On Tue, Jan 15, 2019 at 7:54 AM Iago Toral Quiroga <ito...@igalia.com>
wrote:
> Some conversions are not directly supported in hardware and need to be
> split in two conversion instructions going through an intermediary type.
> Doing this at the NIR level simplifies a bit the complexity in the backend.
>
> v2:
> - Consider fp16 rounding conversion opcodes
> - Properly handle swizzles on conversion sources.
>
> Reviewed-by: Topi Pohjolainen <topi.pohjolai...@intel.com> (v1)
> ---
> src/intel/Makefile.sources | 1 +
> src/intel/compiler/brw_nir.c | 1 +
> src/intel/compiler/brw_nir.h | 2 +
> .../compiler/brw_nir_lower_conversions.c | 158 ++++++++++++++++++
> src/intel/compiler/meson.build | 1 +
> 5 files changed, 163 insertions(+)
> create mode 100644 src/intel/compiler/brw_nir_lower_conversions.c
>
> diff --git a/src/intel/Makefile.sources b/src/intel/Makefile.sources
> index 94a28d370e8..9975daa3ad1 100644
> --- a/src/intel/Makefile.sources
> +++ b/src/intel/Makefile.sources
> @@ -83,6 +83,7 @@ COMPILER_FILES = \
> compiler/brw_nir_analyze_boolean_resolves.c \
> compiler/brw_nir_analyze_ubo_ranges.c \
> compiler/brw_nir_attribute_workarounds.c \
> + compiler/brw_nir_lower_conversions.c \
> compiler/brw_nir_lower_cs_intrinsics.c \
> compiler/brw_nir_lower_image_load_store.c \
> compiler/brw_nir_lower_mem_access_bit_sizes.c \
> diff --git a/src/intel/compiler/brw_nir.c b/src/intel/compiler/brw_nir.c
> index 92d7fe4bede..572ab824a94 100644
> --- a/src/intel/compiler/brw_nir.c
> +++ b/src/intel/compiler/brw_nir.c
> @@ -882,6 +882,7 @@ brw_postprocess_nir(nir_shader *nir, const struct
> brw_compiler *compiler,
> OPT(nir_opt_move_comparisons);
>
> OPT(nir_lower_bool_to_int32);
> + OPT(brw_nir_lower_conversions);
>
This is *really* late and I don't think you actually want this to run after
we apply source/destination modifiers. If you just move it to right after
nir_opt_algebraic_late, that will fix a multitude of issues.
>
> OPT(nir_lower_locals_to_regs);
>
> diff --git a/src/intel/compiler/brw_nir.h b/src/intel/compiler/brw_nir.h
> index bc81950d47e..662b2627e95 100644
> --- a/src/intel/compiler/brw_nir.h
> +++ b/src/intel/compiler/brw_nir.h
> @@ -114,6 +114,8 @@ void brw_nir_lower_tcs_outputs(nir_shader *nir, const
> struct brw_vue_map *vue,
> GLenum tes_primitive_mode);
> void brw_nir_lower_fs_outputs(nir_shader *nir);
>
> +bool brw_nir_lower_conversions(nir_shader *nir);
> +
> bool brw_nir_lower_image_load_store(nir_shader *nir,
> const struct gen_device_info
> *devinfo);
> void brw_nir_rewrite_image_intrinsic(nir_intrinsic_instr *intrin,
> diff --git a/src/intel/compiler/brw_nir_lower_conversions.c
> b/src/intel/compiler/brw_nir_lower_conversions.c
> new file mode 100644
> index 00000000000..583167c7753
> --- /dev/null
> +++ b/src/intel/compiler/brw_nir_lower_conversions.c
> @@ -0,0 +1,158 @@
> +/*
> + * 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 "brw_nir.h"
> +#include "compiler/nir/nir_builder.h"
> +
> +static nir_op
> +get_conversion_op(nir_alu_type src_type,
> + unsigned src_bit_size,
> + nir_alu_type dst_type,
> + unsigned dst_bit_size,
> + nir_rounding_mode rounding_mode)
> +{
> + nir_alu_type src_full_type = (nir_alu_type) (src_type | src_bit_size);
> + nir_alu_type dst_full_type = (nir_alu_type) (dst_type | dst_bit_size);
> +
> + return nir_type_conversion_op(src_full_type, dst_full_type,
> rounding_mode);
> +}
> +
> +static nir_rounding_mode
> +get_opcode_rounding_mode(nir_op op)
> +{
> + switch (op) {
> + case nir_op_f2f16_rtz:
> + return nir_rounding_mode_rtz;
> + case nir_op_f2f16_rtne:
> + return nir_rounding_mode_rtne;
> + default:
> + return nir_rounding_mode_undef;
> + }
> +}
> +
> +static void
> +split_conversion(nir_builder *b, nir_alu_instr *alu, nir_op op1, nir_op
> op2)
> +{
> + b->cursor = nir_before_instr(&alu->instr);
> + assert(alu->dest.write_mask == 1);
> + nir_ssa_def *src = nir_ssa_for_alu_src(b, alu, 0);
>
Hrm... Given how late this pass runs, I'm not a fan of using
nir_ssa_for_alu_src because it might insert a MOV and we don't copy-prop
afterwards. Instead, we could assert that the destination is SSA and do
b->cursor = nir_after_instr(&alu->instr);
alu->op = op1;
alu->dest.bit_size =
nir_alu_type_get_type_size(nir_op_infos[alu->op].output_type);
nir_ssa_def *new_res = nir_build_alu(b, op2, &alu->dest.dest.ssa, NULL,
NULL, NULL);
nir_ssa_def_rewrite_uses_after(&alu->dest.dest.ssa,
nir_src_for_ssa(new_res),
new_res->parent_instr);
If you don't feel comfortable whacking the opcode in the original
instruction, then just make a new one and build it directly with the old
instruction's ALU src. Or, we could just move where it's run. (see my
comment above.)
