yuzu/src/shader_recompiler/frontend/maxwell/control_flow.cpp

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// Copyright 2021 yuzu Emulator Project
// Licensed under GPLv2 or any later version
// Refer to the license.txt file included.
#include <algorithm>
#include <array>
#include <optional>
#include <ranges>
#include <string>
#include <utility>
#include <fmt/format.h>
#include "shader_recompiler/exception.h"
#include "shader_recompiler/frontend/maxwell/control_flow.h"
#include "shader_recompiler/frontend/maxwell/decode.h"
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#include "shader_recompiler/frontend/maxwell/indirect_branch_table_track.h"
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#include "shader_recompiler/frontend/maxwell/location.h"
namespace Shader::Maxwell::Flow {
namespace {
struct Compare {
bool operator()(const Block& lhs, Location rhs) const noexcept {
return lhs.begin < rhs;
}
bool operator()(Location lhs, const Block& rhs) const noexcept {
return lhs < rhs.begin;
}
bool operator()(const Block& lhs, const Block& rhs) const noexcept {
return lhs.begin < rhs.begin;
}
};
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u32 BranchOffset(Location pc, Instruction inst) {
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return pc.Offset() + inst.branch.Offset() + 8;
}
void Split(Block* old_block, Block* new_block, Location pc) {
if (pc <= old_block->begin || pc >= old_block->end) {
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throw InvalidArgument("Invalid address to split={}", pc);
}
*new_block = Block{
.begin{pc},
.end{old_block->end},
.end_class{old_block->end_class},
.stack{old_block->stack},
.cond{old_block->cond},
.branch_true{old_block->branch_true},
.branch_false{old_block->branch_false},
};
*old_block = Block{
.begin{old_block->begin},
.end{pc},
.end_class{EndClass::Branch},
.stack{std::move(old_block->stack)},
.cond{true},
.branch_true{new_block},
.branch_false{nullptr},
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};
}
Token OpcodeToken(Opcode opcode) {
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switch (opcode) {
case Opcode::PBK:
case Opcode::BRK:
return Token::PBK;
case Opcode::PCNT:
case Opcode::CONT:
return Token::PBK;
case Opcode::PEXIT:
case Opcode::EXIT:
return Token::PEXIT;
case Opcode::PLONGJMP:
case Opcode::LONGJMP:
return Token::PLONGJMP;
case Opcode::PRET:
case Opcode::RET:
case Opcode::CAL:
return Token::PRET;
case Opcode::SSY:
case Opcode::SYNC:
return Token::SSY;
default:
throw InvalidArgument("{}", opcode);
}
}
bool IsAbsoluteJump(Opcode opcode) {
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switch (opcode) {
case Opcode::JCAL:
case Opcode::JMP:
case Opcode::JMX:
return true;
default:
return false;
}
}
bool HasFlowTest(Opcode opcode) {
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switch (opcode) {
case Opcode::BRA:
case Opcode::BRX:
case Opcode::EXIT:
case Opcode::JMP:
case Opcode::JMX:
case Opcode::KIL:
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case Opcode::BRK:
case Opcode::CONT:
case Opcode::LONGJMP:
case Opcode::RET:
case Opcode::SYNC:
return true;
case Opcode::CAL:
case Opcode::JCAL:
return false;
default:
throw InvalidArgument("Invalid branch {}", opcode);
}
}
std::string NameOf(const Block& block) {
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if (block.begin.IsVirtual()) {
return fmt::format("\"Virtual {}\"", block.begin);
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} else {
return fmt::format("\"{}\"", block.begin);
}
}
} // Anonymous namespace
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void Stack::Push(Token token, Location target) {
entries.push_back({
.token{token},
.target{target},
});
}
std::pair<Location, Stack> Stack::Pop(Token token) const {
const std::optional<Location> pc{Peek(token)};
if (!pc) {
throw LogicError("Token could not be found");
}
return {*pc, Remove(token)};
}
std::optional<Location> Stack::Peek(Token token) const {
const auto reverse_entries{entries | std::views::reverse};
const auto it{std::ranges::find(reverse_entries, token, &StackEntry::token)};
if (it == reverse_entries.end()) {
return std::nullopt;
}
return it->target;
}
Stack Stack::Remove(Token token) const {
const auto reverse_entries{entries | std::views::reverse};
