Revert of Reland: Remove register index/code indirection

src/mips64/lithium-codegen-mips64.cc

Index: src/mips64/lithium-codegen-mips64.cc
diff --git a/src/mips64/lithium-codegen-mips64.cc b/src/mips64/lithium-codegen-mips64.cc
index 99b19500734bae43f2e1c2e8c576588356b979cd..5e1312e1b032129bb07d22bd9d5dcdc127f5da2f 100644
--- a/src/mips64/lithium-codegen-mips64.cc
+++ b/src/mips64/lithium-codegen-mips64.cc
@@ -71,7 +71,7 @@
   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++;
@@ -87,7 +87,7 @@
   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++;
@@ -385,12 +385,12 @@
 
 
 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);
 }