Files
Giacomo Vercesi 27f419c8cd Fix and ban namespace clobbering
Fix an instance where the `std` namespace got clobbered into the global
namespace by accident.
2026-02-16 10:34:38 +01:00

636 lines
25 KiB
C++

//
// This file is distributed under the MIT License. See LICENSE.md for details.
//
#include <unordered_map>
#include "llvm/ADT/PostOrderIterator.h"
#include "llvm/Support/FormatVariadic.h"
#include "revng/GraphLayout/SugiyamaStyle/Compute.h"
#include "revng/Model/Binary.h"
#include "revng/Model/NameBuilder.h"
#include "revng/PTML/Tag.h"
#include "revng/Support/GraphAlgorithms.h"
#include "revng/Yield/CallGraphs/CallGraphSlices.h"
#include "revng/Yield/ControlFlow/Configuration.h"
#include "revng/Yield/ControlFlow/Extraction.h"
#include "revng/Yield/ControlFlow/NodeSizeCalculation.h"
#include "revng/Yield/CrossRelations/CrossRelations.h"
#include "revng/Yield/PTML.h"
#include "revng/Yield/SVG.h"
using ptml::Tag;
namespace tags {
static constexpr auto UnconditionalEdge = "unconditional";
static constexpr auto CallEdge = "call";
static constexpr auto TakenEdge = "taken";
static constexpr auto RefusedEdge = "refused";
static constexpr auto NodeBody = "node-body";
static constexpr auto NodeContents = "node-contents";
static constexpr auto UnconditionalArrowHead = "unconditional-arrow-head";
static constexpr auto CallArrowHead = "call-arrow-head";
static constexpr auto TakenArrowHead = "taken-arrow-head";
static constexpr auto RefusedArrowHead = "refused-arrow-head";
} // namespace tags
static llvm::StringRef edgeTypeAsString(const yield::cfg::Edge &Edge) {
switch (Edge.Type) {
case yield::cfg::EdgeType::Unconditional:
return tags::UnconditionalEdge;
case yield::cfg::EdgeType::Call:
return tags::CallEdge;
case yield::cfg::EdgeType::Taken:
return tags::TakenEdge;
case yield::cfg::EdgeType::Refused:
return tags::RefusedEdge;
default:
revng_abort("Unknown edge type");
}
}
static llvm::StringRef edgeTypeAsString(const yield::calls::Edge &Edge) {
// TODO: we might want to use separate set of tags for call graphs.
return Edge.IsBackwards ? tags::RefusedEdge : tags::TakenEdge;
}
template<uintmax_t Numerator = 8, uintmax_t Denominator = 10>
static std::string cubicBend(const yield::layout::Point &From,
const yield::layout::Point &To,
bool VerticalCurves,
std::ratio<Numerator, Denominator> &&Bend = {}) {
using Coordinate = yield::layout::Coordinate;
constexpr Coordinate Factor = Coordinate(Numerator) / Denominator;
Coordinate XModifier = Factor * (To.X - From.X);
Coordinate YModifier = Factor * (To.Y - From.Y);
if (VerticalCurves)
XModifier = 0;
else
YModifier = 0;
return llvm::formatv("C {0} {1} {2} {3} {4} {5} ",
From.X + XModifier,
-From.Y - YModifier,
To.X - XModifier,
-To.Y + YModifier,
To.X,
-To.Y);
}
static std::string edge(const ptml::MarkupBuilder &B,
const yield::layout::Path &Path,
const llvm::StringRef Type,
bool UseOrthogonalBends = true,
bool UseVerticalCurves = false) {
std::string Points;
revng_assert(!Path.empty());
const auto &First = Path.front();
Points += llvm::formatv("M {0} {1} ", First.X, -First.Y);
if (UseOrthogonalBends) {
for (size_t Index = 1; Index < Path.size(); ++Index)
Points += llvm::formatv("L {0} {1} ", Path[Index].X, -Path[Index].Y);
} else {
revng_assert(Path.size() >= 2);
for (auto Iter = Path.begin(); Iter != std::prev(Path.end()); ++Iter)
Points += cubicBend(*Iter, *std::next(Iter), UseVerticalCurves);
}
revng_assert(!Points.empty());
revng_assert(Points.back() == ' ');
Points.pop_back(); // Remove an extra space at the end.
