115 lines
3.5 KiB
C++
115 lines
3.5 KiB
C++
/*
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* Copyright © 2019 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 "aco_ir.h"
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#include <algorithm>
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#include <vector>
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/*
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* Implements an analysis pass to determine the number of uses
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* for each SSA-definition.
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*/
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namespace aco {
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namespace {
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struct dce_ctx {
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int current_block;
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std::vector<uint16_t> uses;
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std::vector<std::vector<bool>> live;
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dce_ctx(Program* program)
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: current_block(program->blocks.size() - 1), uses(program->peekAllocationId())
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{
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live.reserve(program->blocks.size());
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for (Block& block : program->blocks)
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live.emplace_back(block.instructions.size());
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}
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};
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void
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process_block(dce_ctx& ctx, Block& block)
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{
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std::vector<bool>& live = ctx.live[block.index];
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assert(live.size() == block.instructions.size());
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bool process_predecessors = false;
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for (int idx = block.instructions.size() - 1; idx >= 0; idx--) {
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if (live[idx])
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continue;
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aco_ptr<Instruction>& instr = block.instructions[idx];
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if (!is_dead(ctx.uses, instr.get())) {
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for (const Operand& op : instr->operands) {
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if (op.isTemp()) {
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if (ctx.uses[op.tempId()] == 0)
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process_predecessors = true;
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ctx.uses[op.tempId()]++;
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}
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}
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live[idx] = true;
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}
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}
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if (process_predecessors) {
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for (unsigned pred_idx : block.linear_preds)
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ctx.current_block = std::max(ctx.current_block, (int)pred_idx);
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}
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}
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} /* end namespace */
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bool
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is_dead(const std::vector<uint16_t>& uses, Instruction* instr)
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{
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if (instr->definitions.empty() || instr->isBranch() ||
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instr->opcode == aco_opcode::p_init_scratch)
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return false;
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if (std::any_of(instr->definitions.begin(), instr->definitions.end(),
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[&uses](const Definition& def) { return !def.isTemp() || uses[def.tempId()]; }))
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return false;
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return !(get_sync_info(instr).semantics & (semantic_volatile | semantic_acqrel));
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}
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std::vector<uint16_t>
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dead_code_analysis(Program* program)
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{
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dce_ctx ctx(program);
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while (ctx.current_block >= 0) {
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unsigned next_block = ctx.current_block--;
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process_block(ctx, program->blocks[next_block]);
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}
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/* add one use to exec to prevent startpgm from being removed */
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aco_ptr<Instruction>& startpgm = program->blocks[0].instructions[0];
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assert(startpgm->opcode == aco_opcode::p_startpgm);
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ctx.uses[startpgm->definitions.back().tempId()]++;
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return ctx.uses;
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}
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} // namespace aco
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