Skip AssertAssignable in code generator if optimizer could establish that

runtime/vm/flow_graph_compiler_ia32.cc

Index: runtime/vm/flow_graph_compiler_ia32.cc
===================================================================
--- runtime/vm/flow_graph_compiler_ia32.cc	(revision 28233)
+++ runtime/vm/flow_graph_compiler_ia32.cc	(working copy)
@@ -663,9 +663,12 @@
   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.