Fix the eviction of a congruence class in the case a complete eviction is requested.

Change-Id: I4e88f87b661c19863f4ca7b0dc3239ca7b994e2a

Author: ktrifunovic

IGC/Compiler/CISACodeGen/CoalescingEngine.cpp

@@ -727,6 +727,14 @@ void CoalescingEngine::PrepareInsertionSlot(
             }
             NewParent = ImmediateDominatingParent[NewParent];
         }
+
+        //it might turn out, that rootNode does not dominate 'inst'
+        //since it is in another branch of DT
+        //do not forget to delete it as well
+        if (getRegRoot(RootNode->value)) {
+            isolateReg(RootNode->value);
+        }
+
     } else {
         //Evict dominating parent from CC.
         Value* NewParent = GetActualDominatingParent(RootNode->value, inst);