VM: Fix frame size computation for optimized DBC code

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 219 matching lines @@
     __ Push(locs->in(0).reg());
     __ Push(locs->in(1).reg());
   }
   __ PushConstant(dst_type);
   __ PushConstant(dst_name);
   __ AssertAssignable(__ AddConstant(test_cache));
   RecordSafepoint(locs);
   AddCurrentDescriptor(RawPcDescriptors::kOther, deopt_id, token_pos);
   if (is_optimizing()) {
     // Assert assignable keeps the instance on the stack as the result,
-    // all other arguments are popped. Since there may have been a GC during
-    // the runtime call, we have to reload the instance.
-    __ PopLocal(locs->out(0).reg());
+    // all other arguments are popped.
+    ASSERT(locs->out(0).reg() == locs->in(0).reg());
+    __ Drop1();
   }
 }
 
 
 void FlowGraphCompiler::EmitInstructionEpilogue(Instruction* instr) {
   if (!is_optimizing()) {
     Definition* defn = instr->AsDefinition();
     if ((defn != NULL) &&
         (defn->tag() != Instruction::kPushArgument) &&
         (defn->tag() != Instruction::kStoreIndexed) &&
@@ skipping 243 matching lines @@
 void ParallelMoveResolver::RestoreFpuScratch(FpuRegister reg) {
   UNIMPLEMENTED();
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_DBC