SILGen: Emit cleanups before returning from enum case constructors.

We were leaking dealloc_stacks when the enum constructor had to create temporary allocations in order to implode address-only tuple payloads.

Swift SVN r8971

test/SILGen/enum.swift

@@ -0,0 +1,11 @@
+// RUN: %swift -emit-silgen %s | FileCheck %s
+protocol P {}
+
+// Regression test for a bug where temporary allocations created as a result of
+// tuple implosion were not deallocated in enum constructors.
+enum Foo { case A(P, String) }
+
+// CHECK: sil [transparent] @_TO4enum3Foo1AfMS0_FTPS_1P_SS_S0_ : $[thin] ((P, String), Foo.metatype) -> Foo {
+// CHECK:   [[ALLOC:%.*]] = alloc_stack $(P, String)
+// CHECK:   dealloc_stack [[ALLOC]]#0
+// CHECK: }