re PR tree-optimization/60902 (ffmpeg built with gcc 4.9 RC produces incorrect flac playback code)

	PR tree-optimization/60902
	* tree-ssa-threadedge.c
	(record_temporary_equivalences_from_stmts_at_dest): Make sure to
	invalidate outputs from statements that do not produce useful
	outputs for threading.

	PR tree-optimization/60902
	* gcc.target/i386/pr60902.c: New test.

From-SVN: r209716

gcc/ChangeLog

+2014-04-23  Jeff Law  <law@redhat.com>
+
+	PR tree-optimization/60902
+	* tree-ssa-threadedge.c
+	(record_temporary_equivalences_from_stmts_at_dest): Make sure to
+	invalidate outputs from statements that do not produce useful
+	outputs for threading.
+
 2014-04-23 Venkataramanan Kumar  <venkataramanan.kumar@linaro.org>
 
 	* config/aarch64/aarch64.md (stack_protect_set, stack_protect_test)

gcc/testsuite/ChangeLog

+2014-04-23  Jeff Law  <law@redhat.com>
+
+	PR tree-optimization/60902
+	* gcc.target/i386/pr60902.c: New test.
+
 2014-04-23  Alex Velenko  <Alex.Velenko@arm.com>
 
 	* gcc.target/aarch64/vdup_lane_1.c: New testcase.

gcc/testsuite/gcc.target/i386/pr60902.c

+/* { dg-do run } */
+/* { dg-options "-O2" } */
+extern void abort ();
+extern void exit (int);
+
+int x;
+
+foo()
+{
+  static int count;
+  count++;
+  if (count > 1)
+    abort ();
+}
+
+static inline int
+frob ()
+{
+  int a;
+  __asm__ ("mov %1, %0\n\t" : "=r" (a) : "m" (x));
+  x++;
+  return a;
+}
+
+int
+main ()
+{
+  int i;
+  for (i = 0; i < 10 && frob () == 0; i++)
+    foo();
+  exit (0);
+}

gcc/tree-ssa-threadedge.c

@@ -387,7 +387,34 @@ record_temporary_equivalences_from_stmts_at_dest (edge e,
           && (gimple_code (stmt) != GIMPLE_CALL
               || gimple_call_lhs (stmt) == NULL_TREE
               || TREE_CODE (gimple_call_lhs (stmt)) != SSA_NAME))
-	continue;
+	{
+	  /* STMT might still have DEFS and we need to invalidate any known
+	     equivalences for them.
+
+	     Consider if STMT is a GIMPLE_ASM with one or more outputs that
+	     feeds a conditional inside a loop.  We might derive an equivalence
+	     due to the conditional.  */
+	  tree op;
+	  ssa_op_iter iter;
+
+	  if (backedge_seen)
+	    FOR_EACH_SSA_TREE_OPERAND (op, stmt, iter, SSA_OP_ALL_DEFS)
+	      {
+		/* This call only invalidates equivalences created by
+		   PHI nodes.  This is by design to keep the cost of
+		   of invalidation reasonable.  */
+		invalidate_equivalences (op, stack, src_map, dst_map);
+
+		/* However, conditionals can imply values for real
+		   operands as well.  And those won't be recorded in the
+		   maps.  In fact, those equivalences may be recorded totally
+		   outside the threading code.  We can just create a new
+		   temporary NULL equivalence here.  */
+	        record_temporary_equivalence (op, NULL_TREE, stack);
+	      }
+
+	  continue;
+	}
 
       /* The result of __builtin_object_size depends on all the arguments
 	 of a phi node. Temporarily using only one edge produces invalid