[wasm] Decode and use module name

* add functionality to wasm-module-builder.js to emit the module name
  in the name section.
* extend WasmModule to store the module name length and offset.
* add functionality to module-decoder.cc to decode the module name.
* use the module name for printing stack traces. more uses should
  follow.
* extend one message test to contain a module name.

R=ahaas@chromium.org

Change-Id: I94e6f1f2eb99cb656a92a85bb7afe0742292046f
Reviewed-on: https://chromium-review.googlesource.com/530366Reviewed-by: Andreas Haas <ahaas@chromium.org>
Commit-Queue: Clemens Hammacher <clemensh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#45846}

src/messages.cc

@@ -674,9 +674,23 @@ Handle<Object> WasmStackFrame::GetFunctionName() {
 MaybeHandle<String> WasmStackFrame::ToString() {
   IncrementalStringBuilder builder(isolate_);
 
-  Handle<Object> name = GetFunctionName();
-  if (!name->IsNull(isolate_)) {
-    builder.AppendString(Handle<String>::cast(name));
+  Handle<WasmCompiledModule> compiled_module(wasm_instance_->compiled_module(),
+                                             isolate_);
+  MaybeHandle<String> module_name =
+      WasmCompiledModule::GetModuleNameOrNull(isolate_, compiled_module);
+  MaybeHandle<String> function_name = WasmCompiledModule::GetFunctionNameOrNull(
+      isolate_, compiled_module, wasm_func_index_);
+  bool has_name = !module_name.is_null() || !function_name.is_null();
+  if (has_name) {
+    if (module_name.is_null()) {
+      builder.AppendString(function_name.ToHandleChecked());
+    } else {
+      builder.AppendString(module_name.ToHandleChecked());
+      if (!function_name.is_null()) {
+        builder.AppendCString(".");
+        builder.AppendString(function_name.ToHandleChecked());
+      }
+    }
     builder.AppendCString(" (");
   }
 
@@ -689,7 +703,7 @@ MaybeHandle<String> WasmStackFrame::ToString() {
   SNPrintF(ArrayVector(buffer), ":%d", GetPosition());
   builder.AppendCString(buffer);
 
-  if (!name->IsNull(isolate_)) builder.AppendCString(")");
+  if (has_name) builder.AppendCString(")");
 
   return builder.Finish();
 }

src/wasm/module-decoder.cc

@@ -728,28 +728,45 @@ class ModuleDecoder : public Decoder {
 
       // Decode function names, ignore the rest.
       // Local names will be decoded when needed.
-      if (name_type == NameSectionType::kFunction) {
-        uint32_t functions_count = inner.consume_u32v("functions count");
-
-        for (; inner.ok() && functions_count > 0; --functions_count) {
-          uint32_t function_index = inner.consume_u32v("function index");
+      switch (name_type) {
+        case NameSectionType::kModule: {
           uint32_t name_length = 0;
           uint32_t name_offset =
-              wasm::consume_string(inner, &name_length, false, "function name");
-
-          // Be lenient with errors in the name section: Ignore illegal
-          // or out-of-order indexes and non-UTF8 names. You can even assign
-          // to the same function multiple times (last valid one wins).
-          if (inner.ok() && function_index < module_->functions.size() &&
+              wasm::consume_string(inner, &name_length, false, "module name");
+          if (inner.ok() &&
               unibrow::Utf8::ValidateEncoding(
                   inner.start() + inner.GetBufferRelativeOffset(name_offset),
                   name_length)) {
-            module_->functions[function_index].name_offset = name_offset;
-            module_->functions[function_index].name_length = name_length;
+            module_->name_length = name_length;
+            module_->name_offset = name_offset;
           }
+          break;
         }
-      } else {
-        inner.consume_bytes(name_payload_len, "name subsection payload");
+        case NameSectionType::kFunction: {
+          uint32_t functions_count = inner.consume_u32v("functions count");
+
+          for (; inner.ok() && functions_count > 0; --functions_count) {
+            uint32_t function_index = inner.consume_u32v("function index");
+            uint32_t name_length = 0;
+            uint32_t name_offset = wasm::consume_string(inner, &name_length,
+                                                        false, "function name");
+
+            // Be lenient with errors in the name section: Ignore illegal
+            // or out-of-order indexes and non-UTF8 names. You can even assign
+            // to the same function multiple times (last valid one wins).
+            if (inner.ok() && function_index < module_->functions.size() &&
+                unibrow::Utf8::ValidateEncoding(
+                    inner.start() + inner.GetBufferRelativeOffset(name_offset),
+                    name_length)) {
+              module_->functions[function_index].name_offset = name_offset;
+              module_->functions[function_index].name_length = name_length;
+            }
+          }
+          break;
+        }
+        default:
+          inner.consume_bytes(name_payload_len, "name subsection payload");
+          break;
       }
     }
     // Skip the whole names section in the outer decoder.

