Make register allocator to disregard constant computation with no uses.

runtime/vm/assembler_ia32.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"
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/assembler.h"
 #include "vm/heap.h"
 #include "vm/memory_region.h"
@@ skipping 867 matching lines @@
 }
 
 
 void Assembler::xorl(Register dst, Register src) {
   AssemblerBuffer::EnsureCapacity ensured(&buffer_);
   EmitUint8(0x33);
   EmitOperand(dst, Operand(src));
 }
 
 
+void Assembler::xorl(Register dst, const Immediate& imm) {
+  AssemblerBuffer::EnsureCapacity ensured(&buffer_);
+  EmitComplex(6, Operand(dst), imm);
+}
+
+
 void Assembler::addl(Register reg, const Immediate& imm) {
   AssemblerBuffer::EnsureCapacity ensured(&buffer_);
   EmitComplex(0, Operand(reg), imm);
 }
 
 
 void Assembler::addl(const Address& address, Register reg) {
   AssemblerBuffer::EnsureCapacity ensured(&buffer_);
   EmitUint8(0x01);
   EmitOperand(reg, address);
@@ skipping 936 matching lines @@
 
 const char* Assembler::XmmRegisterName(XmmRegister reg) {
   ASSERT((0 <= reg) && (reg < kNumberOfXmmRegisters));
   return xmm_reg_names[reg];
 }
 
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32