Revert of Reland: Remove register index/code indirection

src/x64/lithium-codegen-x64.cc

Index: src/x64/lithium-codegen-x64.cc
diff --git a/src/x64/lithium-codegen-x64.cc b/src/x64/lithium-codegen-x64.cc
index b083f8abd45a9ebaf3f8762d4ef8b5d439cd02ae..b97dfa8ce7108232c71fb9dbafb2b9b881b518de 100644
--- a/src/x64/lithium-codegen-x64.cc
+++ b/src/x64/lithium-codegen-x64.cc
@@ -89,7 +89,7 @@
   BitVector::Iterator save_iterator(doubles);
   while (!save_iterator.Done()) {
     __ movsd(MemOperand(rsp, count * kDoubleSize),
-             XMMRegister::from_code(save_iterator.Current()));
+             XMMRegister::FromAllocationIndex(save_iterator.Current()));
     save_iterator.Advance();
     count++;
   }
@@ -104,7 +104,7 @@
   BitVector::Iterator save_iterator(doubles);
   int count = 0;
   while (!save_iterator.Done()) {
-    __ movsd(XMMRegister::from_code(save_iterator.Current()),
+    __ movsd(XMMRegister::FromAllocationIndex(save_iterator.Current()),
              MemOperand(rsp, count * kDoubleSize));
     save_iterator.Advance();
     count++;
@@ -436,12 +436,12 @@
 
 
 Register LCodeGen::ToRegister(int index) const {
-  return Register::from_code(index);
+  return Register::FromAllocationIndex(index);
 }
 
 
 XMMRegister LCodeGen::ToDoubleRegister(int index) const {
-  return XMMRegister::from_code(index);
+  return XMMRegister::FromAllocationIndex(index);
 }