Re: [PATCH 2/7] Do not query SCEV in range_of_phi unless dominators are available.

[Andrew MacLeod <amacleod@redhat.com>]

On 9/21/21 12:53 PM, Aldy Hernandez wrote:
> SCEV won't work without dominators and we can get called without
> dominators from debug_ranger.
>
> Another option would be to rename scev_initialized_p to something like
> scev_available_p and move the check there.  For now, this will do.
>
> Committed.
>
> gcc/ChangeLog:
>
> 	* gimple-range-fold.cc (fold_using_range::range_of_phi): Check
> 	dom_info_available_p.
> ---
>   gcc/gimple-range-fold.cc | 4 +++-
>   1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/gcc/gimple-range-fold.cc b/gcc/gimple-range-fold.cc
> index 997d02dd4b9..4dbf4188ec2 100644
> --- a/gcc/gimple-range-fold.cc
> +++ b/gcc/gimple-range-fold.cc
> @@ -781,7 +781,9 @@ fold_using_range::range_of_phi (irange &r, gphi *phi, fur_source &src)
>       }
>   
>     // If SCEV is available, query if this PHI has any knonwn values.
> -  if (scev_initialized_p () && !POINTER_TYPE_P (TREE_TYPE (phi_def)))
> +  if (dom_info_available_p (CDI_DOMINATORS)
> +      && scev_initialized_p ()
> +      && !POINTER_TYPE_P (TREE_TYPE (phi_def)))
>       {
>         value_range loop_range;
>         class loop *l = loop_containing_stmt (phi);

Im confused.. if scev doesn't work without dominators, how is 
scev_initialized_p() true if there are no dominators?     Are we 
initializing it somewhere without dominators?  Maybe there should be a 
check in the scev init routine?  seems like something else is amok.


void
scev_initialize (void)
{
   gcc_assert (! scev_initialized_p ());

   scalar_evolution_info = hash_table<scev_info_hasher>::create_ggc (100);

   for (auto loop : loops_list (cfun, 0))
     loop->nb_iterations = NULL_TREE;
}

/* Return true if SCEV is initialized.  */

bool
scev_initialized_p (void)
{
   return scalar_evolution_info != NULL;
}