Add support for function attribute 'disable_tail_calls'.

The ``disable_tail_calls`` attribute instructs the backend to not
perform tail call optimization inside the marked function.

For example, 

int callee(int);

int foo(int a) __attribute__((disable_tail_calls)) {
  return callee(a); // This call is not tail-call optimized.
}

Note that this attribute is different from 'not_tail_called', which
prevents tail-call optimization to the marked function.

rdar://problem/8973573

Differential Revision: http://reviews.llvm.org/D12547


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@252986 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 13 insertions, 0 deletions

diff --git a/test/Sema/attr-disable-tail-calls.c b/test/Sema/attr-disable-tail-calls.c
new file mode 100644
index 0000000000..4574d5e0b6
--- /dev/null
+++ b/test/Sema/attr-disable-tail-calls.c
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 -fsyntax-only -verify %s
+
+void __attribute__((disable_tail_calls,naked)) foo1(int a) { // expected-error {{'disable_tail_calls' and 'naked' attributes are not compatible}} expected-note {{conflicting attribute is here}}
+  __asm__("");
+}
+
+void __attribute__((naked,disable_tail_calls)) foo2(int a) { // expected-error {{'naked' and 'disable_tail_calls' attributes are not compatible}} expected-note {{conflicting attribute is here}}
+  __asm__("");
+}
+
+int g0 __attribute__((disable_tail_calls)); // expected-warning {{'disable_tail_calls' attribute only applies to functions and methods}}
+
+int foo3(int a) __attribute__((disable_tail_calls("abc"))); // expected-error {{'disable_tail_calls' attribute takes no arguments}}