On Wed, Jul 4, 2018 at 2:22 AM, Grazvydas Ignotas <nota...@gmail.com> wrote:
> On Wed, Jul 4, 2018 at 9:13 AM, Jason Ekstrand <ja...@jlekstrand.net>
> wrote:
> > Many fragment shaders do a discard using relatively little information
> > but still put the discard fairly far down in the shader for no good
> > reason. If the discard is moved higher up, we can possibly avoid doing
> > some or almost all of the work in the shader. When this lets us skip
> > texturing operations, it's an especially high win.
> >
> > One of the biggest offenders here is DXVK. The D3D APIs have different
> > rules for discards than OpenGL and Vulkan. One effective way (which is
> > what DXVK uses) to implement DX behavior on top of GL or Vulkan is to
> > wait until the very end of the shader to discard. This ends up in the
> > pessimal case where we always do all of the work before discarding.
> > This pass helps some DXVK shaders significantly.
> > ---
> > src/compiler/Makefile.sources | 1 +
> > src/compiler/nir/meson.build | 1 +
> > src/compiler/nir/nir.h | 10 +
> > src/compiler/nir/nir_opt_discard.c | 404 +++++++++++++++++++++++++++++
> > 4 files changed, 416 insertions(+)
> > create mode 100644 src/compiler/nir/nir_opt_discard.c
> >
> > diff --git a/src/compiler/Makefile.sources b/src/compiler/Makefile.
> sources
> > index 9e3fbdc2612..8600ce81281 100644
> > --- a/src/compiler/Makefile.sources
> > +++ b/src/compiler/Makefile.sources
> > @@ -271,6 +271,7 @@ NIR_FILES = \
> > nir/nir_opt_cse.c \
> > nir/nir_opt_dce.c \
> > nir/nir_opt_dead_cf.c \
> > + nir/nir_opt_discard.c \
> > nir/nir_opt_gcm.c \
> > nir/nir_opt_global_to_local.c \
> > nir/nir_opt_if.c \
> > diff --git a/src/compiler/nir/meson.build b/src/compiler/nir/meson.build
> > index 28aa8de7014..e339258bb94 100644
> > --- a/src/compiler/nir/meson.build
> > +++ b/src/compiler/nir/meson.build
> > @@ -156,6 +156,7 @@ files_libnir = files(
> > 'nir_opt_cse.c',
> > 'nir_opt_dce.c',
> > 'nir_opt_dead_cf.c',
> > + 'nir_opt_discard.c',
> > 'nir_opt_gcm.c',
> > 'nir_opt_global_to_local.c',
> > 'nir_opt_if.c',
> > diff --git a/src/compiler/nir/nir.h b/src/compiler/nir/nir.h
> > index 92ab3a699cc..44006dac160 100644
> > --- a/src/compiler/nir/nir.h
> > +++ b/src/compiler/nir/nir.h
> > @@ -2022,6 +2022,13 @@ typedef struct nir_shader_compiler_options {
> > */
> > bool vs_inputs_dual_locations;
> >
> > + /**
> > + * Whether or not derivatives are still a safe operation after a
> discard
> > + * has occurred. Optimization passes may be able to be a bit more
> > + * agressive if this is true.
> > + */
> > + bool derivatives_safe_after_discard;
> > +
> > unsigned max_unroll_iterations;
> > } nir_shader_compiler_options;
> >
> > @@ -2899,6 +2906,9 @@ bool nir_opt_dce(nir_shader *shader);
> >
> > bool nir_opt_dead_cf(nir_shader *shader);
> >
> > +bool nir_opt_discard_if(nir_shader *shader);
> > +bool nir_opt_move_discards_to_top(nir_shader *shader);
> > +
> > bool nir_opt_gcm(nir_shader *shader, bool value_number);
> >
> > bool nir_opt_if(nir_shader *shader);
> > diff --git a/src/compiler/nir/nir_opt_discard.c
> b/src/compiler/nir/nir_opt_discard.c
> > new file mode 100644
> > index 00000000000..eb1a8296282
> > --- /dev/null
> > +++ b/src/compiler/nir/nir_opt_discard.c
> > @@ -0,0 +1,404 @@
> > +/*
> > + * Copyright © 2014 Intel Corporation
>
> 2018?
>
Yeah...
> > + *
> > + * 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.
