Add @dynamicCallable SIL gen test.

This test verifies that dynamic calls resolve to the correct method.

Author: dan-zheng

test/NameBinding/dynamic-callable-silgen.swift

@@ -0,0 +1,23 @@
+// RUN: %target-swift-frontend -emit-silgen -verify %s | %FileCheck %s
+ 
+@dynamicCallable
+public struct Callable {
+  func dynamicallyCall(withArguments: [Int]) {}
+  func dynamicallyCall(withKeywordArguments: DictionaryLiteral<String, Int>) {}
+}
+ 
+@_silgen_name("foo")
+public func foo(a: Callable) {
+  a()
+  a(1, 2, 3)
+  a(1, 2, 3, label: 4)
+}
+ 
+// CHECK-LABEL: sil @foo
+// CHECK: bb0(%0 : $Callable):
+// CHECK: [[DYN_CALL_1:%.*]] = function_ref @$S4main8CallableV15dynamicallyCall13withArgumentsySaySiG_tF
+// CHECK-NEXT: apply [[DYN_CALL_1]]
+// CHECK: [[DYN_CALL_2:%.*]] = function_ref @$S4main8CallableV15dynamicallyCall13withArgumentsySaySiG_tF
+// CHECK-NEXT: apply [[DYN_CALL_2]]
+// CHECK: [[DYN_CALL_3:%.*]] = function_ref @$S4main8CallableV15dynamicallyCall20withKeywordArgumentsys17DictionaryLiteralVySSSiG_tF
+// CHECK-NEXT: apply [[DYN_CALL_3]]