std::string Marker = llvm::formatv("url(#{0}-arrow-head)", Type);
return B.getTag("path")
.addAttribute("class", std::string(Type) += "-edge")
.addAttribute("d", std::move(Points))
.addAttribute("marker-end", std::move(Marker))
.addAttribute("fill", "none")
.toString();
}
template<typename NodeData, typename EdgeData = Empty>
std::string node(const ptml::MarkupBuilder &B,
const yield::layout::OutputNode<NodeData, EdgeData> *Node,
std::string &&Content,
const yield::cfg::Configuration &Configuration) {
yield::layout::Size HalfSize{ Node->Size.W / 2, Node->Size.H / 2 };
yield::layout::Point TopLeft{ Node->Center.X - HalfSize.W,
-Node->Center.Y - HalfSize.H };
Tag Body = B.getTag("body", std::move(Content));
Body.addAttribute("xmlns", R"(http://www.w3.org/1999/xhtml)");
Tag Text = B.getTag("foreignObject", Body.toString());
Text.addAttribute("class", ::tags::NodeContents)
.addAttribute("x", std::to_string(TopLeft.X))
.addAttribute("y", std::to_string(TopLeft.Y))
.addAttribute("width", std::to_string(Node->Size.W))
.addAttribute("height", std::to_string(Node->Size.H));
Tag Border = B.getTag("rect");
Border.addAttribute("class", ::tags::NodeBody)
.addAttribute("x", std::to_string(TopLeft.X))
.addAttribute("y", std::to_string(TopLeft.Y))
.addAttribute("rx", std::to_string(Configuration.NodeCornerRoundingFactor))
.addAttribute("ry", std::to_string(Configuration.NodeCornerRoundingFactor))
.addAttribute("width", std::to_string(Node->Size.W))
.addAttribute("height", std::to_string(Node->Size.H));
return Text.toString() + Border.toString();
}
struct Viewbox {
yield::layout::Point TopLeft = { -1, -1 };
yield::layout::Point BottomRight = { +1, +1 };
};
template<typename NodeData, typename EdgeData = Empty>
static Viewbox
makeViewbox(const yield::layout::OutputNode<NodeData, EdgeData> *Node) {
yield::layout::Size HalfSize{ Node->Size.W / 2, Node->Size.H / 2 };
yield::layout::Point TopLeft{ Node->Center.X - HalfSize.W,
-Node->Center.Y - HalfSize.H };
yield::layout::Point BottomRight{ Node->Center.X + HalfSize.W,
-Node->Center.Y + HalfSize.H };
return Viewbox{ .TopLeft = std::move(TopLeft),
.BottomRight = std::move(BottomRight) };
}
static void expandViewbox(Viewbox &LHS, const Viewbox &RHS) {
if (RHS.TopLeft.X < LHS.TopLeft.X)
LHS.TopLeft.X = RHS.TopLeft.X;
if (RHS.TopLeft.Y < LHS.TopLeft.Y)
LHS.TopLeft.Y = RHS.TopLeft.Y;
if (RHS.BottomRight.X > LHS.BottomRight.X)
LHS.BottomRight.X = RHS.BottomRight.X;
if (RHS.BottomRight.Y > LHS.BottomRight.Y)
LHS.BottomRight.Y = RHS.BottomRight.Y;
}
static void expandViewbox(Viewbox &Box, const yield::layout::Point &Point) {
if (Box.TopLeft.X > Point.X)
Box.TopLeft.X = Point.X;
if (Box.TopLeft.Y > -Point.Y)
Box.TopLeft.Y = -Point.Y;
if (Box.BottomRight.X < Point.X)
Box.BottomRight.X = Point.X;
if (Box.BottomRight.Y < -Point.Y)
Box.BottomRight.Y = -Point.Y;
}
template<SpecializationOf<yield::layout::OutputGraph> GraphType>
Viewbox calculateViewbox(const GraphType &Graph) {
revng_assert(Graph.size() != 0);
// Ensure every node fits.
Viewbox Result = makeViewbox(*Graph.nodes().begin());
for (const auto *Node : Graph.nodes())
expandViewbox(Result, makeViewbox(Node));
// Ensure every edge point fits.
for (const auto *From : Graph.nodes())
for (auto &&[To, Label] : From->successor_edges())
for (const auto &Point : Label->Path)
expandViewbox(Result, Point);
// Add some extra padding for a good measure.
