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

["fxue at os dot amperecomputing.com" <gcc-bugzilla@gcc.gnu.org>]

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

Feng Xue <fxue at os dot amperecomputing.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|INVALID                     |---
             Status|RESOLVED                    |WAITING

--- Comment #4 from Feng Xue <fxue at os dot amperecomputing.com> ---
(In reply to Martin Jambor from comment #2)
> I don't see any correctness issue here.  It is true that when IPA-SRA
> needs to create a temporary SSA_NAME for an assignment with
> VIEW_CONVERT_EXPR (that is the only statement that extra_stmts can
> contain at the moment), the SSA_NAME then get's re-mapped to another
> while woe could have just re-use the existing one, it is already
> created within the new function.
> 
> We could use the knowledge that extra_stmts is really only this one
> statement or nothing and avoid the remapping but that would be at the
> expense of universality and extensibility of the interface between
> tree-inline.cc and ipa-param-manipulations.cc.
> 
> Please let me know if I am missing something (and preferably with a
> test-case that demonstrates the problem).

Sorry for late response.

It is hard to compose a simple test case, since this could only be exposed with
our own private code. To reproduce it is not that straightforward, but we could
forcefully do that with a minor change to
"ipa_param_body_adjustments::modify_assignment" in ipa-param-manipulation.cc.

diff --git a/gcc/ipa-param-manipulation.cc b/gcc/ipa-param-manipulation.cc
index cee0e23f946..202c0fda32b 100644
--- a/gcc/ipa-param-manipulation.cc
+++ b/gcc/ipa-param-manipulation.cc
@@ -1787,7 +1787,7 @@ ipa_param_body_adjustments::modify_assignment (gimple
*stmt,
   any = modify_expression (lhs_p, false);
   any |= modify_expression (rhs_p, false);
   if (any
-      && !useless_type_conversion_p (TREE_TYPE (*lhs_p), TREE_TYPE (*rhs_p)))
+      && true /* !useless_type_conversion_p (TREE_TYPE (*lhs_p), TREE_TYPE
(*rhs_p)) */)
     {
       if (TREE_CODE (*rhs_p) == CONSTRUCTOR)
        {
@@ -1805,7 +1805,14 @@ ipa_param_body_adjustments::modify_assignment (gimple
*stmt,
                                          *rhs_p);
          tree tmp = force_gimple_operand (new_rhs, extra_stmts, true,
                                           NULL_TREE);
-         gimple_assign_set_rhs1 (stmt, tmp);
+
+         tree tmp1 = make_ssa_name (tmp);
+         gimple *copy = gimple_build_assign (tmp1, tmp);
+
+         auto gsi = gsi_last (*extra_stmts);
+         gsi_insert_after_without_update (&gsi, copy, GSI_NEW_STMT);
+
+         gimple_assign_set_rhs1 (stmt, tmp1);
        }
       return true;
     }

The purpose of above code piece is to add trivial ssa copy statement to make
the below "extra_stmts" not empty:

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);
                                             ^^^^^^^^^^^^^^^^^

            ...
        }
    }
   ...
}

Now, we use the case gcc.dg/ipa/ipa-sra-1.c, and option is "-O3 -flto
-fipa-sra". Trace into "remap_gimple_op_r" as above, check remapping on copy:

<&0x7ffff6c282d0> ISRA.0_1 = ISRA.0;

A new SSA name "ISRA.0_2" is created, after setting definition statement for it
via:


  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;
    }

Here, both "ISRA.0_1" and "ISRA.O_2" belong to same function, and point to same
def stmt.