perf: avoid multiple cfg reverses

Author: EagleoutIce

src/control-flow/basic-cfg-guided-visitor.ts

@@ -6,6 +6,7 @@ import {
 	, CfgVertexType } from './control-flow-graph';
 import type { NodeId } from '../r-bridge/lang-4.x/ast/model/processing/node-id';
 import { assertUnreachable } from '../util/assert';
+import { invertCfg } from './invert-cfg';
 
 export interface BasicCfgGuidedVisitorConfiguration<
 	ControlFlow extends ControlFlowInformation = ControlFlowInformation,
@@ -49,10 +50,14 @@ export class BasicCfgGuidedVisitor<
 
 	protected startVisitor(start: readonly NodeId[]): void {
 		const graph = this.config.controlFlow.graph;
-		const getNext = this.config.defaultVisitingOrder === 'forward' ?
-			(node: NodeId) => graph.ingoingEdges(node)?.keys().toArray().toReversed() :
-			(node: NodeId) => graph.outgoingEdges(node)?.keys().toArray();
-		const stack = [...start];
+		let getNext: (node: NodeId) => MapIterator<NodeId> | NodeId[] | undefined;
+		if(this.config.defaultVisitingOrder === 'forward') {
+			const inverseGraph = invertCfg(graph);
+			getNext = (node: NodeId) => inverseGraph.outgoingEdges(node)?.keys().toArray().reverse();
+		} else {
+			getNext = (node: NodeId) => graph.outgoingEdges(node)?.keys();
+		}
+		const stack = Array.from(start);
 		while(stack.length > 0) {
 			const current = stack.pop() as NodeId;
 

src/control-flow/cfg-dead-code.ts

@@ -1,5 +1,5 @@
 /* currently this does not do work on function definitions */
-import type { ControlFlowInformation } from './control-flow-graph';
+import type { ControlFlowGraph, ControlFlowInformation } from './control-flow-graph';
 import { CfgEdgeType } from './control-flow-graph';
 import type { NodeId } from '../r-bridge/lang-4.x/ast/model/processing/node-id';
 import { Ternary } from '../util/logic';
@@ -13,6 +13,7 @@ import { EmptyArgument } from '../r-bridge/lang-4.x/ast/model/nodes/r-function-c
 import { valueSetGuard } from '../dataflow/eval/values/general';
 import { isValue } from '../dataflow/eval/values/r-value';
 import { visitCfgInOrder } from './simple-visitor';
+import { invertCfg } from './invert-cfg';
 
 type CachedValues<Val> = Map<NodeId, Val>;
 
@@ -21,6 +22,7 @@ class CfgConditionalDeadCodeRemoval extends SemanticCfgGuidedVisitor {
 	private readonly cachedConditions: CachedValues<Ternary> = new Map();
 	private readonly cachedStatements: CachedValues<boolean> = new Map();
 	private readonly inTry:            Set<NodeId> = new Set<NodeId>();
+	private invertedCfg:               ControlFlowGraph | undefined;
 
 	private getValue(id: NodeId): Ternary {
 		const has = this.cachedConditions.get(id);
@@ -52,6 +54,7 @@ class CfgConditionalDeadCodeRemoval extends SemanticCfgGuidedVisitor {
 	}
 
 	protected override startVisitor(): void {
+		this.invertedCfg = invertCfg(this.config.controlFlow.graph);
 		for(const [from, targets] of this.config.controlFlow.graph.edges()) {
 			for(const [target, edge] of targets) {
 				if(edge.label === CfgEdgeType.Cd) {
@@ -65,7 +68,7 @@ class CfgConditionalDeadCodeRemoval extends SemanticCfgGuidedVisitor {
 				} else if(edge.label === CfgEdgeType.Fd && this.isUnconditionalJump(target)) {
 					// for each unconditional jump, we find the corresponding end/exit nodes and remove any flow edges
 					for(const end of this.getCfgVertex(target)?.end as NodeId[] ?? []) {
-						for(const [target, edge] of this.config.controlFlow.graph.ingoingEdges(end) ?? []) {
+						for(const [target, edge] of this.invertedCfg.outgoingEdges(end) ?? []) {
 							if(edge.label === CfgEdgeType.Fd) {
 								this.config.controlFlow.graph.removeEdge(target, end);
 							}
@@ -152,7 +155,7 @@ class CfgConditionalDeadCodeRemoval extends SemanticCfgGuidedVisitor {
 			}
 			this.inTry.add(n);
 			return false;
-		});
+		}, this.invertedCfg);
 	}
 }
 
@@ -168,7 +171,7 @@ export function cfgAnalyzeDeadCode(cfg: ControlFlowInformation, info: CfgPassInf
 		normalizedAst:        info.ast,
 		dfg:                  info.dfg,
 		ctx:                  info.ctx,
-		defaultVisitingOrder: 'forward',
+		defaultVisitingOrder: 'backward'
 	});
 	visitor.start();
 	return cfg;

src/control-flow/control-flow-graph.ts

@@ -280,8 +280,9 @@ export class ControlFlowGraph<Vertex extends CfgSimpleVertex = CfgSimpleVertex>
 	ingoingEdges(id: NodeId): ReadonlyMap<NodeId, CfgEdge> | undefined {
 		const edges = new Map<NodeId, CfgEdge>();
 		for(const [source, outgoing] of this.edgeInformation.entries()) {
-			if(outgoing.has(id)) {
-				edges.set(source, outgoing.get(id) as CfgEdge);
+			const o = outgoing.get(id);
+			if(o) {
+				edges.set(source, o);
 			}
 		}
 		return edges;

src/control-flow/simple-visitor.ts

@@ -49,6 +49,7 @@ export function visitCfgInReverseOrder(
  * @param graph      - The control flow graph.
  * @param startNodes - The nodes to start the traversal from.
  * @param visitor    - The visitor function to call for each node, if you return true the traversal from this node will be stopped.
+ * @param invertedCfg  - Optionally provide an inverted control flow graph, if not provided the function will create one by inverting the given graph, which can be expensive for large graphs.
  *
  * This function is of type {@link SimpleCfgVisitor}.
  * @see {@link visitCfgInReverseOrder} for a traversal in reversed order
@@ -57,12 +58,13 @@ export function visitCfgInOrder(
 	graph: ControlFlowGraph,
 	startNodes: readonly NodeId[],
 	// eslint-disable-next-line @typescript-eslint/no-invalid-void-type -- void is used to indicate that the return value is ignored/we never stop
-	visitor: (node: NodeId) => boolean | void
+	visitor: (node: NodeId) => boolean | void,
+	invertedCfg?: ControlFlowGraph
 ): Set<NodeId> {
 	const visited = new Set<NodeId>();
 	let queue = startNodes.slice();
 	const hasBb = graph.mayHaveBasicBlocks();
-	const g = invertCfg(graph);
+	const g = invertedCfg ?? invertCfg(graph);
 	while(queue.length > 0) {
 		const current = queue.shift() as NodeId;
 		if(visited.has(current)) {