tree-optimization/110298 - CFG cleanup and stale nb_iterations

When unrolling we eventually kill nb_iterations info since it may
refer to removed SSA names.  But we do this only after cleaning
up the CFG which in turn can end up accessing it.  Fixed by
swapping the two.

	PR tree-optimization/110298
	* tree-ssa-loop-ivcanon.cc (tree_unroll_loops_completely):
	Clear number of iterations info before cleaning up the CFG.

	* gcc.dg/torture/pr110298.c: New testcase.

(cherry picked from commit 916add3bf6e46467e4391e358b11ecfbc4daa275)

diff --git a/gcc/testsuite/gcc.dg/torture/pr110298.c b/gcc/testsuite/gcc.dg/torture/pr110298.c
new file mode 100644 (file)
index 0000000..139f5c7
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/torture/pr110298.c
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+
+int a, b, c, d, e;
+int f() {
+  c = 0;
+  for (; c >= 0; c--) {
+    d = 0;
+    for (; d <= 0; d++) {
+      e = 0;
+      for (; d + c + e >= 0; e--)
+        ;
+      a = 1;
+      b = 0;
+      for (; a; ++b)
+        a *= 2;
+      for (; b + d >= 0;)
+        return 0;
+    }
+  }
+}

diff --git a/gcc/tree-ssa-loop-ivcanon.cc b/gcc/tree-ssa-loop-ivcanon.cc
index ddc31a82fdc784658c3b4cd659fea2bce03457e0..9dc4ee4ca72b226e944bee9436c86de885ebfa7f 100644 (file)
--- a/gcc/tree-ssa-loop-ivcanon.cc
+++ b/gcc/tree-ssa-loop-ivcanon.cc
@@ -1486,15 +1486,16 @@ tree_unroll_loops_completely (bool may_increase_size, bool unroll_outer)
            }
          BITMAP_FREE (fathers);
 
+         /* Clean up the information about numbers of iterations, since
+            complete unrolling might have invalidated it.  */
+         scev_reset ();
+
          /* This will take care of removing completely unrolled loops
             from the loop structures so we can continue unrolling now
             innermost loops.  */
          if (cleanup_tree_cfg ())
            update_ssa (TODO_update_ssa_only_virtuals);
 
-         /* Clean up the information about numbers of iterations, since
-            complete unrolling might have invalidated it.  */
-         scev_reset ();
          if (flag_checking && loops_state_satisfies_p (LOOP_CLOSED_SSA))
            verify_loop_closed_ssa (true);
        }