Use a uniform way to emit code for all instructions.

runtime/vm/flow_graph_compiler_x64.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_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/flow_graph_compiler.h"
 
 #include "lib/error.h"
@@ skipping 706 matching lines @@
 }
 
 
 void FlowGraphCompiler::EmitInstructionPrologue(Instruction* instr) {
   if (!is_optimizing()) {
     if (FLAG_enable_type_checks && instr->IsAssertAssignable()) {
       AssertAssignableInstr* assert = instr->AsAssertAssignable();
       AddCurrentDescriptor(PcDescriptors::kDeopt,
                            assert->deopt_id(),
                            assert->token_pos());
-    } else if (instr->IsGuardField()) {
-      GuardFieldInstr* guard = instr->AsGuardField();
-      AddCurrentDescriptor(PcDescriptors::kDeopt,
-                           guard->deopt_id(),
-                           Scanner::kDummyTokenIndex);
-    } else if (instr->CanBeDeoptimizationTarget()) {
+    } else if (instr->CanBeDeoptimizationTarget() || instr->IsGuardField()) {
       AddCurrentDescriptor(PcDescriptors::kDeopt,
                            instr->deopt_id(),
                            Scanner::kDummyTokenIndex);
     }
     AllocateRegistersLocally(instr);
   } else if (instr->MayThrow()  &&
              (CurrentTryIndex() != CatchClauseNode::kInvalidTryIndex)) {
     // Optimized try-block: Sync locals to fixed stack locations.
     EmitTrySync(instr, CurrentTryIndex());
   }
@@ skipping 1190 matching lines @@
   __ movups(reg, Address(RSP, 0));
   __ addq(RSP, Immediate(kFpuRegisterSize));
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64