[LLVMdev] Increase the number of registers in ARM

[Kito Cheng]

> I almost change all the instruction formats. It was a huge work. I am going
> to compile and run it now.

We have done the similar work[1] on this topic by gcc and we have
start migrate our platform to LLVM.
In my experience, you need to take care the follow part:
* ARMBaseRegisterInfo::getRegPressureLimit
* ARMBaseRegisterInfo::getRawAllocationOrder
* CalleeSavedRegs
* ARMFrameLowering::emitPrologue

[1] Doubling the Number of Registers on ARM Processors
http://aces.snu.ac.kr/interact-16/papers/interact-16-paper-1.pdf