Cache current thread in a reserved register and use it in LoadIsolate

runtime/vm/flow_graph_compiler.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_XXX.
 
 #include "vm/flow_graph_compiler.h"
 
 #include "vm/bit_vector.h"
 #include "vm/cha.h"
@@ skipping 1223 matching lines @@
   blocked_registers[FPREG] = true;
   if (TMP != kNoRegister) {
     blocked_registers[TMP] = true;
   }
   if (TMP2 != kNoRegister) {
     blocked_registers[TMP2] = true;
   }
   if (PP != kNoRegister) {
     blocked_registers[PP] = true;
   }
+  blocked_registers[THR] = true;
 
   // Block all non-free registers.
   for (intptr_t i = 0; i < kFirstFreeCpuRegister; i++) {
     blocked_registers[i] = true;
   }
   for (intptr_t i = kLastFreeCpuRegister + 1; i < kNumberOfCpuRegisters; i++) {
     blocked_registers[i] = true;
   }
 
   // Allocate all unallocated input locations.
@@ skipping 473 matching lines @@
 
 
 void FlowGraphCompiler::FrameStateClear() {
   ASSERT(!is_optimizing());
   frame_state_.TruncateTo(0);
 }
 #endif
 
 
 }  // namespace dart