[llvm-commits] [PATCH] fix #13035 (Thumb LDRD/STRD with negative #0 offset is decoded as a positive #0 offset)

[Jiangning Liu]

> -----Original Message-----
> From: rengolin at gmail.com [mailto:rengolin at gmail.com] On Behalf Of Renato
> Golin
> Sent: Thursday, August 02, 2012 12:09 AM
> To: Jiangning Liu
> Cc: llvm-commits at cs.uiuc.edu
> Subject: Re: [llvm-commits] [PATCH] fix #13035 (Thumb LDRD/STRD with
> negative #0 offset is decoded as a positive #0 offset)
> 
> On 1 August 2012 16:12, Jiangning Liu <jiangning.liu at arm.com> wrote:
> > Hi,
> >
> > The patch is fix http://llvm.org/bugs/show_bug.cgi?id=13035, and the
> > solution is to use INT32_MIN to describe #-0.
> 
> Hi Jiangning,
> 
> In DecodeT2Imm8S4():
> 
> +  if (Val == 0)
> +    Inst.addOperand(MCOperand::CreateImm(INT32_MIN));
> 
> If 0 is the representation of #-0, what is the representation of #0?

Renato,

#0 is 0x100, because bit 'U' needs to be set for add operation in this
instruction.

ARM ARM says, add = (U == '1');

Thanks,
-Jiangning

> 
> Otherwise, looks good.
> 
> --
> cheers,
> --renato
> 
> http://systemcall.org/