Skip AssertAssignable in code generator if optimizer could establish that

runtime/vm/flow_graph_compiler_ia32.cc

 // Copyright (c) 2013, 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_IA32.
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/ast_printer.h"
@@ skipping 645 matching lines @@
 // Performance notes: positive checks must be quick, negative checks can be slow
 // as they throw an exception.
 void FlowGraphCompiler::GenerateAssertAssignable(intptr_t token_pos,
                                                  intptr_t deopt_id,
                                                  const AbstractType& dst_type,
                                                  const String& dst_name,
                                                  LocationSummary* locs) {
   ASSERT(token_pos >= 0);
   ASSERT(!dst_type.IsNull());
   ASSERT(dst_type.IsFinalized());
-  // Assignable check is skipped in FlowGraphBuilder, not here.
-  ASSERT(dst_type.IsMalformed() || dst_type.IsMalbounded() ||
-         (!dst_type.IsDynamicType() && !dst_type.IsObjectType()));
+  // Assignable check is skipped in FlowGraphBuilder, when possible.
+  // The optimizer may have instantiated dst_type to dynamic or Object.
+  if (!dst_type.IsMalformed() && !dst_type.IsMalbounded() &&
+      (dst_type.IsDynamicType() || dst_type.IsObjectType())) {
+    return;
+  }

[srdjan, 2013/10/03 18:00:09]

This elimination belongs in AssertAssignableInstr::Canonicalize:

if (.....) {
  return value()->definition()
}

[regis, 2013/10/03 18:20:53]

Done.

   __ pushl(ECX);  // Store instantiator.
   __ pushl(EDX);  // Store instantiator type arguments.
   // A null object is always assignable and is returned as result.
   const Immediate& raw_null =
       Immediate(reinterpret_cast<intptr_t>(Object::null()));
   Label is_assignable, runtime_call;
   __ cmpl(EAX, raw_null);
   __ j(EQUAL, &is_assignable);
 
   if (!FLAG_eliminate_type_checks || dst_type.IsMalformed()) {
@@ skipping 1236 matching lines @@
   __ movups(reg, Address(ESP, 0));
   __ addl(ESP, Immediate(kFpuRegisterSize));
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32