Fix expand_builtin_atomic_fetch_op for pre-op (PR80902)

__atomic_add_fetch adds a value to some memory, and returns the result.
If there is no direct support for this, expand_builtin_atomic_fetch_op
is asked to implement this as __atomic_fetch_add (which returns the
original value of the mem), followed by the addition.  Now, the
__atomic_add_fetch could have been a tail call, but we shouldn't
perform the __atomic_fetch_add as a tail call: following code would
not be executed, and in fact thrown away because there is a barrier
after tail calls.

This fixes it.

	PR middle-end/80902
	* builtins.c (expand_builtin_atomic_fetch_op): If emitting code after
	a call, force the call to not be a tail call.

From-SVN: r249603

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 130fa37ad349b8098c5af293ed575ae466ff589e..ff2c7238ee662f81b2c0a26727a8f4d43ea27153 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2017-06-23  Segher Boessenkool  <segher@kernel.crashing.org>
+
+       PR middle-end/80902
+       * builtins.c (expand_builtin_atomic_fetch_op): If emitting code after
+       a call, force the call to not be a tail call.
+
 2017-06-23  Jeff Law  <law@redhat.com>
 
        * doc/contrib.texi: Add entry for Steven Pemberton's work on

diff --git a/gcc/builtins.c b/gcc/builtins.c
index ce657bf9e30a248e30abf8e3f71bee10bb2efe69..7e829ef1408c9b6feb5cc939c98dd77f9ca41995 100644 (file)
--- a/gcc/builtins.c
+++ b/gcc/builtins.c
@@ -6079,6 +6079,12 @@ expand_builtin_atomic_fetch_op (machine_mode mode, tree exp, rtx target,
   gcc_assert (TREE_OPERAND (addr, 0) == fndecl);
   TREE_OPERAND (addr, 0) = builtin_decl_explicit (ext_call);
 
+  /* If we will emit code after the call, the call can not be a tail call.
+     If it is emitted as a tail call, a barrier is emitted after it, and
+     then all trailing code is removed.  */
+  if (!ignore)
+    CALL_EXPR_TAILCALL (exp) = 0;
+
   /* Expand the call here so we can emit trailing code.  */
   ret = expand_call (exp, target, ignore);