[wasm] Add support for a start function.

src/wasm/wasm-module.h

 // 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.
 
 #ifndef V8_WASM_MODULE_H_
 #define V8_WASM_MODULE_H_
 
 #include "src/wasm/wasm-opcodes.h"
 #include "src/wasm/wasm-result.h"
 
@@ skipping 14 matching lines @@
 
 enum WasmSectionDeclCode {
   kDeclMemory = 0x00,
   kDeclSignatures = 0x01,
   kDeclFunctions = 0x02,
   kDeclGlobals = 0x03,
   kDeclDataSegments = 0x04,
   kDeclFunctionTable = 0x05,
   kDeclWLL = 0x11,
   kDeclEnd = 0x06,
+  kDeclStartFunction = 0x07,
 };
 
 static const int kMaxModuleSectionCode = 6;
 
 enum WasmFunctionDeclBit {
   kDeclFunctionName = 0x01,
   kDeclFunctionImport = 0x02,
   kDeclFunctionLocals = 0x04,
   kDeclFunctionExport = 0x08
 };
@@ skipping 41 matching lines @@
   static const uint8_t kMinMemSize = 12;  // Minimum memory size = 4kb
   static const uint8_t kMaxMemSize = 30;  // Maximum memory size = 1gb
 
   Isolate* shared_isolate;    // isolate for storing shared code.
   const byte* module_start;   // starting address for the module bytes.
   const byte* module_end;     // end address for the module bytes.
   uint8_t min_mem_size_log2;  // minimum size of the memory (log base 2).
   uint8_t max_mem_size_log2;  // maximum size of the memory (log base 2).
   bool mem_export;            // true if the memory is exported.
   bool mem_external;          // true if the memory is external.
+  int start_function_index;   // start function, if any.
 
   std::vector<WasmGlobal>* globals;             // globals in this module.
   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.
   std::vector<uint16_t>* function_table;        // function table.
 
   WasmModule();
   ~WasmModule();
 
@@ skipping 97 matching lines @@
                                 const byte* module_end, bool asm_js = false);
 
 // For testing. Decode, verify, and run the last exported function in the
 // given decoded module.
 int32_t CompileAndRunWasmModule(Isolate* isolate, WasmModule* module);
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_WASM_MODULE_H_