[Mesa-dev] [PATCH v2 08/18] compiler/nir: add a lowering pass to convert the bit size of ALU operations
Jason Ekstrand
jason at jlekstrand.net
Mon Apr 30 21:27:45 UTC 2018
On Mon, Apr 30, 2018 at 7:18 AM, Iago Toral Quiroga <itoral at igalia.com>
wrote:
> Not all bit-sizes may be supported natively in hardware for all operations.
> This pass allows drivers to lower such operations to a bit-size that is
> actually supported and then converts the result back to the original
> bit-size.
>
> Compiler backends control which operations and wich bit-sizes require
> the lowering through a callback function.
>
> v2: generalize this pass and make it available in NIR core (Rob, Jason)
> ---
> src/compiler/Makefile.sources | 1 +
> src/compiler/nir/meson.build | 1 +
> src/compiler/nir/nir.h | 6 ++
> src/compiler/nir/nir_lower_bit_size.c | 127
> ++++++++++++++++++++++++++++++++++
> 4 files changed, 135 insertions(+)
> create mode 100644 src/compiler/nir/nir_lower_bit_size.c
>
> diff --git a/src/compiler/Makefile.sources b/src/compiler/Makefile.sources
> index aca9dab476..b5321588be 100644
> --- a/src/compiler/Makefile.sources
> +++ b/src/compiler/Makefile.sources
> @@ -237,6 +237,7 @@ NIR_FILES = \
> nir/nir_lower_phis_to_scalar.c \
> nir/nir_lower_regs_to_ssa.c \
> nir/nir_lower_returns.c \
> + nir/nir_lower_bit_size.c \
> nir/nir_lower_samplers.c \
> nir/nir_lower_samplers_as_deref.c \
> nir/nir_lower_subgroups.c \
> diff --git a/src/compiler/nir/meson.build b/src/compiler/nir/meson.build
> index b28a565d0c..62fe5167d3 100644
> --- a/src/compiler/nir/meson.build
> +++ b/src/compiler/nir/meson.build
> @@ -144,6 +144,7 @@ files_libnir = files(
> 'nir_lower_vec_to_movs.c',
> 'nir_lower_wpos_center.c',
> 'nir_lower_wpos_ytransform.c',
> + 'nir_lower_bit_size.c',
> 'nir_metadata.c',
> 'nir_move_vec_src_uses_to_dest.c',
> 'nir_normalize_cubemap_coords.c',
> diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
> index f3326e6df9..e7f2b145b3 100644
> --- a/src/compiler/nir/nir.h
> +++ b/src/compiler/nir/nir.h
> @@ -2763,6 +2763,12 @@ bool nir_lower_to_source_mods(nir_shader *shader);
>
> bool nir_lower_gs_intrinsics(nir_shader *shader);
>
> +typedef unsigned (*nir_lower_bit_size_callback)(const nir_alu_instr *,
> void *);
> +
> +bool nir_lower_bit_size(nir_shader *shader,
> + nir_lower_bit_size_callback callback,
> + void *callback_data);
> +
> typedef enum {
> nir_lower_imul64 = (1 << 0),
> nir_lower_isign64 = (1 << 1),
> diff --git a/src/compiler/nir/nir_lower_bit_size.c
> b/src/compiler/nir/nir_lower_bit_size.c
> new file mode 100644
> index 0000000000..8e0fd663a1
> --- /dev/null
> +++ b/src/compiler/nir/nir_lower_bit_size.c
> @@ -0,0 +1,127 @@
> +/*
> + * Copyright © 2018 Intel Corporation
> + *
> + * 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_builder.h"
> +
> +/**
> + * Some ALU operations may not be supported in hardware in specific
> bit-sizes.
> + * This pass allows implementations to selectively lower such operations
> to
> + * a bit-size that is supported natively and the converts the result back
> to
> + * the original bit-size.
