Revert "Void is not required to be `null` anymore."

runtime/vm/flow_graph_compiler_arm64.cc

 // Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_ARM64.
 #if defined(TARGET_ARCH_ARM64)
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/ast_printer.h"
@@ skipping 506 matching lines @@
 //   optional function type arguments in R2.
 // Note that this inlined code must be followed by the runtime_call code, as it
 // may fall through to it. Otherwise, this inline code will jump to the label
 // is_instance or to the label is_not_instance.
 RawSubtypeTestCache* FlowGraphCompiler::GenerateInlineInstanceof(
     TokenPosition token_pos,
     const AbstractType& type,
     Label* is_instance_lbl,
     Label* is_not_instance_lbl) {
   __ Comment("InlineInstanceof");
+  if (type.IsVoidType()) {
+    // A non-null value is returned from a void function, which will result in a
+    // type error. A null value is handled prior to executing this inline code.
+    return SubtypeTestCache::null();
+  }
   if (type.IsInstantiated()) {
     const Class& type_class = Class::ZoneHandle(zone(), type.type_class());
     // A class equality check is only applicable with a dst type (not a
     // function type) of a non-parameterized class or with a raw dst type of
     // a parameterized class.
     if (type.IsFunctionType() || (type_class.NumTypeArguments() > 0)) {
       return GenerateInstantiatedTypeWithArgumentsTest(
           token_pos, type, is_instance_lbl, is_not_instance_lbl);
       // Fall through to runtime call.
     }
@@ skipping 22 matching lines @@
 // - R0: object.
 // - R1: instantiator type arguments or raw_null.
 // - R2: function type arguments or raw_null.
 // Returns:
 // - true or false in R0.
 void FlowGraphCompiler::GenerateInstanceOf(TokenPosition token_pos,
                                            intptr_t deopt_id,
                                            const AbstractType& type,
                                            LocationSummary* locs) {
   ASSERT(type.IsFinalized() && !type.IsMalformed() && !type.IsMalbounded());
-  ASSERT(!type.IsObjectType() && !type.IsDynamicType() && !type.IsVoidType());
+  ASSERT(!type.IsObjectType() && !type.IsDynamicType());
   const Register kInstantiatorTypeArgumentsReg = R1;
   const Register kFunctionTypeArgumentsReg = R2;
   __ PushPair(kFunctionTypeArgumentsReg, kInstantiatorTypeArgumentsReg);
   Label is_instance, is_not_instance;
   // If type is instantiated and non-parameterized, we can inline code
   // checking whether the tested instance is a Smi.
   if (type.IsInstantiated()) {
     // A null object is only an instance of Null, Object, and dynamic.
     // Object and dynamic have already been checked above (if the type is
     // instantiated). So we can return false here if the instance is null,
@@ skipping 58 matching lines @@
 void FlowGraphCompiler::GenerateAssertAssignable(TokenPosition token_pos,
                                                  intptr_t deopt_id,
                                                  const AbstractType& dst_type,
                                                  const String& dst_name,
                                                  LocationSummary* locs) {
   ASSERT(!TokenPosition(token_pos).IsClassifying());
   ASSERT(!dst_type.IsNull());
   ASSERT(dst_type.IsFinalized());
   // Assignable check is skipped in FlowGraphBuilder, not here.
   ASSERT(dst_type.IsMalformedOrMalbounded() ||
-         (!dst_type.IsDynamicType() && !dst_type.IsObjectType() &&
-          !dst_type.IsVoidType()));
+         (!dst_type.IsDynamicType() && !dst_type.IsObjectType()));
+  const Register kInstantiatorTypeArgumentsReg = R1;
   const Register kFunctionTypeArgumentsReg = R2;
   __ PushPair(kFunctionTypeArgumentsReg, kInstantiatorTypeArgumentsReg);
   // A null object is always assignable and is returned as result.
   Label is_assignable, runtime_call;
   __ CompareObject(R0, Object::null_object());
   __ b(&is_assignable, EQ);
 
   // Generate throw new TypeError() if the type is malformed or malbounded.
   if (dst_type.IsMalformedOrMalbounded()) {
     __ PushObject(Object::null_object());  // Make room for the result.
@@ skipping 1111 matching lines @@
 void ParallelMoveResolver::RestoreFpuScratch(FpuRegister reg) {
   __ PopDouble(reg);
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64