llvm dev - Jul 2011 - [LLVMdev] problems with single byte stores in the arm backend

I have been struggling with this for way too long now, so hopefully the
mighty list can help:

I am trying to generate a byte store  instruction storing the constant value
4 at some given address
in a new helper function inside ARMISelLowering.cpp

I tried:

  SDValue Val = DAG.getConstant(4, MVT::i8);
  SDValue Store = DAG.getStore(chain,
                                 dl,
                                 Val,
                                 Addr,
                                 MachinePointerInfo(),
                                 false, false, 0);


This gives me a a legalizer assert for MVT::i8.

If I change it to MVT::i32 the code works but instead of
a single byte store (STRB) I get a word store (STR).

How can I force the width of the store?

Thanks,
Robert
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Hi Robert,

You probably want getTruncStore() instead of getStore().

-Jim

On Jul 13, 2011, at 9:09 AM, Robert Muth wrote:
> I have been struggling with this for way too long now, so hopefully the
mighty list can help:
> 
> I am trying to generate a byte store  instruction storing the constant
value 4 at some given address
> in a new helper function inside ARMISelLowering.cpp
> 
> I tried:
> 
>   SDValue Val = DAG.getConstant(4, MVT::i8);
>   SDValue Store = DAG.getStore(chain,
>                                  dl,
>                                  Val,
>                                  Addr,
>                                  MachinePointerInfo(),
>                                  false, false, 0);
> 
> 
> This gives me a a legalizer assert for MVT::i8.
> 
> If I change it to MVT::i32 the code works but instead of
> a single byte store (STRB) I get a word store (STR).
> 
> How can I force the width of the store?
> 
> Thanks,
> Robert
> 
> 
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