ILSpy/src/ControlFlow/Nodes.cs

using System;
using System.Collections.Generic;

using Mono.Cecil.Cil;

namespace Decompiler.ControlFlow
{
	public class MethodBodyGraph: Node
	{
		BasicBlock methodEntry;
		
		public BasicBlock MethodEntry {
			get { return methodEntry; }
		}
		
		public MethodBodyGraph(StackExpressionCollection exprs)
		{
			if (exprs.Count == 0) throw new ArgumentException("Count == 0", "exprs");
			
			BasicBlock basicBlock = null;
			for(int i = 0; i < exprs.Count; i++) {
				// Start new basic block if
				//  - this is first expression
				//  - last expression was branch
				//  - this expression is branch target
				if (i == 0 || exprs[i - 1].BranchTarget != null || exprs[i].BranchesHere.Count > 0){
					basicBlock = new BasicBlock();
					this.Childs.Add(basicBlock);
				}
				basicBlock.Body.Add(exprs[i]);
				exprs[i].BasicBlock = basicBlock;
			}
			
			// Add fall-through links to BasicBlocks
			for(int i = 0; i < exprs.Count - 1; i++) {
				BasicBlock node = exprs[i].BasicBlock;
				BasicBlock target = exprs[i + 1].BasicBlock;
				
				// Still same basic block - ignore
				if (node == target) continue;
				
				// Non-conditional branch does not fall-through
				if (exprs[i].LastByteCode.OpCode.Code == Code.Br) continue;
				
				node.FallThroughBasicBlock = target;
				target.BasicBlockPredecessors.Add(node);
			}
			
			// Add branch links to BasicBlocks
			for(int i = 0; i < exprs.Count; i++) {
				if (exprs[i].BranchTarget != null) {
					BasicBlock node = exprs[i].BasicBlock;
					BasicBlock target = exprs[i].BranchTarget.BasicBlock;
					
					node.BranchBasicBlock = target;
					target.BasicBlockPredecessors.Add(node);
				}
			}
			
			this.methodEntry = (BasicBlock)this.HeadChild;
		}
	}
	
	public class AcyclicGraph: Node
	{
	}
	
	public class Loop: Node
	{
	}
	
	public class BasicBlock: Node
	{
		List<StackExpression> body = new List<StackExpression>();
		List<BasicBlock> basicBlockPredecessors = new List<BasicBlock>();
		BasicBlock fallThroughBasicBlock;
		BasicBlock branchBasicBlock;
		
		public List<StackExpression> Body {
			get { return body; }
		}
		
		public List<BasicBlock> BasicBlockPredecessors {
			get { return basicBlockPredecessors; }
		}
		
		public BasicBlock FallThroughBasicBlock {
			get { return fallThroughBasicBlock; }
			set { fallThroughBasicBlock = value; }
		}
		
		public BasicBlock BranchBasicBlock {
			get { return branchBasicBlock; }
			set { branchBasicBlock = value; }
		}
		
		public IEnumerable<BasicBlock> BasicBlockSuccessors {
			get {
				if (this.FallThroughBasicBlock != null) {
					yield return this.FallThroughBasicBlock;
				}
				if (this.BranchBasicBlock != null) {
					yield return this.BranchBasicBlock;
				}
			}
		}
	}
}