[PATCH] Add verify_sese

[Tom de Vries <Tom_deVries at mentor dot com>]

Richard,

I ran into a problem with my oacc kernels directive patch series where 
tail-merge added another entry into a region that was previously 
single-entry-single-exit.

That resulted in hitting this assert in calc_dfs_tree:
...
  /* This aborts e.g. when there is _no_ path from ENTRY to EXIT at all.  */
  gcc_assert (di->nodes == (unsigned int) n_basic_blocks_for_fn (cfun) - 1);
...
during a call to move_sese_region_to_fn.

This patch makes sure that we abort earlier, with a clearer message of what is 
actually wrong.

Bootstrapped and reg-tested on x86_64.

OK for trunk/stage3?

Thanks,
- Tom

2014-11-23  Tom de Vries  <tom@codesourcery.com>

	* tree-cfg.c (verify_sese): New function.
	(move_sese_region_to_fn): Call verify_sese.
	* tree-cfg.h (verify_sese): Declare.
---
 gcc/tree-cfg.c | 55 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 gcc/tree-cfg.h |  1 +
 2 files changed, 56 insertions(+)

diff --git a/gcc/tree-cfg.c b/gcc/tree-cfg.c
index e78554f..db9f6c2 100644
--- a/gcc/tree-cfg.c
+++ b/gcc/tree-cfg.c
@@ -6870,6 +6870,58 @@ fixup_loop_arrays_after_move (struct function *fn1, struct function *fn2,
     fixup_loop_arrays_after_move (fn1, fn2, loop);
 }
 
+DEBUG_FUNCTION void
+verify_sese (basic_block entry, basic_block exit, vec<basic_block> *bbs_p)
+{
+  basic_block bb;
+  edge_iterator ei;
+  edge e;
+  bitmap bbs = BITMAP_ALLOC (NULL);
+  int i;
+
+  gcc_assert (entry != NULL);
+  gcc_assert (entry != exit);
+  gcc_assert (bbs_p != NULL);
+
+  gcc_assert (bbs_p->length () > 0);
+
+  FOR_EACH_VEC_ELT (*bbs_p, i, bb)
+    bitmap_set_bit (bbs, bb->index);
+
+  gcc_assert (bitmap_bit_p (bbs, entry->index));
+  gcc_assert (exit == NULL || bitmap_bit_p (bbs, exit->index));
+
+  FOR_EACH_VEC_ELT (*bbs_p, i, bb)
+    {
+      if (bb == entry)
+	{
+	  gcc_assert (single_pred_p (entry));
+	  gcc_assert (!bitmap_bit_p (bbs, single_pred (entry)->index));
+	}
+      else
+	for (ei = ei_start (bb->preds); !ei_end_p (ei); ei_next (&ei))
+	  {
+	    e = ei_edge (ei);
+	    gcc_assert (bitmap_bit_p (bbs, e->src->index));
+	  }
+
+      if (bb == exit)
+	{
+	  gcc_assert (single_succ_p (exit));
+	  gcc_assert (!bitmap_bit_p (bbs, single_succ (exit)->index));
+	}
+      else
+	for (ei = ei_start (bb->succs); !ei_end_p (ei); ei_next (&ei))
+	  {
+	    e = ei_edge (ei);
+	    gcc_assert (bitmap_bit_p (bbs, e->dest->index));
+	  }
+    }
+
+  BITMAP_FREE (bbs);
+}
+
+
 /* Move a single-entry, single-exit region delimited by ENTRY_BB and
    EXIT_BB to function DEST_CFUN.  The whole region is replaced by a
    single basic block in the original CFG and the new basic block is
@@ -6918,6 +6970,9 @@ move_sese_region_to_fn (struct function *dest_cfun, basic_block entry_bb,
   bbs.create (0);
   bbs.safe_push (entry_bb);
   gather_blocks_in_sese_region (entry_bb, exit_bb, &bbs);
+#ifdef ENABLE_CHECKING
+  verify_sese (entry_bb, exit_bb, &bbs);
+#endif
 
   /* The blocks that used to be dominated by something in BBS will now be
      dominated by the new block.  */
diff --git a/gcc/tree-cfg.h b/gcc/tree-cfg.h
index 626e973..d35e5ba 100644
--- a/gcc/tree-cfg.h
+++ b/gcc/tree-cfg.h
@@ -73,6 +73,7 @@ extern bool gimple_duplicate_sese_tail (edge, edge, basic_block *, unsigned,
 				      basic_block *);
 extern void gather_blocks_in_sese_region (basic_block entry, basic_block exit,
 					  vec<basic_block> *bbs_p);
+extern void verify_sese (basic_block, basic_block, vec<basic_block> *);
 extern basic_block move_sese_region_to_fn (struct function *, basic_block,
 				           basic_block, tree);
 extern void dump_function_to_file (tree, FILE *, int);
-- 
1.9.1