[wasm][asm.js] Allow a function to be exported more than once.

Allow a function to be exported multiple times in a asm.js
module.
Remarkably, this had not been working before.

BUG=670057
R=titzer@chromium.org

Review-Url: https://codereview.chromium.org/2535723009
Cr-Commit-Position: refs/heads/master@{#41416}

src/asmjs/asm-wasm-builder.cc

@@ -715,8 +715,7 @@ class AsmWasmBuilderImpl final : public AstVisitor<AsmWasmBuilderImpl> {
       const AstRawString* raw_name = name->AsRawPropertyName();
       if (var->is_function()) {
         WasmFunctionBuilder* function = LookupOrInsertFunction(var);
-        function->Export();
-        function->SetName({reinterpret_cast<const char*>(raw_name->raw_data()),
+        function->ExportAs({reinterpret_cast<const char*>(raw_name->raw_data()),
                             raw_name->length()});
       }
     }

src/wasm/wasm-module-builder.cc

@@ -50,11 +50,10 @@ WasmFunctionBuilder::WasmFunctionBuilder(WasmModuleBuilder* builder)
     : builder_(builder),
       locals_(builder->zone()),
       signature_index_(0),
-      exported_(0),
       func_index_(static_cast<uint32_t>(builder->functions_.size())),
       body_(builder->zone()),
       name_(builder->zone()),
-      exported_name_(builder->zone()),
+      exported_names_(builder->zone()),
       i32_temps_(builder->zone()),
       i64_temps_(builder->zone()),
       f32_temps_(builder->zone()),
@@ -141,12 +140,9 @@ void WasmFunctionBuilder::EmitDirectCallIndex(uint32_t index) {
   EmitCode(code, sizeof(code));
 }
 
-void WasmFunctionBuilder::Export() { exported_ = true; }
-
 void WasmFunctionBuilder::ExportAs(Vector<const char> name) {
-  exported_ = true;
-  exported_name_.resize(name.length());
-  memcpy(exported_name_.data(), name.start(), name.length());
+  exported_names_.push_back(ZoneVector<char>(
+      name.start(), name.start() + name.length(), builder_->zone()));
 }
 
 void WasmFunctionBuilder::SetName(Vector<const char> name) {
@@ -172,13 +168,10 @@ void WasmFunctionBuilder::WriteSignature(ZoneBuffer& buffer) const {
   buffer.write_u32v(signature_index_);
 }
 
-void WasmFunctionBuilder::WriteExport(ZoneBuffer& buffer) const {
-  if (exported_) {
-    const ZoneVector<char>* exported_name =
-        exported_name_.size() == 0 ? &name_ : &exported_name_;
-    buffer.write_size(exported_name->size());
-    buffer.write(reinterpret_cast<const byte*>(exported_name->data()),
-                 exported_name->size());
+void WasmFunctionBuilder::WriteExports(ZoneBuffer& buffer) const {
+  for (auto name : exported_names_) {
+    buffer.write_size(name.size());
+    buffer.write(reinterpret_cast<const byte*>(name.data()), name.size());
     buffer.write_u8(kExternalFunction);
     buffer.write_u32v(func_index_ +
                       static_cast<uint32_t>(builder_->imports_.size()));
@@ -348,7 +341,7 @@ void WasmModuleBuilder::WriteTo(ZoneBuffer& buffer) const {
     buffer.write_size(functions_.size());
     for (auto function : functions_) {
       function->WriteSignature(buffer);
-      if (function->exported()) exports++;
+      exports += function->exported_names_.size();
       if (function->name_.size() > 0) has_names = true;
     }
     FixupSection(buffer, start);
@@ -451,7 +444,7 @@ void WasmModuleBuilder::WriteTo(ZoneBuffer& buffer) const {
   if (exports > 0) {
     size_t start = EmitSection(kExportSectionCode, buffer);
     buffer.write_u32v(exports);
-    for (auto function : functions_) function->WriteExport(buffer);
+    for (auto function : functions_) function->WriteExports(buffer);
     FixupSection(buffer, start);
   }
 
@@ -524,10 +517,8 @@ void WasmModuleBuilder::WriteTo(ZoneBuffer& buffer) const {
     }
     for (auto function : functions_) {
       buffer.write_size(function->name_.size());
-      if (function->name_.size() > 0) {
-        buffer.write(reinterpret_cast<const byte*>(&function->name_[0]),
+      buffer.write(reinterpret_cast<const byte*>(function->name_.data()),
                    function->name_.size());
-      }
       buffer.write_u8(0);
     }
     FixupSection(buffer, start);

src/wasm/wasm-module-builder.h

@@ -132,17 +132,15 @@ class V8_EXPORT_PRIVATE WasmFunctionBuilder : public ZoneObject {
   void EmitWithU8U8(WasmOpcode opcode, const byte imm1, const byte imm2);
   void EmitWithVarInt(WasmOpcode opcode, uint32_t immediate);
   void EmitDirectCallIndex(uint32_t index);
-  void Export();
   void ExportAs(Vector<const char> name);
   void SetName(Vector<const char> name);
   void AddAsmWasmOffset(int asm_position);
 
   void WriteSignature(ZoneBuffer& buffer) const;
-  void WriteExport(ZoneBuffer& buffer) const;
+  void WriteExports(ZoneBuffer& buffer) const;
   void WriteBody(ZoneBuffer& buffer) const;
   void WriteAsmWasmOffsetTable(ZoneBuffer& buffer) const;
 
-  bool exported() { return exported_; }
   uint32_t func_index() { return func_index_; }
   FunctionSig* signature();
 
@@ -159,11 +157,10 @@ class V8_EXPORT_PRIVATE WasmFunctionBuilder : public ZoneObject {
   WasmModuleBuilder* builder_;
   LocalDeclEncoder locals_;
   uint32_t signature_index_;
-  bool exported_;
   uint32_t func_index_;
   ZoneVector<uint8_t> body_;
   ZoneVector<char> name_;
-  ZoneVector<char> exported_name_;
+  ZoneVector<ZoneVector<char>> exported_names_;
   ZoneVector<uint32_t> i32_temps_;
   ZoneVector<uint32_t> i64_temps_;
   ZoneVector<uint32_t> f32_temps_;

test/mjsunit/wasm/asm-wasm.js

@@ -1675,3 +1675,17 @@ function TestFloatGlobals(stdlib) {
 }
 
 assertWasm(3.25, TestFloatGlobals);
+
+
+(function TestExportTwice() {
+  function asmModule() {
+    "use asm";
+    function foo() {
+      return 42;
+    }
+    return {bar: foo, baz: foo};
+  }
+  var m = asmModule();
+  assertEquals(42, m.bar());
+  assertEquals(42, m.baz());
+})();