Result.TopLeft.X -= 50;
Result.TopLeft.Y -= 50;
Result.BottomRight.X += 50;
Result.BottomRight.Y += 50;
return Result;
}
/// A really simple arrow head marker generator.
///
/// \param B: PTML builder that should be used to make ptml::Tags.
/// \param Name: the id of the marker as referred to by the objects using it.
/// \param Size: the size of the marker. It sets both width and height to force
/// the marker to be square-shaped.
/// \param Concave: the size of the concave at the rear side of the arrow.
/// \param Shift: the position of the arrow "origin". It is set to 0 by default
/// (arrow origin the same as its tip), positive values shift arrow back,
/// leaving some space between the tip and its target, negative values shift it
/// closer to the target possibly causing an overlap.
static std::string arrowHead(const ptml::MarkupBuilder &B,
llvm::StringRef Name,
float Size,
float Concave,
float Shift = 0) {
std::string Points = llvm::formatv("{0}, {1} {3}, {2} {0}, {0} {1}, {2}",
"0",
std::to_string(Size),
std::to_string(Size / 2),
std::to_string(Concave));
return B
.getTag("marker",
B.getTag("polygon")
.addAttribute("points", std::move(Points))
.toString())
.addAttribute("id", Name)
.addAttribute("markerWidth", std::to_string(Size))
.addAttribute("markerHeight", std::to_string(Size))
.addAttribute("refX", std::to_string(Size - Shift))
.addAttribute("refY", std::to_string(Size / 2))
.addAttribute("refY", std::to_string(Size / 2))
.addAttribute("orient", "auto")
.toString();
}
static std::string duplicateArrowHeadsImpl(const ptml::MarkupBuilder &B,
float Size,
float Dip,
float Shift = 0) {
return arrowHead(B, tags::UnconditionalArrowHead, Size, Dip, Shift)
+ arrowHead(B, tags::CallArrowHead, Size, Dip, Shift)
+ arrowHead(B, tags::TakenArrowHead, Size, Dip, Shift)
+ arrowHead(B, tags::RefusedArrowHead, Size, Dip, Shift);
}
static std::string
defaultArrowHeads(const ptml::MarkupBuilder &B,
const yield::cfg::Configuration &Configuration) {
if (Configuration.UseOrthogonalBends == true)
return duplicateArrowHeadsImpl(B, 8, 3, 0);
else
return duplicateArrowHeadsImpl(B, 8, 3, 2);
}
constexpr bool isVertical(yield::layout::sugiyama::Orientation Orientation) {
return Orientation == yield::layout::sugiyama::Orientation::TopToBottom
|| Orientation == yield::layout::sugiyama::Orientation::BottomToTop;
}
template<typename CallableType, typename NodeType>
concept NodeExporter = requires(CallableType &&Callable, const NodeType &Node) {
{ Callable(Node) } -> std::convertible_to<std::string>;
};
template<bool ShouldEmitEmptyNodes,
SpecializationOf<yield::layout::OutputGraph> PostLayoutGraph,
NodeExporter<typename PostLayoutGraph::Node> ContentsLambda>
static std::string exportGraph(const ptml::MarkupBuilder &B,
const PostLayoutGraph &Graph,
const yield::cfg::Configuration &Configuration,
yield::layout::sugiyama::Orientation Orientation,
ContentsLambda &&NodeContents) {
std::string Result;
// Short circuit the execution for an empty graph.
if (Graph.size() == 0)
return Result;
// Export all the edges.
for (const auto *From : Graph.nodes()) {
if (ShouldEmitEmptyNodes || !From->isEmpty()) {
for (auto &&[To, Edge] : From->successor_edges()) {
if (ShouldEmitEmptyNodes || !To->isEmpty()) {
revng_assert(Edge != nullptr);
Result += edge(B,
Edge->Path,
edgeTypeAsString(*Edge),
Configuration.UseOrthogonalBends,
isVertical(Orientation));
}
}
}
}
// Export all the nodes.
