On 06/19/2018 08:24 AM, Rob Clark wrote:
> v2: reword comment about lower_helper_invocations to be more clear
> that it might not work on all hardware
> v3: add special variant of load_sample_id which does not imply per-
> sample shading
>
> Signed-off-by: Rob Clark <robdcl...@gmail.com>
> ---
> Yeah, new intrinsic name is a bit funny sounding, but I couldn't
> think of anything better.
>
> src/compiler/nir/nir.h | 12 ++++++++++++
> src/compiler/nir/nir_intrinsics.py | 3 +++
> src/compiler/nir/nir_lower_system_values.c | 17 +++++++++++++++++
> .../drivers/freedreno/ir3/ir3_compiler_nir.c | 1 +
> src/gallium/drivers/freedreno/ir3/ir3_nir.c | 1 +
> 5 files changed, 34 insertions(+)
>
> diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
> index 2d620454796..cb9a4af64cf 100644
> --- a/src/compiler/nir/nir.h
> +++ b/src/compiler/nir/nir.h
> @@ -1981,6 +1981,18 @@ typedef struct nir_shader_compiler_options {
> */
> bool lower_base_vertex;
>
> + /**
> + * If enabled, gl_HelperInvocation will be lowered as:
> + *
> + * !((1 << sample_id) & sample_mask_in))
I recently encountered something related to this. Issue #22 of the
GL_ARB_shader_image_load_store spec suggests using (gl_SampleMaskIn[0]
== 0) to detect a helper invocation. There's a note that
implementations that support > 32 samples will also need to check
gl_SampleMaskIn[1]. Did you try that? It should generate less code.
See also piglit commit c89439fcaba7259b25d090df43a6bf2aac6483d7.
> + *
> + * This depends on some possibly hw implementation details, which may
> + * not be true for all hw. In particular that the FS is only executed
> + * for covered samples or for helper invocations. So, do not blindly
> + * enable this option.
> + */
> + bool lower_helper_invocation;
> +
> bool lower_cs_local_index_from_id;
>
> bool lower_device_index_to_zero;
> diff --git a/src/compiler/nir/nir_intrinsics.py
> b/src/compiler/nir/nir_intrinsics.py
> index 484b2d4fd68..5523243a564 100644
> --- a/src/compiler/nir/nir_intrinsics.py
> +++ b/src/compiler/nir/nir_intrinsics.py
> @@ -422,6 +422,9 @@ system_value("instance_id", 1)
> system_value("base_instance", 1)
> system_value("draw_id", 1)
> system_value("sample_id", 1)
> +# sample_id_no_per_sample is like sample_id but does not imply per-
> +# sample shading. See the lower_helper_invocation option.
> +system_value("sample_id_no_per_sample", 1)
> system_value("sample_pos", 2)
> system_value("sample_mask_in", 1)
> system_value("primitive_id", 1)
> diff --git a/src/compiler/nir/nir_lower_system_values.c
> b/src/compiler/nir/nir_lower_system_values.c
> index 487da042620..8c5fdbb1f54 100644
> --- a/src/compiler/nir/nir_lower_system_values.c
> +++ b/src/compiler/nir/nir_lower_system_values.c
> @@ -136,6 +136,23 @@ convert_block(nir_block *block, nir_builder *b)
> nir_load_first_vertex(b));
> break;
>
> + case SYSTEM_VALUE_HELPER_INVOCATION:
> + if (b->shader->options->lower_helper_invocation) {
> + nir_ssa_def *tmp;
> +
> + tmp = nir_ishl(b,
> + nir_imm_int(b, 1),
> + nir_load_sample_id_no_per_sample(b));
> +
> + tmp = nir_iand(b,
> + nir_load_sample_mask_in(b),
> + tmp);
> +
> + sysval = nir_inot(b, nir_i2b(b, tmp));
> + }
> +
> + break;
> +
> case SYSTEM_VALUE_INSTANCE_INDEX:
> sysval = nir_iadd(b,
> nir_load_instance_id(b),
> diff --git a/src/gallium/drivers/freedreno/ir3/ir3_compiler_nir.c
> b/src/gallium/drivers/freedreno/ir3/ir3_compiler_nir.c
> index ed87eff9976..9cad7c6e559 100644
> --- a/src/gallium/drivers/freedreno/ir3/ir3_compiler_nir.c
> +++ b/src/gallium/drivers/freedreno/ir3/ir3_compiler_nir.c
> @@ -2360,6 +2360,7 @@ emit_intrinsic(struct ir3_context *ctx,
> nir_intrinsic_instr *intr)
> dst[0] = ctx->instance_id;
> break;
> case nir_intrinsic_load_sample_id:
> + case nir_intrinsic_load_sample_id_no_per_sample:
> if (!ctx->samp_id) {
> ctx->samp_id = create_input(b, 0);
> ctx->samp_id->regs[0]->flags |= IR3_REG_HALF;
> diff --git a/src/gallium/drivers/freedreno/ir3/ir3_nir.c
> b/src/gallium/drivers/freedreno/ir3/ir3_nir.c
> index 9ada3889eb9..e665fb933b9 100644
> --- a/src/gallium/drivers/freedreno/ir3/ir3_nir.c
> +++ b/src/gallium/drivers/freedreno/ir3/ir3_nir.c
> @@ -52,6 +52,7 @@ static const nir_shader_compiler_options options = {
> .lower_extract_byte = true,
> .lower_extract_word = true,
> .lower_all_io_to_temps = true,
> + .lower_helper_invocation = true,
> };
>
> struct nir_shader *
>
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