public SsaInstruction(SsaBlock parentBlock, Instruction instruction, SsaVariable target, SsaVariable[] operands,
Instruction[] prefixes = null, SpecialOpCode specialOpCode = SpecialOpCode.None,
TypeReference typeOperand = null)
{
this.ParentBlock = parentBlock;
this.Instruction = instruction;
this.Prefixes = prefixes ?? emptyInstructionArray;
this.Target = target;
this.Operands = operands ?? emptyVariableArray;
this.SpecialOpCode = specialOpCode;
this.TypeOperand = typeOperand;
Debug.Assert((typeOperand != null) == (specialOpCode == SpecialOpCode.Exception || specialOpCode == SpecialOpCode.InitObj));
}
void CreateGraphStructure()
{
for (int i = 0; i < blocks.Length; i++)
{
blocks[i] = new SsaBlock(cfg.Nodes[i]);
}
for (int i = 0; i < blocks.Length; i++)
{
foreach (ControlFlowNode node in cfg.Nodes[i].Successors)
{
blocks[i].Successors.Add(blocks[node.BlockIndex]);
blocks[node.BlockIndex].Predecessors.Add(blocks[i]);
}
}
}
internal SsaForm(SsaBlock[] blocks, SsaVariable[] parameters, SsaVariable[] locals, SsaVariable[] stackLocations, bool methodHasThis)
{
this.parameters = parameters;
this.locals = locals;
this.Blocks = new ReadOnlyCollection<SsaBlock>(blocks);
this.OriginalVariables = new ReadOnlyCollection<SsaVariable>(parameters.Concat(locals).Concat(stackLocations).ToList());
this.methodHasThis = methodHasThis;
Debug.Assert(EntryPoint.NodeType == ControlFlowNodeType.EntryPoint);
Debug.Assert(RegularExit.NodeType == ControlFlowNodeType.RegularExit);
Debug.Assert(ExceptionalExit.NodeType == ControlFlowNodeType.ExceptionalExit);
for (int i = 0; i < this.OriginalVariables.Count; i++) {
this.OriginalVariables[i].OriginalVariableIndex = i;
}
}
void MakeByRefCallSimple(SsaBlock block, ref int instructionIndexInBlock, IMethodSignature targetMethod)
{
SsaInstruction inst = block.Instructions[instructionIndexInBlock];
for (int i = 0; i < inst.Operands.Length; i++)
{
SsaVariable operand = inst.Operands[i];
if (operand.IsSingleAssignment && operand.Usage.Count == 1 && IsLoadAddress(operand.Definition))
{
// address is used for this method call only
Instruction loadAddressInstruction = operand.Definition.Instruction;
// find target parameter type:
bool isOut;
if (i == 0 && targetMethod.HasThis)
{
isOut = false;
}
else
{
ParameterDefinition parameter = targetMethod.Parameters[i - (targetMethod.HasThis ? 1 : 0)];
isOut = parameter.IsOut;
}
SsaVariable addressTakenOf = GetVariableFromLoadAddressInstruction(loadAddressInstruction);
// insert "Prepare" instruction on front
SpecialOpCode loadOpCode = isOut ? SpecialOpCode.PrepareByOutCall : SpecialOpCode.PrepareByRefCall;
block.Instructions.Insert(instructionIndexInBlock++, new SsaInstruction(
block, null, operand, new SsaVariable[] { addressTakenOf }, specialOpCode: loadOpCode));
// insert "WriteAfterByRefOrOutCall" instruction after call
block.Instructions.Insert(instructionIndexInBlock + 1, new SsaInstruction(
block, null, addressTakenOf, new SsaVariable[] { operand }, specialOpCode: SpecialOpCode.WriteAfterByRefOrOutCall));
couldSimplifySomething = true;
// remove the loadAddressInstruction later
// (later because it might be defined in the current block and we don't want instructionIndex to become invalid)
redundantLoadAddressInstructions.Add(operand.Definition);
}
}
}
void MakeLoadFieldCallSimple(SsaBlock block, ref int instructionIndexInBlock)
{
SsaInstruction inst = block.Instructions[instructionIndexInBlock];
Debug.Assert(inst.Operands.Length == 1);
SsaVariable operand = inst.Operands[0];