for (const auto *Node : Graph.nodes())
if (ShouldEmitEmptyNodes || !Node->isEmpty())
Result += node(B, Node, NodeContents(*Node), Configuration);
Viewbox Box = calculateViewbox(Graph);
std::string SerializedBox = llvm::formatv("{0} {1} {2} {3}",
Box.TopLeft.X,
Box.TopLeft.Y,
Box.BottomRight.X - Box.TopLeft.X,
Box.BottomRight.Y - Box.TopLeft.Y);
Tag ArrowHeads = B.getTag("defs", defaultArrowHeads(B, Configuration));
return B.getTag("svg", ArrowHeads.toString() + std::move(Result))
.addAttribute("xmlns", R"(http://www.w3.org/2000/svg)")
.addAttribute("viewbox", std::move(SerializedBox))
.addAttribute("width", std::to_string(Box.BottomRight.X - Box.TopLeft.X))
.addAttribute("height", std::to_string(Box.BottomRight.Y - Box.TopLeft.Y))
.toString();
}
namespace yield::layout::sugiyama {
/// A helper for invoking sugiyama style layouter with the configuration
/// filled in based on the relevant cfg::Configuration.
///
/// \tparam Node The type of the data attached to each graph node
/// \tparam Edge The type of the data attached to each graph edge
///
/// \param Graph An input graph
/// \param CFG An object describing the desired CFG configuration
/// \param LayoutOrientation The direction of the desired layout
/// \param Ranking The ranking strategy
/// \param UseSimpleTreeOptimization A flag deciding whether simple tree
/// optimization should be used.
///
/// \return The laid out version of the graph corresponding to \ref Graph
template<typename Node, typename Edge = Empty>
inline std::optional<OutputGraph<Node, Edge>>
compute(const InputGraph<Node, Edge> &Graph,
const cfg::Configuration &CFG,
Orientation LayoutOrientation = Orientation::TopToBottom,
RankingStrategy Ranking = RankingStrategy::DisjointDepthFirstSearch,
bool UseSimpleTreeOptimization = false) {
return compute(Graph,
Configuration{
.Ranking = Ranking,
.Orientation = LayoutOrientation,
.UseOrthogonalBends = CFG.UseOrthogonalBends,
.PreserveLinearSegments = CFG.PreserveLinearSegments,
.UseSimpleTreeOptimization = UseSimpleTreeOptimization,
.VirtualNodeWeight = CFG.VirtualNodeWeight,
.NodeMarginSize = CFG.ExternalNodeMarginSize,
.EdgeMarginSize = CFG.EdgeMarginSize });
}
} // namespace yield::layout::sugiyama
std::string
yield::svg::controlFlowGraph(const ::ptml::MarkupBuilder &B,
const yield::Function &InternalFunction,
const model::Binary &Binary) {
constexpr auto Configuration = cfg::Configuration::getDefault();
using Pre = cfg::PreLayoutGraph;
Pre Graph = cfg::extractFromInternal(InternalFunction, Binary, Configuration);
model::CNameBuilder NB = Binary;
// This is somewhat crude, as it forces each node's text to be manifested
// twice: once without any ptml tags and once containing them.
// TODO: clean this up if it ever becomes a performance concern.
::ptml::MarkupBuilder Tagless{ .IsInTaglessMode = true };
for (yield::cfg::PreLayoutNode *Node : Graph.nodes()) {
if (Node->isEmpty()) {
Node->Size = yield::cfg::emptyNodeSize(Configuration);
} else {
auto NodeContents = yield::ptml::controlFlowNode(Tagless,
Node->getBasicBlock(),
InternalFunction,
Binary);
Node->Size = yield::cfg::nodeSize(NodeContents, Configuration);
}
}
constexpr auto TopToBottom = layout::sugiyama::Orientation::TopToBottom;
using Post = std::optional<cfg::PostLayoutGraph>;
Post Result = layout::sugiyama::compute(Graph, Configuration, TopToBottom);
revng_assert(Result.has_value());
auto Content = [&](const yield::cfg::PostLayoutNode &Node) {
if (!Node.isEmpty())
return yield::ptml::controlFlowNode(B,
Node.getBasicBlock(),
InternalFunction,
Binary);
else
return std::string{};
};
return exportGraph<true>(B, *Result, Configuration, TopToBottom, Content);
}
struct LabelNodeHelper {
const ptml::MarkupBuilder &B;
const model::Binary &Binary;
const model::AssemblyNameBuilder &NameBuilder;
const yield::cfg::Configuration Configuration;
std::optional<llvm::StringRef> RootNodeLocation = std::nullopt;
void computeSizes(yield::calls::PreLayoutGraph &Graph) {
for (auto *Node : Graph.nodes()) {
if (Node->isEmpty()) {
Node->Size = yield::cfg::emptyNodeSize(Configuration);
} else {
