[Mesa-dev] [PATCH 1/5/2] i965/fs: Bail out of opt_sampler_eot() if last instruction isn't EOT.

[Francisco Jerez]

Matt Turner <mattst88 at gmail.com> writes:

> ... instead of assert failing. Can only happen when the program has an
> unconditional infinite loop.

I'm curious how the framebuffer write gets eliminated, I don't think DCE
is smart enough currently to find out that the FB write is unreachable?

> ---
> Sigh.
>
>  src/mesa/drivers/dri/i965/brw_fs.cpp | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_fs.cpp b/src/mesa/drivers/dri/i965/brw_fs.cpp
> index d1ac80a..08e9b6c 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs.cpp
> @@ -2511,8 +2511,9 @@ fs_visitor::opt_sampler_eot()
>     /* Look for a texturing instruction immediately before the final FB_WRITE. */
>     bblock_t *block = cfg->blocks[cfg->num_blocks - 1];
>     fs_inst *fb_write = (fs_inst *)block->end();
> -   assert(fb_write->eot);
> -   assert(fb_write->opcode == FS_OPCODE_FB_WRITE_LOGICAL);
> +   if (unlikely(!fb_write->eot) ||
> +       unlikely(fb_write->opcode != FS_OPCODE_FB_WRITE_LOGICAL))
> +      return false;
>  

Maybe we want something in between the two?  Like:

|   if (unlikely(fb_write->opcode != FS_OPCODE_FB_WRITE_LOGICAL))
|      return false;
|
|   assert(fb_write->eot);

My thinking is that *if* the final instruction of the shader is a
framebuffer write it should have already been marked EOT during
translation.

>     /* There wasn't one; nothing to do. */
>     if (unlikely(fb_write->prev->is_head_sentinel()))
> -- 
> 2.7.3
>
> _______________________________________________
> mesa-dev mailing list
> mesa-dev at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/mesa-dev
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 212 bytes
Desc: not available
URL: <https://lists.freedesktop.org/archives/mesa-dev/attachments/20160817/f18ad16b/attachment.sig>