[wasm] Support asm.js modules with a single function.

src/asmjs/asm-wasm-builder.cc

 // Copyright 2015 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/v8.h"
 
 // Required to get M_E etc. in MSVC.
 #if defined(_WIN32)
 #define _USE_MATH_DEFINES
 #endif
@@ skipping 72 matching lines @@
   void BuildForeignInitFunction() {
     foreign_init_function_index_ = builder_->AddFunction();
     FunctionSig::Builder b(zone(), 0, foreign_variables_.size());
     for (auto i = foreign_variables_.begin(); i != foreign_variables_.end();
          ++i) {
       b.AddParam(i->type);
     }
     current_function_builder_ =
         builder_->FunctionAt(foreign_init_function_index_);
     current_function_builder_->SetExported();
-    std::string raw_name = "__foreign_init__";
-    current_function_builder_->SetName(raw_name.data(),
-                                       static_cast<int>(raw_name.size()));
+    current_function_builder_->SetName(
+        AsmWasmBuilder::foreign_init_name,
+        static_cast<int>(strlen(AsmWasmBuilder::foreign_init_name)));
     current_function_builder_->SetSignature(b.Build());
     for (size_t pos = 0; pos < foreign_variables_.size(); ++pos) {
       current_function_builder_->EmitGetLocal(static_cast<uint32_t>(pos));
       ForeignVariable* fv = &foreign_variables_[pos];
       uint32_t index = LookupOrInsertGlobal(fv->var, fv->type);
       current_function_builder_->EmitWithVarInt(kExprSetGlobal, index);
     }
     current_function_builder_ = nullptr;
   }
 
@@ skipping 438 matching lines @@
       }
       LocalType var_type = TypeOf(expr);
       DCHECK_NE(kAstStmt, var_type);
       if (var->IsContextSlot()) {
         current_function_builder_->EmitWithVarInt(
             kExprGetGlobal, LookupOrInsertGlobal(var, var_type));
       } else {
         current_function_builder_->EmitGetLocal(
             LookupOrInsertLocal(var, var_type));
       }
+    } else if (scope_ == kExportScope) {
+      Variable* var = expr->var();
+      DCHECK(var->is_function());
+      uint32_t index = LookupOrInsertFunction(var);
+      builder_->FunctionAt(index)->SetExported();
+      builder_->FunctionAt(index)->SetName(
+          AsmWasmBuilder::single_function_name,
+          static_cast<int>(strlen(AsmWasmBuilder::single_function_name)));
     }
   }
 
   void VisitLiteral(Literal* expr) {
     Handle<Object> value = expr->value();
     if (!value->IsNumber() || (scope_ != kFuncScope && scope_ != kInitScope)) {
       return;
     }
     AsmType* type = typer_->TypeOf(expr);
     DCHECK_NE(type, AsmType::None());
@@ skipping 1221 matching lines @@
 // TODO(aseemgarg): probably should take zone (to write wasm to) as input so
 // that zone in constructor may be thrown away once wasm module is written.
 ZoneBuffer* AsmWasmBuilder::Run(i::Handle<i::FixedArray>* foreign_args) {
   AsmWasmBuilderImpl impl(isolate_, zone_, literal_, typer_);
   impl.Build();
   *foreign_args = impl.GetForeignArgs();
   ZoneBuffer* buffer = new (zone_) ZoneBuffer(zone_);
   impl.builder_->WriteTo(*buffer);
   return buffer;
 }
+
+const char* AsmWasmBuilder::foreign_init_name = "__foreign_init__";
+const char* AsmWasmBuilder::single_function_name = "__single_function__";
+
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8