsewhere.
+        decoder.consume_bytes(name_payload_len);
+        break;
+      case kLocalCode:
+        DecodeIndirectNameMap(local_names_, decoder);
+        break;
+      case kLabelCode:
+        DecodeIndirectNameMap(label_names_, decoder);
+        break;
+      case kTypeCode:
+        DecodeNameMap(type_names_, decoder);
+        break;
+      case kTableCode:
+        DecodeNameMap(table_names_, decoder);
+        break;
+      case kMemoryCode:
+        DecodeNameMap(memory_names_, decoder);
+        break;
+      case kGlobalCode:
+        DecodeNameMap(global_names_, decoder);
+        break;
+      case kElementSegmentCode:
+        DecodeNameMap(element_segment_names_, decoder);
+        break;
+      case kDataSegmentCode:
+        DecodeNameMap(data_segment_names_, decoder);
+        break;
+      case kFieldCode:
+        DecodeIndirectNameMap(field_names_, decoder);
+        break;
+      case kTagCode:
+        DecodeNameMap(tag_names_, decoder);
+        break;
     }
   }
-  std::stable_sort(entries.begin(), entries.end(),
-                   IndirectNameMapEntry::IndexLess{});
-  return IndirectNameMap{std::move(entries)};
 }
 
 #undef TRACE

src/wasm/module-decoder.h

@@ -80,7 +80,7 @@ class NameAssoc {
 class NameMap {
  public:
   // For performance reasons, {NameMap} should not be copied.
-  MOVE_ONLY_NO_DEFAULT_CONSTRUCTOR(NameMap);
+  MOVE_ONLY_WITH_DEFAULT_CONSTRUCTORS(NameMap);
 
   explicit NameMap(std::vector<NameAssoc> names) : names_(std::move(names)) {
     DCHECK(
@@ -123,7 +123,7 @@ class IndirectNameMapEntry : public NameMap {
 class IndirectNameMap {
  public:
   // For performance reasons, {IndirectNameMap} should not be copied.
-  MOVE_ONLY_NO_DEFAULT_CONSTRUCTOR(IndirectNameMap);
+  MOVE_ONLY_WITH_DEFAULT_CONSTRUCTORS(IndirectNameMap);
 
   explicit IndirectNameMap(std::vector<IndirectNameMapEntry> functions)
       : functions_(std::move(functions)) {
@@ -144,6 +144,26 @@ class IndirectNameMap {
   std::vector<IndirectNameMapEntry> functions_;
 };
 
+class DecodedNameSection {
+ public:
+  explicit DecodedNameSection(base::Vector<const uint8_t> wire_bytes,
+                              WireBytesRef name_section);
+
+ private:
+  friend class NamesProvider;
+
+  IndirectNameMap local_names_;
+  IndirectNameMap label_names_;
+  NameMap type_names_;
+  NameMap table_names_;
+  NameMap memory_names_;
+  NameMap global_names_;
+  NameMap element_segment_names_;
+  NameMap data_segment_names_;
+  IndirectNameMap field_names_;
+  NameMap tag_names_;
+};
+
 enum class DecodingMethod {
   kSync,
   kAsync,
@@ -195,16 +215,7 @@ AsmJsOffsetsResult DecodeAsmJsOffsets(
 // unordered map. Only names with valid utf8 encoding are stored and conflicts
 // are resolved by choosing the last name read.
 void DecodeFunctionNames(const byte* module_start, const byte* module_end,
-                         std::unordered_map<uint32_t, WireBytesRef>* names);
-
-// Decode the requested subsection of the name section.
-// The result will be empty if no name section is present. On encountering an
-// error in the name section, returns all information decoded up to the first
-// error.
-NameMap DecodeNameMap(base::Vector<const uint8_t> module_bytes,
-                      uint8_t name_section_kind);
-IndirectNameMap DecodeIndirectNameMap(base::Vector<const uint8_t> module_bytes,
-                                      uint8_t name_section_kind);
+                         std::unordered_map<uint32_t, WireBytesRef>& names);
 
