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llvm-mirror/tools/llvm-exegesis/llvm-exegesis.cpp
Ella Ma 59b89a3124 [llvm][clang][mlir] Add checks for the return values from Target::createXXX to prevent protential null deref 
All these potential null pointer dereferences are reported by my static analyzer for null smart pointer dereferences, which has a different implementation from `alpha.cplusplus.SmartPtr`.

The checked pointers in this patch are initialized by Target::createXXX functions. When the creator function pointer is not correctly set, a null pointer will be returned, or the creator function may originally return a null pointer.

Some of them may not make sense as they may be checked before entering the function, but I fixed them all in this patch. I submit this fix because 1) similar checks are found in some other places in the LLVM codebase for the same return value of the function; and, 2) some of the pointers are dereferenced before they are checked, which may definitely trigger a null pointer dereference if the return value is nullptr.

Reviewed By: tejohnson, MaskRay, jpienaar

Differential Revision: https://reviews.llvm.org/D91410
2020-11-21 21:04:12 -08:00

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//===-- llvm-exegesis.cpp ---------------------------------------*- C++ -*-===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
///
/// \file
/// Measures execution properties (latencies/uops) of an instruction.
///
//===----------------------------------------------------------------------===//
#include "lib/Analysis.h"
#include "lib/BenchmarkResult.h"
#include "lib/BenchmarkRunner.h"
#include "lib/Clustering.h"
#include "lib/Error.h"
#include "lib/LlvmState.h"
#include "lib/PerfHelper.h"
#include "lib/SnippetFile.h"
#include "lib/SnippetRepetitor.h"
#include "lib/Target.h"
#include "lib/TargetSelect.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/Twine.h"
#include "llvm/MC/MCInstBuilder.h"
#include "llvm/MC/MCObjectFileInfo.h"
#include "llvm/MC/MCParser/MCAsmParser.h"
#include "llvm/MC/MCParser/MCTargetAsmParser.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/Object/ObjectFile.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Support/TargetSelect.h"
#include <algorithm>
#include <string>
namespace llvm {
namespace exegesis {
static cl::OptionCategory Options("llvm-exegesis options");
static cl::OptionCategory BenchmarkOptions("llvm-exegesis benchmark options");
static cl::OptionCategory AnalysisOptions("llvm-exegesis analysis options");
static cl::opt<int> OpcodeIndex(
"opcode-index",
cl::desc("opcode to measure, by index, or -1 to measure all opcodes"),
cl::cat(BenchmarkOptions), cl::init(0));
static cl::opt<std::string>
OpcodeNames("opcode-name",
cl::desc("comma-separated list of opcodes to measure, by name"),
cl::cat(BenchmarkOptions), cl::init(""));
static cl::opt<std::string> SnippetsFile("snippets-file",
cl::desc("code snippets to measure"),
cl::cat(BenchmarkOptions),
cl::init(""));
static cl::opt<std::string>
BenchmarkFile("benchmarks-file",
cl::desc("File to read (analysis mode) or write "
"(latency/uops/inverse_throughput modes) benchmark "
"results. “-” uses stdin/stdout."),
cl::cat(Options), cl::init(""));
static cl::opt<exegesis::InstructionBenchmark::ModeE> BenchmarkMode(
"mode", cl::desc("the mode to run"), cl::cat(Options),
cl::values(clEnumValN(exegesis::InstructionBenchmark::Latency, "latency",
"Instruction Latency"),
clEnumValN(exegesis::InstructionBenchmark::InverseThroughput,
"inverse_throughput",
"Instruction Inverse Throughput"),
clEnumValN(exegesis::InstructionBenchmark::Uops, "uops",
"Uop Decomposition"),
// When not asking for a specific benchmark mode,
// we'll analyse the results.
clEnumValN(exegesis::InstructionBenchmark::Unknown, "analysis",
"Analysis")));
static cl::opt<exegesis::InstructionBenchmark::ResultAggregationModeE>
ResultAggMode(
"result-aggregation-mode",
cl::desc("How to aggregate multi-values result"), cl::cat(Options),
cl::values(clEnumValN(exegesis::InstructionBenchmark::Min, "min",
"Keep min reading"),
clEnumValN(exegesis::InstructionBenchmark::Max, "max",
"Keep max reading"),
