Revert of Reland: Remove register index/code indirection

test/cctest/test-code-stubs-x64.cc

Index: test/cctest/test-code-stubs-x64.cc
diff --git a/test/cctest/test-code-stubs-x64.cc b/test/cctest/test-code-stubs-x64.cc
index 8f22dd9fcfc48f595114f7351e7257f1bbddba21..9eb153f65117b4754c2118fe104cd616adc92700 100644
--- a/test/cctest/test-code-stubs-x64.cc
+++ b/test/cctest/test-code-stubs-x64.cc
@@ -33,7 +33,6 @@
 #include "src/code-stubs.h"
 #include "src/factory.h"
 #include "src/macro-assembler.h"
-#include "src/register-configuration.h"
 #include "test/cctest/cctest.h"
 #include "test/cctest/test-code-stubs.h"
 
@@ -63,24 +62,20 @@
   __ pushq(rsi);
   __ pushq(rdi);
 
-
-  const RegisterConfiguration* config = RegisterConfiguration::ArchDefault();
   if (!source_reg.is(rsp)) {
     // The argument we pass to the stub is not a heap number, but instead
     // stack-allocated and offset-wise made to look like a heap number for
     // the stub.  We create that "heap number" after pushing all allocatable
     // registers.
     int double_argument_slot =
-        (config->num_allocatable_general_registers() - 1) * kPointerSize +
-        kDoubleSize;
+        (Register::NumAllocatableRegisters() - 1) * kPointerSize + kDoubleSize;
     __ leaq(source_reg, MemOperand(rsp, -double_argument_slot - offset));
   }
 
   // Save registers make sure they don't get clobbered.
   int reg_num = 0;
-  for (; reg_num < config->num_allocatable_general_registers(); ++reg_num) {
-    Register reg =
-        Register::from_code(config->GetAllocatableGeneralCode(reg_num));
+  for (; reg_num < Register::NumAllocatableRegisters(); ++reg_num) {
+    Register reg = Register::FromAllocationIndex(reg_num);
     if (!reg.is(rsp) && !reg.is(rbp) && !reg.is(destination_reg)) {
       __ pushq(reg);
     }
@@ -97,8 +92,7 @@
 
   // Make sure no registers have been unexpectedly clobbered
   for (--reg_num; reg_num >= 0; --reg_num) {
-    Register reg =
-        Register::from_code(config->GetAllocatableGeneralCode(reg_num));
+    Register reg = Register::FromAllocationIndex(reg_num);
     if (!reg.is(rsp) && !reg.is(rbp) && !reg.is(destination_reg)) {
       __ cmpq(reg, MemOperand(rsp, 0));
       __ Assert(equal, kRegisterWasClobbered);