const auto it{std::ranges::find(reverse_entries, token, &StackEntry::token)};
const auto pos{std::distance(reverse_entries.begin(), it)};
Stack result;
result.entries.insert(result.entries.end(), entries.begin(), entries.end() - pos - 1);
return result;
}
bool Block::Contains(Location pc) const noexcept {
return pc >= begin && pc < end;
}
Function::Function(ObjectPool<Block>& block_pool, Location start_address)
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: entrypoint{start_address}, labels{{
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.address{start_address},
.block{block_pool.Create(Block{
.begin{start_address},
.end{start_address},
.end_class{EndClass::Branch},
.stack{},
.cond{true},
.branch_true{nullptr},
.branch_false{nullptr},
})},
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.stack{},
}} {}
CFG::CFG(Environment& env_, ObjectPool<Block>& block_pool_, Location start_address)
: env{env_}, block_pool{block_pool_} {
functions.emplace_back(block_pool, start_address);
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for (FunctionId function_id = 0; function_id < functions.size(); ++function_id) {
while (!functions[function_id].labels.empty()) {
Function& function{functions[function_id]};
Label label{function.labels.back()};
function.labels.pop_back();
AnalyzeLabel(function_id, label);
}
}
}
void CFG::AnalyzeLabel(FunctionId function_id, Label& label) {
if (InspectVisitedBlocks(function_id, label)) {
// Label address has been visited
return;
}
// Try to find the next block
Function* const function{&functions[function_id]};
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Location pc{label.address};
const auto next_it{function->blocks.upper_bound(pc, Compare{})};
const bool is_last{next_it == function->blocks.end()};
Block* const next{is_last ? nullptr : &*next_it};
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// Insert before the next block
Block* const block{label.block};
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// Analyze instructions until it reaches an already visited block or there's a branch
bool is_branch{false};
while (!next || pc < next->begin) {
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is_branch = AnalyzeInst(block, function_id, pc) == AnalysisState::Branch;
if (is_branch) {
break;
}
++pc;
}
if (!is_branch) {
// If the block finished without a branch,
// it means that the next instruction is already visited, jump to it
block->end = pc;
block->cond = IR::Condition{true};
block->branch_true = next;
block->branch_false = nullptr;
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}
// Function's pointer might be invalid, resolve it again
// Insert the new block
functions[function_id].blocks.insert(*block);
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}
bool CFG::InspectVisitedBlocks(FunctionId function_id, const Label& label) {
const Location pc{label.address};
Function& function{functions[function_id]};
const auto it{
std::ranges::find_if(function.blocks, [pc](auto& block) { return block.Contains(pc); })};
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if (it == function.blocks.end()) {
// Address has not been visited
return false;
}
Block* const visited_block{&*it};
if (visited_block->begin == pc) {
throw LogicError("Dangling block");
}
Block* const new_block{label.block};
Split(visited_block, new_block, pc);
function.blocks.insert(it, *new_block);
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return true;
}
CFG::AnalysisState CFG::AnalyzeInst(Block* block, FunctionId function_id, Location pc) {
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const Instruction inst{env.ReadInstruction(pc.Offset())};
const Opcode opcode{Decode(inst.raw)};
switch (opcode) {
case Opcode::BRA:
case Opcode::JMP:
case Opcode::RET:
if (!AnalyzeBranch(block, function_id, pc, inst, opcode)) {
return AnalysisState::Continue;
}
switch (opcode) {
case Opcode::BRA:
case Opcode::JMP:
AnalyzeBRA(block, function_id, pc, inst, IsAbsoluteJump(opcode));
break;
case Opcode::RET:
block->end_class = EndClass::Return;
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break;
default:
break;
}
block->end = pc;
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return AnalysisState::Branch;
case Opcode::BRK:
case Opcode::CONT:
case Opcode::LONGJMP:
case Opcode::SYNC: {
if (!AnalyzeBranch(block, function_id, pc, inst, opcode)) {
