[LLVMdev] subtarget features

[Reed Kotler]

On 05/16/2012 08:35 PM, reed kotler wrote:
> Is it possible to assign the value of subtarget features using more
> complex expressions with code as opposed to using the mechanism that
> tablegen affords.
>
> For example, if Mips16 or Micro Mips is not present, then I want the
> subfeature "standard encoding".
>
> If I can't do this, then it requires me to write a more complex
> expression for the "standard encoding" expresions.
>
> For mips , mips16 and micro mips are considered to be processor
> extenasions to mips32 and mips64.
>
> So usually you would build a mips32 or mips64 compiler and then add
> -mips16 to the command line.
>
> Right now, there are no implementations of micro mips or mips16 with
> mips 64, though architecturally it is defined.
>
> So the options would be:
>
> -mips16 -mips32 -micromips -mips64
>
> With the implications the -mips16 and -micromips both imply mips32 as
> the base architecture.
>
> mips32 and mips64 have mostly the same instruction encoding (difference
> being the size of the
> registers).
>
> Ideally you would want:
>
> standardencoding = !mips16&  !micrormips
>
> then standardencoding is used to be a predicate for all non mips16 and
> micromips instructions.
>
>
>
>
>
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I think i can just do what I want here with predicates