202 lines
7.8 KiB
C
202 lines
7.8 KiB
C
/*
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* Copyright © 2020 Valve Corporation
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*
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* Permission is hereby granted, free of charge, to any person obtaining a
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* copy of this software and associated documentation files (the "Software"),
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* to deal in the Software without restriction, including without limitation
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* the rights to use, copy, modify, merge, publish, distribute, sublicense,
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* and/or sell copies of the Software, and to permit persons to whom the
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* Software is furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice (including the next
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* paragraph) shall be included in all copies or substantial portions of the
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* Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
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* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
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* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
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* IN THE SOFTWARE.
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*
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*/
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#include "nir.h"
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#include "nir_builder.h"
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static bool
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nir_lower_discard_to_demote_instr(nir_builder *b, nir_instr *instr, void *data)
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{
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if (instr->type != nir_instr_type_intrinsic)
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return false;
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nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
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switch (intrin->intrinsic) {
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case nir_intrinsic_discard:
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intrin->intrinsic = nir_intrinsic_demote;
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return true;
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case nir_intrinsic_discard_if:
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intrin->intrinsic = nir_intrinsic_demote_if;
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return true;
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case nir_intrinsic_load_helper_invocation:
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intrin->intrinsic = nir_intrinsic_is_helper_invocation;
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return true;
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default:
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return false;
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}
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}
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static bool
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nir_lower_demote_to_discard_instr(nir_builder *b, nir_instr *instr, void *data)
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{
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if (instr->type != nir_instr_type_intrinsic)
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return false;
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nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
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switch (intrin->intrinsic) {
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case nir_intrinsic_demote:
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intrin->intrinsic = nir_intrinsic_discard;
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return true;
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case nir_intrinsic_demote_if:
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intrin->intrinsic = nir_intrinsic_discard_if;
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return true;
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case nir_intrinsic_is_helper_invocation:
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case nir_intrinsic_load_helper_invocation: {
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/* If the shader doesn't need helper invocations,
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* we can assume there are none */
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b->cursor = nir_before_instr(instr);
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nir_ssa_def *zero = nir_imm_false(b);
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nir_ssa_def_rewrite_uses(&intrin->dest.ssa, zero);
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nir_instr_remove_v(instr);
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return true;
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}
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default:
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return false;
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}
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}
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static nir_ssa_def *
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insert_is_helper(nir_builder *b, nir_instr *instr)
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{
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/* find best place to insert is_helper */
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nir_cf_node *node = &instr->block->cf_node;
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while (node->parent->type != nir_cf_node_function)
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node = nir_cf_node_prev(node->parent);
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nir_block *block = nir_cf_node_as_block(node);
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if (block == instr->block) {
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b->cursor = nir_before_instr(instr);
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} else {
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b->cursor = nir_after_block_before_jump(block);
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}
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return nir_is_helper_invocation(b, 1);
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}
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static bool
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nir_lower_load_helper_to_is_helper(nir_builder *b, nir_instr *instr, void *data)
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{
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if (instr->type != nir_instr_type_intrinsic)
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return false;
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nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
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nir_ssa_def *is_helper = *(nir_ssa_def**) data;
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switch (intrin->intrinsic) {
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case nir_intrinsic_demote:
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case nir_intrinsic_demote_if:
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/* insert is_helper at last top level occasion */
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if (is_helper == NULL) {
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is_helper = insert_is_helper(b, instr);
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*(nir_ssa_def**)data = is_helper;
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return true;
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} else {
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return false;
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}
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case nir_intrinsic_load_helper_invocation:
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/* Don't update data: as long as we didn't encounter any demote(),
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* we can insert new is_helper() intrinsics. These are placed at
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* top-level blocks to ensure correct behavior w.r.t. loops */
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if (is_helper == NULL)
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is_helper = insert_is_helper(b, instr);
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nir_ssa_def_rewrite_uses(&intrin->dest.ssa, is_helper);
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nir_instr_remove_v(instr);
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return true;
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default:
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return false;
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}
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}
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/**
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* Optimize discard and demote opcodes.
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*
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* If force_correct_quad_ops_after_discard is true and quad operations are
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* used, discard() will be converted to demote() and gl_HelperInvocation will
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* be lowered to helperInvocationEXT(). This is intended as workaround for
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* game bugs to force correct derivatives after kill. This lowering is not
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* valid in the general case as it might change the result of subgroup
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* operations and loop behavior.
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*
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* Otherwise, if demote is used and no ops need helper invocations, demote()
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* will be converted to discard() as an optimization.
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*/
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bool
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nir_lower_discard_or_demote(nir_shader *shader,
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bool force_correct_quad_ops_after_discard)
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{
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if (shader->info.stage != MESA_SHADER_FRAGMENT)
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return false;
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/* We need uses_discard/demote and needs_*_helper_invocations. */
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nir_shader_gather_info(shader, nir_shader_get_entrypoint(shader));
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/* Validate that if uses_demote is set, uses_discard is also be set. */
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assert(!shader->info.fs.uses_demote || shader->info.fs.uses_discard);
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/* Quick skip. */
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if (!shader->info.fs.uses_discard)
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return false;
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bool progress = false;
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if (force_correct_quad_ops_after_discard &&
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shader->info.fs.needs_quad_helper_invocations) {
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/* If we need correct derivatives, convert discard to demote only when
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* derivatives are actually used.
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*/
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progress = nir_shader_instructions_pass(shader,
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nir_lower_discard_to_demote_instr,
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nir_metadata_block_index |
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nir_metadata_dominance |
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nir_metadata_live_ssa_defs |
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nir_metadata_instr_index,
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NULL);
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shader->info.fs.uses_demote = true;
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} else if (!shader->info.fs.needs_quad_helper_invocations &&
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!shader->info.fs.needs_all_helper_invocations &&
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shader->info.fs.uses_demote) {
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/* If we don't need any helper invocations, convert demote to discard. */
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progress = nir_shader_instructions_pass(shader,
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nir_lower_demote_to_discard_instr,
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nir_metadata_block_index |
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nir_metadata_dominance,
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NULL);
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shader->info.fs.uses_demote = false;
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} else if (shader->info.fs.uses_demote &&
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BITSET_TEST(shader->info.system_values_read,
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nir_system_value_from_intrinsic(nir_intrinsic_load_helper_invocation))) {
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/* load_helper needs to preserve the value (whether an invocation is
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* a helper lane) from the beginning of the shader. */
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nir_ssa_def *is_helper = NULL;
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progress = nir_shader_instructions_pass(shader,
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nir_lower_load_helper_to_is_helper,
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nir_metadata_block_index |
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nir_metadata_dominance,
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&is_helper);
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BITSET_CLEAR(shader->info.system_values_read,
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nir_system_value_from_intrinsic(nir_intrinsic_load_helper_invocation));
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}
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/* Validate again that if uses_demote is set, uses_discard is also be set. */
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assert(!shader->info.fs.uses_demote || shader->info.fs.uses_discard);
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return progress;
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}
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