[Mesa-dev] [PATCH 01/23] i965/fs: fix subreg_offset overflow in byte_offset()

[Jordan Justen]

On 2016-05-03 05:21:50, Samuel Iglesias Gonsálvez wrote:
> From: Iago Toral Quiroga <itoral at igalia.com>
> 
> This can happen if the register already has a non-zero subreg_offset
> when byte_offset() is called.
> ---
>  src/mesa/drivers/dri/i965/brw_ir_fs.h | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/src/mesa/drivers/dri/i965/brw_ir_fs.h b/src/mesa/drivers/dri/i965/brw_ir_fs.h
> index 2f72326..8faca08 100644
> --- a/src/mesa/drivers/dri/i965/brw_ir_fs.h
> +++ b/src/mesa/drivers/dri/i965/brw_ir_fs.h
> @@ -109,6 +109,10 @@ byte_offset(fs_reg reg, unsigned delta)
>        assert(delta == 0);
>     }
>     reg.subreg_offset += delta % 32;
> +   if (reg.subreg_offset >= 32) {
> +      reg.reg_offset += reg.subreg_offset / 32;
> +      reg.subreg_offset %= 32;
> +   }

What if at the top of the function, we have

reg.subreg_offset += delta;

Then, in the middle we use reg.subreg_offset instead of delta for
adjusting the register offset.

Then, at the end:

reg.subreg_offset = reg.subreg_offset % 32;

-Jordan

>     return reg;
>  }
>  
> -- 
> 2.5.0
> 
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