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.

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 6a962a9f5030794052e2846ad3ee7e72d29873bf..491b57ec0f1dc5bcff88535e8e5bf36609b3f43b 100644 (file)
--- a/gcc/tree-ssa-loop-ivcanon.cc
+++ b/gcc/tree-ssa-loop-ivcanon.cc
@@ -1520,15 +1520,16 @@ 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);
        }