> > + *
> > + * Authors:
> > + * Jason Ekstrand (ja...@jlekstrand.net)
> > + *
> > + */
> > +
> > +#include "nir.h"
> > +#include "nir_builder.h"
> > +#include "nir_control_flow.h"
> > +#include "nir_worklist.h"
> > +
> > +static bool
> > +block_has_only_discard(nir_block *block)
> > +{
> > + nir_instr *instr = nir_block_first_instr(block);
> > + if (instr == NULL || instr != nir_block_last_instr(block))
> > + return false;
> > +
> > + if (instr->type != nir_instr_type_intrinsic)
> > + return false;
> > +
> > + nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
> > + return intrin->intrinsic == nir_intrinsic_discard;
> > +}
> > +
> > +static bool
> > +opt_discard_if_impl(nir_function_impl *impl)
> > +{
> > + bool progress = false;
> > +
> > + nir_builder b;
> > + nir_builder_init(&b, impl);
> > +
> > + nir_foreach_block(block, impl) {
> > + nir_if *nif = nir_block_get_following_if(block);
> > + if (!nif)
> > + continue;
> > +
> > + bool discard_in_then;
> > + if (block_has_only_discard(nir_if_first_then_block(nif)))
> > + discard_in_then = true;
> > + else if (block_has_only_discard(nir_if_first_else_block(nif)))
> > + discard_in_then = false;
> > + else
> > + continue;
> > +
> > + b.cursor = nir_after_block(block);
> > + nir_ssa_def *cond = nir_ssa_for_src(&b, nif->condition, 1);
> > + if (!discard_in_then)
> > + cond = nir_inot(&b, cond);
> > +
> > + nir_intrinsic_instr *discard_if =
> > + nir_intrinsic_instr_create(b.shader,
> nir_intrinsic_discard_if);
> > + discard_if->src[0] = nir_src_for_ssa(cond);
> > + nir_builder_instr_insert(&b, &discard_if->instr);
> > +
> > + nir_lower_phis_to_regs_block(nir_cf_node_as_block(
> > + nir_cf_node_next(&nif->cf_node)));
> > +
> > + nir_cf_list list;
> > + if (discard_in_then)
> > + nir_cf_list_extract(&list, &nif->else_list);
> > + else
> > + nir_cf_list_extract(&list, &nif->then_list);
> > + nir_cf_reinsert(&list, nir_after_instr(&discard_if->instr));
> > +
> > + nir_cf_node_remove(&nif->cf_node);
> > +
> > + progress = true;
> > + }
> > +
> > + /* If we modified control-flow, metadata is toast. Also, we may have
> > + * lowered some phis to registers so we need to back into SSA.
> > + */
> > + if (progress) {
> > + nir_metadata_preserve(impl, 0);
> > + nir_lower_regs_to_ssa_impl(impl);
> > + }
> > +
> > + return progress;
> > +}
> > +
> > +bool
> > +nir_opt_discard_if(nir_shader *shader)
> > +{
> > + assert(shader->info.stage == MESA_SHADER_FRAGMENT);
> > +
> > + bool progress = false;
> > +
> > + nir_foreach_function(function, shader) {
> > + if (function->impl &&
> > + opt_discard_if_impl(function->impl))
> > + progress = true;
> > + }
> > +
> > + return progress;
> > +}
> > +
> > +static bool
> > +nir_variable_mode_is_read_only(nir_variable_mode mode)
> > +{
> > + return mode == nir_var_shader_in ||
> > + mode == nir_var_uniform ||
> > + mode == nir_var_system_value;
> > +}
> > +
> > +static bool
> > +nir_op_is_derivative(nir_op op)
> > +{
> > + return op == nir_op_fddx ||
> > + op == nir_op_fddy ||
> > + op == nir_op_fddx_fine ||
> > + op == nir_op_fddy_fine ||
> > + op == nir_op_fddx_coarse ||
> > + op == nir_op_fddy_coarse;
> > +}
> > +
> > +static bool
> > +nir_texop_implies_derivative(nir_texop op)
> > +{
> > + return op == nir_texop_tex ||
> > + op == nir_texop_txb ||
> > + op == nir_texop_lod;
> > +}
> > +
> > +static bool
> > +nir_intrinsic_writes_external_memory(nir_intrinsic_op intrin)
> > +{
> > + switch (intrin) {
> > + case nir_intrinsic_store_deref:
> > + case nir_intrinsic_copy_deref:
> > + case nir_intrinsic_deref_atomic_add:
> > + case nir_intrinsic_deref_atomic_imin:
> > + case nir_intrinsic_deref_atomic_umin:
> > + case nir_intrinsic_deref_atomic_imax:
> > + case nir_intrinsic_deref_atomic_umax:
> > + case nir_intrinsic_deref_atomic_and:
> > + case nir_intrinsic_deref_atomic_or:
> > + case nir_intrinsic_deref_atomic_xor:
> > + case nir_intrinsic_deref_atomic_exchange:
> > + case nir_intrinsic_deref_atomic_comp_swap:
> > + /* If we ever start using variables for SSBO ops, we'll need to do
> > + * something here. For now, they're safe.
