[Mesa-dev] [PATCH] intel/fs: Don't emit a des copy for image ops with has_dest == false

[Ian Romanick]

On 03/27/2018 04:29 PM, Jason Ekstrand wrote:
> This was causing us to walk dest_components times over a thing with no
> destination.  This happened to work because all of the image intrinsics
> without a destination also happened to have dest_components == 0.  We
> shouldn't be reading dest_components if has_dest == false.

I'm assuming we want this fix in addition to the other change to
nir_intrinsics_c.py?  I haven't tested this yet, but, based on the
discussion on IRC, I suspect this will fix my shader-db problem on its
own.  Give me a couple minutes...

> ---
>  src/intel/compiler/brw_fs_nir.cpp | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/src/intel/compiler/brw_fs_nir.cpp b/src/intel/compiler/brw_fs_nir.cpp
> index f5d5399..8d1c387 100644
> --- a/src/intel/compiler/brw_fs_nir.cpp
> +++ b/src/intel/compiler/brw_fs_nir.cpp
> @@ -3848,9 +3848,11 @@ fs_visitor::nir_emit_intrinsic(const fs_builder &bld, nir_intrinsic_instr *instr
>                                   get_image_atomic_op(instr->intrinsic, type));
>  
>        /* Assign the result. */
> -      for (unsigned c = 0; c < info->dest_components; ++c)
> -         bld.MOV(offset(retype(dest, base_type), bld, c),
> -                 offset(tmp, bld, c));
> +      if (nir_intrinsic_infos[instr->intrinsic].has_dest) {
> +         for (unsigned c = 0; c < info->dest_components; ++c)
> +            bld.MOV(offset(retype(dest, base_type), bld, c),
> +                    offset(tmp, bld, c));
> +      }
>        break;
>     }
>  
>