Re: Interaction between bitfields and casts

[Luc Van Oostenryck <luc.vanoostenryck@gmail.com>]

On Wed, Aug 9, 2017 at 10:41 PM, Dibyendu Majumdar
<mobile@majumdar.org.uk> wrote:
> Hi,
>
> When assigning values to bitfields I have noticed that some times
> Sparse generates a CAST instruction with an odd bit size - i.e. not a
> standard integer size. I was wondering if there are specific scenarios
> that lead to this. While LLVM handles the odd cast - I am working with
> another backend (Nanojit) that doesn't.

Yes, I know. There is already one less with:
    [PATCH v4 5/9] change the masking when loading bitfields"

Otherwise, it's really a question of translating then into the right
instruction(s) to truncate/zero extend/sign extend part of a word
(but the casts instructions in sparse's IR are a bit strange and
need special care when the src or the dest is not an integer but
a float or a pointer).

I have an unfinished series that clean this a bit but
it will be after the currently pending series.

-- Luc