Re-reland: Remove register index/code indirection

src/compiler/code-generator.cc

Index: src/compiler/code-generator.cc
diff --git a/src/compiler/code-generator.cc b/src/compiler/code-generator.cc
index 91602a02a3cde1de9f76bd20cd6ba8698c24012d..f702cce1c3c9b801849fa97e1e5d2958c47170a0 100644
--- a/src/compiler/code-generator.cc
+++ b/src/compiler/code-generator.cc
@@ -227,8 +227,7 @@ void CodeGenerator::RecordSafepoint(ReferenceMap* references,
       index -= stackSlotToSpillSlotDelta;
       safepoint.DefinePointerSlot(index, zone());
     } else if (operand.IsRegister() && (kind & Safepoint::kWithRegisters)) {
-      Register reg =
-          Register::FromAllocationIndex(RegisterOperand::cast(operand).index());
+      Register reg = RegisterOperand::cast(operand).GetRegister();
       safepoint.DefinePointerRegister(reg, zone());
     }
   }