 class ModuleDecoderImpl;
 

src/wasm/names-provider.h

+// Copyright 2022 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.
+
+#if !V8_ENABLE_WEBASSEMBLY
+#error This header should only be included if WebAssembly is enabled.
+#endif  // !V8_ENABLE_WEBASSEMBLY
+
+#ifndef V8_WASM_NAMES_PROVIDER_H_
+#define V8_WASM_NAMES_PROVIDER_H_
+
+#include <map>
+#include <string>
+
+#include "src/base/vector.h"
+#include "src/wasm/wasm-module.h"
+
+namespace v8 {
+namespace internal {
+namespace wasm {
+
+class DecodedNameSection;
+class StringBuilder;
+
+class NamesProvider {
+ public:
+  // {kWasmInternal}: only return raw name from name section.
+  // {kDevTools}: prepend '$', use import/export names as fallback,
+  // or "$funcN" as default.
+  enum FunctionNamesBehavior : bool { kWasmInternal = false, kDevTools = true };
+
+  enum IndexAsComment : bool {
+    kDontPrintIndex = false,
+    kIndexAsComment = true
+  };
+
+  NamesProvider(const WasmModule* module,
+                base::Vector<const uint8_t> wire_bytes);
+  ~NamesProvider();
+
+  // Returns {false} if {devtools_behavior} == false and no name for
+  // {function_index} was present in the name section.
+  void PrintFunctionName(StringBuilder& out, uint32_t function_index,
+                         FunctionNamesBehavior behavior = kWasmInternal,
+                         IndexAsComment index_as_comment = kDontPrintIndex);
+  void PrintLocalName(StringBuilder& out, uint32_t function_index,
+                      uint32_t local_index,
+                      IndexAsComment index_as_comment = kDontPrintIndex);
+  void PrintLabelName(StringBuilder& out, uint32_t function_index,
+                      uint32_t label_index, uint32_t fallback_index);
+  void PrintTypeName(StringBuilder& out, uint32_t type_index,
+                     IndexAsComment index_as_comment = kDontPrintIndex);
+  void PrintTableName(StringBuilder& out, uint32_t table_index,
+                      IndexAsComment index_as_comment = kDontPrintIndex);
+  void PrintMemoryName(StringBuilder& out, uint32_t memory_index,
+                       IndexAsComment index_as_comment = kDontPrintIndex);
+  void PrintGlobalName(StringBuilder& out, uint32_t global_index,
+                       IndexAsComment index_as_comment = kDontPrintIndex);
+  void PrintElementSegmentName(StringBuilder& out,
+                               uint32_t element_segment_index);
+  void PrintDataSegmentName(StringBuilder& out, uint32_t data_segment_index);
+  void PrintFieldName(StringBuilder& out, uint32_t struct_index,
+                      uint32_t field_index,
+                      IndexAsComment index_as_comment = kDontPrintIndex);
+  void PrintTagName(StringBuilder& out, uint32_t tag_index,
+                    IndexAsComment index_as_comment = kDontPrintIndex);
+
+  void PrintHeapType(StringBuilder& out, HeapType type);
+  void PrintValueType(StringBuilder& out, ValueType type);
+
+ private:
+  void DecodeNamesIfNotYetDone();
+  void ComputeFunctionNamesFromImportsExports();
+  void ComputeNamesFromImportsExports();
+  void ComputeImportName(const WasmImport& import,
+                         std::map<uint32_t, std::string>& target);
+  void ComputeExportName(const WasmExport& ex,
+                         std::map<uint32_t, std::string>& target);
+  void WriteRef(StringBuilder& out, WireBytesRef ref);
+
+  // Lazy loading must guard against concurrent modifications from multiple
+  // {WasmModuleObject}s.
+  base::Mutex mutex_;
+  bool has_decoded_{false};
+  bool has_computed_function_import_names_{false};
+  bool has_computed_import_names_{false};
+  const WasmModule* module_;
+  base::Vector<const uint8_t> wire_bytes_;
+  std::unique_ptr<DecodedNameSection> name_section_names_{};
+  std::map<uint32_t, std::string> import_export_function_names_;
+  std::map<uint32_t, std::string> import_export_table_names_;
+  std::map<uint32_t, std::string> import_export_memory_names_;
+  std::map<uint32_t, std::string> import_export_global_names_;
+  std::map<uint32_t, std::string> import_export_tag_names_;
+};
+
+}  // namespace wasm
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_WASM_NAMES_PROVIDER_H_

