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

src/wasm/wasm-module.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/base/atomic-utils.h"
 #include "src/macro-assembler.h"
 #include "src/objects.h"
 #include "src/property-descriptor.h"
 #include "src/v8.h"
 
@@ skipping 126 matching lines @@
     CHECK_LE(segment.source_size, mem_size);
     CHECK_LE(segment.dest_addr + segment.source_size, mem_size);
     byte* addr = mem_addr + segment.dest_addr;
     memcpy(addr, module->module_start + segment.source_offset,
            segment.source_size);
   }
 }
 
 Handle<FixedArray> BuildFunctionTable(Isolate* isolate,
                                       const WasmModule* module) {
-  if (module->function_table.size() == 0) {
+  // Compute the size of the indirect function table
+  int table_size = module->FunctionTableSize();

[Mircea Trofin, 2016/06/21 19:46:14]

uint32_t table_size

+  if (table_size == 0) {
     return Handle<FixedArray>::null();
   }
-  int table_size = static_cast<int>(module->function_table.size());
+  int populated_table_size = static_cast<int>(module->function_table.size());

[Mircea Trofin, 2016/06/21 19:46:14]

could you avoid the cast to int here? in fact, you can avoid the temp variable
and just 

for (size_t i = 0; i < module->function_table.size(); ++i)

also, please use the prefix increments in loops, i.e. ++i, not i++. The latter
produces an intermediate value which is unnecessary.

+
   Handle<FixedArray> fixed = isolate->factory()->NewFixedArray(2 * table_size);
-  for (int i = 0; i < table_size; i++) {
+  for (int i = 0; i < populated_table_size; i++) {
     const WasmFunction* function =
         &module->functions[module->function_table[i]];
     fixed->set(i, Smi::FromInt(function->sig_index));
   }
   return fixed;
 }
 
 Handle<JSArrayBuffer> NewArrayBuffer(Isolate* isolate, size_t size,
                                      byte** backing_store) {
   *backing_store = nullptr;
@@ skipping 172 matching lines @@
 }  // namespace
 
 WasmModule::WasmModule()
     : module_start(nullptr),
       module_end(nullptr),
       min_mem_pages(0),
       max_mem_pages(0),
       mem_export(false),
       mem_external(false),
       start_function_index(-1),
-      origin(kWasmOrigin) {}
+      origin(kWasmOrigin),
+      globals_size(0),
+      indirect_table_size(0) {}
 
 static MaybeHandle<JSFunction> ReportFFIError(ErrorThrower& thrower,
                                               const char* error, uint32_t index,
                                               wasm::WasmName module_name,
                                               wasm::WasmName function_name) {
   if (!function_name.is_empty()) {
     thrower.Error("Import #%d module=\"%.*s\" function=\"%.*s\" error: %s",
                   index, module_name.length(), module_name.start(),
                   function_name.length(), function_name.start(), error);
   } else {
@@ skipping 310 matching lines @@
                      str.start());
       break;
     }
       // Install the code into the linker table.
     functions[i] = code;
   }
 }
 
 void PopulateFunctionTable(WasmModuleInstance* instance) {
   if (!instance->function_table.is_null()) {
-    int table_size = static_cast<int>(instance->module->function_table.size());
-    DCHECK_EQ(instance->function_table->length(), table_size * 2);
-    for (int i = 0; i < table_size; i++) {
+    int table_size = instance->module->FunctionTableSize();

[Mircea Trofin, 2016/06/21 19:46:14]

same note as above about avoiding the cast - I realize this was this way before,
but the cleanup would be appreciated. Thanks!

+    DCHECK_EQ(table_size * 2, instance->function_table->length());
+    int populated_table_size =
+        static_cast<int>(instance->module->function_table.size());
+    DCHECK_LE(populated_table_size * 2, instance->function_table->length());
+    for (int i = 0; i < populated_table_size; i++) {
       instance->function_table->set(
           i + table_size,
           *instance->function_code[instance->module->function_table[i]]);
     }
   }
 }
 }  // namespace
 
 void SetDeoptimizationData(Factory* factory, Handle<JSObject> js_object,
                            std::vector<Handle<Code>>& functions) {
@@ skipping 427 matching lines @@
   Object* info = wasm->GetInternalField(kWasmDebugInfo);
   if (!info->IsUndefined(wasm->GetIsolate())) return WasmDebugInfo::cast(info);
   Handle<WasmDebugInfo> new_info = WasmDebugInfo::New(handle(wasm));
   wasm->SetInternalField(kWasmDebugInfo, *new_info);
   return *new_info;
 }
 
 }  // namespace wasm
 }  // namespace internal
 }  // namespace v8