Simplify and improve optimization of is-tests in the precompiler.

runtime/vm/flow_graph_range_analysis.cc

Index: runtime/vm/flow_graph_range_analysis.cc
diff --git a/runtime/vm/flow_graph_range_analysis.cc b/runtime/vm/flow_graph_range_analysis.cc
index 18eaa36036a44537afc2d8089b1d1fc26875b6cd..9b7eb8b510056fbc12c1074fc0f07a1d2a09c30f 100644
--- a/runtime/vm/flow_graph_range_analysis.cc
+++ b/runtime/vm/flow_graph_range_analysis.cc
@@ -1569,7 +1569,8 @@ void RangeAnalysis::MarkUnreachableBlocks() {
           target->PredecessorAt(0)->last_instruction()->AsBranch();
       if (target == branch->true_successor()) {
         // True unreachable.
-        if (FLAG_trace_constant_propagation) {
+        if (FLAG_trace_constant_propagation &&
+            FlowGraphPrinter::ShouldPrint(flow_graph_->function())) {
           THR_Print("Range analysis: True unreachable (B%" Pd ")\n",
                     branch->true_successor()->block_id());
         }
@@ -1577,7 +1578,8 @@ void RangeAnalysis::MarkUnreachableBlocks() {
       } else {
         ASSERT(target == branch->false_successor());
         // False unreachable.
-        if (FLAG_trace_constant_propagation) {
+        if (FLAG_trace_constant_propagation &&
+            FlowGraphPrinter::ShouldPrint(flow_graph_->function())) {
           THR_Print("Range analysis: False unreachable (B%" Pd ")\n",
                     branch->false_successor()->block_id());
         }