return AnalysisState::Continue;
}
const auto [stack_pc, new_stack]{block->stack.Pop(OpcodeToken(opcode))};
block->branch_true = AddLabel(block, new_stack, stack_pc, function_id);
block->end = pc;
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return AnalysisState::Branch;
}
case Opcode::KIL: {
const Predicate pred{inst.Pred()};
const auto ir_pred{static_cast<IR::Pred>(pred.index)};
const IR::Condition cond{inst.branch.flow_test, ir_pred, pred.negated};
AnalyzeCondInst(block, function_id, pc, EndClass::Kill, cond);
return AnalysisState::Branch;
}
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case Opcode::PBK:
case Opcode::PCNT:
case Opcode::PEXIT:
case Opcode::PLONGJMP:
case Opcode::SSY:
block->stack.Push(OpcodeToken(opcode), BranchOffset(pc, inst));
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return AnalysisState::Continue;
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case Opcode::BRX:
case Opcode::JMX:
return AnalyzeBRX(block, pc, inst, IsAbsoluteJump(opcode), function_id);
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case Opcode::EXIT:
return AnalyzeEXIT(block, function_id, pc, inst);
case Opcode::PRET:
throw NotImplementedException("PRET flow analysis");
case Opcode::CAL:
case Opcode::JCAL: {
const bool is_absolute{IsAbsoluteJump(opcode)};
const Location cal_pc{is_absolute ? inst.branch.Absolute() : BranchOffset(pc, inst)};
// Technically CAL pushes into PRET, but that's implicit in the function call for us
// Insert the function into the list if it doesn't exist
const auto it{std::ranges::find(functions, cal_pc, &Function::entrypoint)};
const bool exists{it != functions.end()};
const FunctionId call_id{exists ? std::distance(functions.begin(), it) : functions.size()};
if (!exists) {
functions.emplace_back(block_pool, cal_pc);
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}
block->end_class = EndClass::Call;
block->function_call = call_id;
block->return_block = AddLabel(block, block->stack, pc + 1, function_id);
block->end = pc;
return AnalysisState::Branch;
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}
default:
break;
}
const Predicate pred{inst.Pred()};
if (pred == Predicate{true} || pred == Predicate{false}) {
return AnalysisState::Continue;
}
const IR::Condition cond{static_cast<IR::Pred>(pred.index), pred.negated};
AnalyzeCondInst(block, function_id, pc, EndClass::Branch, cond);
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return AnalysisState::Branch;
}
void CFG::AnalyzeCondInst(Block* block, FunctionId function_id, Location pc,
EndClass insn_end_class, IR::Condition cond) {
if (block->begin != pc) {
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// If the block doesn't start in the conditional instruction
// mark it as a label to visit it later
block->end = pc;
block->cond = IR::Condition{true};
block->branch_true = AddLabel(block, block->stack, pc, function_id);
block->branch_false = nullptr;
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return;
}
// Create a virtual block and a conditional block
Block* const conditional_block{block_pool.Create()};
Block virtual_block{
.begin{block->begin.Virtual()},
.end{block->begin.Virtual()},
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.end_class{EndClass::Branch},
.stack{block->stack},
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.cond{cond},
.branch_true{conditional_block},
.branch_false{nullptr},
};
// Save the contents of the visited block in the conditional block
*conditional_block = std::move(*block);
// Impersonate the visited block with a virtual block
*block = std::move(virtual_block);
// Set the end properties of the conditional instruction
conditional_block->end = pc + 1;
conditional_block->end_class = insn_end_class;
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// Add a label to the instruction after the conditional instruction
Block* const endif_block{AddLabel(conditional_block, block->stack, pc + 1, function_id)};
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// Branch to the next instruction from the virtual block
block->branch_false = endif_block;
// And branch to it from the conditional instruction if it is a branch or a kill instruction
// Kill instructions are considered a branch because they demote to a helper invocation and
// execution may continue.
