llvm dev - Dec 2012 - [LLVMdev] Increase the number of registers in ARM

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

Best Regards,
A. Yazdanbakhsh
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
PhD. Student
School of Electrical and Computer Engineering
University of Wisconsin-Madison
E-mail:     yazdanbakhsh at wisc.edu


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On Thu, Dec 6, 2012 at 7:27 PM, 陳韋任 (Wei-Ren Chen) <chenwj at
iis.sinica.edu.tw
> wrote:
> On Thu, Dec 06, 2012 at 09:13:53AM +0000, David Chisnall wrote:
> > On 6 Dec 2012, at 07:46, 陳韋任 (Wei-Ren Chen) wrote:
> >
> > >  The code below in lib/Target/ARM/ARMRegisterInfo.td is where you
> > > should look into,
> > >
> > > // Integer registers
> > > def R0  : ARMReg< 0, "r0">, 
DwarfRegNum<[0]>;
> > > def R1  : ARMReg< 1, "r1">, 
DwarfRegNum<[1]>;
> > >
> > >  ...
> >
> > That's the easy part.  ARM (AArch32) has 16 registers because
register
> operands are stored in a 4-bit bitfield in the instructions.  If you want
> to add more registers, then you will also need to modify the instruction
> encoding of every instruction, or place them in a separate namespace (as
> with the NEON / VFP registers) and add instructions for explicitly
> modifying them.
>
>   Oh, I miss that part. So since the ARM only save 4 bits for register
> operand, I don't see there is a easy way to do what you said. Sounds
> like a huge work?
>
> Regards,
> chenwj
>
> --
> Wei-Ren Chen (陳韋任)
> Computer Systems Lab, Institute of Information Science,
> Academia Sinica, Taiwan (R.O.C.)
> Tel:886-2-2788-3799 #1667
> Homepage: http://people.cs.nctu.edu.tw/~chenwj
>
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
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> 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

Thanks Kito. It is very helpful.

Best Regards,
A. Yazdanbakhsh
>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>
PhD. Student
School of Electrical and Computer Engineering
University of Wisconsin-Madison
E-mail:     yazdanbakhsh at wisc.edu


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On Fri, Dec 7, 2012 at 1:40 AM, Kito Cheng <kito at 0xlab.org> wrote:
> > 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
>
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