> + */
> +static nir_ssa_def *
> +convert_to_bit_size(nir_builder *bld,
> + nir_ssa_def *src,
> + nir_alu_type type,
> + unsigned bit_size)
> +{
> + nir_alu_type base_type = nir_alu_type_get_base_type(type);
> + nir_alu_type lowered_type = bit_size | base_type;
> +
> + nir_op opcode =
> + nir_type_conversion_op(type, lowered_type, nir_rounding_mode_undef);
> +
> + return nir_build_alu(bld, opcode, src, NULL, NULL, NULL);
> +}
> +
> +static void
> +lower_instr(nir_builder *bld, nir_alu_instr *alu, unsigned bit_size)
> +{
> + const nir_op op = alu->op;
> +
> + bld->cursor = nir_before_instr(&alu->instr);
> +
> + /* Convert each source to the requested bit-size */
> + nir_ssa_def *srcs[4] = { NULL, NULL, NULL, NULL };
> + const unsigned num_inputs = nir_op_infos[op].num_inputs;'
>
I don't know that we need the num_inputs temporary
> + for (unsigned i = 0; i < num_inputs; i++) {
> + nir_ssa_def *src = nir_ssa_for_alu_src(bld, alu, i);
> +
> + nir_alu_type type = nir_op_infos[op].input_types[i];
> + unsigned type_size = nir_alu_type_get_type_size(type);
>
Again, I don't think this temporary is needed.
> + if (type_size == 0)
> + srcs[i] = convert_to_bit_size(bld, src, type, bit_size);
> + else
> + srcs[i] = src;
> + }
> +
> + /* Emit the lowered ALU instruction */
> + nir_ssa_def *lowered_dst =
> + nir_build_alu(bld, op, srcs[0], srcs[1], srcs[2], srcs[3]);
> +
> + /* Convert result back to the original bit-size */
> + unsigned dst_bit_size = alu->dest.dest.ssa.bit_size;
> + nir_alu_type type = nir_op_infos[op].output_type;
> + nir_ssa_def *dst = convert_to_bit_size(bld, lowered_dst, type,
> dst_bit_size);
> + nir_ssa_def_rewrite_uses(&alu->dest.dest.ssa, nir_src_for_ssa(dst));
> +}
> +
> +static bool
> +lower_impl(nir_function_impl *impl,
> + nir_lower_bit_size_callback callback,
> + void *callback_data)
> +{
> + nir_builder b;
> + nir_builder_init(&b, impl);
> + bool progress = false;
> +
> + nir_foreach_block(block, impl) {
> + nir_foreach_instr_safe(instr, block) {
> + if (instr->type == nir_instr_type_alu) {
>
I'd make this "if (!= alu) continue;" so we can keep the nesting depth down.
All my comments are fairly trivial so
Reviewed-by: Jason Ekstrand <jason at jlekstrand.net>
> + nir_alu_instr *alu = nir_instr_as_alu(instr);
> + assert(alu->dest.dest.is_ssa);
> +
> + unsigned lower_bit_size = callback(alu, callback_data);
> + if (lower_bit_size == 0)
> + continue;
> +
> + assert(lower_bit_size != alu->dest.dest.ssa.bit_size);
> +
> + lower_instr(&b, alu, lower_bit_size);
> + progress = true;
> + }
> + }
> + }
> +
> + if (progress) {
> + nir_metadata_preserve(impl, nir_metadata_block_index |
> + nir_metadata_dominance);
> + }
> +
> + return progress;
> +}
> +
> +bool
> +nir_lower_bit_size(nir_shader *shader,
> + nir_lower_bit_size_callback callback,
> + void *callback_data)
> +{
> + bool progress = false;
> +
> + nir_foreach_function(function, shader) {
> + if (function->impl)
> + progress |= lower_impl(function->impl, callback, callback_data);
> + }
> +
> + return progress;
> +}
> --
> 2.14.1
>
>
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