// this function generates code for an opaque predicate that evaluates to "true"
// => the "taken" branch of the conditional branch have to be taken for the correct code path
private void createCodeTruePredicate(ref BasicBlock outStartBasicBlock, ref ConditionalBranchTarget outConditionalBranch,
BasicBlockGraphNodeLink link, LocalDefinition currentNodeLocal) {
// create a basic block that checks the opaque predicate (this check evaluates to "true")
BasicBlock startBasicBlock = new BasicBlock();
startBasicBlock.startIdx = 0;
startBasicBlock.endIdx = 0;
// add graph transformer metadata to the basic block
GraphTransformerPredicateBasicBlock metadata = new GraphTransformerPredicateBasicBlock();
metadata.predicateType = GraphOpaquePredicate.True;
metadata.correspondingGraphNodes.Add(link);
startBasicBlock.transformationMetadata.Add(metadata);
// search for the valid and invalid interfaces list of the current valid path id
List<ITypeReference> validInterfaces = null;
List<ITypeReference> invalidInterfaces = null;
foreach (PathElement pathElement in link.graphNode.pathElements) {
if (pathElement.validPathId == link.validPathId) {
validInterfaces = pathElement.validInterfaces;
invalidInterfaces = pathElement.invalidInterfaces;
}
}
if (validInterfaces == null
|| invalidInterfaces == null) {
throw new ArgumentException("No valid/invalid interface list was found.");
}
emitPredicateCode(startBasicBlock, currentNodeLocal, validInterfaces, invalidInterfaces);
// create the conditional branch for the checking basic block (taken => correct code; not taken => dead code)
ConditionalBranchTarget startBasicBlockExitBranch = new ConditionalBranchTarget();
startBasicBlockExitBranch.sourceBasicBlock = startBasicBlock;
startBasicBlock.exitBranch = startBasicBlockExitBranch;
// create the dead code for this opaque predicate
BasicBlock deadCodeBasicBlock = new BasicBlock();
deadCodeBasicBlock.startIdx = 0;
deadCodeBasicBlock.endIdx = 0;
// set the dead code basic block as "not taken" target for the conditional branch of the checking basic block
deadCodeBasicBlock.entryBranches.Add(startBasicBlockExitBranch);
startBasicBlockExitBranch.notTakenTarget = deadCodeBasicBlock;
// generate dead code for the dead code basic block
GraphTransformerDeadCodeBasicBlock deadCodeMetadata = new GraphTransformerDeadCodeBasicBlock();
deadCodeBasicBlock.transformationMetadata.Add(deadCodeMetadata);
// set the created basic block and conditional jumps as output
outStartBasicBlock = startBasicBlock;
outConditionalBranch = startBasicBlockExitBranch;
}
// this function generates code for an opaque predicate that evaluates to "false"
// => the "not taken" branch of the conditional branch have to be taken for the correct code path
private void createCodeFalsePredicate(ref BasicBlock outStartBasicBlock, ref ConditionalBranchTarget outConditionalBranch, BasicBlockGraphNodeLink link, LocalDefinition currentNodeLocal) {
// create a basic block that checks the opaque predicate (this check evaluates to "false")
BasicBlock startBasicBlock = new BasicBlock();
startBasicBlock.startIdx = 0;
startBasicBlock.endIdx = 0;
// add graph transformer metadata to the basic block
GraphTransformerPredicateBasicBlock metadata = new GraphTransformerPredicateBasicBlock();
metadata.predicateType = GraphOpaquePredicate.False;
metadata.correspondingGraphNodes.Add(link);
startBasicBlock.transformationMetadata.Add(metadata);
// search for the valid and invalid interfaces list of the current valid path id
List<ITypeReference> validInterfaces = null;
List<ITypeReference> invalidInterfaces = null;
foreach (PathElement pathElement in link.graphNode.pathElements) {
if (pathElement.validPathId == link.validPathId) {
validInterfaces = pathElement.validInterfaces;
invalidInterfaces = pathElement.invalidInterfaces;
}
}
if(validInterfaces == null
|| invalidInterfaces == null) {
throw new ArgumentException("No valid/invalid interface list was found.");
}
// add a random check to the code
// important: for this predicate the dead code is reached by the "taken" branch and the correct code is reached by the "not taken" branch
int randPosition;
ITypeReference interfaceToCheck = null;
switch (this.prng.Next(8)) {
case 0:
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ldloc, currentNodeLocal));
randPosition = this.prng.Next(validInterfaces.Count());
interfaceToCheck = validInterfaces.ElementAt(randPosition);
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Isinst, interfaceToCheck));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ldnull));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Cgt_Un));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Brfalse, 0));
break;
case 1:
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ldloc, currentNodeLocal));
randPosition = this.prng.Next(validInterfaces.Count());
interfaceToCheck = validInterfaces.ElementAt(randPosition);
