[gcc r12-3758] Do not query SCEV in range_of_phi unless dominators are available.

[Aldy Hernandez <aldyh@gcc.gnu.org>]

https://gcc.gnu.org/g:64b80b8819f9ea74712625bceb0ec4388e25f67d

commit r12-3758-g64b80b8819f9ea74712625bceb0ec4388e25f67d
Author: Aldy Hernandez <aldyh@redhat.com>
Date:   Tue Sep 21 08:28:28 2021 +0200

    Do not query SCEV in range_of_phi unless dominators are available.
    
    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.
    
    gcc/ChangeLog:
    
            * gimple-range-fold.cc (fold_using_range::range_of_phi): Check
            dom_info_available_p.

Diff:
---
 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 80cc5c0dc0c..770a6c9b4da 100644
--- a/gcc/gimple-range-fold.cc
+++ b/gcc/gimple-range-fold.cc
@@ -814,7 +814,9 @@ 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);