Restore x64 performance by reinstering an accidentally deleted LoadClassId instruction.

runtime/vm/intermediate_language_x64.cc

 // Copyright (c) 2012, 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/intermediate_language.h"
 
 #include "lib/error.h"
@@ skipping 2043 matching lines @@
   Label is_ok;
   intptr_t cix = 0;
   if (unary_checks().GetReceiverClassIdAt(cix) == kSmiCid) {
     __ testq(value, Immediate(kSmiTagMask));
     __ j(ZERO, &is_ok);
     cix++;  // Skip first check.
   } else {
     __ testq(value, Immediate(kSmiTagMask));
     __ j(ZERO, deopt);
   }
+  __ LoadClassId(temp, value);
   const intptr_t num_checks = unary_checks().NumberOfChecks();
   const bool use_near_jump = num_checks < 5;
   for (intptr_t i = cix; i < num_checks; i++) {
     ASSERT(unary_checks().GetReceiverClassIdAt(i) != kSmiCid);
     __ cmpl(temp, Immediate(unary_checks().GetReceiverClassIdAt(i)));
     if (i == (num_checks - 1)) {
       __ j(NOT_EQUAL, deopt);
     } else {
       if (use_near_jump) {
         __ j(EQUAL, &is_ok, Assembler::kNearJump);
@@ skipping 121 matching lines @@
 void UnaryMintOpInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   UNIMPLEMENTED();
 }
 
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_X64