if (operand.IsSingleAssignment && operand.Usage.Count == 1 && IsLoadAddress(operand.Definition))
{
// insert special "PrepareForFieldAccess" instruction in front
block.Instructions.Insert(instructionIndexInBlock++, new SsaInstruction(
inst.ParentBlock, null, operand,
new SsaVariable[] { GetVariableFromLoadAddressInstruction(operand.Definition.Instruction) },
specialOpCode: SpecialOpCode.PrepareForFieldAccess));
couldSimplifySomething = true;
// remove the loadAddressInstruction later
redundantLoadAddressInstructions.Add(operand.Definition);
}
}
void MakeInitObjCallSimple(SsaBlock block, ref int instructionIndexInBlock)
{
SsaInstruction inst = block.Instructions[instructionIndexInBlock];
Debug.Assert(inst.Operands.Length == 1);
SsaVariable operand = inst.Operands[0];
if (operand.IsSingleAssignment && operand.Usage.Count == 1 && IsLoadAddress(operand.Definition))
{
// replace instruction with special "InitObj" instruction
block.Instructions[instructionIndexInBlock] = new SsaInstruction(
inst.ParentBlock, null, GetVariableFromLoadAddressInstruction(operand.Definition.Instruction), null,
specialOpCode: SpecialOpCode.InitObj,
typeOperand: (TypeReference)inst.Instruction.Operand);
couldSimplifySomething = true;
// remove the loadAddressInstruction later
redundantLoadAddressInstructions.Add(operand.Definition);
}
}
void PlacePhiFunctions(SsaVariable variable)
{
cfg.ResetVisited();
HashSet <SsaBlock> blocksWithPhi = new HashSet <SsaBlock>();
Queue <ControlFlowNode> worklist = new Queue <ControlFlowNode>();
foreach (SsaInstruction writeInstruction in writeToOriginalVariables[variable.OriginalVariableIndex])
{
ControlFlowNode cfgNode = cfg.Nodes[writeInstruction.ParentBlock.BlockIndex];
if (!cfgNode.Visited)
{
cfgNode.Visited = true;
worklist.Enqueue(cfgNode);
}
}
while (worklist.Count > 0)
{
ControlFlowNode cfgNode = worklist.Dequeue();
foreach (ControlFlowNode dfNode in cfgNode.DominanceFrontier)
{
// we don't need phi functions in the exit node
if (dfNode.NodeType == ControlFlowNodeType.RegularExit || dfNode.NodeType == ControlFlowNodeType.ExceptionalExit)
{
continue;
}
SsaBlock y = ssaForm.Blocks[dfNode.BlockIndex];
if (blocksWithPhi.Add(y))
{
// add a phi instruction in y
SsaVariable[] operands = Enumerable.Repeat(variable, dfNode.Incoming.Count).ToArray();
y.Instructions.Insert(0, new SsaInstruction(y, null, variable, operands, specialOpCode: SpecialOpCode.Phi));
if (!dfNode.Visited)
{
dfNode.Visited = true;
worklist.Enqueue(dfNode);
}
}
}
}
}
public SsaInstruction(SsaBlock parentBlock, Instruction instruction, SsaVariable target, SsaVariable[] operands,
Instruction[] prefixes = null, SpecialOpCode specialOpCode = SpecialOpCode.None,
TypeReference typeOperand = null)
{
this.ParentBlock = parentBlock;
this.Instruction = instruction;
this.Prefixes = prefixes ?? emptyInstructionArray;
this.Target = target;
this.Operands = operands ?? emptyVariableArray;
this.SpecialOpCode = specialOpCode;
this.TypeOperand = typeOperand;
Debug.Assert((typeOperand != null) == (specialOpCode == SpecialOpCode.Exception || specialOpCode == SpecialOpCode.InitObj));
}
void CreateInstructions(int blockIndex)
{
ControlFlowNode cfgNode = cfg.Nodes[blockIndex];
SsaBlock block = blocks[blockIndex];
int stackSize = stackSizeAtBlockStart[blockIndex];
Debug.Assert(stackSize >= 0);
List <Instruction> prefixes = new List <Instruction>();
foreach (Instruction inst in cfgNode.Instructions)
{
if (inst.OpCode.OpCodeType == OpCodeType.Prefix)
{
prefixes.Add(inst);
continue;
}
int popCount = inst.GetPopDelta(method) ?? stackSize;
stackSize -= popCount;
