Matt Turner <matts...@gmail.com> writes: > On Fri, Aug 7, 2015 at 9:31 AM, Neil Roberts <n...@linux.intel.com> wrote: >> 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 possible sample number. >> This is necessary because the indirect send message doesn't seem to >> have a way to specify a different value for each fragment. > > Heh, I think this was the solution Curro had in mind a couple of years ago. :) > > I've Cc'd him. It'd be good for him to review this. > Sigh, it's really awful that our hardware only supports a single sample index for the whole SIMD thread... I was thinking though that there might be a better alternative to running the sample-index interpolator query in a loop: The "Per Slot Offset" interpolator query does allow independent offsets for each channel, couldn't we pass the hard-coded table of sample offsets (see brw_multisample_state.h) to the shader (e.g. as push constants or hard-coded as vector immediates), use VxH indirect indexing to fetch the right offset for each channel and then lower it into a non-dynamically-uniform interpolateAtOffset, which the hardware can handle natively?
>> The range of possible sample numbers is determined using
>> STATE_NUM_SAMPLES. When linking the shader it will now add a reference
>> to this state if any dynamically non-uniform calls to
>> interpolateAtSample are found.
>>
>> 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.
>> ---
>> 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 | 119
>> +++++++++++++++++++++----
>> src/mesa/drivers/dri/i965/brw_program.c | 54 +++++++++++
>> src/mesa/drivers/dri/i965/brw_program.h | 1 +
>> src/mesa/drivers/dri/i965/brw_shader.cpp | 2 +
>> 7 files changed, 185 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 4d39762..25524d4 100644
>> --- a/src/mesa/drivers/dri/i965/brw_eu_emit.c
>> +++ b/src/mesa/drivers/dri/i965/brw_eu_emit.c
>> @@ -3192,26 +3192,38 @@ 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;
>>
>> - 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_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 c86ca04..88dbc62 100644
>> --- a/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
>> +++ b/src/mesa/drivers/dri/i965/brw_fs_generator.cpp
>> @@ -1328,15 +1328,14 @@
>> 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 ee964a0..0fdb9ae 100644
>> --- a/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
>> +++ b/src/mesa/drivers/dri/i965/brw_fs_nir.cpp
>> @@ -1167,6 +1167,47 @@ fs_visitor::emit_percomp(const fs_builder &bld, const
>> fs_inst &inst,
>> }
>> }
>>
>> +/* 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;
>> +}
>> +
>> +static fs_reg
>> +get_num_samples_reg(fs_visitor *v)
>> +{
>> + struct gl_program_parameter_list *params = v->prog->Parameters;
>> + static gl_state_index tokens[STATE_LENGTH] = {
>
> I suspect this isn't thread-safe.
>
>> + STATE_NUM_SAMPLES
>> + };
>> + GLuint index = _mesa_add_state_reference(params, tokens);
>> + unsigned i;
>> +
>> + /* Try to find an existing copy of the uniform */
>> + for (i = 0; i < v->uniforms; i++) {
>> + if (v->stage_prog_data->param[i] ==
>> + &v->prog->Parameters->ParameterValues[index][0])
>> + goto found;
>> + }
>> +
>> + v->stage_prog_data->param[v->uniforms++] =
>> + &v->prog->Parameters->ParameterValues[index][0];
>> +
>> +found:
>> + return retype(fs_reg(UNIFORM, i), BRW_REGISTER_TYPE_UD);
>> +}
>> +
>> void
>> fs_visitor::nir_emit_intrinsic(const fs_builder &bld, nir_intrinsic_instr
>> *instr)
>> {
>> @@ -1438,27 +1479,73 @@ 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);
>> + 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);
>> + 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 each possible sample number so that each individual
>> + * message will be dynamically uniform. The number of samples
>> + * is determined by accessing the STATE_NUM_SAMPLES state
>> var.
>> + */
>> + fs_reg i_reg = vgrf(glsl_type::uint_type);
>> + fs_reg sample_id_reg = vgrf(glsl_type::uint_type);
>> + fs_reg num_samples_reg = get_num_samples_reg(this);
>> +
>> + bld.MOV(i_reg, fs_reg(0u));
>> +
>> + bld.emit(BRW_OPCODE_DO);
>> +
>> + bld.CMP(bld.null_reg_ud(),
>> + sample_src, i_reg,
>> + BRW_CONDITIONAL_EQ);
>
> I think you might be able to put all of this on one line.
