Add upcall compiler.

Upcall compiler compiles the invoke stub for native-to-managed
method invocation.

Change-Id: I09fb1e4b3f166e8da5de73e8f39509cd9be6c152
diff --git a/src/compiler_llvm/ir_builder.cc b/src/compiler_llvm/ir_builder.cc
index b2c795b..4c43271 100644
--- a/src/compiler_llvm/ir_builder.cc
+++ b/src/compiler_llvm/ir_builder.cc
@@ -35,6 +35,10 @@
   CHECK_NE(jobject_struct_type, static_cast<llvm::Type*>(NULL));
   jobject_type_ = jobject_struct_type->getPointerTo();
 
+  // Create JEnv* type
+  llvm::Type* jenv_struct_type = llvm::StructType::create(context, "JEnv");
+  jenv_type_ = jenv_struct_type->getPointerTo();
+
   // Load the runtime support function declaration from module
   InitRuntimeSupportFuncDecl(module);
 }