Revert of Reland: Remove register index/code indirection

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

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Rrdistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Rrdistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Rrdistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 58 matching lines @@
   // Push the double argument.
   __ sub(sp, sp, Operand(kDoubleSize));
   __ vstr(d0, sp, 0);
   if (!source_reg.is(sp)) {
     __ mov(source_reg, sp);
   }
 
   // Save registers make sure they don't get clobbered.
   int source_reg_offset = kDoubleSize;
   int reg_num = 0;
-  for (; reg_num < Register::kNumRegisters; ++reg_num) {
+  for (; reg_num < Register::NumAllocatableRegisters(); ++reg_num) {
     Register reg = Register::from_code(reg_num);
-    if (reg.IsAllocatable()) {
-      if (!reg.is(destination_reg)) {
-        __ push(reg);
-        source_reg_offset += kPointerSize;
-      }
+    if (!reg.is(destination_reg)) {
+      __ push(reg);
+      source_reg_offset += kPointerSize;
     }
   }
 
   // Re-push the double argument.
   __ sub(sp, sp, Operand(kDoubleSize));
   __ vstr(d0, sp, 0);
 
   // Call through to the actual stub
   if (inline_fastpath) {
     __ vldr(d0, MemOperand(source_reg));
     __ TryInlineTruncateDoubleToI(destination_reg, d0, &done);
     if (destination_reg.is(source_reg) && !source_reg.is(sp)) {
       // Restore clobbered source_reg.
       __ add(source_reg, sp, Operand(source_reg_offset));
     }
   }
   __ Call(start, RelocInfo::EXTERNAL_REFERENCE);
   __ bind(&done);
 
   __ add(sp, sp, Operand(kDoubleSize));
 
   // 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(destination_reg)) {
-        __ ldr(ip, MemOperand(sp, 0));
-        __ cmp(reg, ip);
-        __ Assert(eq, kRegisterWasClobbered);
-        __ add(sp, sp, Operand(kPointerSize));
-      }
+    if (!reg.is(destination_reg)) {
+      __ ldr(ip, MemOperand(sp, 0));
+      __ cmp(reg, ip);
+      __ Assert(eq, kRegisterWasClobbered);
+      __ add(sp, sp, Operand(kPointerSize));
     }
   }
 
   __ add(sp, sp, Operand(kDoubleSize));
 
   if (!destination_reg.is(r0))
     __ mov(r0, destination_reg);
 
   // Restore callee save registers.
   __ Pop(lr);
@@ skipping 52 matching lines @@
                                         false));
       RunAllTruncationTests(
           RunGeneratedCodeCallWrapper,
           MakeConvertDToIFuncTrampoline(isolate,
                                         source_registers[s],
                                         dest_registers[d],
                                         true));
     }
   }
 }