private SsaFormBuilder(MethodDefinition method, ControlFlowGraph cfg)
{
this.method = method;
this.cfg = cfg;
this.blocks = new SsaBlock[cfg.Nodes.Count];
this.stackSizeAtBlockStart = new int[cfg.Nodes.Count];
for (int i = 0; i < stackSizeAtBlockStart.Length; i++) {
stackSizeAtBlockStart[i] = -1;
}
stackSizeAtBlockStart[cfg.EntryPoint.BlockIndex] = 0;
this.parameters = new SsaVariable[method.Parameters.Count + (method.HasThis ? 1 : 0)];
if (method.HasThis)
parameters[0] = new SsaVariable(method.Body.ThisParameter);
for (int i = 0; i < method.Parameters.Count; i++)
parameters[i + (method.HasThis ? 1 : 0)] = new SsaVariable(method.Parameters[i]);
this.locals = new SsaVariable[method.Body.Variables.Count];
for (int i = 0; i < locals.Length; i++)
locals[i] = new SsaVariable(method.Body.Variables[i]);
this.stackLocations = new SsaVariable[method.Body.MaxStackSize];
for (int i = 0; i < stackLocations.Length; i++) {
stackLocations[i] = new SsaVariable(i);
}
}
private SsaFormBuilder(MethodDefinition method, ControlFlowGraph cfg)
{
this.method = method;
this.cfg = cfg;
this.blocks = new SsaBlock[cfg.Nodes.Count];
this.stackSizeAtBlockStart = new int[cfg.Nodes.Count];
for (int i = 0; i < stackSizeAtBlockStart.Length; i++)
{
stackSizeAtBlockStart[i] = -1;
}
stackSizeAtBlockStart[cfg.EntryPoint.BlockIndex] = 0;
this.parameters = new SsaVariable[method.Parameters.Count + (method.HasThis ? 1 : 0)];
if (method.HasThis)
{
parameters[0] = new SsaVariable(method.Body.ThisParameter);
}
for (int i = 0; i < method.Parameters.Count; i++)
{
parameters[i + (method.HasThis ? 1 : 0)] = new SsaVariable(method.Parameters[i]);
}
this.locals = new SsaVariable[method.Body.Variables.Count];
for (int i = 0; i < locals.Length; i++)
{
locals[i] = new SsaVariable(method.Body.Variables[i]);
}
this.stackLocations = new SsaVariable[method.Body.MaxStackSize];
for (int i = 0; i < stackLocations.Length; i++)
{
stackLocations[i] = new SsaVariable(i);
}
}
public SsaVariable(SsaVariable original, string newName)
{
this.Name = newName;
this.IsStackLocation = original.IsStackLocation;
this.OriginalVariableIndex = original.OriginalVariableIndex;
this.Parameter = original.Parameter;
this.Variable = original.Variable;
}
public void ReplaceVariableInOperands(SsaVariable oldVar, SsaVariable newVar)
{
for (int i = 0; i < this.Operands.Length; i++)
{
if (this.Operands[i] == oldVar)
{
this.Operands[i] = newVar;
}
}
}
public static void RemoveDeadAssignments(SsaForm ssaForm)
{
HashSet <SsaVariable> liveVariables = new HashSet <SsaVariable>();
// find variables that are used directly
foreach (SsaBlock block in ssaForm.Blocks)
{
foreach (SsaInstruction inst in block.Instructions)
{
if (!CanRemoveAsDeadCode(inst))
{
if (inst.Target != null)
{
liveVariables.Add(inst.Target);
}
foreach (SsaVariable op in inst.Operands)
{
liveVariables.Add(op);
}
}
}
}
Queue <SsaVariable> queue = new Queue <SsaVariable>(liveVariables);
// find variables that are used indirectly
while (queue.Count > 0)
{
SsaVariable v = queue.Dequeue();
if (v.IsSingleAssignment)
{
foreach (SsaVariable op in v.Definition.Operands)
{
if (liveVariables.Add(op))
{
queue.Enqueue(op);
}
}
}
}
// remove assignments to all unused variables
foreach (SsaBlock block in ssaForm.Blocks)
{
block.Instructions.RemoveAll(
inst => {
if (inst.Target != null && !liveVariables.Contains(inst.Target))
{
Debug.Assert(inst.Target.IsSingleAssignment);
return(true);
}
return(false);
});
}
ssaForm.ComputeVariableUsage(); // update usage after we modified stuff
}
void DetermineOperands(int stackSize, Instruction inst, int popCount, int pushCount, out SsaVariable target, out SsaVariable[] operands)
{
switch (inst.OpCode.Code)
{
case Code.Ldarg:
operands = new SsaVariable[] { ssaForm.GetOriginalVariable((ParameterReference)inst.Operand) };
target = stackLocations[stackSize];
break;
case Code.Starg:
operands = new SsaVariable[] { stackLocations[stackSize] };
target = ssaForm.GetOriginalVariable((ParameterReference)inst.Operand);
break;
case Code.Ldloc:
operands = new SsaVariable[] { ssaForm.GetOriginalVariable((VariableReference)inst.Operand) };
