Revert of Reland: Remove register index/code indirection

src/arm/constants-arm.cc

Index: src/arm/constants-arm.cc
diff --git a/src/arm/constants-arm.cc b/src/arm/constants-arm.cc
index 915d9030e8922a6f8c4e433a1936b692540d5090..9fefc3140a999429d0a1853bf75ae08ce59224ca 100644
--- a/src/arm/constants-arm.cc
+++ b/src/arm/constants-arm.cc
@@ -49,6 +49,17 @@
   {15, "r15"},
   {kNoRegister, NULL}
 };
+
+
+const char* Registers::Name(int reg) {
+  const char* result;
+  if ((0 <= reg) && (reg < kNumRegisters)) {
+    result = names_[reg];
+  } else {
+    result = "noreg";
+  }
+  return result;
+}
 
 
 // Support for VFP registers s0 to s31 (d0 to d15) and d16-d31.