[gcc r14-9460] gimple-iterator: Some gsi_safe_insert_*before fixes

[gcc r14-9460] gimple-iterator: Some gsi_safe_insert_*before fixes

[Jakub Jelinek]

https://gcc.gnu.org/g:8f6e0814b4bfd0a399055e9214562aebfcd902ad

commit r14-9460-g8f6e0814b4bfd0a399055e9214562aebfcd902ad
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Thu Mar 14 09:57:13 2024 +0100

    gimple-iterator: Some gsi_safe_insert_*before fixes
    
    When trying to use the gsi_safe_insert*before APIs in bitint lowering,
    I've discovered 3 issues and the following patch addresses those:
    
    1) both split_block and split_edge update CDI_DOMINATORS if they are
       available, but because edge_before_returns_twice_call first splits
       and then adds an extra EDGE_ABNORMAL edge and then removes another
       one, the immediate dominators of both the new bb and the bb with
       returns_twice call need to change
    2) the new EDGE_ABNORMAL edge had uninitialized probability; this patch
       copies the probability from the edge that is going to be removed
       and similarly copies other flags (EDGE_EXECUTABLE, EDGE_DFS_BACK,
       EDGE_IRREDUCIBLE_LOOP etc.)
    3) if edge_before_returns_twice_call splits a block, then the bb with
       returns_twice call changes, so the gimple_stmt_iterator for it is
       no longer accurate, it points to the right statement, but gsi_bb
       and gsi_seq are no longer correct; the patch updates it
    
    2024-03-14  Jakub Jelinek  <jakub@redhat.com>
    
            * gimple-iterator.cc (edge_before_returns_twice_call): Copy all
            flags and probability from ad_edge to e edge.  If CDI_DOMINATORS
            are computed, recompute immediate dominator of other_edge->src
            and other_edge->dest.
            (gsi_safe_insert_before, gsi_safe_insert_seq_before): Update *iter
            for the returns_twice call case to the gsi_for_stmt (stmt) to deal
            with update it for bb splitting.

Diff:
---
 gcc/gimple-iterator.cc | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/gcc/gimple-iterator.cc b/gcc/gimple-iterator.cc
index 531c8aed824..ac6cb4aa414 100644
--- a/gcc/gimple-iterator.cc
+++ b/gcc/gimple-iterator.cc
@@ -997,7 +997,18 @@ edge_before_returns_twice_call (basic_block bb)
 	  add_phi_arg (new_phi, gimple_phi_arg_def_from_edge (phi, ad_edge),
 		       e, gimple_phi_arg_location_from_edge (phi, ad_edge));
 	}
+      e->flags = ad_edge->flags;
+      e->probability = ad_edge->probability;
       remove_edge (ad_edge);
+      if (dom_info_available_p (CDI_DOMINATORS))
+	{
+	  set_immediate_dominator (CDI_DOMINATORS, other_edge->src,
+				   recompute_dominator (CDI_DOMINATORS,
+							other_edge->src));
+	  set_immediate_dominator (CDI_DOMINATORS, other_edge->dest,
+				   recompute_dominator (CDI_DOMINATORS,
+							other_edge->dest));
+	}
     }
   return other_edge;
 }
@@ -1045,6 +1056,7 @@ gsi_safe_insert_before (gimple_stmt_iterator *iter, gimple *g)
       if (new_bb)
 	e = single_succ_edge (new_bb);
       adjust_before_returns_twice_call (e, g);
+      *iter = gsi_for_stmt (stmt);
     }
   else
     gsi_insert_before (iter, g, GSI_SAME_STMT);
@@ -1075,6 +1087,7 @@ gsi_safe_insert_seq_before (gimple_stmt_iterator *iter, gimple_seq seq)
 	  if (g == l)
 	    break;
 	}
+      *iter = gsi_for_stmt (stmt);
     }
   else
     gsi_insert_seq_before (iter, seq, GSI_SAME_STMT);