On 05/12/17 23:47, Jason Ekstrand wrote:
> On Tue, Dec 5, 2017 at 1:36 PM, Jose Maria Casanova Crespo
> <jmcasan...@igalia.com <mailto:jmcasan...@igalia.com>> wrote:
>
> SSBO loads were using byte_scattered read messages as they allow
> reading 16-bit size components. byte_scattered messages can only
> operate one component at a time so we needed to emit as many messages
> as components.
>
> But for vec2 and vec4 of 16-bit, being multiple of 32-bit we can use the
> untyped_surface_read message to read pairs of 16-bit components using
> only one message. Once each pair is read it is unshuffled to return the
> proper 16-bit components. vec3 case is assimilated to vec4 but the 4th
> component is ignored.
>
> 16-bit scalars are read using one byte_scattered_read message.
>
> v2: Removed use of stride = 2 on sources (Jason Ekstrand)
> Rework optimization using unshuffle 16 reads (Chema Casanova)
> v3: Use W and D types insead of HF and F in shuffle to avoid rounding
> erros (Jason Ekstrand)
> Use untyped_surface_read for 16-bit vec3. (Jason Ekstrand)
>
> CC: Jason Ekstrand <ja...@jlekstrand.net <mailto:ja...@jlekstrand.net>>
> ---
> src/intel/compiler/brw_fs_nir.cpp | 29 ++++++++++++++++++++++-------
> 1 file changed, 22 insertions(+), 7 deletions(-)
>
> diff --git a/src/intel/compiler/brw_fs_nir.cpp
> b/src/intel/compiler/brw_fs_nir.cpp
> index e11e75e6332..8deec082d59 100644
> --- a/src/intel/compiler/brw_fs_nir.cpp
> +++ b/src/intel/compiler/brw_fs_nir.cpp
> @@ -2303,16 +2303,31 @@ do_untyped_vector_read(const fs_builder &bld,
> unsigned num_components)
> {
> if (type_sz(dest.type) <= 2) {
> - fs_reg read_offset = bld.vgrf(BRW_REGISTER_TYPE_UD);
> - bld.MOV(read_offset, offset_reg);
> - for (unsigned i = 0; i < num_components; i++) {
> - fs_reg read_reg =
> - emit_byte_scattered_read(bld, surf_index, read_offset,
> + assert(dest.stride == 1);
> +
> + if (num_components > 1) {
> + /* Pairs of 16-bit components can be read with untyped
> read, for 16-bit
> + * vec3 4th component is ignored.
> + */
> + fs_reg read_result =
> + emit_untyped_read(bld, surf_index, offset_reg,
> + 1 /* dims */,
> DIV_ROUND_UP(num_components, 2),
> + BRW_PREDICATE_NONE);
> + shuffle_32bit_load_result_to_16bit_data(bld,
> + retype(dest, BRW_REGISTER_TYPE_W),
> + retype(read_result, BRW_REGISTER_TYPE_D),
> + num_components);
> + } else {
> + assert(num_components == 1);
> + /* scalar 16-bit are read using one byte_scattered_read
> message */
> + fs_reg read_result =
> + emit_byte_scattered_read(bld, surf_index, offset_reg,
> 1 /* dims */, 1,
> type_sz(dest.type) * 8 /*
> bit_size */,
> BRW_PREDICATE_NONE);
> - bld.MOV(offset(dest, bld, i), subscript(read_reg,
> dest.type, 0));
> - bld.ADD(read_offset, read_offset,
> brw_imm_ud(type_sz(dest.type)));
> + read_result.type = dest.type;
> + read_result.stride = 2;
> + bld.MOV(dest, read_result);
>
>
> If read_reg has a 32-bit type, you could use subscript here. Meh.
Fixed locally.
> Reviewed-by: Jason Ekstrand <ja...@jlekstrand.net
Thanks for the reviews. This was the last pending review to address
before being ready to land this part of the series.
I'm waiting to confirm with Jenkins that I fixed a regression it found
in the 16-bit load_ubo implementation with the sampler.
>
>
> }
> } else if (type_sz(dest.type) == 4) {
> fs_reg read_result = emit_untyped_read(bld, surf_index,
> offset_reg,
> --
> 2.11.0
>
>
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