123 lines
4.1 KiB
C
123 lines
4.1 KiB
C
/*
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* Copyright (C) 2021 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 FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
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* SOFTWARE.
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*/
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#include "ir3.h"
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/* Sometimes we can get unreachable blocks from NIR. In particular this happens
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* for blocks after an if where both sides end in a break/continue. These blocks
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* are then reachable only via the physical CFG. This pass deletes these blocks
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* and reroutes the physical edge past it.
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*/
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static void
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delete_block(struct ir3 *ir, struct ir3_block *block)
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{
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struct ir3_instruction *end = NULL;
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foreach_instr (instr, &block->instr_list) {
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if (instr->opc == OPC_END) {
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end = instr;
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break;
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}
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}
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/* The end block can be legitimately unreachable if the shader only exits via
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* discarding. ir3_legalize will then insert a branch to the end. Keep the
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* block around but delete all the other instructions and make the end not
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* take any sources, so that we don't have any dangling references to other
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* unreachable blocks.
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*/
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if (end) {
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foreach_instr_safe (instr, &block->instr_list) {
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if (instr != end)
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list_delinit(&instr->node);
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}
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end->srcs_count = 0;
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return;
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}
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for (unsigned i = 0; i < 2; i++) {
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struct ir3_block *succ = block->successors[i];
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if (!succ)
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continue;
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unsigned pred_idx = ir3_block_get_pred_index(succ, block);
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/* If this isn't the last predecessor, we swap it with the last before
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* removing it.
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*/
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bool swap_pred = pred_idx != succ->predecessors_count - 1;
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foreach_instr (phi, &succ->instr_list) {
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if (phi->opc != OPC_META_PHI)
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break;
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if (swap_pred)
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phi->srcs[pred_idx] = phi->srcs[phi->srcs_count - 1];
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phi->srcs_count--;
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}
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if (swap_pred) {
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succ->predecessors[pred_idx] =
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succ->predecessors[succ->predecessors_count - 1];
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}
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succ->predecessors_count--;
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}
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for (unsigned i = 0; i < 2; i++) {
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struct ir3_block *succ = block->physical_successors[i];
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if (!succ)
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continue;
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ir3_block_remove_physical_predecessor(succ, block);
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}
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if (block->physical_predecessors_count != 0) {
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/* There should be only one physical predecessor, for the fallthrough
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* edge.
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*/
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assert(block->physical_predecessors_count == 1);
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struct ir3_block *pred = block->physical_predecessors[0];
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assert(block->node.next != &ir->block_list);
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struct ir3_block *next = list_entry(block->node.next, struct ir3_block, node);
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if (pred->physical_successors[1] == block)
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pred->physical_successors[1] = next;
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else
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pred->physical_successors[0] = next;
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ir3_block_add_physical_predecessor(next, pred);
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}
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}
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bool
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ir3_remove_unreachable(struct ir3 *ir)
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{
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bool progress = false;
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foreach_block_safe (block, &ir->block_list) {
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if (block != ir3_start_block(ir) && block->predecessors_count == 0) {
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delete_block(ir, block);
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list_del(&block->node);
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progress = true;
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}
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}
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return progress;
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}
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