Revert of Reland: Remove register index/code indirection

test/cctest/test-code-stubs-ia32.cc

Index: test/cctest/test-code-stubs-ia32.cc
diff --git a/test/cctest/test-code-stubs-ia32.cc b/test/cctest/test-code-stubs-ia32.cc
index e0f9a453ed20fc65c8fea39f37aa47fc145efe8a..ef44f5420b3cab82add4634bf0c839d4f8a28e03 100644
--- a/test/cctest/test-code-stubs-ia32.cc
+++ b/test/cctest/test-code-stubs-ia32.cc
@@ -70,13 +70,11 @@
   int param_offset = 7 * kPointerSize;
   // Save registers make sure they don't get clobbered.
   int reg_num = 0;
-  for (; reg_num < Register::kNumRegisters; ++reg_num) {
-    Register reg = Register::from_code(reg_num);
-    if (reg.IsAllocatable()) {
-      if (!reg.is(esp) && !reg.is(ebp) && !reg.is(destination_reg)) {
-        __ push(reg);
-        param_offset += kPointerSize;
-      }
+  for (; reg_num < Register::NumAllocatableRegisters(); ++reg_num) {
+    Register reg = Register::FromAllocationIndex(reg_num);
+    if (!reg.is(esp) && !reg.is(ebp) && !reg.is(destination_reg)) {
+      __ push(reg);
+      param_offset += kPointerSize;
     }
   }
 
@@ -91,13 +89,11 @@
 
   // Make sure no registers have been unexpectedly clobbered
   for (--reg_num; reg_num >= 0; --reg_num) {
-    Register reg = Register::from_code(reg_num);
-    if (reg.IsAllocatable()) {
-      if (!reg.is(esp) && !reg.is(ebp) && !reg.is(destination_reg)) {
-        __ cmp(reg, MemOperand(esp, 0));
-        __ Assert(equal, kRegisterWasClobbered);
-        __ add(esp, Immediate(kPointerSize));
-      }
+    Register reg = Register::FromAllocationIndex(reg_num);
+    if (!reg.is(esp) && !reg.is(ebp) && !reg.is(destination_reg)) {
+      __ cmp(reg, MemOperand(esp, 0));
+      __ Assert(equal, kRegisterWasClobbered);
+      __ add(esp, Immediate(kPointerSize));
     }
   }