Revert of Remove register index/code indirection

src/arm64/lithium-codegen-arm64.cc

Index: src/arm64/lithium-codegen-arm64.cc
diff --git a/src/arm64/lithium-codegen-arm64.cc b/src/arm64/lithium-codegen-arm64.cc
index 0067abfe240b671b6174fd227b0736cebdbc3fc3..488e14f82c5b7ba974f099fddeb7344c9648583f 100644
--- a/src/arm64/lithium-codegen-arm64.cc
+++ b/src/arm64/lithium-codegen-arm64.cc
@@ -593,7 +593,7 @@
   while (!iterator.Done()) {
     // TODO(all): Is this supposed to save just the callee-saved doubles? It
     // looks like it's saving all of them.
-    FPRegister value = FPRegister::from_code(iterator.Current());
+    FPRegister value = FPRegister::FromAllocationIndex(iterator.Current());
     __ Poke(value, count * kDoubleSize);
     iterator.Advance();
     count++;
@@ -611,7 +611,7 @@
   while (!iterator.Done()) {
     // TODO(all): Is this supposed to restore just the callee-saved doubles? It
     // looks like it's restoring all of them.
-    FPRegister value = FPRegister::from_code(iterator.Current());
+    FPRegister value = FPRegister::FromAllocationIndex(iterator.Current());
     __ Peek(value, count * kDoubleSize);
     iterator.Advance();
     count++;
@@ -1158,7 +1158,7 @@
 Register LCodeGen::ToRegister(LOperand* op) const {
   // TODO(all): support zero register results, as ToRegister32.
   DCHECK((op != NULL) && op->IsRegister());
-  return Register::from_code(op->index());
+  return Register::FromAllocationIndex(op->index());
 }
 
 
@@ -1182,7 +1182,7 @@
 
 DoubleRegister LCodeGen::ToDoubleRegister(LOperand* op) const {
   DCHECK((op != NULL) && op->IsDoubleRegister());
-  return DoubleRegister::from_code(op->index());
+  return DoubleRegister::FromAllocationIndex(op->index());
 }