void ComputeInstructionData(IDictionary visited, int stackHeight, InstructionBlock block)
{
if (visited.Contains(block))
{
return;
}
visited.Add(block, block);
foreach (Instruction instruction in block)
{
stackHeight = ComputeInstructionData(stackHeight, instruction);
}
foreach (InstructionBlock successor in block.Successors)
{
ComputeInstructionData(visited, stackHeight, successor);
}
}
static InstructionBlock GetThen (InstructionBlock block)
{
return block.Successors [0];
}
void MarkProcessed (InstructionBlock block)
{
_processed [block] = block;
}
static bool IsFalse (InstructionBlock block)
{
return block.FirstInstruction == block.LastInstruction
&& block.FirstInstruction.OpCode.Value == OpCodes.Ldc_I4_0.Value;
}
void ProcessNestedExpression (InstructionBlock block)
{
switch (block.Successors.Length) {
case 1:
BuildExpression (block);
break;
case 2:
ProcessLogicalExpressionBlock (block);
break;
default:
throw new ArgumentException ("block");
}
}
void ProcessNotAnd (InstructionBlock block)
{
BuildNegateExpression (block);
ProcessNestedExpression (GetElse (block));
_expressionDecompiler.PushBinaryExpression (BinaryOperator.LogicalAnd);
}
static ExpressionPattern DetectExpressionPattern (InstructionBlock block)
{
InstructionBlock then = GetThen (block);
if (IsTrue (then)) return ExpressionPattern.SimpleOr;
if (IsFalse (then)) return ExpressionPattern.SimpleNotAnd;
// the following flow graph patterns are described in
// Decompilation of .NET Bytecode, Computer Science Tripos Part II
// Trinity Hall, May 13, 2004
// Fig. 3.10 on pg. 43
// pattern 4: !x && y
if (GetElse (GetElse (block)) == then) return ExpressionPattern.NestedNotAnd;
return ExpressionPattern.Unknown;
}
void ProcessSimpleBlock (InstructionBlock block)
{
foreach (Instruction instruction in block) {
_expressionDecompiler.Visit (instruction);
if (0 == GetStackAfter (instruction)) {
CreateActionBlock (instruction);
_current = instruction.Next;
}
}
}
void ConnectBlock (InstructionBlock block)
{
if (block.LastInstruction == null)
throw new ApplicationException ("Undelimited block at offset " + block.FirstInstruction.Offset);
Instruction instruction = block.LastInstruction;
switch (instruction.OpCode.FlowControl) {
case FlowControl.Branch:
case FlowControl.Cond_Branch: {
if (HasMultipleBranches (instruction)) {
InstructionBlock [] blocks = GetBranchTargetsBlocks (instruction);
if (instruction.Next != null)
blocks = AddBlock (GetBlock (instruction.Next), blocks);
block.SetSuccessors (blocks);
break;
}
InstructionBlock target = GetBranchTargetBlock (instruction);
if (instruction.OpCode.FlowControl == FlowControl.Cond_Branch && instruction.Next != null)
block.SetSuccessors (new InstructionBlock [] { target, GetBlock (instruction.Next) });
else
block.SetSuccessors (new InstructionBlock [] { target });
break;
}
case FlowControl.Call:
case FlowControl.Next:
if (null != instruction.Next)
block.SetSuccessors (new InstructionBlock [] { GetBlock (instruction.Next) });
break;
case FlowControl.Return:
break;
default:
throw new ApplicationException (
string.Format ("Unhandled instruction flow behavior {0}: {1}",
instruction.OpCode.FlowControl,
Formatter.FormatInstruction (instruction)));
}
}
void ComputeInstructionData (IDictionary visited, int stackHeight, InstructionBlock block)
{
if (visited.Contains (block)) return;
visited.Add (block, block);
foreach (Instruction instruction in block) {
stackHeight = ComputeInstructionData (stackHeight, instruction);
}
foreach (InstructionBlock successor in block.Successors) {
ComputeInstructionData (visited, stackHeight, successor);
}
}
void MarkBlockStart (Instruction instruction)
{
InstructionBlock block = GetBlock (instruction);
if (null != block) return;
block = new InstructionBlock (instruction);
RegisterBlock (block);
}
void RegisterBlock(InstructionBlock block)
{
_blocks.Add(block.FirstInstruction.Offset, block);
}
void MarkProcessed (InstructionBlock block)
{
_processed.Add (block);
}
/// <summary>
/// Checks if the subgraph starting at block represents
/// a logical expression.
