2010-07-26 Richard Guenther <rguenther@suse.de>

	PR tree-optimization/43784
	* tree-nrv.c (dest_safe_for_nrv_p): It's not safe to NRV
	if the destination is used by the call.

	* gcc.c-torture/execute/pr43784.c: New testcase.
	* g++.dg/torture/pr43784.C: Likewise.


git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@162539 138bc75d-0d04-0410-961f-82ee72b054a4

5 files changed, 73 insertions, 4 deletions

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 66a86e5c731..93d0c7ea091 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,5 +1,11 @@
 2010-07-26  Richard Guenther  <rguenther@suse.de>
 
+	PR tree-optimization/43784
+	* tree-nrv.c (dest_safe_for_nrv_p): It's not safe to NRV
+	if the destination is used by the call.
+
+2010-07-26  Richard Guenther  <rguenther@suse.de>
+
 	PR middle-end/45073
 	* gimple-fold.c (gimplify_and_update_call_from_tree): Conditionalize
 	SSA updating on being in SSA form.
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 52d94d2166d..cd7de607c77 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,5 +1,11 @@
 2010-07-26  Richard Guenther  <rguenther@suse.de>
 
+	PR tree-optimization/43784
+	* gcc.c-torture/execute/pr43784.c: New testcase.
+	* g++.dg/torture/pr43784.C: Likewise.
+
+2010-07-26  Richard Guenther  <rguenther@suse.de>
+
 	PR middle-end/45056
 	* g++.dg/pr45056.C: New testcase.
 
diff --git a/gcc/testsuite/g++.dg/torture/pr43784.C b/gcc/testsuite/g++.dg/torture/pr43784.C
new file mode 100644
index 00000000000..a83a6f374d7
--- /dev/null
+++ b/gcc/testsuite/g++.dg/torture/pr43784.C
@@ -0,0 +1,24 @@
+/* { dg-do run } */
+/* { dg-options "-fno-tree-sra" } */
+
+struct S {int x, y, makemelarge[5];};
+S __attribute__((noinline)) f (S &s) {
+    S r;
+    r.x = s.y;
+    r.y = s.x;
+    return r;
+}
+int __attribute__((noinline)) glob (int a, int b)
+{
+  S local = { a, b };
+  local = f (local);
+  return local.y;
+}
+extern "C" void abort (void);
+int main (void)
+{
+  if (glob (1, 3) != 1)
+    abort ();
+  return 0;
+}
+
diff --git a/gcc/testsuite/gcc.c-torture/execute/pr43784.c b/gcc/testsuite/gcc.c-torture/execute/pr43784.c
new file mode 100644
index 00000000000..622232725a2
--- /dev/null
+++ b/gcc/testsuite/gcc.c-torture/execute/pr43784.c
@@ -0,0 +1,33 @@
+struct s {
+  unsigned char a[256];
+};
+union u {
+  struct { struct s b; int c; } d;
+  struct { int c; struct s b; } e;
+};
+
+static union u v;
+static struct s *p = &v.d.b;
+static struct s *q = &v.e.b;
+
+static struct s __attribute__((noinline)) rp(void)
+{
+  return *p;
+}
+
+static void qp(void)
+{
+  *q = rp();
+}
+
+int main()
+{
+  int i;
+  for (i = 0; i < 256; i++)
+    p->a[i] = i;
+  qp();
+  for (i = 0; i < 256; i++)
+    if (q->a[i] != i)
+      __builtin_abort();
+  return 0;
+}
diff --git a/gcc/tree-nrv.c b/gcc/tree-nrv.c
index 2f40d563d33..8ee3b8b0a4b 100644
--- a/gcc/tree-nrv.c
+++ b/gcc/tree-nrv.c
@@ -296,7 +296,7 @@ struct gimple_opt_pass pass_nrv =
    optimization, where DEST is expected to be the LHS of a modify
    expression where the RHS is a function returning an aggregate.
 
-   DEST is available if it is not clobbered by the call.  */
+   DEST is available if it is not clobbered or used by the call.  */
 
 static bool
 dest_safe_for_nrv_p (gimple call)
@@ -310,7 +310,8 @@ dest_safe_for_nrv_p (gimple call)
   if (TREE_CODE (dest) == SSA_NAME)
     return true;
 
-  if (call_may_clobber_ref_p (call, dest))
+  if (call_may_clobber_ref_p (call, dest)
+      || ref_maybe_used_by_stmt_p (call, dest))
     return false;
 
   return true;
@@ -345,8 +346,7 @@ execute_return_slot_opt (void)
 	      && gimple_call_lhs (stmt)
 	      && !gimple_call_return_slot_opt_p (stmt)
 	      && aggregate_value_p (TREE_TYPE (gimple_call_lhs (stmt)),
-				    gimple_call_fndecl (stmt))
-	     )
+				    gimple_call_fndecl (stmt)))
 	    {
 	      /* Check if the location being assigned to is
 	         clobbered by the call.  */