if (stackSize < 0)
{
throw new InvalidProgramException("IL stack underflow");
}
int pushCount = inst.GetPushDelta();
if (stackSize + pushCount > stackLocations.Length)
{
throw new InvalidProgramException("IL stack overflow");
}
SsaVariable target;
SsaVariable[] operands;
DetermineOperands(stackSize, inst, popCount, pushCount, out target, out operands);
Instruction[] prefixArray = prefixes.Count > 0 ? prefixes.ToArray() : null;
prefixes.Clear();
// ignore NOP instructions
if (!(inst.OpCode == OpCodes.Nop || inst.OpCode == OpCodes.Pop))
{
block.Instructions.Add(new SsaInstruction(block, inst, target, operands, prefixArray));
}
stackSize += pushCount;
}
foreach (ControlFlowEdge edge in cfgNode.Outgoing)
{
int newStackSize;
switch (edge.Type)
{
case JumpType.Normal:
newStackSize = stackSize;
break;
case JumpType.EndFinally:
if (stackSize != 0)
{
throw new NotSupportedException("stacksize must be 0 in endfinally edge");
}
newStackSize = 0;
break;
case JumpType.JumpToExceptionHandler:
switch (edge.Target.NodeType)
{
case ControlFlowNodeType.FinallyOrFaultHandler:
newStackSize = 0;
break;
case ControlFlowNodeType.ExceptionalExit:
case ControlFlowNodeType.CatchHandler:
newStackSize = 1;
break;
default:
throw new NotSupportedException("unsupported target node type: " + edge.Target.NodeType);
}
break;
default:
throw new NotSupportedException("unsupported jump type: " + edge.Type);
}
int nextStackSize = stackSizeAtBlockStart[edge.Target.BlockIndex];
if (nextStackSize == -1)
{
stackSizeAtBlockStart[edge.Target.BlockIndex] = newStackSize;
CreateInstructions(edge.Target.BlockIndex);
}
else if (nextStackSize != newStackSize)
{
throw new InvalidProgramException("Stack size doesn't match");
}
}
}
internal void Visit(SsaBlock block)
{
// duplicate top of all stacks
foreach (var stack in versionStacks) {
if (stack != null)
stack.Push(stack.Peek());
}
foreach (SsaInstruction s in block.Instructions) {
// replace all uses of variables being processed with their current version.
if (s.SpecialOpCode != SpecialOpCode.Phi) {
for (int i = 0; i < s.Operands.Length; i++) {
var stack = versionStacks[s.Operands[i].OriginalVariableIndex];
if (stack != null)
s.Operands[i] = stack.Peek();
}
}
// if we're writing to a variable we should process:
if (s.Target != null) {
int targetIndex = s.Target.OriginalVariableIndex;
if (versionStacks[targetIndex] != null) {
s.Target = MakeNewVersion(targetIndex);
s.Target.IsSingleAssignment = true;
s.Target.Definition = s;
// we already pushed our entry for this SsaBlock at the beginning (where we duplicated all stacks),
// so now replace the top element
versionStacks[targetIndex].Pop();
versionStacks[targetIndex].Push(s.Target);
}
}
}
foreach (SsaBlock succ in block.Successors) {
int j = succ.Predecessors.IndexOf(block);
Debug.Assert(j >= 0);
foreach (SsaInstruction f in succ.Instructions) {
if (f.SpecialOpCode == SpecialOpCode.Phi) {
var stack = versionStacks[f.Target.OriginalVariableIndex];
if (stack != null) {
f.Operands[j] = stack.Peek();
}
}
}
}
foreach (ControlFlowNode child in transform.cfg.Nodes[block.BlockIndex].DominatorTreeChildren)
Visit(transform.ssaForm.Blocks[child.BlockIndex]);
// restore stacks:
foreach (var stack in versionStacks) {
if (stack != null)
stack.Pop();
}
}
internal void Visit(SsaBlock block)
{
// duplicate top of all stacks
foreach (var stack in versionStacks)
{
if (stack != null)
{
stack.Push(stack.Peek());
}
}
foreach (SsaInstruction s in block.Instructions)
{
// replace all uses of variables being processed with their current version.
