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* Copyright © 2016 Red Hat
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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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* 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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* 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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#include "nir_builder.h"
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/** @file nir_opt_conditional_discard.c
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* Handles optimization of lowering of
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* - if (cond) discard to discard_if(cond) and
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* - if (cond) demote to demote_if(cond)
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* - if (cond) terminate to terminate_if(cond)
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nir_opt_conditional_discard_block(nir_builder *b, nir_block *block)
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if (nir_cf_node_is_first(&block->cf_node))
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nir_cf_node *prev_node = nir_cf_node_prev(&block->cf_node);
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if (prev_node->type != nir_cf_node_if)
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nir_if *if_stmt = nir_cf_node_as_if(prev_node);
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nir_block *then_block = nir_if_first_then_block(if_stmt);
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nir_block *else_block = nir_if_first_else_block(if_stmt);
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/* check there is only one else block and it is empty */
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if (nir_if_last_else_block(if_stmt) != else_block)
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if (!exec_list_is_empty(&else_block->instr_list))
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/* check there is only one then block and it has only one instruction in it */
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if (nir_if_last_then_block(if_stmt) != then_block)
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if (exec_list_is_empty(&then_block->instr_list))
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if (exec_list_length(&then_block->instr_list) > 1)
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* make sure no subsequent phi nodes point at this if.
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nir_block *after = nir_cf_node_as_block(nir_cf_node_next(&if_stmt->cf_node));
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nir_foreach_instr_safe(instr, after) {
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if (instr->type != nir_instr_type_phi)
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nir_phi_instr *phi = nir_instr_as_phi(instr);
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nir_foreach_phi_src(phi_src, phi) {
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if (phi_src->pred == then_block ||
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phi_src->pred == else_block)
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/* Get the first instruction in the then block and confirm it is
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* a discard or a demote instruction.
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nir_instr *instr = nir_block_first_instr(then_block);
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if (instr->type != nir_instr_type_intrinsic)
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nir_intrinsic_instr *intrin = nir_instr_as_intrinsic(instr);
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nir_intrinsic_op op = intrin->intrinsic;
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assert(if_stmt->condition.is_ssa);
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nir_ssa_def *cond = if_stmt->condition.ssa;
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b->cursor = nir_before_cf_node(prev_node);
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switch (intrin->intrinsic) {
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case nir_intrinsic_discard:
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op = nir_intrinsic_discard_if;
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case nir_intrinsic_demote:
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op = nir_intrinsic_demote_if;
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case nir_intrinsic_terminate:
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op = nir_intrinsic_terminate_if;
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case nir_intrinsic_discard_if:
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case nir_intrinsic_demote_if:
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case nir_intrinsic_terminate_if:
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assert(intrin->src[0].is_ssa);
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cond = nir_iand(b, cond, intrin->src[0].ssa);
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nir_intrinsic_instr *discard_if =
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nir_intrinsic_instr_create(b->shader, op);
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discard_if->src[0] = nir_src_for_ssa(cond);
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nir_instr_insert_before_cf(prev_node, &discard_if->instr);
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nir_instr_remove(&intrin->instr);
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nir_cf_node_remove(&if_stmt->cf_node);
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nir_opt_conditional_discard(nir_shader *shader)
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bool progress = false;
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nir_foreach_function(function, shader) {
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if (function->impl) {
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nir_builder_init(&builder, function->impl);
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bool impl_progress = false;
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nir_foreach_block_safe(block, function->impl) {
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if (nir_opt_conditional_discard_block(&builder, block))
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impl_progress = true;
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nir_metadata_preserve(function->impl, nir_metadata_none);
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nir_metadata_preserve(function->impl, nir_metadata_all);