[Mesa-dev] [PATCH] nir: Add an IO scalarizing pass using the intrinsic's first_component.
Kenneth Graunke
kenneth at whitecape.org
Wed Aug 10 07:08:57 UTC 2016
On Friday, August 5, 2016 4:27:03 PM PDT Eric Anholt wrote:
> vc4 wants to have per-scalar IO load/stores so that dead code elimination
> can happen on a more granular basis, which it has been doing in the
> backend using a multiplication by 4 of the intrinsic's driver_location.
> We can represent it properly in the NIR using the first_component field,
> though.
> ---
>
> Next part of the vc4 GTN series. I can't do uniforms because they
> don't have a first-component field.
>
> NIR developers -- is this the right usage of the first-component
> field?
It looks right to me.
> Also, do I need to be splitting up the variable declarations
> if I do this?
Leaving them as-is should be fine. Variables are pretty meaningless
after nir_lower_io(). i965 basically doesn't use them at all
anymore...with my FS input rework, everything's in the intrinsics.
> There's a check during shader printing that the
> fractional component of the variable matches the component field of
> the intrinsic, even if the intrinsics's component value would lie
> within the vector variable.
Not seeing that code offhand...my guess is that it's trying to print
the name of the variable being loaded. It's probably just looking for
one with location_frac == component, instead of checking whether
location_frac <= component < location_frac + vector_elements
That could probably be spiffed up for nicer pretty printing, but
it shouldn't actually affect any functionality.
I think it'd be great to handle load_interpolated_input here too;
I'll send a follow-up patch to do that. Feel free to review/squash
as you see fit.
Reviewed-by: Kenneth Graunke <kenneth at whitecape.org>
>
> src/compiler/Makefile.sources | 1 +
> src/compiler/nir/nir.h | 1 +
> src/compiler/nir/nir_lower_io_to_scalar.c | 129 ++++++++++++++++++++++++++++++
> 3 files changed, 131 insertions(+)
> create mode 100644 src/compiler/nir/nir_lower_io_to_scalar.c
>
> diff --git a/src/compiler/Makefile.sources b/src/compiler/Makefile.sources
> index 0ff9b23e4c38..04016d32db56 100644
> --- a/src/compiler/Makefile.sources
> +++ b/src/compiler/Makefile.sources
> @@ -201,6 +201,7 @@ NIR_FILES = \
> nir/nir_lower_indirect_derefs.c \
> nir/nir_lower_io.c \
> nir/nir_lower_io_to_temporaries.c \
> + nir/nir_lower_io_to_scalar.c \
> nir/nir_lower_io_types.c \
> nir/nir_lower_passthrough_edgeflags.c \
> nir/nir_lower_phis_to_scalar.c \
> diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
> index 9ce5be2176d9..379a5f8e022e 100644
> --- a/src/compiler/nir/nir.h
> +++ b/src/compiler/nir/nir.h
> @@ -2398,6 +2398,7 @@ void nir_lower_alu_to_scalar(nir_shader *shader);
> void nir_lower_load_const_to_scalar(nir_shader *shader);
>
> void nir_lower_phis_to_scalar(nir_shader *shader);
> +void nir_lower_io_to_scalar(nir_shader *shader, nir_variable_mode mask);
>
> void nir_lower_samplers(nir_shader *shader,
> const struct gl_shader_program *shader_program);
> diff --git a/src/compiler/nir/nir_lower_io_to_scalar.c b/src/compiler/nir/nir_lower_io_to_scalar.c
> new file mode 100644
> index 000000000000..f2345d58acfc
> --- /dev/null
> +++ b/src/compiler/nir/nir_lower_io_to_scalar.c
> @@ -0,0 +1,129 @@
> +/*
> + * Copyright © 2016 Broadcom
> + *
> + * Permission is hereby granted, free of charge, to any person obtaining a
> + * copy of this software and associated documentation files (the "Software"),
> + * to deal in the Software without restriction, including without limitation
> + * the rights to use, copy, modify, merge, publish, distribute, sublicense,
> + * and/or sell copies of the Software, and to permit persons to whom the
> + * Software is furnished to do so, subject to the following conditions:
> + *
> + * The above copyright notice and this permission notice (including the next
> + * paragraph) shall be included in all copies or substantial portions of the
> + * Software.