if (s.SpecialOpCode != SpecialOpCode.Phi)
{
for (int i = 0; i < s.Operands.Length; i++)
{
var stack = versionStacks[s.Operands[i].OriginalVariableIndex];
if (stack != null)
{
s.Operands[i] = stack.Peek();
}
}
}
// if we're writing to a variable we should process:
if (s.Target != null)
{
int targetIndex = s.Target.OriginalVariableIndex;
if (versionStacks[targetIndex] != null)
{
s.Target = MakeNewVersion(targetIndex);
s.Target.IsSingleAssignment = true;
s.Target.Definition = s;
// we already pushed our entry for this SsaBlock at the beginning (where we duplicated all stacks),
// so now replace the top element
versionStacks[targetIndex].Pop();
versionStacks[targetIndex].Push(s.Target);
}
}
}
foreach (SsaBlock succ in block.Successors)
{
int j = succ.Predecessors.IndexOf(block);
Debug.Assert(j >= 0);
foreach (SsaInstruction f in succ.Instructions)
{
if (f.SpecialOpCode == SpecialOpCode.Phi)
{
var stack = versionStacks[f.Target.OriginalVariableIndex];
if (stack != null)
{
f.Operands[j] = stack.Peek();
}
}
}
}
foreach (ControlFlowNode child in transform.cfg.Nodes[block.BlockIndex].DominatorTreeChildren)
{
Visit(transform.ssaForm.Blocks[child.BlockIndex]);
}
// restore stacks:
foreach (var stack in versionStacks)
{
if (stack != null)
{
stack.Pop();
}
}
}
void MakeLoadFieldCallSimple(SsaBlock block, ref int instructionIndexInBlock)
{
SsaInstruction inst = block.Instructions[instructionIndexInBlock];
Debug.Assert(inst.Operands.Length == 1);
SsaVariable operand = inst.Operands[0];
if (operand.IsSingleAssignment && operand.Usage.Count == 1 && IsLoadAddress(operand.Definition)) {
// insert special "PrepareForFieldAccess" instruction in front
block.Instructions.Insert(instructionIndexInBlock++, new SsaInstruction(
inst.ParentBlock, null, operand,
new SsaVariable[] { GetVariableFromLoadAddressInstruction(operand.Definition.Instruction) },
specialOpCode: SpecialOpCode.PrepareForFieldAccess));
couldSimplifySomething = true;
// remove the loadAddressInstruction later
redundantLoadAddressInstructions.Add(operand.Definition);
}
}
void MakeInitObjCallSimple(SsaBlock block, ref int instructionIndexInBlock)
{
SsaInstruction inst = block.Instructions[instructionIndexInBlock];
Debug.Assert(inst.Operands.Length == 1);
SsaVariable operand = inst.Operands[0];
if (operand.IsSingleAssignment && operand.Usage.Count == 1 && IsLoadAddress(operand.Definition)) {
// replace instruction with special "InitObj" instruction
block.Instructions[instructionIndexInBlock] = new SsaInstruction(
inst.ParentBlock, null, GetVariableFromLoadAddressInstruction(operand.Definition.Instruction), null,
specialOpCode: SpecialOpCode.InitObj,
typeOperand: (TypeReference)inst.Instruction.Operand);
couldSimplifySomething = true;
// remove the loadAddressInstruction later
redundantLoadAddressInstructions.Add(operand.Definition);
}
}
void MakeByRefCallSimple(SsaBlock block, ref int instructionIndexInBlock, IMethodSignature targetMethod)
{
SsaInstruction inst = block.Instructions[instructionIndexInBlock];
for (int i = 0; i < inst.Operands.Length; i++) {
SsaVariable operand = inst.Operands[i];
if (operand.IsSingleAssignment && operand.Usage.Count == 1 && IsLoadAddress(operand.Definition)) {
// address is used for this method call only
Instruction loadAddressInstruction = operand.Definition.Instruction;
// find target parameter type:
bool isOut;
if (i == 0 && targetMethod.HasThis) {
isOut = false;
} else {
ParameterDefinition parameter = targetMethod.Parameters[i - (targetMethod.HasThis ? 1 : 0)];
isOut = parameter.IsOut;
}
SsaVariable addressTakenOf = GetVariableFromLoadAddressInstruction(loadAddressInstruction);
// insert "Prepare" instruction on front
SpecialOpCode loadOpCode = isOut ? SpecialOpCode.PrepareByOutCall : SpecialOpCode.PrepareByRefCall;
block.Instructions.Insert(instructionIndexInBlock++, new SsaInstruction(
block, null, operand, new SsaVariable[] { addressTakenOf }, specialOpCode: loadOpCode));
// insert "WriteAfterByRefOrOutCall" instruction after call
block.Instructions.Insert(instructionIndexInBlock + 1, new SsaInstruction(
block, null, addressTakenOf, new SsaVariable[] { operand }, specialOpCode: SpecialOpCode.WriteAfterByRefOrOutCall));
couldSimplifySomething = true;
// remove the loadAddressInstruction later
// (later because it might be defined in the current block and we don't want instructionIndex to become invalid)
redundantLoadAddressInstructions.Add(operand.Definition);
}
}
}
void CreateGraphStructure()
{
for (int i = 0; i < blocks.Length; i++) {
blocks[i] = new SsaBlock(cfg.Nodes[i]);
}
for (int i = 0; i < blocks.Length; i++) {
foreach (ControlFlowNode node in cfg.Nodes[i].Successors) {
blocks[i].Successors.Add(blocks[node.BlockIndex]);
blocks[node.BlockIndex].Predecessors.Add(blocks[i]);
}
}
}