[Mesa-dev] [PATCH v3 02/42] intel/compiler: add a NIR pass to lower conversions
Iago Toral
itoral at igalia.com
Fri Jan 18 07:48:24 UTC 2019
On Thu, 2019-01-17 at 13:42 -0600, Jason Ekstrand wrote:
> On Tue, Jan 15, 2019 at 7:54 AM Iago Toral Quiroga <itoral at 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.pohjolainen at 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.
Sure, I'll move it there.
> >
> > 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
I did this because I found cases where we would have things like a vec4
load and then a handful of swizzled MOVs to extract the components of
the vec4 into scalars and this helper would handle the swizzled sources
gracefully.However, I think what you suggest below should be just fine,
so I'll do that.
> 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.
Right, will do that.
> > +
> >
> > + /* 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?
Yes, I knew that this was not going to only let conversions through and
was relying on what you say above. Adding an is_conversion field souns
good to me, alternatively I guess we could add a is_conversion()
helper, but I guess having the field in nir_op_infos maye be a bit
easier to maintain if we want to add more opcodes in the future.
>
> > + 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',
> >
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