Revert "VM: Simplify lowering of is-tests."

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 e7b7db1bb2b01f043bd7b929081d3cbc79c681c4..fc44e42addfe8a39128cfd3d1c1c68801d0d214d 100644
--- a/runtime/vm/flow_graph_compiler_x64.cc
+++ b/runtime/vm/flow_graph_compiler_x64.cc
@@ -556,6 +556,7 @@ RawSubtypeTestCache* FlowGraphCompiler::GenerateInlineInstanceof(
 void FlowGraphCompiler::GenerateInstanceOf(TokenPosition token_pos,
                                            intptr_t deopt_id,
                                            const AbstractType& type,
+                                           bool negate_result,
                                            LocationSummary* locs) {
   ASSERT(type.IsFinalized() && !type.IsMalformedOrMalbounded());
   ASSERT(!type.IsObjectType() && !type.IsDynamicType());
@@ -596,15 +597,23 @@ void FlowGraphCompiler::GenerateInstanceOf(TokenPosition token_pos,
     // Pop the parameters supplied to the runtime entry. The result of the
     // instanceof runtime call will be left as the result of the operation.
     __ Drop(4);
-    __ popq(RAX);
+    if (negate_result) {
+      __ popq(RDX);
+      __ LoadObject(RAX, Bool::True());
+      __ cmpq(RDX, RAX);
+      __ j(NOT_EQUAL, &done, Assembler::kNearJump);
+      __ LoadObject(RAX, Bool::False());
+    } else {
+      __ popq(RAX);
+    }
     __ jmp(&done, Assembler::kNearJump);
   }
   __ Bind(&is_not_instance);
-  __ LoadObject(RAX, Bool::Get(false));
+  __ LoadObject(RAX, Bool::Get(negate_result));
   __ jmp(&done, Assembler::kNearJump);
 
   __ Bind(&is_instance);
-  __ LoadObject(RAX, Bool::Get(true));
+  __ LoadObject(RAX, Bool::Get(!negate_result));
   __ Bind(&done);
   __ popq(RDX);  // Remove pushed instantiator type arguments.
 }