[Bug tree-optimization/108819] [12/13 Regression] ICE on valid code at -O1 with "-fno-tree-ccp -fno-tree-forwprop" on x86_64-linux-gnu: tree check: expected ssa_name, have integer_cst in number_of_iterations_cltz, at tree-ssa-loop-niter.cc:2394

["jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108819

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #3)
> --- a/gcc/tree-ssa-reassoc.cc
> +++ b/gcc/tree-ssa-reassoc.cc
> @@ -2950,6 +2950,9 @@ update_range_test (struct range_entry *range, struct
> range_entry *otherrange,
>      }
>    if (stmt == NULL)
>      gcc_checking_assert (tem == op);
> +  /* When range->exp is a constant, we can use it as-is.  */
> +  else if (is_gimple_min_invariant (tem))
> +    ;
>    /* In rare cases range->exp can be equal to lhs of stmt.
>       In that case we have to insert after the stmt rather then before
>       it.  If stmt is a PHI, insert it at the start of the basic block.  */

That would make things worse, not better (i.e. constants could appear more
often and we could trigger these problems more often), no?
forwprop/ccp etc. should optimize it later...

I wonder if we just can't do:
--- gcc/tree-ssa-reassoc.cc.jj  2023-02-16 10:41:11.000000000 +0100
+++ gcc/tree-ssa-reassoc.cc     2023-02-17 17:43:52.169452832 +0100
@@ -4687,6 +4687,8 @@ update_ops (tree var, enum tree_code cod
       gimple_set_uid (g, gimple_uid (stmt));
       gimple_set_visited (g, true);
       gsi_insert_before (&gsi, g, GSI_SAME_STMT);
+      gimple_stmt_iterator gsi2 = gsi_for_stmt (g);
+      fold_stmt_inplace (&gsi2);
     }
   return var;
 }
or if the in-place folding wouldn't be appropriate, at least fold it by hand if
both arguments are constants.  Though, there is also the case of commutative
ops and just the first one turned into constant etc.