Add tests

test/ConstValues/Modules.swift

@@ -0,0 +1,20 @@
+// Constant values should be able to call "const" functions from other modules
+
+// RUN: %empty-directory(%t)
+// RUN: split-file %s %t
+
+// RUN: %target-swift-frontend -emit-module -o %t/MyModule.swiftmodule %t/MyModule.swift -parse-as-library
+// RUN: %target-swift-frontend -emit-ir -I %t %t/Main.swift
+
+//--- MyModule.swift
+
+_const
+public func foo() -> Int {
+	return 42
+}
+
+//--- Main.swift
+
+import MyModule
+
+_const let constGlobal1: Int = foo()