size_t NameLength = 0;
if (std::optional<model::Function::Key> Key = Node->getFunction()) {
auto Iterator = Binary.Functions().find(std::get<0>(*Key));
revng_assert(Iterator != Binary.Functions().end());
NameLength = NameBuilder.name(*Iterator).size();
} else if (auto DynamicFunctionKey = Node->getDynamicFunction()) {
const std::string &Key = std::get<0>(*DynamicFunctionKey);
auto Iterator = Binary.ImportedDynamicFunctions().find(Key);
revng_assert(Iterator != Binary.ImportedDynamicFunctions().end());
NameLength = NameBuilder.name(*Iterator).size();
} else {
revng_abort("Unsupported node type.");
}
revng_assert(NameLength != 0);
Node->Size = yield::cfg::nodeSize(NameLength, 1, Configuration);
}
}
}
std::string operator()(const yield::calls::PostLayoutNode &Node) const {
if (Node.isEmpty())
return "";
llvm::StringRef Location = Node.getLocationString();
if (Node.IsShallow)
return yield::ptml::shallowFunctionLink(B, Location, Binary, NameBuilder);
if (!RootNodeLocation.has_value() || *RootNodeLocation == Location)
return yield::ptml::functionNameDefinition(B,
Location,
Binary,
NameBuilder);
else
return yield::ptml::functionLink(B, Location, Binary, NameBuilder);
}
};
using CrossRelations = yield::crossrelations::CrossRelations;
std::string yield::svg::callGraph(const ::ptml::MarkupBuilder &B,
const CrossRelations &Relations,
const model::Binary &Binary) {
// TODO: make configuration accessible from outside.
auto Configuration = cfg::Configuration::getDefault();
Configuration.UseOrthogonalBends = false;
constexpr auto LeftToRight = layout::sugiyama::Orientation::LeftToRight;
constexpr auto BFS = layout::sugiyama::RankingStrategy::BreadthFirstSearch;
model::AssemblyNameBuilder NameBuilder = Binary;
LabelNodeHelper Helper{ B, Binary, NameBuilder, Configuration };
yield::calls::PreLayoutGraph Result = Relations.toYieldGraph();
auto EntryPoints = entryPoints(&Result);
revng_assert(!EntryPoints.empty());
if (EntryPoints.size() > 1) {
// Add an artificial "root" node to make sure there's a single entry point.
yield::calls::PreLayoutNode *Root = Result.addNode();
for (yield::calls::PreLayoutNode *Entry : EntryPoints)
Root->addSuccessor(Entry);
Result.setEntryNode(Root);
} else {
Result.setEntryNode(EntryPoints.front());
}
auto Tree = calls::makeCalleeTree(Result);
Helper.computeSizes(Tree);
namespace sugiyama = layout::sugiyama;
auto LT = sugiyama::compute(Tree, Configuration, LeftToRight, BFS, true);
revng_assert(LT.has_value());
return exportGraph<false>(B, *LT, Configuration, LeftToRight, Helper);
}
static auto flipPoint(yield::layout::Point const &Point) {
return yield::layout::Point{ -Point.X, -Point.Y };
};
static auto calculateDelta(yield::layout::Point const &LHS,
yield::layout::Point const &RHS) {
return yield::layout::Point{ RHS.X - LHS.X, RHS.Y - LHS.Y };
}
static auto translatePoint(yield::layout::Point const &Point,
yield::layout::Point const &Delta) {
return yield::layout::Point{ Point.X + Delta.X, Point.Y + Delta.Y };
}
static auto convertPoint(yield::layout::Point const &Point,
yield::layout::Point const &Delta) {
return translatePoint(flipPoint(Point), Delta);
}
static yield::calls::PostLayoutGraph
combineHalvesHelper(llvm::StringRef SlicePoint,
yield::calls::PostLayoutGraph &&ForwardsSlice,
yield::calls::PostLayoutGraph &&BackwardsSlice) {
revng_assert(ForwardsSlice.size() != 0 && BackwardsSlice.size() != 0);
auto IsSlicePoint = [&SlicePoint](const auto *Node) {
return Node->getLocationString() == SlicePoint;
};
auto ForwardsIterator = llvm::find_if(ForwardsSlice.nodes(), IsSlicePoint);
revng_assert(ForwardsIterator != ForwardsSlice.nodes().end());
auto *ForwardsSlicePoint = *ForwardsIterator;
revng_assert(ForwardsSlicePoint != nullptr);
auto BackwardsIterator = llvm::find_if(BackwardsSlice.nodes(), IsSlicePoint);
revng_assert(BackwardsIterator != BackwardsSlice.nodes().end());
auto *BackwardsSlicePoint = *BackwardsIterator;
revng_assert(BackwardsSlicePoint != nullptr);
// Find the distance all the nodes of one of the graphs need to be shifted so
// that the `SlicePoint`s overlap.
