[PATCH] tree-optimization/110298 - CFG cleanup and stale nb_iterations

[PATCH] tree-optimization/110298 - CFG cleanup and stale nb_iterations

[Richard Biener]

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.

Bootstrapped and tested on x86_64-unknown-linux-gnu, pushed.

	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.
---
 gcc/testsuite/gcc.dg/torture/pr110298.c | 20 ++++++++++++++++++++
 gcc/tree-ssa-loop-ivcanon.cc            |  7 ++++---
 2 files changed, 24 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/gcc.dg/torture/pr110298.c

diff --git a/gcc/testsuite/gcc.dg/torture/pr110298.c b/gcc/testsuite/gcc.dg/torture/pr110298.c
new file mode 100644
index 00000000000..139f5c77d89
--- /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 6a962a9f503..491b57ec0f1 100644
--- 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);
 	}
-- 
2.35.3