dereference compare_term_test args down from stack (#3286, #3295)

src/machine/machine_state_impl.rs

@@ -557,6 +557,11 @@ impl MachineState {
     }
 
     pub fn compare_term_test(&self, h1: HeapCellValue, h2: HeapCellValue) -> Option<Ordering> {
+	// all derefs downstack from this function are heap bound so
+	// dereference stack vars pointing into the heap while possible
+	let h1 = self.store(h1);
+	let h2 = self.store(h2);
+
         for term_pair in ParallelHeapIter::from(self, h1, h2) {
             match term_pair {
                 TermPair::Vars(v1_offset, v2_offset) if v1_offset != v2_offset => {