[Mesa-dev] [PATCH v4] i965/fs: Handle non-const sample number in interpolateAtSample
Francisco Jerez
currojerez at riseup.net
Wed Oct 7 08:08:06 PDT 2015
Neil Roberts <neil at linux.intel.com> writes:
> If a non-const sample number is given to interpolateAtSample it will
> now generate an indirect send message with the sample ID similar to
> how non-const sampler array indexing works. Previously non-const
> values were ignored and instead it ended up using a constant 0 value.
>
> The generator will try to determine if the sample ID is dynamically
> uniform via nir_src_is_dynamically_uniform. If not it will query the
> pixel interpolator in a loop, once for each different live sample
> number. The next live sample number is found using emit_uniformize. If
> multiple live channels have the same sample number then they will be
> handled in a single iteration of the loop. The loop is necessary
> because the indirect send message doesn't seem to have a way to
> specify a different value for each fragment.
>
> This fixes the following two Piglit tests:
>
> arb_gpu_shader5-interpolateAtSample-nonconst
> arb_gpu_shader5-interpolateAtSample-dynamically-nonuniform
>
> v2: Handle dynamically non-uniform sample ids.
> v3: Remove the BREAK instruction and predicate the WHILE directly.
> Make the tokens arrays const.
> v4: Iterate over the live channels instead of each possible sample
> number.
> ---
>
> This version of the patch iterates over each live channel instead of
> each possible sample number. It doesn't need to access
> STATE_NUM_SAMPLES so it avoids the problem that Francisco mentioned.
> Note that if it turns out the fragments are mostly all using the same
> sample number then all of them will be handled at once and the loop
> will bail out early, so it should be more efficient. It also makes the
> patch much simpler.
>
> src/mesa/drivers/dri/i965/brw_eu.h | 2 +-
> src/mesa/drivers/dri/i965/brw_eu_emit.c | 34 +++++++---
> src/mesa/drivers/dri/i965/brw_fs_generator.cpp | 5 +-
> src/mesa/drivers/dri/i965/brw_fs_nir.cpp | 93 +++++++++++++++++++++-----
> 4 files changed, 102 insertions(+), 32 deletions(-)
>
> diff --git a/src/mesa/drivers/dri/i965/brw_eu.h b/src/mesa/drivers/dri/i965/brw_eu.h
> index 761aa0e..0ac1ad9 100644
> --- a/src/mesa/drivers/dri/i965/brw_eu.h
> +++ b/src/mesa/drivers/dri/i965/brw_eu.h
> @@ -461,7 +461,7 @@ brw_pixel_interpolator_query(struct brw_codegen *p,
> struct brw_reg mrf,
> bool noperspective,
> unsigned mode,
> - unsigned data,
> + struct brw_reg data,
> unsigned msg_length,
> unsigned response_length);
>
> diff --git a/src/mesa/drivers/dri/i965/brw_eu_emit.c b/src/mesa/drivers/dri/i965/brw_eu_emit.c
> index dc699bb..9c38e99 100644
> --- a/src/mesa/drivers/dri/i965/brw_eu_emit.c
> +++ b/src/mesa/drivers/dri/i965/brw_eu_emit.c
> @@ -3212,26 +3212,38 @@ brw_pixel_interpolator_query(struct brw_codegen *p,
> struct brw_reg mrf,
> bool noperspective,
> unsigned mode,
> - unsigned data,
> + struct brw_reg data,
> unsigned msg_length,
> unsigned response_length)
> {
> const struct brw_device_info *devinfo = p->devinfo;
> - struct brw_inst *insn = next_insn(p, BRW_OPCODE_SEND);
> + struct brw_inst *insn;
> + uint16_t exec_size;
I suggest you initialize this variable straight away in its declaration
so you can declare it 'const'.
>
> - brw_set_dest(p, insn, dest);
> - brw_set_src0(p, insn, mrf);
> - brw_set_message_descriptor(p, insn, GEN7_SFID_PIXEL_INTERPOLATOR,
> - msg_length, response_length,
> - false /* header is never present for PI */,
> - false);
> + if (data.file == BRW_IMMEDIATE_VALUE) {
> + insn = next_insn(p, BRW_OPCODE_SEND);
> + brw_set_dest(p, insn, dest);
> + brw_set_src0(p, insn, mrf);
> + brw_set_message_descriptor(p, insn, GEN7_SFID_PIXEL_INTERPOLATOR,
> + msg_length, response_length,
> + false /* header is never present for PI */,
> + false);
> + brw_inst_set_pi_message_data(devinfo, insn, data.dw1.ud);
> + } else {
> + insn = brw_send_indirect_message(p,
> + GEN7_SFID_PIXEL_INTERPOLATOR,
> + dest,
> + mrf,
> + vec1(data));
brw_send_indirect_message() does the right thing regardless of whether
the "desc" argument is an immediate or a register. You shouldn't need
the other branch of this conditional special-casing immediates.
