[Mesa-dev] [PATCH] i965: Respect stride and subreg_offset for ATTR registers

[Jason Ekstrand]

On Wed, Sep 23, 2015 at 5:11 PM, Kristian Høgsberg Kristensen
<krh at bitplanet.net> wrote:
> When we assign hw regs to attributes, we don't incorporate the stride
> and subreg_offset from the fs_reg. It's rarely used, but the integer
> multiplication lowering uses unusual stride and subreg_offset
> combination breaks when one source is an attribute.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=91970
> Cc: "11.0" <mesa-stable at lists.freedesktop.org>
> Signed-off-by: Kristian Høgsberg Kristensen <krh at bitplanet.net>
> ---
>  src/mesa/drivers/dri/i965/brw_fs.cpp | 5 ++++-
>  1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
> index 225a312..618bbd2 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
> @@ -1564,7 +1564,10 @@ fs_visitor::assign_vs_urb_setup()
>
>              inst->src[i].file = HW_REG;
>              inst->src[i].fixed_hw_reg =
> -               retype(brw_vec8_grf(grf, 0), inst->src[i].type);
> +               stride(byte_offset(retype(brw_vec8_grf(grf, 0), inst->src[i].type),
> +                                  inst->src[i].subreg_offset),
> +                      inst->exec_size * inst->src[i].stride,
> +                      inst->exec_size, inst->src[i].stride);

I made this comment to Kristian today in the office, but I figure I'll
also put it on the list:

I'm not 100% convinced that I like having subreg offsets and strides
respected on the ATTR.  We do respect subreg offset on the UNIFORM
file so I guess there's some precedent for it.  If we didn't, another
option would be to simply emit a MOV to a grf during lowering if we
ever detect ATTR.  Given that this is only on CHV and probably not hit
that often, I think that would be my minor preference.  That said,
this patch does work.

>           }
>        }
>     }
> --
> 2.5.3
>
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