fix regression with MEM commoning

This fixes a regression when canonicalizing refs for LIM PR84362.
This possibly unshares and rewrites the refs in the internal data
and thus pointer equality no longer works in ref_always_accessed
computation.

2020-04-29  Richard Biener  <rguenther@suse.de>

	* tree-ssa-loop-im.c (ref_always_accessed::operator ()):
	Just check whether the stmt stores.

gcc/ChangeLog

+2020-04-29  Richard Biener  <rguenther@suse.de>
+
+	* tree-ssa-loop-im.c (ref_always_accessed::operator ()):
+	Just check whether the stmt stores.
+
 2020-04-28  Alexandre Oliva <oliva@adacore.com>
 
 	PR target/94812

gcc/tree-ssa-loop-im.c

@@ -2179,20 +2179,21 @@ ref_always_accessed::operator () (mem_ref_loc *loc)
 {
   class loop *must_exec;
 
-  if (!get_lim_data (loc->stmt))
+  struct lim_aux_data *lim_data = get_lim_data (loc->stmt);
+  if (!lim_data)
     return false;
 
   /* If we require an always executed store make sure the statement
-     stores to the reference.  */
+     is a store.  */
   if (stored_p)
     {
       tree lhs = gimple_get_lhs (loc->stmt);
       if (!lhs
-	  || lhs != *loc->ref)
+	  || !(DECL_P (lhs) || REFERENCE_CLASS_P (lhs)))
 	return false;
     }
 
-  must_exec = get_lim_data (loc->stmt)->always_executed_in;
+  must_exec = lim_data->always_executed_in;
   if (!must_exec)
     return false;