[gcc r15-851] Fix points-to SCC collapsing bug

[Richard Biener via Gcc-cvs]

https://gcc.gnu.org/g:07cdba6294756af350198fbb01ea8c8efeac54dd

commit r15-851-g07cdba6294756af350198fbb01ea8c8efeac54dd
Author: Richard Biener <rguent...@suse.de>
Date:   Mon May 27 13:50:14 2024 +0200

    Fix points-to SCC collapsing bug
    
    When points-to analysis finds SCCs it marks the wrong node as being
    part of a found cycle.  It only wants to mark the node it collapses
    to but marked the entry node found rather than the one it collapses
    to.  This causes fallout in the patch for PR115236 but generally
    weakens the points-to solution by collapsing too many nodes.  Note
    that this fix might slow down points-to solving.
    
            * tree-ssa-structalias.cc (scc_visit): Mark the node we
            collapse to as being in a component.

Diff:
---
 gcc/tree-ssa-structalias.cc | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/gcc/tree-ssa-structalias.cc b/gcc/tree-ssa-structalias.cc
index a39b36c146e..f93c5df0767 100644
--- a/gcc/tree-ssa-structalias.cc
+++ b/gcc/tree-ssa-structalias.cc
@@ -1534,8 +1534,10 @@ scc_visit (constraint_graph_t graph, class scc_info *si, 
unsigned int n)
                  graph->indirect_cycles[i - FIRST_REF_NODE] = lowest_node;
                }
            }
+         bitmap_set_bit (si->deleted, lowest_node);
        }
-      bitmap_set_bit (si->deleted, n);
+      else
+       bitmap_set_bit (si->deleted, n);
     }
   else
     si->scc_stack.safe_push (n);