target = stackLocations[stackSize];
break;
case Code.Stloc:
operands = new SsaVariable[] { stackLocations[stackSize] };
target = ssaForm.GetOriginalVariable((VariableReference)inst.Operand);
break;
case Code.Dup:
operands = new SsaVariable[] { stackLocations[stackSize] };
target = stackLocations[stackSize + 1];
break;
default:
operands = new SsaVariable[popCount];
for (int i = 0; i < popCount; i++)
{
operands[i] = stackLocations[stackSize + i];
}
switch (pushCount)
{
case 0:
target = null;
break;
case 1:
target = stackLocations[stackSize];
break;
default:
throw new NotSupportedException("unsupported pushCount=" + pushCount);
}
break;
}
}
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));
}
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 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);
}
}
SsaVariable MakeNewVersion(int variableIndex)
{
int versionCounter = ++versionCounters[variableIndex];
SsaVariable x = inputVariables[variableIndex];
if (versionCounter == 1)
{
return(x);
}
else
{
if (x.IsStackLocation)
{
return(new SsaVariable(x, "temp" + (transform.tempVariableCounter++)));
}
else
{
return(new SsaVariable(x, x.Name + "_" + versionCounter));
}
}
}
/// <summary>
/// When any instructions stores its result in a stack location that's used only once in a 'stloc' or 'starg' instruction,
/// we optimize this to directly store in the target location.
/// As optimization this is redundant (does the same as copy propagation), but it'll make us keep the variables named
/// after locals instead of keeping the temps as using only the simple copy propagation would do.
/// </summary>
public static void DirectlyStoreToVariables(SsaForm ssaForm)
{
foreach (SsaBlock block in ssaForm.Blocks)
{
block.Instructions.RemoveAll(
inst => {
if (inst.Instruction != null && (inst.Instruction.OpCode == OpCodes.Stloc || inst.Instruction.OpCode == OpCodes.Starg))
{
SsaVariable target = inst.Target;
SsaVariable temp = inst.Operands[0];
if (target.IsSingleAssignment && temp.IsSingleAssignment && temp.Usage.Count == 1 && temp.IsStackLocation)
{
temp.Definition.Target = target;
return(true);
}
}
return(false);
});
}
ssaForm.ComputeVariableUsage(); // update usage after we modified stuff
}
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 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));
}
public void ReplaceVariableInOperands(SsaVariable oldVar, SsaVariable newVar)
{
for (int i = 0; i < this.Operands.Length; i++) {
if (this.Operands[i] == oldVar)
this.Operands[i] = newVar;
}
}
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 SsaVariable(SsaVariable original, string newName)
{
this.Name = newName;
this.IsStackLocation = original.IsStackLocation;
this.OriginalVariableIndex = original.OriginalVariableIndex;
this.Parameter = original.Parameter;
this.Variable = original.Variable;
}
void DetermineOperands(int stackSize, Instruction inst, int popCount, int pushCount, out SsaVariable target, out SsaVariable[] operands)
{
switch (inst.OpCode.Code) {
case Code.Ldarg:
operands = new SsaVariable[] { ssaForm.GetOriginalVariable((ParameterReference)inst.Operand) };
target = stackLocations[stackSize];
break;
case Code.Starg:
operands = new SsaVariable[] { stackLocations[stackSize] };
target = ssaForm.GetOriginalVariable((ParameterReference)inst.Operand);
break;
case Code.Ldloc:
operands = new SsaVariable[] { ssaForm.GetOriginalVariable((VariableReference)inst.Operand) };
target = stackLocations[stackSize];
break;
case Code.Stloc:
operands = new SsaVariable[] { stackLocations[stackSize] };
target = ssaForm.GetOriginalVariable((VariableReference)inst.Operand);
break;
case Code.Dup:
operands = new SsaVariable[] { stackLocations[stackSize] };
target = stackLocations[stackSize + 1];
break;
default:
operands = new SsaVariable[popCount];
for (int i = 0; i < popCount; i++) {
operands[i] = stackLocations[stackSize + i];
}
switch (pushCount) {
case 0:
target = null;
break;
case 1:
target = stackLocations[stackSize];
break;
default:
throw new NotSupportedException("unsupported pushCount=" + pushCount);
}
break;
}
}