DBC: Add Smi fastpath to AssertAssignable

runtime/vm/flow_graph_compiler_dbc.cc

 // Copyright (c) 2016, 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_DBC.
 #if defined(TARGET_ARCH_DBC)
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/ast_printer.h"
@@ skipping 216 matching lines @@
   if (is_optimizing()) {
     __ Push(locs->in(0).reg());
     __ Push(locs->in(1).reg());
   }
   __ PushConstant(dst_type);
   __ PushConstant(dst_name);
 
   if (dst_type.IsMalformedOrMalbounded()) {
     __ BadTypeError();
   } else {
-    __ AssertAssignable(__ AddConstant(test_cache));
+    bool may_be_smi = false;
+    if (!dst_type.IsVoidType() && dst_type.IsInstantiated()) {
+      const Class& type_class = Class::Handle(zone(), dst_type.type_class());
+      if (type_class.NumTypeArguments() == 0) {
+        const Class& smi_class = Class::Handle(zone(), Smi::Class());
+        may_be_smi = smi_class.IsSubtypeOf(TypeArguments::Handle(zone()),
+                                           type_class,
+                                           TypeArguments::Handle(zone()),
+                                           NULL,
+                                           NULL,
+                                           Heap::kOld);
+      }
+    }
+    __ AssertAssignable(may_be_smi ? 1 : 0, __ AddConstant(test_cache));
   }
 
   if (is_optimizing()) {
     // Register allocator does not think that our first input (also used as
     // output) needs to be kept alive across the call because that is how code
     // is written on other platforms (where registers are always spilled across
     // the call): inputs are consumed by operation and output is produced so
     // neither are alive at the safepoint.
     // We have to mark the slot alive manually to ensure that GC
     // visits it.
@@ skipping 296 matching lines @@
 void ParallelMoveResolver::RestoreFpuScratch(FpuRegister reg) {
   UNIMPLEMENTED();
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_DBC