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

runtime/vm/constant_propagator.cc

Index: runtime/vm/constant_propagator.cc
diff --git a/runtime/vm/constant_propagator.cc b/runtime/vm/constant_propagator.cc
index 4409f3f274b783e9ed8cd91aa6babce1423402cb..6b97f7d20ce31f99b881c248d284f9334f42d15e 100644
--- a/runtime/vm/constant_propagator.cc
+++ b/runtime/vm/constant_propagator.cc
@@ -1514,8 +1514,9 @@ void ConstantPropagator::EliminateRedundantBranches() {
 
           changed = true;
 
-          if (FLAG_trace_constant_propagation) {
-            OS::Print("Eliminated branch in B%" Pd " common target B%" Pd "\n",
+          if (FLAG_trace_constant_propagation &&
+              FlowGraphPrinter::ShouldPrint(graph_->function())) {
+            THR_Print("Eliminated branch in B%" Pd " common target B%" Pd "\n",
                       block->block_id(), join->block_id());
           }
         }
@@ -1533,7 +1534,8 @@ void ConstantPropagator::EliminateRedundantBranches() {
 
 
 void ConstantPropagator::Transform() {
-  if (FLAG_trace_constant_propagation) {
+  if (FLAG_trace_constant_propagation &&
+      FlowGraphPrinter::ShouldPrint(graph_->function())) {
     FlowGraphPrinter::PrintGraph("Before CP", graph_);
   }
 
@@ -1546,8 +1548,9 @@ void ConstantPropagator::Transform() {
        b.Advance()) {
     BlockEntryInstr* block = b.Current();
     if (!reachable_->Contains(block->preorder_number())) {
-      if (FLAG_trace_constant_propagation) {
-        OS::Print("Unreachable B%" Pd "\n", block->block_id());
+      if (FLAG_trace_constant_propagation &&
+          FlowGraphPrinter::ShouldPrint(graph_->function())) {
+        THR_Print("Unreachable B%" Pd "\n", block->block_id());
       }
       // Remove all uses in unreachable blocks.
       block->ClearAllInstructions();
@@ -1618,8 +1621,9 @@ void ConstantPropagator::Transform() {
           !defn->IsStoreIndexed() &&
           !defn->IsStoreInstanceField() &&
           !defn->IsStoreStaticField()) {
-        if (FLAG_trace_constant_propagation) {
-          OS::Print("Constant v%" Pd " = %s\n",
+        if (FLAG_trace_constant_propagation &&
+            FlowGraphPrinter::ShouldPrint(graph_->function())) {
+          THR_Print("Constant v%" Pd " = %s\n",
                     defn->ssa_temp_index(),
                     defn->constant_value().ToCString());
         }
@@ -1681,7 +1685,8 @@ void ConstantPropagator::Transform() {
   GrowableArray<BitVector*> dominance_frontier;
   graph_->ComputeDominators(&dominance_frontier);
 
-  if (FLAG_trace_constant_propagation) {
+  if (FLAG_trace_constant_propagation &&
+      FlowGraphPrinter::ShouldPrint(graph_->function())) {
     FlowGraphPrinter::PrintGraph("After CP", graph_);
   }
 }