src/wasm/module-decoder.h

@@ -39,7 +39,7 @@ enum SectionCode : int8_t {
   kFirstSectionInModule = kTypeSectionCode,
 };
 
-enum NameSectionType : uint8_t { kFunction = 1, kLocal = 2 };
+enum NameSectionType : uint8_t { kModule = 0, kFunction = 1, kLocal = 2 };
 
 inline bool IsValidSectionCode(uint8_t byte) {
   return kTypeSectionCode <= byte && byte <= kDataSectionCode;

src/wasm/wasm-module.h

@@ -169,6 +169,9 @@ struct V8_EXPORT_PRIVATE WasmModule {
   uint32_t num_imported_functions = 0;         // number of imported functions.
   uint32_t num_declared_functions = 0;         // number of declared functions.
   uint32_t num_exported_functions = 0;         // number of exported functions.
+  uint32_t name_offset = 0;  // offset in the module bytes of the name, if any.
+  uint32_t name_length = 0;  // length in bytes of the name.
+  // TODO(wasm): Add url here, for spec'ed location information.
   std::vector<FunctionSig*> signatures;        // signatures in this module.
   std::vector<WasmFunction> functions;         // functions in this module.
   std::vector<WasmDataSegment> data_segments;  // data segments in this module.

src/wasm/wasm-objects.cc

@@ -1218,6 +1218,15 @@ uint32_t WasmCompiledModule::default_mem_size() const {
   return min_mem_pages() * WasmModule::kPageSize;
 }
 
+MaybeHandle<String> WasmCompiledModule::GetModuleNameOrNull(
+    Isolate* isolate, Handle<WasmCompiledModule> compiled_module) {
+  WasmModule* module = compiled_module->module();
+  DCHECK_IMPLIES(module->name_offset == 0, module->name_length == 0);
+  if (!module->name_offset) return {};
+  return WasmCompiledModule::ExtractUtf8StringFromModuleBytes(
+      isolate, compiled_module, module->name_offset, module->name_length);
+}
+
 MaybeHandle<String> WasmCompiledModule::GetFunctionNameOrNull(
     Isolate* isolate, Handle<WasmCompiledModule> compiled_module,
     uint32_t func_index) {

src/wasm/wasm-objects.h

@@ -442,6 +442,10 @@ class WasmCompiledModule : public FixedArray {
   static void ReinitializeAfterDeserialization(Isolate*,
                                                Handle<WasmCompiledModule>);
 
+  // Get the module name, if set. Returns an empty handle otherwise.
+  static MaybeHandle<String> GetModuleNameOrNull(
+      Isolate* isolate, Handle<WasmCompiledModule> compiled_module);
+
   // 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.

