[wasm] Add support for compiling WASM_INTERPRETER_ENTRY stubs

src/runtime/runtime-wasm.cc

 // Copyright 2016 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/runtime/runtime-utils.h"
 
 #include "src/arguments.h"
 #include "src/assembler.h"
 #include "src/compiler/wasm-compiler.h"
 #include "src/conversions.h"
@@ skipping 134 matching lines @@
   HandleScope scope(isolate);
   DCHECK_EQ(1, args.length());
   Object* exception = args[0];
   // The unwinder will only deliver exceptions to wasm if the exception is a
   // Number or a Smi (which we have just converted to a Number.) This logic
   // lives in Isolate::is_catchable_by_wasm(Object*).
   CHECK(exception->IsNumber());
   return exception;
 }
 
+RUNTIME_FUNCTION(Runtime_WasmRunInterpreter) {
+  DCHECK(args.length() == 3);
+  HandleScope scope(isolate);
+  CONVERT_ARG_HANDLE_CHECKED(JSObject, instance_obj, 0);
+  CONVERT_NUMBER_CHECKED(int32_t, func_index, Int32, args[1]);
+  CONVERT_ARG_HANDLE_CHECKED(Object, arg_buffer_obj, 2);

[titzer, 2017/01/11 15:52:34]

Hmmm, not sure converting the argument buffer to Object is a good idea. You
maybe want to convert it to a SMI, but unchecked, since the SMI check will break
on 64-bit as mentioned previously.

[Clemens Hammacher, 2017/01/11 16:56:10]

But what do I do with the Smi? I would just reinterpret_cast it as below.
I added another comment here, and CHECK(arg_buffer_obj->IsSmi()), but I don't
want to assign it to a Smi*, as it's not really a Smi.

+  CHECK(WasmInstanceObject::IsWasmInstanceObject(*instance_obj));
+
+  // The arg buffer is the raw pointer to the caller's stack.
+  CHECK(!arg_buffer_obj->IsHeapObject());
+  void* arg_buffer = *arg_buffer_obj;
+
+  Handle<WasmInstanceObject> instance =
+      Handle<WasmInstanceObject>::cast(instance_obj);
+  Handle<WasmDebugInfo> debug_info =
+      WasmInstanceObject::GetOrCreateDebugInfo(instance);
+  WasmDebugInfo::RunInterpreter(debug_info, func_index, arg_buffer);
+  return isolate->heap()->undefined_value();
+}
+
 }  // namespace internal
 }  // namespace v8