src/wasm/string-builder.h

+// Copyright 2022 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.
+
+#if !V8_ENABLE_WEBASSEMBLY
+#error This header should only be included if WebAssembly is enabled.
+#endif  // !V8_ENABLE_WEBASSEMBLY
+
+#ifndef V8_WASM_STRING_BUILDER_H_
+#define V8_WASM_STRING_BUILDER_H_
+
+#include <cstring>
+#include <string>
+#include <vector>
+
+#include "src/common/globals.h"
+
+namespace v8 {
+namespace internal {
+namespace wasm {
+
+// Similar to std::ostringstream, but about 4x faster.
+// This base class works best for small-ish strings (up to kChunkSize); for
+// producing large amounts of text, you probably want a subclass like
+// MultiLineStringBuilder.
+class StringBuilder {
+ public:
+  explicit StringBuilder() : on_growth_(kReplacePreviousChunk) {}
+  explicit StringBuilder(const StringBuilder&) = delete;
+  StringBuilder& operator=(const StringBuilder&) = delete;
+  ~StringBuilder() {
+    for (char* chunk : chunks_) delete[] chunk;
+  }
+
+  // Reserves space for {n} characters and returns a pointer to its beginning.
+  // Clients *must* write all {n} characters after calling this!
+  // Don't call this directly, use operator<< overloads instead.
+  char* write(size_t n) {
+    if (remaining_bytes_ < n) Grow();
+    char* result = cursor_;
+    cursor_ += n;
+    remaining_bytes_ -= n;
+    return result;
+  }
+  // Convenience wrappers.
+  void write(const byte* data, size_t n) {
+    char* ptr = write(n);
+    memcpy(ptr, data, n);
+  }
+  void write(const char* data, size_t n) {
+    char* ptr = write(n);
+    memcpy(ptr, data, n);
+  }
+
+  const char* start() const { return start_; }
+  const char* cursor() const { return cursor_; }
+  size_t length() const { return static_cast<size_t>(cursor_ - start_); }
+
+ protected:
+  enum OnGrowth : bool { kKeepOldChunks, kReplacePreviousChunk };
+
+  // Useful for subclasses that divide the text into ranges, e.g. lines.
+  explicit StringBuilder(OnGrowth on_growth) : on_growth_(on_growth) {}
+  void start_here() { start_ = cursor_; }
+  void rewind_to_start() {
+    remaining_bytes_ += length();
+    cursor_ = start_;
+  }
+
+ private:
+  void Grow() {
+    size_t used = length();
+    // Safety net for super-long strings/lines.
+    size_t chunk_size = used < kChunkSize ? kChunkSize : used * 2;
+    char* new_chunk = new char[chunk_size];
+    memcpy(new_chunk, start_, used);
+    if (on_growth_ == kKeepOldChunks) {
+      chunks_.push_back(new_chunk);
+    }
+    start_ = new_chunk;
+    cursor_ = new_chunk + used;
+    remaining_bytes_ = chunk_size - used;
+  }
+
+  // Start small, to be cheap for the common case.
+  static constexpr size_t kStackSize = 256;
+  // If we have to grow, grow in big steps.
+  static constexpr size_t kChunkSize = 1024 * 1024;
+
+  char stack_buffer_[kStackSize];
+  std::vector<char*> chunks_;  // A very simple Zone, essentially.
+  char* start_ = stack_buffer_;
+  char* cursor_ = stack_buffer_;
+  size_t remaining_bytes_ = kStackSize;
+  const OnGrowth on_growth_;
+};
+
+inline StringBuilder& operator<<(StringBuilder& sb, const char* str) {
+  size_t len = strlen(str);
+  char* ptr = sb.write(len);
+  memcpy(ptr, str, len);
+  return sb;
+}
+
+inline StringBuilder& operator<<(StringBuilder& sb, char c) {
+  *sb.write(1) = c;
+  return sb;
+}
+
+inline StringBuilder& operator<<(StringBuilder& sb, const std::string& s) {
+  sb.write(s.data(), s.length());
+  return sb;
+}
+
+inline StringBuilder& operator<<(StringBuilder& sb, uint32_t n) {
+  if (n == 0) {
+    *sb.write(1) = '0';
+    return sb;
+  }
+  static constexpr size_t kBufferSize = 10;  // Just enough for a uint32.
+  char buffer[kBufferSize];
+  char* end = buffer + kBufferSize;
+  char* out = end;
+  while (n != 0) {
+    *(--out) = '0' + (n % 10);
+    n /= 10;
+  }
+  sb.write(out, static_cast<size_t>(end - out));
+  return sb;
+}
+
+inline StringBuilder& operator<<(StringBuilder& sb, int value) {
+  if (value >= 0) {
+    sb << static_cast<uint32_t>(value);
+  } else {
+    sb << "-" << ((~static_cast<uint32_t>(value)) + 1);
+  }
+  return sb;
+}
+
+}  // namespace wasm
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_WASM_STRING_BUILDER_H_