> > + */
> > + return false;
> > +
> > + case nir_intrinsic_store_ssbo:
> > + case nir_intrinsic_ssbo_atomic_add:
> > + case nir_intrinsic_ssbo_atomic_imin:
> > + case nir_intrinsic_ssbo_atomic_umin:
> > + case nir_intrinsic_ssbo_atomic_imax:
> > + case nir_intrinsic_ssbo_atomic_umax:
> > + case nir_intrinsic_ssbo_atomic_and:
> > + case nir_intrinsic_ssbo_atomic_or:
> > + case nir_intrinsic_ssbo_atomic_xor:
> > + case nir_intrinsic_ssbo_atomic_exchange:
> > + case nir_intrinsic_ssbo_atomic_comp_swap:
> > + return true;
> > +
> > + case nir_intrinsic_image_deref_store:
> > + case nir_intrinsic_image_deref_atomic_add:
> > + case nir_intrinsic_image_deref_atomic_min:
> > + case nir_intrinsic_image_deref_atomic_max:
> > + case nir_intrinsic_image_deref_atomic_and:
> > + case nir_intrinsic_image_deref_atomic_or:
> > + case nir_intrinsic_image_deref_atomic_xor:
> > + case nir_intrinsic_image_deref_atomic_exchange:
> > + case nir_intrinsic_image_deref_atomic_comp_swap:
> > + return true;
> > +
> > + default:
> > + return false;
> > + }
> > +}
> > +
> > +static bool
> > +add_src_instr_to_worklist(nir_src *src, void *wl)
> > +{
> > + if (!src->is_ssa)
> > + return false;
> > +
> > + nir_instr_worklist_push_tail(wl, src->ssa->parent_instr);
> > + return true;
> > +}
> > +
> > +static bool
> > +try_move_discard(nir_builder *b, nir_intrinsic_instr *discard)
> > +{
> > + /* We require the discard to be in the top level of control flow. We
> > + * could, in theory, move discards that are inside ifs or loops but
> that
> > + * would be a lot more work.
> > + */
> > + if (discard->instr.block->cf_node.parent->type !=
> nir_cf_node_function)
> > + return false;
> > +
> > + /* Build the set of all instructions discard depends on. While
> we're at
> > + * it, we watch out for any cases that would prevent us from moving
> the
> > + * instruction.
> > + */
> > + struct set *dep_instrs = _mesa_set_create(NULL, _mesa_hash_pointer,
> > + _mesa_key_pointer_equal);
> > +
> > + bool can_move_discard = true;
> > + nir_instr_worklist *work = nir_instr_worklist_create();
> > + add_src_instr_to_worklist(&discard->src[0], work);
> > + nir_foreach_instr_in_worklist(instr, work) {
> > + /* Don't process an instruction twice */
> > + if (_mesa_set_search(dep_instrs, instr))
> > + continue;
> > +
> > + /* Phi instructions can't be moved at all. Also, if we're
> dependent on
> > + * a phi then we are dependent on some other bit of control flow
> and
> > + * it's hard to figure out the proper condition.
> > + */
> > + if (instr->type == nir_instr_type_phi) {
> > + can_move_discard = false;
> > + break;
> > + }
> > +
> > + if (instr->type == nir_instr_type_intrinsic) {
> > + nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
> > + if (intrin->intrinsic == nir_intrinsic_load_deref) {
> > + nir_deref_instr *deref = nir_src_as_deref(intrin->src[0]);
> > + if (!nir_variable_mode_is_read_only(deref->mode)) {
> > + can_move_discard = false;
> > + break;
> > + }
> > + } else if (!(nir_intrinsic_infos[intrin->intrinsic].flags &
> > + NIR_INTRINSIC_CAN_REORDER)) {
> > + can_move_discard = false;
> > + break;
> > + }
> > + }
> > +
> > + if (!nir_foreach_src(instr, add_src_instr_to_worklist, work)) {
> > + can_move_discard = false;
> > + break;
> > + }
> > +
> > + _mesa_set_add(dep_instrs, instr);
> > + }
> > +
> > + if (!can_move_discard) {
> > + nir_instr_worklist_destroy(work);
> > + _mesa_set_destroy(dep_instrs, NULL);
> > + return false;
> > + }
> > +
> > + nir_function_impl *impl =
> > + nir_cf_node_as_function(discard->instr.block->cf_node.parent);
> > +
> > + /* Walk the list of instructions and move the discard and everything
> it
> > + * depends on to the top. We walk the instruction list here because
> it
> > + * ensures that everything stays in its original order. This
> provides
> > + * stability for the algorithm and ensures that we don't
> accidentalyly
>
> accidentally
>
Thanks! Both fixed locally.
--Jason
_______________________________________________
mesa-dev mailing list
mesa-dev@lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/mesa-dev
