PR c++/39786

[pf3gnuchains/gcc-fork.git] / gcc / tree-scalar-evolution.c

diff --git a/gcc/tree-scalar-evolution.c b/gcc/tree-scalar-evolution.c
index 02a4eed..70af0fd 100644 (file)
--- a/gcc/tree-scalar-evolution.c
+++ b/gcc/tree-scalar-evolution.c
@@ -1492,18 +1492,29 @@ analyze_evolution_in_loop (gimple loop_phi_node,
       bb = gimple_phi_arg_edge (loop_phi_node, i)->src;
       if (!flow_bb_inside_loop_p (loop, bb))
        continue;
-      
+
       if (TREE_CODE (arg) == SSA_NAME)
        {
+         bool val = false;
+
          ssa_chain = SSA_NAME_DEF_STMT (arg);
 
          /* Pass in the initial condition to the follow edge function.  */
          ev_fn = init_cond;
          res = follow_ssa_edge (loop, ssa_chain, loop_phi_node, &ev_fn, 0);
+
+         /* If ev_fn has no evolution in the inner loop, and the
+            init_cond is not equal to ev_fn, then we have an
+            ambiguity between two possible values, as we cannot know
+            the number of iterations at this point.  */
+         if (TREE_CODE (ev_fn) != POLYNOMIAL_CHREC
+             && no_evolution_in_loop_p (ev_fn, loop->num, &val) && val
+             && !operand_equal_p (init_cond, ev_fn, 0))
+           ev_fn = chrec_dont_know;
        }
       else
        res = t_false;
-             
+
       /* When it is impossible to go back on the same
         loop_phi_node by following the ssa edges, the
         evolution is represented by a peeled chrec, i.e. the