> + brw_inst_set_mlen(devinfo, insn, msg_length);
> + brw_inst_set_rlen(devinfo, insn, response_length);
> + }
>
> - brw_inst_set_pi_simd_mode(
> - devinfo, insn, brw_inst_exec_size(devinfo, insn) == BRW_EXECUTE_16);
> + exec_size = brw_inst_exec_size(devinfo, p->current);
> + brw_inst_set_pi_simd_mode(devinfo, insn, exec_size == BRW_EXECUTE_16);
> brw_inst_set_pi_slot_group(devinfo, insn, 0); /* zero unless 32/64px dispatch */
> brw_inst_set_pi_nopersp(devinfo, insn, noperspective);
> brw_inst_set_pi_message_type(devinfo, insn, mode);
> - brw_inst_set_pi_message_data(devinfo, insn, data);
> }
>
> void
> diff --git a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
> index 6f8b75e..17e19cf 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
> @@ -1377,15 +1377,14 @@ fs_generator::generate_pixel_interpolator_query(fs_inst *inst,
> struct brw_reg msg_data,
> unsigned msg_type)
> {
> - assert(msg_data.file == BRW_IMMEDIATE_VALUE &&
> - msg_data.type == BRW_REGISTER_TYPE_UD);
> + assert(msg_data.type == BRW_REGISTER_TYPE_UD);
>
> brw_pixel_interpolator_query(p,
> retype(dst, BRW_REGISTER_TYPE_UW),
> src,
> inst->pi_noperspective,
> msg_type,
> - msg_data.dw1.ud,
> + msg_data,
> inst->mlen,
> inst->regs_written);
> }
> diff --git a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
> index 03fe680..8a73bda 100644
> --- a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
> +++ b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
> @@ -1180,6 +1180,23 @@ get_image_atomic_op(nir_intrinsic_op op, const glsl_type *type)
> }
> }
>
> +/* For most messages, we need one reg of ignored data; the hardware requires
> + * mlen==1 even when there is no payload. in the per-slot offset case, we'll
> + * replace this with the proper source data.
> + */
> +static void
> +setup_pixel_interpolater_instruction(fs_visitor *v,
> + nir_intrinsic_instr *instr,
> + fs_inst *inst,
> + int mlen = 1)
> +{
> + inst->mlen = mlen;
> + /* 2 floats per slot returned */
> + inst->regs_written = 2 * v->dispatch_width / 8;
> + inst->pi_noperspective = instr->variables[0]->var->data.interpolation ==
> + INTERP_QUALIFIER_NOPERSPECTIVE;
> +}
> +
It may be a good idea to change this into something like:
| static fs_inst *
| emit_pixel_interpolater_send(const fs_builder &bld,
| enum opcode opcode,
| const fs_reg &dst,
| const fs_reg &src,
| const fs_reg &desc,
| glsl_interp_qualifier interpolation)
in order to make sure that we don't forget to set these fields whenever
an interpolation instruction is created. The function could also take
care of allocating a dummy payload register in cases where src.file ==
BAD_FILE, and otherwise assume mlen == 2 * bld.dispatch_width() / 8, so
the caller doesn't need to care about that restriction.
> void
> fs_visitor::nir_emit_intrinsic(const fs_builder &bld, nir_intrinsic_instr *instr)
> {
> @@ -1584,27 +1601,71 @@ fs_visitor::nir_emit_intrinsic(const fs_builder &bld, nir_intrinsic_instr *instr
>
> fs_reg dst_xy = bld.vgrf(BRW_REGISTER_TYPE_F, 2);
>
> - /* For most messages, we need one reg of ignored data; the hardware
> - * requires mlen==1 even when there is no payload. in the per-slot
> - * offset case, we'll replace this with the proper source data.
> - */
> fs_reg src = vgrf(glsl_type::float_type);
> - int mlen = 1; /* one reg unless overriden */
> fs_inst *inst;
>
> switch (instr->intrinsic) {
> case nir_intrinsic_interp_var_at_centroid:
> inst = bld.emit(FS_OPCODE_INTERPOLATE_AT_CENTROID,
> dst_xy, src, fs_reg(0u));
> + setup_pixel_interpolater_instruction(this, instr, inst);
> break;
>
> case nir_intrinsic_interp_var_at_sample: {
> - /* XXX: We should probably handle non-constant sample id's */
> nir_const_value *const_sample = nir_src_as_const_value(instr->src[0]);
> - assert(const_sample);
> - unsigned msg_data = const_sample ? const_sample->i[0] << 4 : 0;
> - inst = bld.emit(FS_OPCODE_INTERPOLATE_AT_SAMPLE, dst_xy, src,
> - fs_reg(msg_data));
> +
> + if (const_sample) {
> + unsigned msg_data = const_sample->i[0] << 4;
> +
> + inst = bld.emit(FS_OPCODE_INTERPOLATE_AT_SAMPLE, dst_xy, src,
> + fs_reg(msg_data));
> +
> + setup_pixel_interpolater_instruction(this, instr, inst);
> + } else {
> + fs_reg sample_src = retype(get_nir_src(instr->src[0]),
> + BRW_REGISTER_TYPE_UD);
This could be declared const.