if (insn_end_class == EndClass::Branch || insn_end_class == EndClass::Kill) {
conditional_block->cond = IR::Condition{true};
conditional_block->branch_true = endif_block;
conditional_block->branch_false = nullptr;
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}
// Finally insert the condition block into the list of blocks
functions[function_id].blocks.insert(*conditional_block);
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}
bool CFG::AnalyzeBranch(Block* block, FunctionId function_id, Location pc, Instruction inst,
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Opcode opcode) {
if (inst.branch.is_cbuf) {
throw NotImplementedException("Branch with constant buffer offset");
}
const Predicate pred{inst.Pred()};
if (pred == Predicate{false}) {
return false;
}
const bool has_flow_test{HasFlowTest(opcode)};
const IR::FlowTest flow_test{has_flow_test ? inst.branch.flow_test.Value() : IR::FlowTest::T};
if (pred != Predicate{true} || flow_test != IR::FlowTest::T) {
block->cond = IR::Condition(flow_test, static_cast<IR::Pred>(pred.index), pred.negated);
block->branch_false = AddLabel(block, block->stack, pc + 1, function_id);
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} else {
block->cond = IR::Condition{true};
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}
return true;
}
void CFG::AnalyzeBRA(Block* block, FunctionId function_id, Location pc, Instruction inst,
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bool is_absolute) {
const Location bra_pc{is_absolute ? inst.branch.Absolute() : BranchOffset(pc, inst)};
block->branch_true = AddLabel(block, block->stack, bra_pc, function_id);
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}
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CFG::AnalysisState CFG::AnalyzeBRX(Block* block, Location pc, Instruction inst, bool is_absolute,
FunctionId function_id) {
const std::optional brx_table{TrackIndirectBranchTable(env, pc, block->begin)};
if (!brx_table) {
TrackIndirectBranchTable(env, pc, block->begin);
throw NotImplementedException("Failed to track indirect branch");
}
const IR::FlowTest flow_test{inst.branch.flow_test};
const Predicate pred{inst.Pred()};
if (flow_test != IR::FlowTest::T || pred != Predicate{true}) {
throw NotImplementedException("Conditional indirect branch");
}
std::vector<u32> targets;
targets.reserve(brx_table->num_entries);
for (u32 i = 0; i < brx_table->num_entries; ++i) {
u32 target{env.ReadCbufValue(brx_table->cbuf_index, brx_table->cbuf_offset + i * 4)};
if (!is_absolute) {
target += pc.Offset();
}
target += brx_table->branch_offset;
target += 8;
targets.push_back(target);
}
std::ranges::sort(targets);
targets.erase(std::unique(targets.begin(), targets.end()), targets.end());
block->indirect_branches.reserve(targets.size());
for (const u32 target : targets) {
Block* const branch{AddLabel(block, block->stack, target, function_id)};
block->indirect_branches.push_back(branch);
}
block->cond = IR::Condition{true};
block->end = pc + 1;
block->end_class = EndClass::IndirectBranch;
block->branch_reg = brx_table->branch_reg;
block->branch_offset = brx_table->branch_offset + 8;
if (!is_absolute) {
block->branch_offset += pc.Offset();
}
return AnalysisState::Branch;
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}
CFG::AnalysisState CFG::AnalyzeEXIT(Block* block, FunctionId function_id, Location pc,
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Instruction inst) {
const IR::FlowTest flow_test{inst.branch.flow_test};
const Predicate pred{inst.Pred()};
if (pred == Predicate{false} || flow_test == IR::FlowTest::F) {
// EXIT will never be taken
return AnalysisState::Continue;
}
if (pred != Predicate{true} || flow_test != IR::FlowTest::T) {
if (block->stack.Peek(Token::PEXIT).has_value()) {
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throw NotImplementedException("Conditional EXIT with PEXIT token");
}
const IR::Condition cond{flow_test, static_cast<IR::Pred>(pred.index), pred.negated};
AnalyzeCondInst(block, function_id, pc, EndClass::Exit, cond);
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return AnalysisState::Branch;
}
if (const std::optional<Location> exit_pc{block->stack.Peek(Token::PEXIT)}) {