> + *
> + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
> + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
> + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
> + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
> + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
> + * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
> + * IN THE SOFTWARE.
> + */
> +
> +#include "nir.h"
> +#include "nir_builder.h"
> +
> +/** @file nir_lower_io_to_scalar.c
> + *
> + * Replaces nir_load_input/nir_store_output operations with num_components !=
> + * 1 with individual per-channel operations.
> + */
> +
> +static void
> +lower_load_input_to_scalar(nir_builder *b, nir_intrinsic_instr *intr)
> +{
> + b->cursor = nir_before_instr(&intr->instr);
> +
> + assert(intr->dest.is_ssa);
> +
> + nir_ssa_def *loads[4];
> +
> + for (unsigned i = 0; i < intr->num_components; i++) {
> + nir_intrinsic_instr *chan_intr =
> + nir_intrinsic_instr_create(b->shader, intr->intrinsic);
> + nir_ssa_dest_init(&chan_intr->instr, &chan_intr->dest,
> + 1, intr->dest.ssa.bit_size, NULL);
> + chan_intr->num_components = 1;
> +
> + nir_intrinsic_set_base(chan_intr, nir_intrinsic_base(intr));
> + nir_intrinsic_set_component(chan_intr, nir_intrinsic_component(intr) + i);
> + /* offset */
> + chan_intr->src[0] = intr->src[0];
> +
> + nir_builder_instr_insert(b, &chan_intr->instr);
> +
> + loads[i] = &chan_intr->dest.ssa;
> + }
> +
> + nir_ssa_def_rewrite_uses(&intr->dest.ssa,
> + nir_src_for_ssa(nir_vec(b, loads,
> + intr->num_components)));
> + nir_instr_remove(&intr->instr);
> +}
> +
> +static void
> +lower_store_output_to_scalar(nir_builder *b, nir_intrinsic_instr *intr)
> +{
> + b->cursor = nir_before_instr(&intr->instr);
> +
> + nir_ssa_def *value = nir_ssa_for_src(b, intr->src[0], intr->num_components);
> +
> + for (unsigned i = 0; i < intr->num_components; i++) {
> + if (!(nir_intrinsic_write_mask(intr) & (1 << i)))
> + continue;
> +
> + nir_intrinsic_instr *chan_intr =
> + nir_intrinsic_instr_create(b->shader, intr->intrinsic);
> + chan_intr->num_components = 1;
> +
> + nir_intrinsic_set_base(chan_intr, nir_intrinsic_base(intr));
> + nir_intrinsic_set_write_mask(chan_intr, 0x1);
> + nir_intrinsic_set_component(chan_intr, nir_intrinsic_component(intr) + i);
> +
> + /* value */
> + chan_intr->src[0] = nir_src_for_ssa(nir_channel(b, value, i));
> + /* offset */
> + chan_intr->src[1] = intr->src[1];
> +
> + nir_builder_instr_insert(b, &chan_intr->instr);
> + }
> +
> + nir_instr_remove(&intr->instr);
> +}
> +
> +void
> +nir_lower_io_to_scalar(nir_shader *shader, nir_variable_mode mask)
> +{
> + nir_foreach_function(function, shader) {
> + if (function->impl) {
> + nir_builder b;
> + nir_builder_init(&b, function->impl);
> +
> + nir_foreach_block(block, function->impl) {
> + nir_foreach_instr_safe(instr, block) {
> + if (instr->type != nir_instr_type_intrinsic)
> + continue;
> +
> + nir_intrinsic_instr *intr = nir_instr_as_intrinsic(instr);
> +
> + if (intr->num_components == 1)
> + continue;
> +
> + switch (intr->intrinsic) {
> + case nir_intrinsic_load_input:
> + if (mask & nir_var_shader_in)
> + lower_load_input_to_scalar(&b, intr);
> + break;
> + case nir_intrinsic_store_output:
> + if (mask & nir_var_shader_out)
> + lower_store_output_to_scalar(&b, intr);
> + break;
> + default:
> + break;
> + }
> + }
> + }
> + }
> + }
> +}
>
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