test/message/wasm-function-name.js

+// Copyright 2017 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.
+
+// Flags: --expose-wasm
+
+load("test/mjsunit/wasm/wasm-constants.js");
+load("test/mjsunit/wasm/wasm-module-builder.js");
+
+var builder = new WasmModuleBuilder();
+builder.addFunction('main', kSig_i_v).addBody([kExprUnreachable]).exportFunc();
+builder.instantiate().exports.main();

test/message/wasm-function-name.out

+wasm-function[0]:1: RuntimeError: unreachable
+RuntimeError: unreachable
+    at main (wasm-function[0]:1)
+    at *%(basename)s:12:31
+

test/message/wasm-module-and-function-name.js

+// Copyright 2017 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.
+
+// Flags: --expose-wasm
+
+load("test/mjsunit/wasm/wasm-constants.js");
+load("test/mjsunit/wasm/wasm-module-builder.js");
+
+var builder = new WasmModuleBuilder();
+builder.setName('test-module');
+builder.addFunction('main', kSig_i_v).addBody([kExprUnreachable]).exportFunc();
+builder.instantiate().exports.main();

test/message/wasm-module-and-function-name.out

+wasm-function[0]:1: RuntimeError: unreachable
+RuntimeError: unreachable
+    at test-module.main (wasm-function[0]:1)
+    at *%(basename)s:13:31

test/message/wasm-module-name.js

+// Copyright 2017 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.
+
+// Flags: --expose-wasm
+
+load("test/mjsunit/wasm/wasm-constants.js");
+load("test/mjsunit/wasm/wasm-module-builder.js");
+
+var builder = new WasmModuleBuilder();
+builder.setName('test-module');
+builder.addFunction(undefined, kSig_i_v)
+    .addBody([kExprUnreachable])
+    .exportAs('main');
+builder.instantiate().exports.main();

test/message/wasm-module-name.out

+wasm-function[0]:1: RuntimeError: unreachable
+RuntimeError: unreachable
+    at test-module (wasm-function[0]:1)
+    at *%(basename)s:15:31
+

test/message/wasm-no-name.js

+// Copyright 2017 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.
+
+// Flags: --expose-wasm
+
+load("test/mjsunit/wasm/wasm-constants.js");
+load("test/mjsunit/wasm/wasm-module-builder.js");
+
+var builder = new WasmModuleBuilder();
+builder.addFunction(undefined, kSig_i_v)
+    .addBody([kExprUnreachable])
+    .exportAs('main');
+builder.instantiate().exports.main();

test/message/wasm-no-name.out

+wasm-function[0]:1: RuntimeError: unreachable
+RuntimeError: unreachable
+    at wasm-function[0]:1
+    at *%(basename)s:14:31
+

test/mjsunit/wasm/wasm-constants.js

@@ -66,6 +66,7 @@ let kDataSectionCode = 11;     // Data segments
 let kNameSectionCode = 12;     // Name section (encoded as string)
 
 // Name section types
+let kModuleNameCode = 0;
 let kFunctionNamesCode = 1;
 let kLocalNamesCode = 2;
 

test/mjsunit/wasm/wasm-module-builder.js

@@ -277,6 +277,11 @@ class WasmModuleBuilder {
     return this;
   }
 
+  setName(name) {
+    this.name = name;
+    return this;
+  }
+
   toArray(debug = false) {
     let binary = new Binary;
     let wasm = this;
@@ -545,19 +550,26 @@ class WasmModuleBuilder {
       binary.emit_bytes(exp);
     }
 
-    // Add function names.
-    if (num_function_names > 0) {
+    // Add names.
+    if (num_function_names > 0 || wasm.name !== undefined) {
       if (debug) print('emitting names @ ' + binary.length);
       binary.emit_section(kUnknownSectionCode, section => {
         section.emit_string('name');
-        section.emit_section(kFunctionNamesCode, name_section => {
-          name_section.emit_u32v(num_function_names);
-          for (let func of wasm.functions) {
-            if (func.name === undefined) continue;
-            name_section.emit_u32v(func.index);
-            name_section.emit_string(func.name);
-          }
-        });
+        if (wasm.name !== undefined) {
+          section.emit_section(kModuleNameCode, name_section => {
+            name_section.emit_string(wasm.name);
+          });
+        }
+        if (num_function_names > 0) {
+          section.emit_section(kFunctionNamesCode, name_section => {
+            name_section.emit_u32v(num_function_names);
+            for (let func of wasm.functions) {
+              if (func.name === undefined) continue;
+              name_section.emit_u32v(func.index);
+              name_section.emit_string(func.name);
+            }
+          });
+        }
       });
     }