Reland "VM: Improve single-target polymorphic calls."

runtime/vm/intermediate_language.h

Index: runtime/vm/intermediate_language.h
diff --git a/runtime/vm/intermediate_language.h b/runtime/vm/intermediate_language.h
index b0705d4e801c76cdb841e1f82c4d87130a752500..392993ed13773f54af4fc1a504e24e0e52b8d868 100644
--- a/runtime/vm/intermediate_language.h
+++ b/runtime/vm/intermediate_language.h
@@ -7805,6 +7805,7 @@ class CheckClassInstr : public TemplateInstruction<1, NoThrow> {
   bool DeoptIfNotNull() const;
 
   bool IsDenseSwitch() const;
+  static bool IsDenseCidRange(const ICData& unary_checks);
   intptr_t ComputeCidMask() const;
   static bool IsDenseMask(intptr_t mask);
 
@@ -7823,6 +7824,7 @@ class CheckClassInstr : public TemplateInstruction<1, NoThrow> {
   const ICData& unary_checks_;
   GrowableArray<intptr_t> cids_;  // Sorted, lowest first.
   bool licm_hoisted_;
+  bool is_dense_switch_;
   const TokenPosition token_pos_;
 
   DISALLOW_COPY_AND_ASSIGN(CheckClassInstr);