Iago Toral Quiroga <ito...@igalia.com> writes: > The previous implementation relied on the std140 alignment rules to > avoid handling misalignment in the case where we are loading more than > 2 double components from a vector, which requires to emit a second load > message. > > This alternative implementation deals with misalignment and is more > flexible going forward. All credit for this goes to Curro, since he > not only suggested this but also wrote the implementation in the > mailing list. > --- > > Curro, maybe I should make you the author and me the reviewer then? :) > It's up to you, feel free to add either my:
Signed-off-by: Francisco Jerez <curroje...@riseup.net>
along with your R-b, or:
Reviewed-by: Francisco Jerez <curroje...@riseup.net>
> src/mesa/drivers/dri/i965/brw_fs_nir.cpp | 59
> +++++++-------------------------
> 1 file changed, 13 insertions(+), 46 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
> b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
> index ebcc92a..35a6aed 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
> @@ -3583,9 +3583,6 @@ fs_visitor::nir_emit_intrinsic(const fs_builder &bld,
> nir_intrinsic_instr *instr
> nir->info.num_ubos - 1);
> }
>
> - /* Number of 32-bit slots in the type */
> - unsigned type_slots = MAX2(1, type_sz(dest.type) / 4);
> -
> nir_const_value *const_offset = nir_src_as_const_value(instr->src[1]);
> if (const_offset == NULL) {
> fs_reg base_offset = retype(get_nir_src(instr->src[1]),
> @@ -3603,55 +3600,25 @@ fs_visitor::nir_emit_intrinsic(const fs_builder &bld,
> nir_intrinsic_instr *instr
> * we let CSE deal with duplicate loads. Here we see a vector access
> * and we have to split it if necessary.
> */
> - fs_reg packed_consts = vgrf(glsl_type::float_type);
> - packed_consts.type = dest.type;
> + const unsigned type_size = type_sz(dest.type);
> + const fs_reg packed_consts = bld.vgrf(BRW_REGISTER_TYPE_F);
> + for (unsigned c = 0; c < instr->num_components;) {
> + const unsigned base = const_offset->u32[0] + c * type_size;
>
> - unsigned const_offset_aligned = const_offset->u32[0] & ~15;
> + /* Number of usable components in the next 16B-aligned load */
> + const unsigned count = MIN2(instr->num_components - c,
> + (16 - base % 16) / type_size);
>
> - /* A vec4 only contains half of a dvec4, if we need more than 2
> - * components of a dvec4 we will have to issue another load for
> - * components z and w.
> - */
> - int num_components;
> - if (type_slots == 1)
> - num_components = instr->num_components;
> - else
> - num_components = MIN2(2, instr->num_components);
> -
> - /* The computation of num_components doesn't take into account
> - * misalignment, which should be okay according to std140 vector
> - * alignment rules.
> - */
> - assert(const_offset->u32[0] % 16 +
> - type_sz(dest.type) * num_components <= 16);
> -
> - int remaining_components = instr->num_components;
> - while (remaining_components > 0) {
> - /* Read the vec4 from a 16-byte aligned offset */
> - struct brw_reg const_offset_reg =
> brw_imm_ud(const_offset_aligned);
> bld.emit(FS_OPCODE_UNIFORM_PULL_CONSTANT_LOAD,
> - retype(packed_consts, BRW_REGISTER_TYPE_F),
> - surf_index, const_offset_reg);
> -
> - const fs_reg consts = byte_offset(packed_consts,
> (const_offset->u32[0] % 16));
> - unsigned dest_offset = instr->num_components -
> remaining_components;
> + packed_consts, surf_index, brw_imm_ud(base & ~15));
>
> - /* XXX: This doesn't update the sub-16B offset across iterations
> of
> - * the loop, which should work for std140 vector alignment rules.
> - */
> - assert(dest_offset == 0 || const_offset->u32[0] % 16 == 0);
> + const fs_reg consts =
> + retype(byte_offset(packed_consts, base & 15), dest.type);
>
> - for (int i = 0; i < num_components; i++)
> - bld.MOV(offset(dest, bld, i + dest_offset), component(consts,
> i));
> + for (unsigned d = 0; d < count; d++)
> + bld.MOV(offset(dest, bld, c + d), component(consts, d));
>
> - /* If this is a large enough 64-bit load, we will need to emit
> - * another message
> - */
> - remaining_components -= num_components;
> - assert(remaining_components == 0 ||
> - (remaining_components <= 2 && type_slots == 2));
> - num_components = remaining_components;
> - const_offset_aligned += 16;
> + c += count;
> }
> }
> break;
> --
> 1.9.1
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