auto Delta = calculateDelta(flipPoint((*BackwardsIterator)->Center),
(*ForwardsIterator)->Center);
// Ready the backwards part of the graph
for (auto *From : BackwardsSlice.nodes()) {
From->Center = convertPoint(From->Center, Delta);
for (auto &&[Neighbor, Label] : From->successor_edges())
for (auto &Point : Label->Path)
Point = convertPoint(Point, Delta);
}
// Define a map for faster node lookup.
using PostNode = yield::calls::PostLayoutGraph::Node;
llvm::DenseMap<PostNode *, PostNode *> Lookup;
auto AccessLookup = [&Lookup](PostNode *Key) {
auto Iterator = Lookup.find(Key);
revng_assert(Iterator != Lookup.end() && Iterator->second != nullptr);
return Iterator->second;
};
// Move the nodes from the backwards slice into the forwards one.
for (auto *Node : BackwardsSlice.nodes()) {
revng_assert(Node != nullptr);
if (Node != BackwardsSlicePoint) {
auto NewNode = ForwardsSlice.addNode(Node->moveData());
auto &&[Iterator, Success] = Lookup.try_emplace(Node, NewNode);
revng_assert(Success == true);
} else {
auto &&[Iterator, Success] = Lookup.try_emplace(BackwardsSlicePoint,
ForwardsSlicePoint);
revng_assert(Success == true);
}
}
// Move all the edges while also inverting their direction.
for (auto *From : BackwardsSlice.nodes()) {
for (auto &&[To, Label] : From->successor_edges()) {
std::reverse(Label->Path.begin(), Label->Path.end());
AccessLookup(To)->addSuccessor(AccessLookup(From), std::move(*Label));
}
}
return std::move(ForwardsSlice);
}
std::string yield::svg::callGraphSlice(const ::ptml::MarkupBuilder &B,
llvm::StringRef SlicePoint,
const CrossRelations &Relations,
const model::Binary &Binary) {
// TODO: make configuration accessible from outside.
auto Configuration = cfg::Configuration::getDefault();
Configuration.UseOrthogonalBends = false;
constexpr auto LeftToRight = layout::sugiyama::Orientation::LeftToRight;
constexpr auto BFS = layout::sugiyama::RankingStrategy::BreadthFirstSearch;
model::AssemblyNameBuilder NameBuilder = Binary;
LabelNodeHelper Helper{ B, Binary, NameBuilder, Configuration, SlicePoint };
// Ready the forwards facing part of the slice
auto Forward = calls::makeCalleeTree(Relations.toYieldGraph(), SlicePoint);
for (auto *From : Forward.nodes())
for (auto &&[To, Label] : From->successor_edges())
Label->IsBackwards = false;
Helper.computeSizes(Forward);
auto LaidOutForwardsGraph = layout::sugiyama::compute(Forward,
Configuration,
LeftToRight,
BFS,
true);
revng_assert(LaidOutForwardsGraph.has_value());
// Ready the backwards facing part of the slice
auto Backwards = calls::makeCallerTree(Relations.toYieldGraph(), SlicePoint);
for (auto *From : Backwards.nodes())
for (auto &&[To, Label] : From->successor_edges())
Label->IsBackwards = true;
Helper.computeSizes(Backwards);
auto LaidOutBackwardsGraph = layout::sugiyama::compute(Backwards,
Configuration,
LeftToRight,
BFS,
true);
revng_assert(LaidOutBackwardsGraph.has_value());
// Consume the halves to produce a combined graph and export it.
auto CombinedGraph = combineHalvesHelper(SlicePoint,
std::move(*LaidOutForwardsGraph),
std::move(*LaidOutBackwardsGraph));
return exportGraph<false>(B,
CombinedGraph,
Configuration,
LeftToRight,
Helper);
}