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Isinst, interfaceToCheck));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ldnull));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Cgt_Un));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ldc_I4_0));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ceq));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Brtrue, 0));
break;
case 2:
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ldloc, currentNodeLocal));
randPosition = this.prng.Next(validInterfaces.Count());
interfaceToCheck = validInterfaces.ElementAt(randPosition);
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Isinst, interfaceToCheck));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ldnull));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Cgt_Un));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ldc_I4_1));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ceq));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Brfalse, 0));
break;
case 3:
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ldloc, currentNodeLocal));
randPosition = this.prng.Next(validInterfaces.Count());
interfaceToCheck = validInterfaces.ElementAt(randPosition);
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Isinst, interfaceToCheck));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ldnull));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ceq));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Brtrue, 0));
break;
case 4:
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ldloc, currentNodeLocal));
randPosition = this.prng.Next(invalidInterfaces.Count());
interfaceToCheck = invalidInterfaces.ElementAt(randPosition);
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Isinst, interfaceToCheck));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ldnull));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Cgt_Un));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Brtrue, 0));
break;
case 5:
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ldloc, currentNodeLocal));
randPosition = this.prng.Next(invalidInterfaces.Count());
interfaceToCheck = invalidInterfaces.ElementAt(randPosition);
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Isinst, interfaceToCheck));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ldnull));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Cgt_Un));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ldc_I4_0));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ceq));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Brfalse, 0));
break;
case 6:
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ldloc, currentNodeLocal));
randPosition = this.prng.Next(invalidInterfaces.Count());
interfaceToCheck = invalidInterfaces.ElementAt(randPosition);
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Isinst, interfaceToCheck));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ldnull));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Cgt_Un));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ldc_I4_1));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ceq));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Brtrue, 0));
break;
case 7:
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ldloc, currentNodeLocal));
randPosition = this.prng.Next(invalidInterfaces.Count());
interfaceToCheck = invalidInterfaces.ElementAt(randPosition);
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Isinst, interfaceToCheck));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ldnull));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Ceq));
startBasicBlock.operations.Add(this.helperClass.createNewOperation(OperationCode.Brfalse, 0));
break;
default:
throw new ArgumentException("This case should never be reached.");
}
// create the conditional branch for the checking basic block (not taken => correct code; taken => dead code)
ConditionalBranchTarget startBasicBlockExitBranch = new ConditionalBranchTarget();
startBasicBlockExitBranch.sourceBasicBlock = startBasicBlock;
startBasicBlock.exitBranch = startBasicBlockExitBranch;
// create the dead code for this opaque predicate
BasicBlock deadCodeBasicBlock = new BasicBlock();
deadCodeBasicBlock.startIdx = 0;
deadCodeBasicBlock.endIdx = 0;
// set the dead code basic block as "taken" target for the conditional branch of the checking basic block
deadCodeBasicBlock.entryBranches.Add(startBasicBlockExitBranch);
startBasicBlockExitBranch.takenTarget = deadCodeBasicBlock;
// generate dead code for the dead code basic block
GraphTransformerDeadCodeBasicBlock deadCodeMetadata = new GraphTransformerDeadCodeBasicBlock();
deadCodeBasicBlock.transformationMetadata.Add(deadCodeMetadata);
// set the created basic block and conditional jumps as output
outStartBasicBlock = startBasicBlock;
outConditionalBranch = startBasicBlockExitBranch;
}
