Update stack map computation to match the way XMM registers are spilled on the slow path.

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 1310 matching lines @@
   __ Drop(1);
   __ jmp(skip_call);
   __ Bind(&is_false);
   __ LoadObject(result, Bool::False());
   __ Drop(1);
   __ jmp(skip_call);
   __ Bind(&fall_through);
 }
 
 
+// This function must be in sync with FlowGraphCompiler::RecordSafepoint.
 void FlowGraphCompiler::SaveLiveRegisters(LocationSummary* locs) {
   // TODO(vegorov): consider saving only caller save (volatile) registers.
   const intptr_t xmm_regs_count = locs->live_registers()->fpu_regs_count();
   if (xmm_regs_count > 0) {
     __ subq(RSP, Immediate(xmm_regs_count * kFpuRegisterSize));
     // Store XMM registers with the lowest register number at the lowest
     // address.
     intptr_t offset = 0;
     for (intptr_t reg_idx = 0; reg_idx < kNumberOfXmmRegisters; ++reg_idx) {
       XmmRegister xmm_reg = static_cast<XmmRegister>(reg_idx);
@@ skipping 347 matching lines @@
 void ParallelMoveResolver::Exchange(const Address& mem1, const Address& mem2) {
   __ Exchange(mem1, mem2);
 }
 
 
 #undef __
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_X64