CGCleanup: (NFC) add another test for r304335 - Don't try to spill static allocas

[GorNishanov]

Summary

Coroutine related test that used to trigger broken IR prior to r304335.

%x = alloca i32, align 4
store i32* %x, i32** %tmp.exprcleanup, align 4 ; <===== HERE
%ref.tmp3 = alloca %struct.A, align 1
%agg.tmp5 = alloca %"struct.std::experimental::coroutines_v1::coroutine_handle.0", align 4
%tmp.exprcleanup = alloca i32*, align 4
%allocapt = bitcast i32 undef to i32
store i32 %0, i32* %.addr, align 4

Fixed with r304335

cfe/trunk/test/CodeGenCoroutines/coro-await-domination.cpp

+// RUN: %clang_cc1 -triple x86_64-unknown-linux-gnu -fcoroutines-ts -std=c++14 -emit-llvm %s -o - | FileCheck %s
+#include "Inputs/coroutine.h"
+
+using namespace std::experimental;
+
+struct coro {
+  struct promise_type {
+    coro get_return_object();
+    suspend_never initial_suspend();
+    suspend_never final_suspend();
+    void return_void();
+    static void unhandled_exception();
+  };
+};
+
+struct A {
+  ~A();
+  bool await_ready();
+  int await_resume() { return 8; }
+  template <typename F> void await_suspend(F);
+};
+
+extern "C" void consume(int);
+
+// Verifies that domination is properly built during cleanup.
+// Without CGCleanup.cpp fix verifier was reporting:
+// Instruction does not dominate all uses!
+//  %tmp.exprcleanup = alloca i32*, align 8
+//  store i32* %x, i32** %tmp.exprcleanup, align 8
+
+
+// CHECK-LABEL: f(
+extern "C" coro f(int) {
+  int x = 42;
+  x = co_await A{};
+  consume(x);
+}
+