re PR tree-optimization/57303 (struct miscompiled at -O1 and above)

2013-05-21  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/57303
	* tree-ssa-sink.c (statement_sink_location): Improve killing
	stmt detection and properly handle self-assignments.

	* gcc.dg/torture/pr57303.c: New testcase.

From-SVN: r199135

gcc/ChangeLog

+2013-05-21  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/57303
+	* tree-ssa-sink.c (statement_sink_location): Improve killing
+	stmt detection and properly handle self-assignments.
+
 2013-05-21  Christian Bruel  <christian.bruel@st.com>
 
         * dwarf2out.c (multiple_reg_loc_descriptor): Use dbx_reg_number for

gcc/testsuite/ChangeLog

+2013-05-21  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/57303
+	* gcc.dg/torture/pr57303.c: New testcase.
+
 2013-05-21  Jakub Jelinek  <jakub@redhat.com>
 
 	PR tree-optimization/57321

gcc/testsuite/gcc.dg/torture/pr57303.c

+/* { dg-do run } */
+
+void abort (void);
+
+struct S0
+{
+  int f0;
+};
+struct S1
+{
+  struct S0 f0;
+};
+
+struct S1 x = { {0} };
+struct S1 y = { {1} };
+
+static void
+foo (struct S0 p)
+{
+  struct S0 *l = &y.f0;
+  *l = x.f0;
+  if (p.f0)
+    *l = *l;
+}
+
+int
+main ()
+{
+  foo(y.f0);
+  if (y.f0.f0 != 0)
+    abort ();
+  return 0;
+}

gcc/tree-ssa-sink.c

@@ -331,11 +331,19 @@ statement_sink_location (gimple stmt, basic_block frombb,
 	  gimple use_stmt = USE_STMT (use_p);
 
 	  /* A killing definition is not a use.  */
-	  if (gimple_assign_single_p (use_stmt)
-	      && gimple_vdef (use_stmt)
-	      && operand_equal_p (gimple_assign_lhs (stmt),
-				  gimple_assign_lhs (use_stmt), 0))
-	    continue;
+	  if ((gimple_has_lhs (use_stmt)
+	       && operand_equal_p (gimple_assign_lhs (stmt),
+				   gimple_get_lhs (use_stmt), 0))
+	      || stmt_kills_ref_p (use_stmt, gimple_assign_lhs (stmt)))
+	    {
+	      /* If use_stmt is or might be a nop assignment then USE_STMT
+	         acts as a use as well as definition.  */
+	      if (stmt != use_stmt
+		  && ref_maybe_used_by_stmt_p (use_stmt,
+					       gimple_assign_lhs (stmt)))
+		return false;
+	      continue;
+	    }
 
 	  if (gimple_code (use_stmt) != GIMPLE_PHI)
 	    return false;