> + fs_reg sample_id_reg;
> +
> + if (nir_src_is_dynamically_uniform(instr->src[0])) {
> + sample_id_reg = vgrf(glsl_type::uint_type);
> + bld.SHL(sample_id_reg, sample_src, fs_reg(4u));
> + sample_id_reg = bld.emit_uniformize(sample_id_reg);
You could make the SHL instruction scalar by reordering it with respect
to the emit_uniformize(), like:
| const fs_reg sample_id = bld.emit_uniformize(sample_src);
| bld.exec_all().group(1, 0)
| .SHL(sample_id, sample_id, fs_reg(4u));
> + inst = bld.emit(FS_OPCODE_INTERPOLATE_AT_SAMPLE, dst_xy, src,
> + sample_id_reg);
> + setup_pixel_interpolater_instruction(this, instr, inst);
> + } else {
> + /* Make a loop that sends a message to the pixel interpolator
> + * for the sample number in each live channel. If there are
> + * multiple channels with the same sample number then these
> + * will be handled simultaneously with a single interation of
> + * the loop.
> + */
> + bld.emit(BRW_OPCODE_DO);
> +
> + /* Get the next live sample number into sample_id_reg */
> + sample_id_reg = bld.emit_uniformize(sample_src);
> +
Could declare this here at the same point you initialize it so you can
make it const.
> + /* Set the flag register so that we can perform the send
> + * message on all channels that have the same sample number
> + */
> + bld.CMP(bld.null_reg_ud(),
> + sample_src, sample_id_reg,
> + BRW_CONDITIONAL_EQ);
> + fs_reg msg_data = component(vgrf(glsl_type::uint_type), 0);
> + bld.SHL(msg_data, sample_id_reg, fs_reg(4u))
> + ->force_writemask_all = true;
You could make this SHL instruction scalar as well.
> + inst = bld.emit(FS_OPCODE_INTERPOLATE_AT_SAMPLE, dst_xy, src,
> + msg_data);
> + setup_pixel_interpolater_instruction(this, instr, inst);
> + set_predicate(BRW_PREDICATE_NORMAL, inst);
> +
> + /* Continue the loop if there are any live channels left */
> + set_predicate_inv(BRW_PREDICATE_NORMAL,
> + true, /* inverse */
> + bld.emit(BRW_OPCODE_WHILE));
Looks good. :)
> + }
> + }
> +
> break;
> }
>
> @@ -1617,6 +1678,7 @@ fs_visitor::nir_emit_intrinsic(const fs_builder &bld, nir_intrinsic_instr *instr
>
> inst = bld.emit(FS_OPCODE_INTERPOLATE_AT_SHARED_OFFSET, dst_xy, src,
> fs_reg(off_x | (off_y << 4)));
> + setup_pixel_interpolater_instruction(this, instr, inst);
> } else {
> src = vgrf(glsl_type::ivec2_type);
> fs_reg offset_src = retype(get_nir_src(instr->src[0]),
> @@ -1646,9 +1708,12 @@ fs_visitor::nir_emit_intrinsic(const fs_builder &bld, nir_intrinsic_instr *instr
> bld.SEL(offset(src, bld, i), itemp, fs_reg(7)));
> }
>
> - mlen = 2 * dispatch_width / 8;
> inst = bld.emit(FS_OPCODE_INTERPOLATE_AT_PER_SLOT_OFFSET, dst_xy, src,
> fs_reg(0u));
> + setup_pixel_interpolater_instruction(this,
> + instr,
> + inst,
> + 2 * dispatch_width / 8);
> }
> break;
> }
> @@ -1657,12 +1722,6 @@ fs_visitor::nir_emit_intrinsic(const fs_builder &bld, nir_intrinsic_instr *instr
> unreachable("Invalid intrinsic");
> }
>
> - inst->mlen = mlen;
> - /* 2 floats per slot returned */
> - inst->regs_written = 2 * dispatch_width / 8;
> - inst->pi_noperspective = instr->variables[0]->var->data.interpolation ==
> - INTERP_QUALIFIER_NOPERSPECTIVE;
> -
> for (unsigned j = 0; j < instr->num_components; j++) {
> fs_reg src = interp_reg(instr->variables[0]->var->data.location, j);
> src.type = dest.type;
> --
> 1.9.3
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