llvm dev - Feb 2008 - [LLVMdev] expanding i16 operations in presence of an i16 regclass.

Reframing and Reposting my earlier query:

My target has 16-bit registers for indirect address of data.
All other registers are 8-bit.

Therefore I have added regclasses for i8 and i16 types.

All arithmetic operations (including pointer arithmetic ) are 8-bit
operations.

The problem is that LLVM does not expand i16 operations to i8 operations in
presence of i16 regclass.

What is the best way to tackle this?

Do I need to custom lower arithmetic operations during Legalize using
LowerOperation ( )?

- Sanjiv
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On Feb 28, 2008, at 6:31 AM, Sanjiv Gupta wrote:
> Reframing and Reposting my earlier query:
>
> My target has 16-bit registers for indirect address of data.
> All other registers are 8-bit.
>
> Therefore I have added regclasses for i8 and i16 types.
>
> All arithmetic operations (including pointer arithmetic ) are 8-bit  
> operations.
>
> The problem is that LLVM does not expand i16 operations to i8  
> operations in presence of i16 regclass.
>
> What is the best way to tackle this?
>
> Do I need to custom lower arithmetic operations during Legalize  
> using LowerOperation ( )?
What happens if you mark i16 arithmetic operations expand? i.e.  
setOperationAction(ISD::ADD, MVT::i16, Expand);

Evan
>
> - Sanjiv
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