const Stack popped_stack{block->stack.Remove(Token::PEXIT)};
block->cond = IR::Condition{true};
block->branch_true = AddLabel(block, popped_stack, *exit_pc, function_id);
block->branch_false = nullptr;
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return AnalysisState::Branch;
}
block->end = pc + 1;
block->end_class = EndClass::Exit;
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return AnalysisState::Branch;
}
Block* CFG::AddLabel(Block* block, Stack stack, Location pc, FunctionId function_id) {
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Function& function{functions[function_id]};
if (block->begin == pc) {
// Jumps to itself
return block;
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}
if (const auto it{function.blocks.find(pc, Compare{})}; it != function.blocks.end()) {
// Block already exists and it has been visited
return &*it;
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}
Block* const new_block{block_pool.Create(Block{
.begin{pc},
.end{pc},
.end_class{EndClass::Branch},
.stack{stack},
.cond{true},
.branch_true{nullptr},
.branch_false{nullptr},
})};
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function.labels.push_back(Label{
.address{pc},
.block{new_block},
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.stack{std::move(stack)},
});
return new_block;
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}
std::string CFG::Dot() const {
int node_uid{0};
std::string dot{"digraph shader {\n"};
for (const Function& function : functions) {
dot += fmt::format("\tsubgraph cluster_{} {{\n", function.entrypoint);
dot += fmt::format("\t\tnode [style=filled];\n");
for (const Block& block : function.blocks) {
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const std::string name{NameOf(block)};
const auto add_branch = [&](Block* branch, bool add_label) {
dot += fmt::format("\t\t{}->{}", name, NameOf(*branch));
if (add_label && block.cond != IR::Condition{true} &&
block.cond != IR::Condition{false}) {
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dot += fmt::format(" [label=\"{}\"]", block.cond);
}
dot += '\n';
};
dot += fmt::format("\t\t{};\n", name);
switch (block.end_class) {
case EndClass::Branch:
if (block.cond != IR::Condition{false}) {
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add_branch(block.branch_true, true);
}
if (block.cond != IR::Condition{true}) {
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add_branch(block.branch_false, false);
}
break;
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case EndClass::IndirectBranch:
for (Block* const branch : block.indirect_branches) {
add_branch(branch, false);
}
break;
case EndClass::Call:
dot += fmt::format("\t\t{}->N{};\n", name, node_uid);
dot += fmt::format("\t\tN{}->{};\n", node_uid, NameOf(*block.return_block));
dot += fmt::format("\t\tN{} [label=\"Call {}\"][shape=square][style=stripped];\n",
node_uid, block.function_call);
dot += '\n';
++node_uid;
break;
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case EndClass::Exit:
dot += fmt::format("\t\t{}->N{};\n", name, node_uid);
dot += fmt::format("\t\tN{} [label=\"Exit\"][shape=square][style=stripped];\n",
node_uid);
++node_uid;
break;
case EndClass::Return:
dot += fmt::format("\t\t{}->N{};\n", name, node_uid);
dot += fmt::format("\t\tN{} [label=\"Return\"][shape=square][style=stripped];\n",
node_uid);
++node_uid;
break;
case EndClass::Kill:
dot += fmt::format("\t\t{}->N{};\n", name, node_uid);
dot += fmt::format("\t\tN{} [label=\"Kill\"][shape=square][style=stripped];\n",
node_uid);
++node_uid;
break;
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}
}
if (function.entrypoint == 8) {
dot += fmt::format("\t\tlabel = \"main\";\n");
} else {
dot += fmt::format("\t\tlabel = \"Function {}\";\n", function.entrypoint);
}
dot += "\t}\n";
}
if (!functions.empty()) {
auto& function{functions.front()};
if (function.blocks.empty()) {
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dot += "Start;\n";
} else {
dot += fmt::format("\tStart -> {};\n", NameOf(*function.blocks.begin()));
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}
dot += fmt::format("\tStart [shape=diamond];\n");
}
dot += "}\n";
return dot;
}
} // namespace Shader::Maxwell::Flow