src/wasm/wasm-code-manager.cc

@@ -32,6 +32,7 @@
 #include "src/wasm/jump-table-assembler.h"
 #include "src/wasm/memory-protection-key.h"
 #include "src/wasm/module-compiler.h"
+#include "src/wasm/names-provider.h"
 #include "src/wasm/wasm-debug.h"
 #include "src/wasm/wasm-engine.h"
 #include "src/wasm/wasm-import-wrapper-cache.h"
@@ -2503,6 +2504,16 @@ DebugInfo* NativeModule::GetDebugInfo() {
   return debug_info_.get();
 }
 
+NamesProvider* NativeModule::GetNamesProvider() {
+  DCHECK(HasWireBytes());
+  base::RecursiveMutexGuard guard(&allocation_mutex_);
+  if (!names_provider_) {
+    names_provider_ =
+        std::make_unique<NamesProvider>(module_.get(), wire_bytes());
+  }
+  return names_provider_.get();
+}
+
 void WasmCodeManager::FreeNativeModule(
     base::Vector<VirtualMemory> owned_code_space, size_t committed_size) {
   base::MutexGuard lock(&native_modules_mutex_);

src/wasm/wasm-code-manager.h

@@ -42,6 +42,7 @@ class Isolate;
 namespace wasm {
 
 class DebugInfo;
+class NamesProvider;
 class NativeModule;
 struct WasmCompilationResult;
 class WasmEngine;
@@ -847,6 +848,9 @@ class V8_EXPORT_PRIVATE NativeModule final {
   // Get or create the debug info for this NativeModule.
   DebugInfo* GetDebugInfo();
 
+  // Get or create the NamesProvider. Requires {HasWireBytes()}.
+  NamesProvider* GetNamesProvider();
+
   uint32_t* tiering_budget_array() { return tiering_budgets_.get(); }
 
   Counters* counters() const { return code_allocator_.counters(); }
@@ -990,6 +994,8 @@ class V8_EXPORT_PRIVATE NativeModule final {
   // mutex.
   std::unique_ptr<DebugInfo> debug_info_;
 
+  std::unique_ptr<NamesProvider> names_provider_;
+
   TieringState tiering_state_ = kTieredUp;
 
