107 lines
3.5 KiB
C++
107 lines
3.5 KiB
C++
// Copyright 2021 yuzu Emulator Project
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// Licensed under GPLv2 or any later version
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// Refer to the license.txt file included.
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#include <algorithm>
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#include <boost/container/small_vector.hpp>
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#include "shader_recompiler/frontend/ir/basic_block.h"
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#include "shader_recompiler/frontend/ir/value.h"
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#include "shader_recompiler/ir_opt/passes.h"
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namespace Shader::Optimization {
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namespace {
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template <bool TEST_USES>
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void DeadInstElimination(IR::Block* const block) {
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// We iterate over the instructions in reverse order.
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// This is because removing an instruction reduces the number of uses for earlier instructions.
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auto it{block->end()};
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while (it != block->begin()) {
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--it;
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if constexpr (TEST_USES) {
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if (it->HasUses() || it->MayHaveSideEffects()) {
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continue;
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}
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}
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it->Invalidate();
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it = block->Instructions().erase(it);
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}
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}
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void DeletedPhiArgElimination(IR::Program& program, std::span<const IR::Block*> dead_blocks) {
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for (IR::Block* const block : program.blocks) {
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for (IR::Inst& phi : *block) {
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if (!IR::IsPhi(phi)) {
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continue;
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}
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for (size_t i = 0; i < phi.NumArgs(); ++i) {
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if (std::ranges::find(dead_blocks, phi.PhiBlock(i)) == dead_blocks.end()) {
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continue;
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}
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// Phi operand at this index is an unreachable block
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phi.ErasePhiOperand(i);
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--i;
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}
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}
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}
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}
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void DeadBranchElimination(IR::Program& program) {
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boost::container::small_vector<const IR::Block*, 3> dead_blocks;
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const auto begin_it{program.syntax_list.begin()};
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for (auto node_it = begin_it; node_it != program.syntax_list.end(); ++node_it) {
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if (node_it->type != IR::AbstractSyntaxNode::Type::If) {
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continue;
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}
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IR::Inst* const cond_ref{node_it->data.if_node.cond.Inst()};
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const IR::U1 cond{cond_ref->Arg(0)};
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if (!cond.IsImmediate()) {
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continue;
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}
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if (cond.U1()) {
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continue;
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}
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// False immediate condition. Remove condition ref, erase the entire branch.
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cond_ref->Invalidate();
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// Account for nested if-statements within the if(false) branch
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u32 nested_ifs{1u};
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while (node_it->type != IR::AbstractSyntaxNode::Type::EndIf || nested_ifs > 0) {
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node_it = program.syntax_list.erase(node_it);
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switch (node_it->type) {
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case IR::AbstractSyntaxNode::Type::If:
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++nested_ifs;
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break;
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case IR::AbstractSyntaxNode::Type::EndIf:
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--nested_ifs;
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break;
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case IR::AbstractSyntaxNode::Type::Block: {
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IR::Block* const block{node_it->data.block};
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DeadInstElimination<false>(block);
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dead_blocks.push_back(block);
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break;
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}
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default:
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break;
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}
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}
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// Erase EndIf node of the if(false) branch
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node_it = program.syntax_list.erase(node_it);
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// Account for loop increment
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--node_it;
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}
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if (!dead_blocks.empty()) {
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DeletedPhiArgElimination(program, std::span(dead_blocks.data(), dead_blocks.size()));
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}
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}
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} // namespace
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void DeadCodeEliminationPass(IR::Program& program) {
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DeadBranchElimination(program);
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for (IR::Block* const block : program.post_order_blocks) {
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DeadInstElimination<true>(block);
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}
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}
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} // namespace Shader::Optimization
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