--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/clang/test/CodeGenCXX/stack-reuse.cpp	Thu Feb 13 15:10:13 2020 +0900
@@ -0,0 +1,146 @@
+// RUN: %clang_cc1 -triple armv7-unknown-linux-gnueabihf %s -o - -emit-llvm -O2 | FileCheck %s
+
+// Stack should be reused when possible, no need to allocate two separate slots
+// if they have disjoint lifetime.
+
+// Sizes of objects are related to previously existed threshold of 32.  In case
+// of S_large stack size is rounded to 40 bytes.
+
+// 32B
+struct S_small {
+  int a[8];
+};
+
+// 36B
+struct S_large {
+  int a[9];
+};
+
+// Helper class for lifetime scope absence testing
+struct Combiner {
+  S_large a, b;
+
+  Combiner(S_large);
+  Combiner f();
+};
+
+extern S_small foo_small();
+extern S_large foo_large();
+extern void bar_small(S_small*);
+extern void bar_large(S_large*);
+
+// Prevent mangling of function names.
+extern "C" {
+
+void small_rvoed_unnamed_temporary_object() {
+// CHECK-LABEL: define void @small_rvoed_unnamed_temporary_object
+// CHECK: call void @llvm.lifetime.start
+// CHECK: call void @_Z9foo_smallv
+// CHECK: call void @llvm.lifetime.end
+// CHECK: call void @llvm.lifetime.start
+// CHECK: call void @_Z9foo_smallv
+// CHECK: call void @llvm.lifetime.end
+
+  foo_small();
+  foo_small();
+}
+
+void large_rvoed_unnamed_temporary_object() {
+// CHECK-LABEL: define void @large_rvoed_unnamed_temporary_object
+// CHECK: call void @llvm.lifetime.start
+// CHECK: call void @_Z9foo_largev
+// CHECK: call void @llvm.lifetime.end
+// CHECK: call void @llvm.lifetime.start
+// CHECK: call void @_Z9foo_largev
+// CHECK: call void @llvm.lifetime.end
+
+  foo_large();
+  foo_large();
+}
+
+void small_rvoed_named_temporary_object() {
+// CHECK-LABEL: define void @small_rvoed_named_temporary_object
+// CHECK: call void @llvm.lifetime.start
+// CHECK: call void @_Z9foo_smallv
+// CHECK: call void @llvm.lifetime.end
+// CHECK: call void @llvm.lifetime.start
+// CHECK: call void @_Z9foo_smallv
+// CHECK: call void @llvm.lifetime.end
+
+  {
+    S_small s = foo_small();
+  }
+  {
+    S_small s = foo_small();
+  }
+}
+
+void large_rvoed_named_temporary_object() {
+// CHECK-LABEL: define void @large_rvoed_named_temporary_object
+// CHECK: call void @llvm.lifetime.start
+// CHECK: call void @_Z9foo_largev
+// CHECK: call void @llvm.lifetime.end
+// CHECK: call void @llvm.lifetime.start
+// CHECK: call void @_Z9foo_largev
+// CHECK: call void @llvm.lifetime.end
+
+  {
+    S_large s = foo_large();
+  }
+  {
+    S_large s = foo_large();
+  }
+}
+
+void small_auto_object() {
+// CHECK-LABEL: define void @small_auto_object
+// CHECK: call void @llvm.lifetime.start
+// CHECK: call void @_Z9bar_smallP7S_small
+// CHECK: call void @llvm.lifetime.end
+// CHECK: call void @llvm.lifetime.start
+// CHECK: call void @_Z9bar_smallP7S_small
+// CHECK: call void @llvm.lifetime.end
+
+  {
+    S_small s;
+    bar_small(&s);
+  }
+  {
+    S_small s;
+    bar_small(&s);
+  }
+}
+
+void large_auto_object() {
+// CHECK-LABEL: define void @large_auto_object
+// CHECK: call void @llvm.lifetime.start
+// CHECK: call void @_Z9bar_largeP7S_large
+// CHECK: call void @llvm.lifetime.end
+// CHECK: call void @llvm.lifetime.start
+// CHECK: call void @_Z9bar_largeP7S_large
+// CHECK: call void @llvm.lifetime.end
+
+  {
+    S_large s;
+    bar_large(&s);
+  }
+  {
+    S_large s;
+    bar_large(&s);
+  }
+}
+
+int large_combiner_test(S_large s) {
+// CHECK-LABEL: define i32 @large_combiner_test
+// CHECK: [[T2:%.*]] = alloca %struct.Combiner
+// CHECK: [[T1:%.*]] = alloca %struct.Combiner
+// CHECK: [[T3:%.*]] = call %struct.Combiner* @_ZN8CombinerC1E7S_large(%struct.Combiner* nonnull [[T1]], [9 x i32] %s.coerce)
+// CHECK: call void @_ZN8Combiner1fEv(%struct.Combiner* nonnull sret [[T2]], %struct.Combiner* nonnull [[T1]])
+// CHECK: [[T4:%.*]] = getelementptr inbounds %struct.Combiner, %struct.Combiner* [[T2]], i32 0, i32 0, i32 0, i32 0
+// CHECK: [[T5:%.*]] = load i32, i32* [[T4]]
+// CHECK: ret i32 [[T5]]
+
+  return Combiner(s).f().a.a[0];
+}
+
+}