   // Cache both baseline and top-tier code if we are debugging, to speed up

src/wasm/wasm-constants.h

@@ -143,7 +143,9 @@ enum NameSectionKindCode : uint8_t {
   kElementSegmentCode = 8,
   kDataSegmentCode = 9,
   // https://github.com/WebAssembly/gc/issues/193
-  kFieldCode = 10
+  kFieldCode = 10,
+  // https://github.com/WebAssembly/exception-handling/pull/213
+  kTagCode = 11,
 };
 
 // What to do when treating a stringref as WTF-8 and we see an isolated

src/wasm/wasm-debug.cc

@@ -157,66 +157,6 @@ class DebugInfoImpl {
     return module->functions[scope.code->index()];
   }
 
-  WireBytesRef GetExportName(ImportExportKindCode kind, uint32_t index) {
-    base::MutexGuard guard(&mutex_);
-    if (!export_names_) {
-      export_names_ =
-          std::make_unique<std::map<ImportExportKey, WireBytesRef>>();
-      for (auto exp : native_module_->module()->export_table) {
-        auto exp_key = std::make_pair(exp.kind, exp.index);
-        if (export_names_->find(exp_key) != export_names_->end()) continue;
-        export_names_->insert(std::make_pair(exp_key, exp.name));
-      }
-    }
-    auto it = export_names_->find(std::make_pair(kind, index));
-    if (it != export_names_->end()) return it->second;
-    return {};
-  }
-
-  std::pair<WireBytesRef, WireBytesRef> GetImportName(ImportExportKindCode kind,
-                                                      uint32_t index) {
-    base::MutexGuard guard(&mutex_);
-    if (!import_names_) {
-      import_names_ = std::make_unique<
-          std::map<ImportExportKey, std::pair<WireBytesRef, WireBytesRef>>>();
-      for (auto imp : native_module_->module()->import_table) {
-        import_names_->insert(
-            std::make_pair(std::make_pair(imp.kind, imp.index),
-                           std::make_pair(imp.module_name, imp.field_name)));
-      }
-    }
-    auto it = import_names_->find(std::make_pair(kind, index));
-    if (it != import_names_->end()) return it->second;
-    return {};
-  }
-
-  WireBytesRef GetTypeName(int type_index) {
-    base::MutexGuard guard(&mutex_);
-    if (!type_names_) {
-      type_names_ = std::make_unique<NameMap>(DecodeNameMap(
-          native_module_->wire_bytes(), NameSectionKindCode::kTypeCode));
-    }
-    return type_names_->GetName(type_index);
-  }
-
-  WireBytesRef GetLocalName(int func_index, int local_index) {
-    base::MutexGuard guard(&mutex_);
-    if (!local_names_) {
-      local_names_ = std::make_unique<IndirectNameMap>(DecodeIndirectNameMap(
-          native_module_->wire_bytes(), NameSectionKindCode::kLocalCode));
-    }
-    return local_names_->GetName(func_index, local_index);
-  }
-
-  WireBytesRef GetFieldName(int struct_index, int field_index) {
-    base::MutexGuard guard(&mutex_);
-    if (!field_names_) {
-      field_names_ = std::make_unique<IndirectNameMap>(DecodeIndirectNameMap(
-          native_module_->wire_bytes(), NameSectionKindCode::kFieldCode));
-    }
-    return field_names_->GetName(struct_index, field_index);
-  }
-
   // If the frame position is not in the list of breakpoints, return that
   // position. Return 0 otherwise.
   // This is used to generate a "dead breakpoint" in Liftoff, which is necessary
@@ -765,21 +705,6 @@ class DebugInfoImpl {
   };
   std::vector<CachedDebuggingCode> cached_debugging_code_;
 
