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//===--- llvm-isel-fuzzer.cpp - Fuzzer for instruction selection ----------===//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
// Tool to fuzz instruction selection using libFuzzer.
#include "llvm/ADT/StringRef.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/Bitcode/BitcodeReader.h"
#include "llvm/Bitcode/BitcodeWriter.h"
#include "llvm/CodeGen/CommandFlags.h"
#include "llvm/FuzzMutate/FuzzerCLI.h"
#include "llvm/FuzzMutate/IRMutator.h"
#include "llvm/FuzzMutate/Operations.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/LegacyPassManager.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Verifier.h"
#include "llvm/IRReader/IRReader.h"
#include "llvm/MC/TargetRegistry.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/DataTypes.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Support/TargetSelect.h"
#include "llvm/Target/TargetMachine.h"
#define DEBUG_TYPE "isel-fuzzer"
using namespace llvm;
static codegen::RegisterCodeGenFlags CGF;
static cl::opt<char>
cl::desc("Optimization level. [-O0, -O1, -O2, or -O3] "
"(default = '-O2')"),
cl::init(' '));
static cl::opt<std::string>
TargetTriple("mtriple", cl::desc("Override target triple for module"));
static std::unique_ptr<TargetMachine> TM;
static std::unique_ptr<IRMutator> Mutator;
std::unique_ptr<IRMutator> createISelMutator() {
std::vector<TypeGetter> Types{
Type::getInt1Ty, Type::getInt8Ty, Type::getInt16Ty, Type::getInt32Ty,
Type::getInt64Ty, Type::getFloatTy, Type::getDoubleTy};
std::vector<std::unique_ptr<IRMutationStrategy>> Strategies;
new InjectorIRStrategy(InjectorIRStrategy::getDefaultOps()));
Strategies.emplace_back(new InstDeleterIRStrategy());
return std::make_unique<IRMutator>(std::move(Types), std::move(Strategies));
extern "C" LLVM_ATTRIBUTE_USED size_t LLVMFuzzerCustomMutator(
uint8_t *Data, size_t Size, size_t MaxSize, unsigned int Seed) {
LLVMContext Context;
std::unique_ptr<Module> M;
if (Size <= 1)
// We get bogus data given an empty corpus - just create a new module.
M.reset(new Module("M", Context));
M = parseModule(Data, Size, Context);
Mutator->mutateModule(*M, Seed, Size, MaxSize);
return writeModule(*M, Data, MaxSize);
extern "C" int LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
if (Size <= 1)
// We get bogus data given an empty corpus - ignore it.
return 0;
LLVMContext Context;
auto M = parseAndVerify(Data, Size, Context);
if (!M) {
errs() << "error: input module is broken!\n";
return 0;
// Set up the module to build for our target.
// Build up a PM to do instruction selection.
legacy::PassManager PM;
TargetLibraryInfoImpl TLII(TM->getTargetTriple());
PM.add(new TargetLibraryInfoWrapperPass(TLII));
raw_null_ostream OS;
TM->addPassesToEmitFile(PM, OS, nullptr, CGFT_Null);*M);
return 0;
static void handleLLVMFatalError(void *, const char *Message, bool) {
// TODO: Would it be better to call into the fuzzer internals directly?
dbgs() << "LLVM ERROR: " << Message << "\n"
<< "Aborting to trigger fuzzer exit handling.\n";
extern "C" LLVM_ATTRIBUTE_USED int LLVMFuzzerInitialize(int *argc,
char ***argv) {
EnableDebugBuffering = true;
parseFuzzerCLOpts(*argc, *argv);
if (TargetTriple.empty()) {
errs() << *argv[0] << ": -mtriple must be specified\n";
Triple TheTriple = Triple(Triple::normalize(TargetTriple));
// Get the target specific parser.
std::string Error;
const Target *TheTarget =
TargetRegistry::lookupTarget(codegen::getMArch(), TheTriple, Error);
if (!TheTarget) {
errs() << argv[0] << ": " << Error;
return 1;
// Set up the pipeline like llc does.
std::string CPUStr = codegen::getCPUStr(),
FeaturesStr = codegen::getFeaturesStr();
CodeGenOpt::Level OLvl = CodeGenOpt::Default;
switch (OptLevel) {
errs() << argv[0] << ": invalid optimization level.\n";
return 1;
case ' ': break;
case '0': OLvl = CodeGenOpt::None; break;
case '1': OLvl = CodeGenOpt::Less; break;
case '2': OLvl = CodeGenOpt::Default; break;
case '3': OLvl = CodeGenOpt::Aggressive; break;
TargetOptions Options = codegen::InitTargetOptionsFromCodeGenFlags(TheTriple);
TheTriple.getTriple(), CPUStr, FeaturesStr, Options,
codegen::getExplicitRelocModel(), codegen::getExplicitCodeModel(), OLvl));
assert(TM && "Could not allocate target machine!");
// Make sure we print the summary and the current unit when LLVM errors out.
install_fatal_error_handler(handleLLVMFatalError, nullptr);
// Finally, create our mutator.
Mutator = createISelMutator();
return 0;