[PATCH] Don't ignore failures from compute_data_dependences_for_loop in build_rdg (PR tree-optimization/52835)

[Jakub Jelinek]

Hi!

On the following testcase compute_data_dependences_for_loop
fails, but build_rdg ignores its return value and happily goes
on as if it didn't fail, optimizing away a call.

Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux,
ok for trunk/4.7?

2012-04-02  Jakub Jelinek  <ja...@redhat.com>

        PR tree-optimization/52835
        * tree-data-ref.c (build_rdg): Return NULL if
        compute_data_dependences_for_loop failed.

        * gfortran.dg/pr52835.f90: New test.

--- gcc/tree-data-ref.c.jj      2012-03-20 08:51:32.000000000 +0100
+++ gcc/tree-data-ref.c 2012-04-02 21:30:13.783378347 +0200
@@ -5129,20 +5129,19 @@ build_rdg (struct loop *loop,
           VEC (data_reference_p, heap) **datarefs)
 {
   struct graph *rdg = NULL;
-  VEC (gimple, heap) *stmts = VEC_alloc (gimple, heap, 10);
 
-  compute_data_dependences_for_loop (loop, false, loop_nest, datarefs,
-                                    dependence_relations);
-
-  if (known_dependences_p (*dependence_relations))
+  if (compute_data_dependences_for_loop (loop, false, loop_nest, datarefs,
+                                        dependence_relations)
+      && known_dependences_p (*dependence_relations))
     {
+      VEC (gimple, heap) *stmts = VEC_alloc (gimple, heap, 10);
       stmts_from_loop (loop, &stmts);
       rdg = build_empty_rdg (VEC_length (gimple, stmts));
       create_rdg_vertices (rdg, stmts);
       create_rdg_edges (rdg, *dependence_relations);
+      VEC_free (gimple, heap, stmts);
     }
 
-  VEC_free (gimple, heap, stmts);
   return rdg;
 }
 
--- gcc/testsuite/gfortran.dg/pr52835.f90.jj    2012-04-02 21:35:42.616505464 
+0200
+++ gcc/testsuite/gfortran.dg/pr52835.f90       2012-04-02 21:35:08.000000000 
+0200
@@ -0,0 +1,16 @@
+! PR tree-optimization/52835
+! { dg-do compile }
+! { dg-options "-O3 -fdump-tree-optimized" }
+
+subroutine foo (x, y, z, n)
+  integer :: n, i
+  real :: x(n), y(n), z(n)
+  do i = 1, n
+    z(i) = 0.0
+    y(i) = 0.0
+    call bar (y(i), z(i), x(i))
+  end do
+end subroutine
+
+! { dg-final { scan-tree-dump "bar " "optimized" } }
+! { dg-final { cleanup-tree-dump "optimized" } }

        Jakub