-  // Names of exports, lazily derived from the exports table.
-  std::unique_ptr<std::map<ImportExportKey, wasm::WireBytesRef>> export_names_;
-
-  // Names of imports, lazily derived from the imports table.
-  std::unique_ptr<std::map<ImportExportKey,
-                           std::pair<wasm::WireBytesRef, wasm::WireBytesRef>>>
-      import_names_;
-
-  // Names of types, lazily decoded from the wire bytes.
-  std::unique_ptr<NameMap> type_names_;
-  // Names of locals, lazily decoded from the wire bytes.
-  std::unique_ptr<IndirectNameMap> local_names_;
-  // Names of struct fields, lazily decoded from the wire bytes.
-  std::unique_ptr<IndirectNameMap> field_names_;
-
   // Isolate-specific data.
   std::unordered_map<Isolate*, PerIsolateDebugData> per_isolate_data_;
 };
@@ -807,28 +732,6 @@ const wasm::WasmFunction& DebugInfo::GetFunctionAtAddress(Address pc) {
   return impl_->GetFunctionAtAddress(pc);
 }
 
-WireBytesRef DebugInfo::GetExportName(ImportExportKindCode code,
-                                      uint32_t index) {
-  return impl_->GetExportName(code, index);
-}
-
-std::pair<WireBytesRef, WireBytesRef> DebugInfo::GetImportName(
-    ImportExportKindCode code, uint32_t index) {
-  return impl_->GetImportName(code, index);
-}
-
-WireBytesRef DebugInfo::GetTypeName(int type_index) {
-  return impl_->GetTypeName(type_index);
-}
-
-WireBytesRef DebugInfo::GetLocalName(int func_index, int local_index) {
-  return impl_->GetLocalName(func_index, local_index);
-}
-
-WireBytesRef DebugInfo::GetFieldName(int struct_index, int field_index) {
-  return impl_->GetFieldName(struct_index, field_index);
-}
-
 void DebugInfo::SetBreakpoint(int func_index, int offset,
                               Isolate* current_isolate) {
   impl_->SetBreakpoint(func_index, offset, current_isolate);

src/wasm/wasm-debug.h

@@ -183,21 +183,6 @@ class V8_EXPORT_PRIVATE DebugInfo {
   WasmValue GetStackValue(int index, Address pc, Address fp,
                           Address debug_break_fp, Isolate* isolate);
 
-  // Returns the name of the entity (with the given |index| and |kind|) derived
-  // from the exports table. If the entity is not exported, an empty reference
-  // will be returned instead.
-  WireBytesRef GetExportName(ImportExportKindCode kind, uint32_t index);
-
-  // Returns the module and field name of the entity (with the given |index|
-  // and |kind|) derived from the imports table. If the entity is not imported,
-  // a pair of empty references will be returned instead.
-  std::pair<WireBytesRef, WireBytesRef> GetImportName(ImportExportKindCode kind,
-                                                      uint32_t index);
-
-  WireBytesRef GetTypeName(int type_index);
-  WireBytesRef GetLocalName(int func_index, int local_index);
-  WireBytesRef GetFieldName(int struct_index, int field_index);
-
   void SetBreakpoint(int func_index, int offset, Isolate* current_isolate);
 
   // Returns true if we stay inside the passed frame (or a called frame) after

src/wasm/wasm-module.cc

@@ -8,17 +8,9 @@
 #include <memory>
 
 #include "src/api/api-inl.h"
-#include "src/base/platform/wrappers.h"
-#include "src/codegen/assembler-inl.h"
 #include "src/compiler/wasm-compiler.h"
-#include "src/debug/interface-types.h"
-#include "src/execution/frames-inl.h"
-#include "src/execution/simulator.h"
-#include "src/init/v8.h"
 #include "src/objects/js-array-inl.h"
 #include "src/objects/objects.h"
-#include "src/objects/property-descriptor.h"
-#include "src/snapshot/snapshot.h"
 #include "src/wasm/module-decoder.h"
 #include "src/wasm/wasm-code-manager.h"
 #include "src/wasm/wasm-init-expr.h"
@@ -32,18 +24,23 @@ namespace internal {
 namespace wasm {
 
