VM: Better code for is-checks and checked mode checks with simple types

runtime/vm/flow_graph_compiler_x64.cc

Index: runtime/vm/flow_graph_compiler_x64.cc
diff --git a/runtime/vm/flow_graph_compiler_x64.cc b/runtime/vm/flow_graph_compiler_x64.cc
index 9118bb12d6e5b3b0ccbd968d7ba376858e670b7c..6cd1301c37b47bd4e7151b144aa0a23e80e765fd 100644
--- a/runtime/vm/flow_graph_compiler_x64.cc
+++ b/runtime/vm/flow_graph_compiler_x64.cc
@@ -387,11 +387,8 @@ bool FlowGraphCompiler::GenerateInstantiatedTypeNoArgumentsTest(
   } else {
     __ j(ZERO, is_not_instance_lbl);
   }
-  // Compare if the classes are equal.
   const Register kClassIdReg = R10;
   __ LoadClassId(kClassIdReg, kInstanceReg);
-  __ cmpl(kClassIdReg, Immediate(type_class.id()));
-  __ j(EQUAL, is_instance_lbl);
   // See ClassFinalizer::ResolveSuperTypeAndInterfaces for list of restricted
   // interfaces.
   // Bool interface can be implemented only by core class Bool.
@@ -401,11 +398,6 @@ bool FlowGraphCompiler::GenerateInstantiatedTypeNoArgumentsTest(
     __ jmp(is_not_instance_lbl);
     return false;
   }
-  if (type.IsDartFunctionType()) {
-    // Check if instance is a closure.
-    __ cmpq(kClassIdReg, Immediate(kClosureCid));
-    __ j(EQUAL, is_instance_lbl);
-  }
   // Custom checking for numbers (Smi, Mint, Bigint and Double).
   // Note that instance is not Smi (checked above).
   if (type.IsSubtypeOf(
@@ -418,6 +410,17 @@ bool FlowGraphCompiler::GenerateInstantiatedTypeNoArgumentsTest(
     GenerateStringTypeCheck(kClassIdReg, is_instance_lbl, is_not_instance_lbl);
     return false;
   }
+  if (type.IsDartFunctionType()) {
+    // Check if instance is a closure.
+    __ cmpq(kClassIdReg, Immediate(kClosureCid));
+    __ j(EQUAL, is_instance_lbl);
+    return true;
+  }
+  // Compare if the classes are equal.
+  if (!type_class.is_abstract()) {
+    __ cmpl(kClassIdReg, Immediate(type_class.id()));
+    __ j(EQUAL, is_instance_lbl);
+  }
   // Otherwise fallthrough.
   return true;
 }