shader: SSA and dominance
This commit is contained in:
ReinUsesLisp
ameerj
parent
2d48a7b4d0
commit
6c4cc0cd06
24 changed files with 569 additions and 76 deletions
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@ -36,6 +36,7 @@ static std::array<Block, 2> Split(Block&& block, Location pc, BlockId new_id) {
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.cond{true},
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.branch_true{new_id},
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.branch_false{UNREACHABLE_BLOCK_ID},
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.imm_predecessors{},
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},
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Block{
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.begin{pc},
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@ -46,6 +47,7 @@ static std::array<Block, 2> Split(Block&& block, Location pc, BlockId new_id) {
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.cond{block.cond},
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.branch_true{block.branch_true},
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.branch_false{block.branch_false},
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.imm_predecessors{},
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},
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};
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}
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@ -108,7 +110,7 @@ static bool HasFlowTest(Opcode opcode) {
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}
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}
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static std::string Name(const Block& block) {
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static std::string NameOf(const Block& block) {
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if (block.begin.IsVirtual()) {
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return fmt::format("\"Virtual {}\"", block.id);
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} else {
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@ -154,13 +156,127 @@ bool Block::Contains(Location pc) const noexcept {
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}
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Function::Function(Location start_address)
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: entrypoint{start_address}, labels{Label{
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: entrypoint{start_address}, labels{{
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.address{start_address},
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.block_id{0},
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.stack{},
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}} {}
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void Function::BuildBlocksMap() {
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const size_t num_blocks{NumBlocks()};
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blocks_map.resize(num_blocks);
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for (size_t block_index = 0; block_index < num_blocks; ++block_index) {
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Block& block{blocks_data[block_index]};
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blocks_map[block.id] = █
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}
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}
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void Function::BuildImmediatePredecessors() {
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for (const Block& block : blocks_data) {
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if (block.branch_true != UNREACHABLE_BLOCK_ID) {
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blocks_map[block.branch_true]->imm_predecessors.push_back(block.id);
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}
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if (block.branch_false != UNREACHABLE_BLOCK_ID) {
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blocks_map[block.branch_false]->imm_predecessors.push_back(block.id);
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}
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}
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}
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void Function::BuildPostOrder() {
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boost::container::small_vector<BlockId, 0x110> block_stack;
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post_order_map.resize(NumBlocks());
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Block& first_block{blocks_data[blocks.front()]};
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first_block.post_order_visited = true;
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block_stack.push_back(first_block.id);
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const auto visit_branch = [&](BlockId block_id, BlockId branch_id) {
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if (branch_id == UNREACHABLE_BLOCK_ID) {
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return false;
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}
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if (blocks_map[branch_id]->post_order_visited) {
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return false;
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}
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blocks_map[branch_id]->post_order_visited = true;
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// Calling push_back twice is faster than insert on msvc
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block_stack.push_back(block_id);
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block_stack.push_back(branch_id);
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return true;
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};
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while (!block_stack.empty()) {
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const Block* const block{blocks_map[block_stack.back()]};
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block_stack.pop_back();
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if (!visit_branch(block->id, block->branch_true) &&
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!visit_branch(block->id, block->branch_false)) {
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post_order_map[block->id] = static_cast<u32>(post_order_blocks.size());
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post_order_blocks.push_back(block->id);
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}
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}
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}
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void Function::BuildImmediateDominators() {
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auto transform_block_id{std::views::transform([this](BlockId id) { return blocks_map[id]; })};
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auto reverse_order_but_first{std::views::reverse | std::views::drop(1) | transform_block_id};
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auto has_idom{std::views::filter([](Block* block) { return block->imm_dominator; })};
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auto intersect{[this](Block* finger1, Block* finger2) {
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while (finger1 != finger2) {
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while (post_order_map[finger1->id] < post_order_map[finger2->id]) {
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finger1 = finger1->imm_dominator;
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}
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while (post_order_map[finger2->id] < post_order_map[finger1->id]) {
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finger2 = finger2->imm_dominator;
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}
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}
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return finger1;
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}};
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for (Block& block : blocks_data) {
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block.imm_dominator = nullptr;
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}