> + nir_ssa_def *tmp = nir_build_alu(b, op1, src, NULL, NULL, NULL);
> + nir_ssa_def *res = nir_build_alu(b, op2, tmp, NULL, NULL, NULL);
> + nir_ssa_def_rewrite_uses(&alu->dest.dest.ssa, nir_src_for_ssa(res));
> + nir_instr_remove(&alu->instr);
> +}
> +
> +static bool
> +lower_instr(nir_builder *b, nir_alu_instr *alu)
> +{
> + unsigned src_bit_size = nir_src_bit_size(alu->src[0].src);
> + nir_alu_type src_type = nir_op_infos[alu->op].input_types[0];
> + nir_alu_type src_full_type = (nir_alu_type) (src_type | src_bit_size);
> +
> + unsigned dst_bit_size = nir_dest_bit_size(alu->dest.dest);
> + nir_alu_type dst_type = nir_op_infos[alu->op].output_type;
>
+ nir_alu_type dst_full_type = (nir_alu_type) (dst_type | dst_bit_size);
>
The nir_op_infos[*].output_type will already be a full type. Maybe just
delete the dst_type temporary so that no one gets confused and thinks it's
a base type.
> +
> + /* BDW PRM, vol02, Command Reference Instructions, mov - MOVE:
> + *
> + * "There is no direct conversion from HF to DF or DF to HF.
> + * Use two instructions and F (Float) as an intermediate type.
> + *
> + * There is no direct conversion from HF to Q/UQ or Q/UQ to HF.
> + * Use two instructions and F (Float) or a word integer type
> + * or a DWord integer type as an intermediate type."
> + */
> + if ((src_full_type == nir_type_float16 && dst_bit_size == 64) ||
> + (src_bit_size == 64 && dst_full_type == nir_type_float16)) {
> + nir_op op1 = get_conversion_op(src_type, src_bit_size, src_type, 32,
> + nir_rounding_mode_undef);
> + nir_op op2 = get_conversion_op(src_type, 32, dst_type, dst_bit_size,
> + get_opcode_rounding_mode(alu->op));
> + split_conversion(b, alu, op1, op2);
> + return true;
> + }
> +
> + /* SKL PRM, vol 02a, Command Reference: Instructions, Move:
> + *
> + * "There is no direct conversion from B/UB to DF or DF to B/UB. Use
> + * two instructions and a word or DWord intermediate type."
> + *
> + * "There is no direct conversion from B/UB to Q/UQ or Q/UQ to B/UB.
> + * Use two instructions and a word or DWord intermediate integer
> + * type."
> + */
> + if ((src_bit_size == 8 && dst_bit_size == 64) ||
> + (src_bit_size == 64 && dst_bit_size == 8)) {
> + nir_op op1 = get_conversion_op(src_type, src_bit_size, src_type, 32,
> + nir_rounding_mode_undef);
> + nir_op op2 = get_conversion_op(src_type, 32, dst_type, dst_bit_size,
> + nir_rounding_mode_undef);
> + split_conversion(b, alu, op1, op2);
> + return true;
> + }
> +
> + return false;
> +}
> +
> +static bool
> +lower_impl(nir_function_impl *impl)
> +{
> + 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)
> + continue;
> +
> + nir_alu_instr *alu = nir_instr_as_alu(instr);
> + assert(alu->dest.dest.is_ssa);
> +
> + if (nir_op_infos[alu->op].num_inputs > 1)
>
I don't think this is a reliable way to detect conversion opcodes. There
are many unary operations that aren't conversions. You're only getting
lucky because there are non which do float16 <-> 64=bit or 8-bit <->
64-bit. I've thought many times about throwing a boolean in nir_op_infos
for is_conversion. Maybe now is a good time to do it?
> + continue;
> +
> + progress = lower_instr(&b, alu) || progress;
> + }
> + }
> +
> + if (progress) {
> + nir_metadata_preserve(impl, nir_metadata_block_index |
> + nir_metadata_dominance);
> + }
> +
> + return progress;
> +}
> +
> +bool
> +brw_nir_lower_conversions(nir_shader *shader)
> +{
> + bool progress = false;
> +
> + nir_foreach_function(function, shader) {
> + if (function->impl)
> + progress |= lower_impl(function->impl);
> + }
> +
> + return progress;
> +}
> diff --git a/src/intel/compiler/meson.build
> b/src/intel/compiler/meson.build
> index f8e5e2518fe..9daf2a94260 100644
> --- a/src/intel/compiler/meson.build
> +++ b/src/intel/compiler/meson.build
> @@ -76,6 +76,7 @@ libintel_compiler_files = files(
> 'brw_nir_analyze_boolean_resolves.c',
> 'brw_nir_analyze_ubo_ranges.c',
> 'brw_nir_attribute_workarounds.c',
> + 'brw_nir_lower_conversions.c',
> 'brw_nir_lower_cs_intrinsics.c',
> 'brw_nir_lower_image_load_store.c',
> 'brw_nir_lower_mem_access_bit_sizes.c',
> --
> 2.17.1
>
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