Fuse comparisons that are used by branches together.

runtime/vm/flow_graph_compiler_x64.h

Index: runtime/vm/flow_graph_compiler_x64.h
diff --git a/runtime/vm/flow_graph_compiler_x64.h b/runtime/vm/flow_graph_compiler_x64.h
index 1977ec07336d726a54bbda46da231062217e55e0..f6b8910412e125ab76718536a5794c3efffb57a5 100644
--- a/runtime/vm/flow_graph_compiler_x64.h
+++ b/runtime/vm/flow_graph_compiler_x64.h
@@ -167,6 +167,9 @@ class FlowGraphCompiler : public ValueObject {
   void FinalizeVarDescriptors(const Code& code);
   void FinalizeComments(const Code& code);
 
+  const Bool& bool_true() const { return bool_true_; }
+  const Bool& bool_false() const { return bool_false_; }
+
   static const int kLocalsOffsetFromFP = (-1 * kWordSize);
 
  private:
@@ -266,6 +269,9 @@ class FlowGraphCompiler : public ValueObject {
   GrowableArray<DeoptimizationStub*> deopt_stubs_;
   const bool is_optimizing_;
 
+  const Bool& bool_true_;
+  const Bool& bool_false_;
+
   DISALLOW_COPY_AND_ASSIGN(FlowGraphCompiler);
 };