[wasm] Support undefined indirect table entries, behind a flag.

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 83 matching lines @@
   kDeclFunctionName = 0x01,
   kDeclFunctionExport = 0x08
 };
 
 // Constants for fixed-size elements within a module.
 static const size_t kDeclMemorySize = 3;
 static const size_t kDeclDataSegmentSize = 13;
 
 static const uint32_t kMaxReturnCount = 1;
 
+// minimum number of entries in the table for JITing
+static const uint32_t kMinimumIndirectTableSize = 1024;
+
 // Static representation of a WASM function.
 struct WasmFunction {
   FunctionSig* sig;      // signature of the function.
   uint32_t func_index;   // index into the function table.
   uint32_t sig_index;    // index into the signature table.
   uint32_t name_offset;  // offset in the module bytes of the name, if any.
   uint32_t name_length;  // length in bytes of the name.
   uint32_t code_start_offset;    // offset in the module bytes of code start.
   uint32_t code_end_offset;      // offset in the module bytes of code end.
 };
@@ skipping 108 matching lines @@
   Handle<JSArrayBuffer> mem_buffer;      // Handle to array buffer of memory.
   Handle<JSArrayBuffer> globals_buffer;  // Handle to array buffer of globals.
   Handle<FixedArray> function_table;     // indirect function table.
   std::vector<Handle<Code>> function_code;  // code objects for each function.
   std::vector<Handle<Code>> import_code;    // code objects for each import.
   // -- raw memory ------------------------------------------------------------
   byte* mem_start;  // start of linear memory.
   size_t mem_size;  // size of the linear memory.
   // -- raw globals -----------------------------------------------------------
   byte* globals_start;  // start of the globals area.
+  // -- indirect function table information -----------------------------------
+  int padded_entries;  // number of entries padded to the indirect func. table
 
   explicit WasmModuleInstance(const WasmModule* m)
       : module(m),
         function_code(m->functions.size()),
         mem_start(nullptr),
         mem_size(0),
         globals_start(nullptr) {}
 };
 
 // forward declaration.
@@ skipping 87 matching lines @@
 // secure. If it turns out that we need more complete checks, we could add a
 // special marker as internal field, which will definitely never occur anywhere
 // else.
 bool IsWasmObject(Handle<JSObject> object);
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_WASM_MODULE_H_