/// </summary>
/// <param name="block"></param>
/// <returns></returns>
bool IsLogicalExpression (InstructionBlock block)
{
return IsLogicalExpression (new HashSet<InstructionBlock> (), block);
}
InstructionBlock [] ToArray (InstructionBlock [] blocks)
{
_blocks.Values.CopyTo (blocks, 0);
Array.Sort (blocks);
return blocks;
}
static InstructionBlock [] AddBlock (InstructionBlock block, InstructionBlock [] blocks)
{
InstructionBlock [] result = new InstructionBlock [blocks.Length + 1];
Array.Copy (blocks, result, blocks.Length);
result [result.Length - 1] = block;
return result;
}
bool IsLogicalExpression (Hashtable visited, InstructionBlock block)
{
if (visited.Contains (block)) return false;
visited.Add (block, block);
foreach (InstructionBlock successor in block.Successors) {
if (GetStackAfter (successor.LastInstruction) > 0) return true;
if (IsLogicalExpression (visited, successor)) return true;
}
return false;
}
InstructionBlock [] GetBranchTargetsBlocks (Instruction instruction)
{
Instruction [] targets = GetBranchTargets (instruction);
InstructionBlock [] blocks = new InstructionBlock [targets.Length];
for (int i = 0; i < targets.Length; i++)
blocks [i] = GetBlock (targets [i]);
return blocks;
}
void ProcessLogicalExpressionBlock (InstructionBlock block)
{
switch (DetectExpressionPattern (block)) {
case ExpressionPattern.SimpleOr:
ProcessOr (block);
break;
case ExpressionPattern.SimpleNotAnd:
ProcessNotAnd (block);
break;
case ExpressionPattern.NestedNotAnd:
ProcessNestedNotAnd (block);
break;
default:
throw new ArgumentException ("Unknown expression pattern starting at " + Formatter.FormatInstruction (block.FirstInstruction), "block");
}
MarkProcessed (block.Successors);
}
void RegisterBlock (InstructionBlock block)
{
_blocks.Add (block.FirstInstruction.Offset, block);
}
void ProcessOr (InstructionBlock block)
{
BuildExpression (block);
ProcessNestedExpression (GetElse (block));
_expressionDecompiler.PushBinaryExpression (BinaryOperator.LogicalOr);
}
internal void SetSuccessors (InstructionBlock [] successors)
{
_successors = successors;
}
void BuildNegateExpression (InstructionBlock block)
{
BuildExpression (block);
_expressionDecompiler.Negate ();
}
private static int GetBlockId(ControlFlowGraph cfg, InstructionBlock block)
{
return ((IList) cfg.Blocks).IndexOf (block) + 1;
}
void BuildExpression (InstructionBlock block)
{
if (WasProcessed (block)) return;
foreach (Instruction instruction in block) {
_expressionDecompiler.Visit (instruction);
}
MarkProcessed (block);
}
void ProcessBlock (InstructionBlock block)
{
switch (block.Successors.Length) {
case 0:
case 1:
ProcessSimpleBlock (block);
break;
case 2:
ProcessTwoWayBlock (block);
break;
default:
throw new ArgumentException ("n-way block not supported", "block");
}
MarkProcessed (block);
}
void MarkProcessed (InstructionBlock [] blocks)
{
foreach (InstructionBlock block in blocks) {
MarkProcessed (block);
}
}
void ProcessTwoWayBlock (InstructionBlock block)
{
if (IsLogicalExpression (block)) {
ProcessLogicalExpressionBlock (block);
} else {
ProcessSimpleBlock (block);
}
}
bool WasProcessed (InstructionBlock block)
{
return _processed.Contains (block);
}
/// <summary>
/// Checks if the subgraph starting at block represents
/// a logical expression.
/// </summary>
/// <param name="block"></param>
/// <returns></returns>
bool IsLogicalExpression (InstructionBlock block)
{
return IsLogicalExpression (new Hashtable (), block);
}
static InstructionBlock GetElse (InstructionBlock block)
{
return block.Successors [1];
}
public ControlFlowGraph (MethodBody body, InstructionBlock [] blocks, IDictionary instructionData)
{
_body = body;
_blocks = blocks;
_data = instructionData;
}