 WireBytesRef LazilyGeneratedNames::LookupFunctionName(
-    const ModuleWireBytes& wire_bytes, uint32_t function_index) const {
+    const ModuleWireBytes& wire_bytes, uint32_t function_index) {
   base::MutexGuard lock(&mutex_);
-  if (!function_names_) {
-    function_names_.reset(new std::unordered_map<uint32_t, WireBytesRef>());
-    DecodeFunctionNames(wire_bytes.start(), wire_bytes.end(),
-                        function_names_.get());
+  if (!has_functions_) {
+    has_functions_ = true;
+    DecodeFunctionNames(wire_bytes.start(), wire_bytes.end(), function_names_);
   }
-  auto it = function_names_->find(function_index);
-  if (it == function_names_->end()) return WireBytesRef();
+  auto it = function_names_.find(function_index);
+  if (it == function_names_.end()) return WireBytesRef();
   return it->second;
 }
 
+bool LazilyGeneratedNames::Has(uint32_t function_index) {
+  DCHECK(has_functions_);
+  base::MutexGuard lock(&mutex_);
+  return function_names_.find(function_index) != function_names_.end();
+}
+
 // static
 int MaxNumExportWrappers(const WasmModule* module) {
   // For each signature there may exist a wrapper, both for imported and
@@ -130,10 +127,7 @@ int GetSubtypingDepth(const WasmModule* module, uint32_t type_index) {
 void LazilyGeneratedNames::AddForTesting(int function_index,
                                          WireBytesRef name) {
   base::MutexGuard lock(&mutex_);
-  if (!function_names_) {
-    function_names_.reset(new std::unordered_map<uint32_t, WireBytesRef>());
-  }
-  function_names_->insert(std::make_pair(function_index, name));
+  function_names_.insert(std::make_pair(function_index, name));
 }
 
 AsmJsOffsetInformation::AsmJsOffsetInformation(

src/wasm/wasm-module.h

@@ -217,17 +217,17 @@ struct ModuleWireBytes;
 class V8_EXPORT_PRIVATE LazilyGeneratedNames {
  public:
   WireBytesRef LookupFunctionName(const ModuleWireBytes& wire_bytes,
-                                  uint32_t function_index) const;
+                                  uint32_t function_index);
 
   void AddForTesting(int function_index, WireBytesRef name);
+  bool Has(uint32_t function_index);
 
  private:
-  // {function_names_} are populated lazily after decoding, and
-  // therefore need a mutex to protect concurrent modifications
-  // from multiple {WasmModuleObject}.
-  mutable base::Mutex mutex_;
-  mutable std::unique_ptr<std::unordered_map<uint32_t, WireBytesRef>>
-      function_names_;
+  // Lazy loading must guard against concurrent modifications from multiple
+  // {WasmModuleObject}s.
+  base::Mutex mutex_;
+  bool has_functions_{false};
+  std::unordered_map<uint32_t, WireBytesRef> function_names_;
 };
 
 class V8_EXPORT_PRIVATE AsmJsOffsetInformation {
@@ -422,6 +422,9 @@ struct V8_EXPORT_PRIVATE WasmModule {
   // ID and length).
   WireBytesRef code = {0, 0};
   WireBytesRef name = {0, 0};
+  // Position and size of the name section (payload only, i.e. without section
+  // ID and length).
+  WireBytesRef name_section = {0, 0};
 
   void add_type(TypeDefinition type) {
     types.push_back(type);
@@ -503,7 +506,7 @@ struct V8_EXPORT_PRIVATE WasmModule {
   mutable TypeFeedbackStorage type_feedback;
 
   ModuleOrigin origin = kWasmOrigin;  // origin of the module
-  LazilyGeneratedNames lazily_generated_names;
+  mutable LazilyGeneratedNames lazily_generated_names;
   WasmDebugSymbols debug_symbols;
 
   // Asm.js source position information. Only available for modules compiled