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Block* const start_block{&blocks_data[blocks.front()]};
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start_block->imm_dominator = start_block;
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bool changed{true};
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while (changed) {
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changed = false;
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for (Block* const block : post_order_blocks | reverse_order_but_first) {
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Block* new_idom{};
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for (Block* predecessor : block->imm_predecessors | transform_block_id | has_idom) {
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new_idom = new_idom ? intersect(predecessor, new_idom) : predecessor;
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}
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changed |= block->imm_dominator != new_idom;
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block->imm_dominator = new_idom;
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}
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}
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}
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void Function::BuildDominanceFrontier() {
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auto transform_block_id{std::views::transform([this](BlockId id) { return blocks_map[id]; })};
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auto has_enough_predecessors{[](Block& block) { return block.imm_predecessors.size() >= 2; }};
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for (Block& block : blocks_data | std::views::filter(has_enough_predecessors)) {
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for (Block* current : block.imm_predecessors | transform_block_id) {
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while (current != block.imm_dominator) {
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current->dominance_frontiers.push_back(current->id);
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current = current->imm_dominator;
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}
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}
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}
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}
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CFG::CFG(Environment& env_, Location start_address) : env{env_} {
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VisitFunctions(start_address);
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for (Function& function : functions) {
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function.BuildBlocksMap();
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function.BuildImmediatePredecessors();
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function.BuildPostOrder();
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function.BuildImmediateDominators();
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function.BuildDominanceFrontier();
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}
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}
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void CFG::VisitFunctions(Location start_address) {
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functions.emplace_back(start_address);
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for (FunctionId function_id = 0; function_id < functions.size(); ++function_id) {
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while (!functions[function_id].labels.empty()) {
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@ -202,6 +318,7 @@ void CFG::AnalyzeLabel(FunctionId function_id, Label& label) {
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.cond{true},
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.branch_true{UNREACHABLE_BLOCK_ID},
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.branch_false{UNREACHABLE_BLOCK_ID},
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.imm_predecessors{},
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};
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// Analyze instructions until it reaches an already visited block or there's a branch
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bool is_branch{false};
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@ -310,7 +427,7 @@ CFG::AnalysisState CFG::AnalyzeInst(Block& block, FunctionId function_id, Locati
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// Technically CAL pushes into PRET, but that's implicit in the function call for us
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// Insert the function into the list if it doesn't exist
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if (std::ranges::find(functions, cal_pc, &Function::entrypoint) == functions.end()) {
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functions.push_back(cal_pc);
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functions.emplace_back(cal_pc);
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}
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// Handle CAL like a regular instruction
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break;
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@ -352,6 +469,7 @@ void CFG::AnalyzeCondInst(Block& block, FunctionId function_id, Location pc,
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.cond{cond},
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.branch_true{conditional_block_id},
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.branch_false{UNREACHABLE_BLOCK_ID},
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.imm_predecessors{},
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})};
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// Set the end properties of the conditional instruction and give it a new identity
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Block& conditional_block{block};
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@ -465,14 +583,14 @@ std::string CFG::Dot() const {
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dot += fmt::format("\t\tnode [style=filled];\n");
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for (const u32 block_index : function.blocks) {
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const Block& block{function.blocks_data[block_index]};
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const std::string name{Name(block)};
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const std::string name{NameOf(block)};
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const auto add_branch = [&](BlockId branch_id, bool add_label) {
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const auto it{std::ranges::find(function.blocks_data, branch_id, &Block::id)};
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dot += fmt::format("\t\t{}->", name);
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if (it == function.blocks_data.end()) {
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dot += fmt::format("\"Unknown label {}\"", branch_id);
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} else {
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dot += Name(*it);
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dot += NameOf(*it);
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};
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if (add_label && block.cond != true && block.cond != false) {
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dot += fmt::format(" [label=\"{}\"]", block.cond);
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@ -520,7 +638,7 @@ std::string CFG::Dot() const {
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if (functions.front().blocks.empty()) {
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dot += "Start;\n";
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} else {
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dot += fmt::format("\tStart -> {};\n", Name(functions.front().blocks_data.front()));
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dot += fmt::format("\tStart -> {};\n", NameOf(functions.front().blocks_data.front()));
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}
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dot += fmt::format("\tStart [shape=diamond];\n");
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}
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