[Bug tree-optimization/107828] New: tree-inlining would generate SSA with incorrect def stmt

[fxue at os dot amperecomputing.com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107828

            Bug ID: 107828
           Summary: tree-inlining would generate SSA with incorrect def
                    stmt
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: tree-optimization
          Assignee: unassigned at gcc dot gnu.org
          Reporter: fxue at os dot amperecomputing.com
  Target Milestone: ---

In the function "remap_gimple_op_r" of tree-inlining.cc:

  ...

  if (TREE_CODE (*tp) == SSA_NAME)
    {
      *tp = remap_ssa_name (*tp, id);
      *walk_subtrees = 0;
      if (is_lhs)
         SSA_NAME_DEF_STMT (*tp) = wi_p->stmt;
      return NULL;
    }

The definition statement of original "*tp" may be same as wi_p->stmt. So, we
will end up with a statement that it is pointed by both old and new SSA name,
while the old one should have been reclaimed.

And this happens when some parameter needs to be adjusted during inline
versioning as:

remap_gimple_stmt()

{
  ...
  if (id->param_body_adjs)
    {
      ...
      if (!gimple_seq_empty_p (extra_stmts))
        {
          memset (&wi, 0, sizeof (wi));
          wi.info = id;
          for (gimple_stmt_iterator egsi = gsi_start (extra_stmts);
               !gsi_end_p (egsi);
               gsi_next (&egsi))
            walk_gimple_op (gsi_stmt (egsi), remap_gimple_op_r, &wi);
                                             ^^^^^^^^^^^^^^^^^

            ...
        }
    }
   ...
}