Revert of Remove register index/code indirection

src/mips/lithium-codegen-mips.cc

Index: src/mips/lithium-codegen-mips.cc
diff --git a/src/mips/lithium-codegen-mips.cc b/src/mips/lithium-codegen-mips.cc
index 36eb821c0aa0cebd59ee6bc9f6e6b9fa5a8fde8f..9e45868f8ed67c69814b94a765a303adeba2eafd 100644
--- a/src/mips/lithium-codegen-mips.cc
+++ b/src/mips/lithium-codegen-mips.cc
@@ -96,7 +96,7 @@
   BitVector* doubles = chunk()->allocated_double_registers();
   BitVector::Iterator save_iterator(doubles);
   while (!save_iterator.Done()) {
-    __ sdc1(DoubleRegister::from_code(save_iterator.Current()),
+    __ sdc1(DoubleRegister::FromAllocationIndex(save_iterator.Current()),
             MemOperand(sp, count * kDoubleSize));
     save_iterator.Advance();
     count++;
@@ -112,7 +112,7 @@
   BitVector::Iterator save_iterator(doubles);
   int count = 0;
   while (!save_iterator.Done()) {
-    __ ldc1(DoubleRegister::from_code(save_iterator.Current()),
+    __ ldc1(DoubleRegister::FromAllocationIndex(save_iterator.Current()),
             MemOperand(sp, count * kDoubleSize));
     save_iterator.Advance();
     count++;
@@ -403,12 +403,12 @@
 
 
 Register LCodeGen::ToRegister(int index) const {
-  return Register::from_code(index);
+  return Register::FromAllocationIndex(index);
 }
 
 
 DoubleRegister LCodeGen::ToDoubleRegister(int index) const {
-  return DoubleRegister::from_code(index);
+  return DoubleRegister::FromAllocationIndex(index);
 }