>
>> + bld.IF(BRW_PREDICATE_NORMAL);
>> + bld.SHL(sample_id_reg, i_reg, fs_reg(4u));
>> + sample_id_reg = bld.emit_uniformize(sample_id_reg);
>> + inst = bld.emit(FS_OPCODE_INTERPOLATE_AT_SAMPLE, dst_xy, src,
>> + sample_id_reg);
>> + setup_pixel_interpolater_instruction(this, instr, inst);
>> + bld.emit(BRW_OPCODE_ENDIF);
>> +
>> + bld.ADD(i_reg, i_reg, fs_reg(1u));
>> + bld.CMP(bld.null_reg_ud(),
>> + i_reg, num_samples_reg,
>> + BRW_CONDITIONAL_GE);
>
> I think you might be able to put all of this on one line.
>
> If you want, you could reverse the order of the loop (that is, iterate
> from num_samples_reg down to 0) and then save the
> opt_cmod_propagation() pass some work and just emit an ADD with a a
> conditional_mod in order to get rid of the CMP instruction.
>
>> + inst = bld.emit(BRW_OPCODE_BREAK);
>> + inst->predicate = BRW_PREDICATE_NORMAL;
>> + bld.emit(BRW_OPCODE_WHILE);
>
> You can actually get rid of the BREAK by predicating the WHILE (and
> setting predicate_inverse on it). There's also a nice
> set_predicate(predicate, inst) function you should use.
>
> If you want to do that, I think it'll take a small amount of work in
> the BRW_OPCODE_WHILE case in brw_cfg.cpp to understand that a
> predicated WHILE has two successors.
>
>> + }
>> + }
>> +
>> break;
>> }
>>
>> @@ -1471,6 +1558,7 @@ 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]),
>> @@ -1500,9 +1588,12 @@ 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;
>> }
>> @@ -1511,12 +1602,6 @@ 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;
>> diff --git a/src/mesa/drivers/dri/i965/brw_program.c
>> b/src/mesa/drivers/dri/i965/brw_program.c
>> index 467a893..6430c5d 100644
>> --- a/src/mesa/drivers/dri/i965/brw_program.c
>> +++ b/src/mesa/drivers/dri/i965/brw_program.c
>> @@ -146,6 +146,8 @@ brwProgramStringNotify(struct gl_context *ctx,
>> prog->nir = brw_create_nir(brw, NULL, prog, MESA_SHADER_FRAGMENT,
>> true);
>> }
>>
>> + brw_add_interpolate_at_sample_params(prog);
>> +
>> brw_fs_precompile(ctx, NULL, prog);
>> break;
>> }
>> @@ -246,6 +248,58 @@ brw_add_texrect_params(struct gl_program *prog)
>> }
>> }
>>
>> +static bool
>> +find_interpolate_at_sample_in_block(nir_block *block,
>> + void *data)
>> +{
>> + nir_foreach_instr_safe(block, instr) {
>
> I don't think you need _safe here. At least I can't see why it's necessary.
>
>> + if (instr->type != nir_instr_type_intrinsic)
>> + continue;
>> +
>> + nir_intrinsic_instr *intrinsic_instr = nir_instr_as_intrinsic(instr);
>> +
>> + if (intrinsic_instr->intrinsic != nir_intrinsic_interp_var_at_sample)
>> + continue;
>> +
>> + /* If the sample number is known to be dynamically uniform then
>> + * the generator won't need the num_samples state.
>> + */
>> + if (nir_src_is_dynamically_uniform(intrinsic_instr->src[0]))
>> + continue;
>> +
>> + return false;
>> + }
>> +
>> + return true;
>> +}
>> +
>> +void
>> +brw_add_interpolate_at_sample_params(struct gl_program *prog)
>> +{
>> + static gl_state_index tokens[STATE_LENGTH] = {
>
> I suspect this isn't thread-safe.
>
>> + STATE_NUM_SAMPLES
>> + };
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