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

src/wasm/wasm-module.cc

Index: src/wasm/wasm-module.cc
diff --git a/src/wasm/wasm-module.cc b/src/wasm/wasm-module.cc
index 07d2ef1113f725ea24bffd1efd64dbd4afa15999..e92f6a88e6b913791c375a92fe348f9c6a206ec3 100644
--- a/src/wasm/wasm-module.cc
+++ b/src/wasm/wasm-module.cc
@@ -140,9 +140,19 @@ class WasmLinker {
     }
     if (!function_table.is_null()) {
       int table_size = static_cast<int>(functions.size());
-      DCHECK_EQ(function_table->length(), table_size * 2);
+      int indirect_table_size;
+      if (FLAG_wasm_jit_prototype) {
+        indirect_table_size = 4 * table_size < kMinimumIndirectTableSize

[bradn, 2016/06/16 08:00:20]

I'd thought we'd talked about adding a field to one of the sections?

+                                  ? kMinimumIndirectTableSize
+                                  : 4 * table_size;
+        DCHECK_EQ(function_table->length(), indirect_table_size);
+      } else {
+        indirect_table_size = 2 * table_size;
+        DCHECK_EQ(function_table->length(), indirect_table_size);
+      }
       for (int i = 0; i < table_size; i++) {
-        function_table->set(i + table_size, *function_code()[functions[i]]);
+        function_table->set(i + indirect_table_size / 2,
+                            *function_code()[functions[i]]);
       }
     }
   }
@@ -232,7 +242,16 @@ Handle<FixedArray> BuildFunctionTable(Isolate* isolate,
     return Handle<FixedArray>::null();
   }
   int table_size = static_cast<int>(module->function_table.size());
-  Handle<FixedArray> fixed = isolate->factory()->NewFixedArray(2 * table_size);
+  int indirect_table_size;
+  if (FLAG_wasm_jit_prototype)
+    indirect_table_size = 4 * table_size < kMinimumIndirectTableSize

[bradn, 2016/06/16 08:00:20]

Definitely don't want to repeat this calculation all over.

+                              ? kMinimumIndirectTableSize
+                              : 4 * table_size;
+  else
+    indirect_table_size = 2 * table_size;
+
+  Handle<FixedArray> fixed =
+      isolate->factory()->NewFixedArray(indirect_table_size);
   for (int i = 0; i < table_size; i++) {
     const WasmFunction* function =
         &module->functions[module->function_table[i]];
@@ -735,6 +754,9 @@ MaybeHandle<JSObject> WasmModule::Instantiate(
       isolate->counters()->wasm_compile_module_time());
 
   instance.function_table = BuildFunctionTable(isolate, this);
+  instance.padded_entries =
+      static_cast<int>(instance.function_table->length() / 2) -
+      static_cast<int>(instance.module->function_table.size());
   WasmLinker linker(isolate, &instance.function_code);
   ModuleEnv module_env;
   module_env.module = this;
@@ -929,6 +951,9 @@ int32_t CompileAndRunWasmModule(Isolate* isolate, const WasmModule* module) {
 
   // Build the function table.
   instance.function_table = BuildFunctionTable(isolate, module);
+  instance.padded_entries =
+      static_cast<int>(instance.function_table->length() / 2) -
+      static_cast<int>(module->function_table.size());
 
   // Create module environment.
   WasmLinker linker(isolate, &instance.function_code);