[PATCH] middle-end: Fix dominator information with loop duplication PR114197

[Edwin Lu]

When adding the new_preheader to the cfg, only the new_preheader's dominator
information is updated. If one of the new basic block's children was part
of the original cfg and adding new_preheader to the cfg introduces another path
to that child, the child's dominator information will not be updated. This may
cause verify_dominator's assertion to fail.

Force recalculating dominators for all duplicated basic blocks and their
successors when updating new_preheader's dominator information.

        PR 114197

gcc/ChangeLog:

        * tree-vect-loop-manip.cc (slpeel_tree_duplicate_loop_to_edge_cfg):
        Recalculate dominator info when adding new_preheader to cfg

gcc/testsuite/ChangeLog:

        * gcc.dg/vect/pr114197.c: New test.

Signed-off-by: Edwin Lu <e...@rivosinc.com>
---
 gcc/testsuite/gcc.dg/vect/pr114197.c | 18 ++++++++++++++++++
 gcc/tree-vect-loop-manip.cc          | 17 ++++++++++++++++-
 2 files changed, 34 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.dg/vect/pr114197.c

diff --git a/gcc/testsuite/gcc.dg/vect/pr114197.c 
b/gcc/testsuite/gcc.dg/vect/pr114197.c
new file mode 100644
index 00000000000..b1fb807729c
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/vect/pr114197.c
@@ -0,0 +1,18 @@
+/* { dg-do compile } */
+/* { dg-additional-options "-O3" } */
+
+
+#pragma pack(push)
+struct a {
+  volatile signed b : 8;
+};
+#pragma pack(pop)
+int c;
+static struct a d = {5};
+void e() {
+f:
+  for (c = 8; c < 55; ++c)
+    if (!d.b)
+      goto f;
+}
+
diff --git a/gcc/tree-vect-loop-manip.cc b/gcc/tree-vect-loop-manip.cc
index f72da915103..0f3a489e78c 100644
--- a/gcc/tree-vect-loop-manip.cc
+++ b/gcc/tree-vect-loop-manip.cc
@@ -1840,7 +1840,22 @@ slpeel_tree_duplicate_loop_to_edge_cfg (class loop 
*loop, edge loop_exit,
        }
 
       if (was_imm_dom || duplicate_outer_loop)
-       set_immediate_dominator (CDI_DOMINATORS, exit_dest, new_exit->src);
+       {
+         set_immediate_dominator (CDI_DOMINATORS, exit_dest, new_exit->src);
+
+         /* Update the dominator info for children of duplicated bbs.  */
+         for (unsigned i = 0; i < scalar_loop->num_nodes; i++)
+           {
+             basic_block dom_bb = NULL;
+             edge e;
+             edge_iterator ei;
+             FOR_EACH_EDGE (e, ei, new_bbs[i]->succs)
+               {
+                 dom_bb = recompute_dominator (CDI_DOMINATORS, e->dest);
+                 set_immediate_dominator (CDI_DOMINATORS, e->dest, dom_bb);
+               }
+           }
+       }
 
       /* And remove the non-necessary forwarder again.  Keep the other
          one so we have a proper pre-header for the loop at the exit edge.  */
-- 
2.34.1