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//===-- IRMutator.cpp -----------------------------------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/FuzzMutate/IRMutator.h"
#include "llvm/ADT/Optional.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/FuzzMutate/Operations.h"
#include "llvm/FuzzMutate/Random.h"
#include "llvm/FuzzMutate/RandomIRBuilder.h"
#include "llvm/IR/BasicBlock.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/Debug.h"
#include "llvm/Transforms/Scalar/DCE.h"
using namespace llvm;
static void createEmptyFunction(Module &M) {
// TODO: Some arguments and a return value would probably be more interesting.
LLVMContext &Context = M.getContext();
Function *F = Function::Create(FunctionType::get(Type::getVoidTy(Context), {},
/*isVarArg=*/false),
GlobalValue::ExternalLinkage, "f", &M);
BasicBlock *BB = BasicBlock::Create(Context, "BB", F);
ReturnInst::Create(Context, BB);
}
void IRMutationStrategy::mutate(Module &M, RandomIRBuilder &IB) {
if (M.empty())
createEmptyFunction(M);
auto RS = makeSampler<Function *>(IB.Rand);
for (Function &F : M)
if (!F.isDeclaration())
RS.sample(&F, /*Weight=*/1);
mutate(*RS.getSelection(), IB);
}
void IRMutationStrategy::mutate(Function &F, RandomIRBuilder &IB) {
mutate(*makeSampler(IB.Rand, make_pointer_range(F)).getSelection(), IB);
}
void IRMutationStrategy::mutate(BasicBlock &BB, RandomIRBuilder &IB) {
mutate(*makeSampler(IB.Rand, make_pointer_range(BB)).getSelection(), IB);
}
void IRMutator::mutateModule(Module &M, int Seed, size_t CurSize,
size_t MaxSize) {
std::vector<Type *> Types;
for (const auto &Getter : AllowedTypes)
Types.push_back(Getter(M.getContext()));
RandomIRBuilder IB(Seed, Types);
auto RS = makeSampler<IRMutationStrategy *>(IB.Rand);
for (const auto &Strategy : Strategies)
RS.sample(Strategy.get(),
Strategy->getWeight(CurSize, MaxSize, RS.totalWeight()));
auto Strategy = RS.getSelection();
Strategy->mutate(M, IB);
}
static void eliminateDeadCode(Function &F) {
FunctionPassManager FPM;
FPM.addPass(DCEPass());
FunctionAnalysisManager FAM;
FAM.registerPass([&] { return TargetLibraryAnalysis(); });
FPM.run(F, FAM);
}
void InjectorIRStrategy::mutate(Function &F, RandomIRBuilder &IB) {
IRMutationStrategy::mutate(F, IB);
eliminateDeadCode(F);
}
std::vector<fuzzerop::OpDescriptor> InjectorIRStrategy::getDefaultOps() {
std::vector<fuzzerop::OpDescriptor> Ops;
describeFuzzerIntOps(Ops);
describeFuzzerFloatOps(Ops);
describeFuzzerControlFlowOps(Ops);
describeFuzzerPointerOps(Ops);
describeFuzzerAggregateOps(Ops);
describeFuzzerVectorOps(Ops);
return Ops;
}
Optional<fuzzerop::OpDescriptor>
InjectorIRStrategy::chooseOperation(Value *Src, RandomIRBuilder &IB) {
auto OpMatchesPred = [&Src](fuzzerop::OpDescriptor &Op) {
return Op.SourcePreds[0].matches({}, Src);
};
auto RS = makeSampler(IB.Rand, make_filter_range(Operations, OpMatchesPred));
if (RS.isEmpty())
return None;
return *RS;
}
void InjectorIRStrategy::mutate(BasicBlock &BB, RandomIRBuilder &IB) {
SmallVector<Instruction *, 32> Insts;
for (auto I = BB.getFirstInsertionPt(), E = BB.end(); I != E; ++I)
Insts.push_back(&*I);
if (Insts.size() < 1)
return;
// Choose an insertion point for our new instruction.
size_t IP = uniform<size_t>(IB.Rand, 0, Insts.size() - 1);
auto InstsBefore = makeArrayRef(Insts).slice(0, IP);
auto InstsAfter = makeArrayRef(Insts).slice(IP);
// Choose a source, which will be used to constrain the operation selection.
SmallVector<Value *, 2> Srcs;
Srcs.push_back(IB.findOrCreateSource(BB, InstsBefore));
// Choose an operation that's constrained to be valid for the type of the
// source, collect any other sources it needs, and then build it.
auto OpDesc = chooseOperation(Srcs[0], IB);
// Bail if no operation was found
if (!OpDesc)
return;
for (const auto &Pred : makeArrayRef(OpDesc->SourcePreds).slice(1))
Srcs.push_back(IB.findOrCreateSource(BB, InstsBefore, Srcs, Pred));
if (Value *Op = OpDesc->BuilderFunc(Srcs, Insts[IP])) {
// Find a sink and wire up the results of the operation.
IB.connectToSink(BB, InstsAfter, Op);
}
}
uint64_t InstDeleterIRStrategy::getWeight(size_t CurrentSize, size_t MaxSize,
uint64_t CurrentWeight) {
// If we have less than 200 bytes, panic and try to always delete.
if (CurrentSize > MaxSize - 200)
return CurrentWeight ? CurrentWeight * 100 : 1;
// Draw a line starting from when we only have 1k left and increasing linearly
// to double the current weight.
int Line = (-2 * CurrentWeight) * (MaxSize - CurrentSize + 1000);
// Clamp negative weights to zero.
if (Line < 0)
return 0;
return Line;
}
void InstDeleterIRStrategy::mutate(Function &F, RandomIRBuilder &IB) {
auto RS = makeSampler<Instruction *>(IB.Rand);
// Avoid terminators so we don't have to worry about keeping the CFG coherent.
for (Instruction &Inst : instructions(F))
if (!Inst.isTerminator())
RS.sample(&Inst, /*Weight=*/1);
if (RS.isEmpty())
return;
// Delete the instruction.
mutate(*RS.getSelection(), IB);
// Clean up any dead code that's left over after removing the instruction.
eliminateDeadCode(F);
}
void InstDeleterIRStrategy::mutate(Instruction &Inst, RandomIRBuilder &IB) {
assert(!Inst.isTerminator() && "Deleting terminators invalidates CFG");
if (Inst.getType()->isVoidTy()) {
// Instructions with void type (ie, store) have no uses to worry about. Just
// erase it and move on.
Inst.eraseFromParent();
return;
}
// Otherwise we need to find some other value with the right type to keep the
// users happy.
auto Pred = fuzzerop::onlyType(Inst.getType());
auto RS = makeSampler<Value *>(IB.Rand);
SmallVector<Instruction *, 32> InstsBefore;
BasicBlock *BB = Inst.getParent();
for (auto I = BB->getFirstInsertionPt(), E = Inst.getIterator(); I != E;
++I) {
if (Pred.matches({}, &*I))
RS.sample(&*I, /*Weight=*/1);
InstsBefore.push_back(&*I);
}
if (!RS)
RS.sample(IB.newSource(*BB, InstsBefore, {}, Pred), /*Weight=*/1);
Inst.replaceAllUsesWith(RS.getSelection());
}
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