Add support for function attribute 'not_tail_called'.

This attribute is used to prevent tail-call optimizations to the marked
function. For example, in the following piece of code, foo1 will not be
tail-call optimized: 

int __attribute__((not_tail_called)) foo1(int);

int foo2(int a) {
  return foo1(a); // Tail-call optimization is not performed.
}

The attribute has effect only on statically bound calls. It has no
effect on indirect calls. Also, virtual functions and objective-c
methods cannot be marked as 'not_tail_called'.

rdar://problem/22667622

Differential Revision: http://reviews.llvm.org/D12922

llvm-svn: 252369

1 files changed, 16 insertions, 0 deletions

diff --git a/clang/test/SemaCXX/attr-notail.cpp b/clang/test/SemaCXX/attr-notail.cpp
new file mode 100644
index 00000000000..2f39746dc85
--- /dev/null
+++ b/clang/test/SemaCXX/attr-notail.cpp
@@ -0,0 +1,16 @@
+// RUN: %clang_cc1 -std=c++11 -fsyntax-only -verify %s
+
+class Base {
+public:
+  [[clang::not_tail_called]] virtual int foo1(); // expected-error {{'not_tail_called' attribute cannot be applied to virtual functions}}
+  virtual int foo2();
+  [[clang::not_tail_called]] int foo3();
+  virtual ~Base() {}
+};
+
+class Derived1 : public Base {
+public:
+  int foo1() override;
+  [[clang::not_tail_called]] int foo2() override; // expected-error {{'not_tail_called' attribute cannot be applied to virtual functions}}
+  [[clang::not_tail_called]] int foo4();
+};