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/*
* Copyright © 2019 Valve Corporation
*
* 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.
*
*/
#include "aco_ir.h"
#include <algorithm>
#include <vector>
/*
* Implements an analysis pass to determine the number of uses
* for each SSA-definition.
*/
namespace aco {
namespace {
struct dce_ctx {
int current_block;
std::vector<uint16_t> uses;
std::vector<std::vector<bool>> live;
dce_ctx(Program* program)
: current_block(program->blocks.size() - 1), uses(program->peekAllocationId())
{
live.reserve(program->blocks.size());
for (Block& block : program->blocks)
live.emplace_back(block.instructions.size());
}
};
void
process_block(dce_ctx& ctx, Block& block)
{
std::vector<bool>& live = ctx.live[block.index];
assert(live.size() == block.instructions.size());
bool process_predecessors = false;
for (int idx = block.instructions.size() - 1; idx >= 0; idx--) {
if (live[idx])
continue;
aco_ptr<Instruction>& instr = block.instructions[idx];
if (!is_dead(ctx.uses, instr.get())) {
for (const Operand& op : instr->operands) {
if (op.isTemp()) {
if (ctx.uses[op.tempId()] == 0)
process_predecessors = true;
ctx.uses[op.tempId()]++;
}
}
live[idx] = true;
}
}
if (process_predecessors) {
for (unsigned pred_idx : block.linear_preds)
ctx.current_block = std::max(ctx.current_block, (int)pred_idx);
}
}
} /* end namespace */
std::vector<uint16_t>
dead_code_analysis(Program* program)
{
dce_ctx ctx(program);
while (ctx.current_block >= 0) {
unsigned next_block = ctx.current_block--;
process_block(ctx, program->blocks[next_block]);
}
return ctx.uses;
}
} // namespace aco
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