diff --git a/gcc/lra-constraints.c b/gcc/lra-constraints.c
index 05cb493852f..9205826960c 100644
--- a/gcc/lra-constraints.c
+++ b/gcc/lra-constraints.c
@@ -3459,7 +3459,7 @@ process_address_1 (int nop, bool check_only_p,
       constraint
 	= skip_contraint_modifiers (curr_static_id->operand[dup].constraint);
     }
-  cn = lookup_constraint (constraint);
+  cn = lookup_constraint (*constraint == '\0' ? "X" : constraint);
   if (insn_extra_address_constraint (cn)
       /* When we find an asm operand with an address constraint that
 	 doesn't satisfy address_operand to begin with, we clear
@@ -3475,9 +3475,8 @@ process_address_1 (int nop, bool check_only_p,
      i.e. bcst_mem_operand in i386 backend.  */
   else if (MEM_P (mem)
 	   && !(INSN_CODE (curr_insn) < 0
-		&& ((cn == CONSTRAINT__UNKNOWN && *constraint != 'g')
-		    || (get_constraint_type (cn) == CT_FIXED_FORM
-			&& constraint_satisfied_p (op, cn)))))
+		&& get_constraint_type (cn) == CT_FIXED_FORM
+		&& constraint_satisfied_p (op, cn)))
     decompose_mem_address (&ad, mem);
   else if (GET_CODE (op) == SUBREG
 	   && MEM_P (SUBREG_REG (op)))