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

runtime/vm/assembler_ia32.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"  // NOLINT
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/assembler.h"
 #include "vm/code_generator.h"
 #include "vm/cpu.h"
@@ skipping 2106 matching lines @@
 
 void Assembler::Drop(intptr_t stack_elements) {
   ASSERT(stack_elements >= 0);
   if (stack_elements > 0) {
     addl(ESP, Immediate(stack_elements * kWordSize));
   }
 }
 
 
 void Assembler::LoadIsolate(Register dst) {
-  movl(dst, Immediate(reinterpret_cast<uword>(Isolate::Current())));
+  movl(dst, Address(THR, Thread::isolate_offset()));
 }
 
 
 void Assembler::LoadObject(Register dst, const Object& object) {
   if (object.IsSmi() || object.InVMHeap()) {
     movl(dst, Immediate(reinterpret_cast<int32_t>(object.raw())));
   } else {
     ASSERT(object.IsNotTemporaryScopedHandle());
     ASSERT(object.IsOld());
     AssemblerBuffer::EnsureCapacity ensured(&buffer_);
@@ skipping 967 matching lines @@
 
 const char* Assembler::FpuRegisterName(FpuRegister reg) {
   ASSERT((0 <= reg) && (reg < kNumberOfXmmRegisters));
   return xmm_reg_names[reg];
 }
 
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32