clEnumValN(exegesis::InstructionBenchmark::Mean, "mean",
"Compute mean of all readings"),
clEnumValN(exegesis::InstructionBenchmark::MinVariance,
"min-variance",
"Keep readings set with min-variance")),
cl::init(exegesis::InstructionBenchmark::Min));
static cl::opt<exegesis::InstructionBenchmark::RepetitionModeE> RepetitionMode(
"repetition-mode", cl::desc("how to repeat the instruction snippet"),
cl::cat(BenchmarkOptions),
cl::values(
clEnumValN(exegesis::InstructionBenchmark::Duplicate, "duplicate",
"Duplicate the snippet"),
clEnumValN(exegesis::InstructionBenchmark::Loop, "loop",
"Loop over the snippet"),
clEnumValN(exegesis::InstructionBenchmark::AggregateMin, "min",
"All of the above and take the minimum of measurements")),
cl::init(exegesis::InstructionBenchmark::Duplicate));
static cl::opt<unsigned>
NumRepetitions("num-repetitions",
cl::desc("number of time to repeat the asm snippet"),
cl::cat(BenchmarkOptions), cl::init(10000));
static cl::opt<unsigned> MaxConfigsPerOpcode(
"max-configs-per-opcode",
cl::desc(
"allow to snippet generator to generate at most that many configs"),
cl::cat(BenchmarkOptions), cl::init(1));
static cl::opt<bool> IgnoreInvalidSchedClass(
"ignore-invalid-sched-class",
cl::desc("ignore instructions that do not define a sched class"),
cl::cat(BenchmarkOptions), cl::init(false));
static cl::opt<exegesis::InstructionBenchmarkClustering::ModeE>
AnalysisClusteringAlgorithm(
"analysis-clustering", cl::desc("the clustering algorithm to use"),
cl::cat(AnalysisOptions),
cl::values(clEnumValN(exegesis::InstructionBenchmarkClustering::Dbscan,
"dbscan", "use DBSCAN/OPTICS algorithm"),
clEnumValN(exegesis::InstructionBenchmarkClustering::Naive,
"naive", "one cluster per opcode")),
cl::init(exegesis::InstructionBenchmarkClustering::Dbscan));
static cl::opt<unsigned> AnalysisDbscanNumPoints(
"analysis-numpoints",
cl::desc("minimum number of points in an analysis cluster (dbscan only)"),
cl::cat(AnalysisOptions), cl::init(3));
static cl::opt<float> AnalysisClusteringEpsilon(
"analysis-clustering-epsilon",
cl::desc("epsilon for benchmark point clustering"),
cl::cat(AnalysisOptions), cl::init(0.1));
static cl::opt<float> AnalysisInconsistencyEpsilon(
"analysis-inconsistency-epsilon",
cl::desc("epsilon for detection of when the cluster is different from the "
"LLVM schedule profile values"),
cl::cat(AnalysisOptions), cl::init(0.1));
static cl::opt<std::string>
AnalysisClustersOutputFile("analysis-clusters-output-file", cl::desc(""),
cl::cat(AnalysisOptions), cl::init(""));
static cl::opt<std::string>
AnalysisInconsistenciesOutputFile("analysis-inconsistencies-output-file",
cl::desc(""), cl::cat(AnalysisOptions),
cl::init(""));
static cl::opt<bool> AnalysisDisplayUnstableOpcodes(
"analysis-display-unstable-clusters",
cl::desc("if there is more than one benchmark for an opcode, said "
"benchmarks may end up not being clustered into the same cluster "
"if the measured performance characteristics are different. by "
"default all such opcodes are filtered out. this flag will "
"instead show only such unstable opcodes"),
cl::cat(AnalysisOptions), cl::init(false));
static cl::opt<std::string> CpuName(
"mcpu",
cl::desc("cpu name to use for pfm counters, leave empty to autodetect"),
cl::cat(Options), cl::init(""));
static cl::opt<bool>
DumpObjectToDisk("dump-object-to-disk",
cl::desc("dumps the generated benchmark object to disk "
"and prints a message to access it"),
cl::cat(BenchmarkOptions), cl::init(true));
static ExitOnError ExitOnErr("llvm-exegesis error: ");
// Helper function that logs the error(s) and exits.
template <typename... ArgTs> static void ExitWithError(ArgTs &&... Args) {
ExitOnErr(make_error<Failure>(std::forward<ArgTs>(Args)...));
}
// Check Err. If it's in a failure state log the file error(s) and exit.
static void ExitOnFileError(const Twine &FileName, Error Err) {
if (Err) {
ExitOnErr(createFileError(FileName, std::move(Err)));
}
}
// Check E. If it's in a success state then return the contained value.
// If it's in a failure state log the file error(s) and exit.
template <typename T>
T ExitOnFileError(const Twine &FileName, Expected<T> &&E) {
ExitOnFileError(FileName, E.takeError());
return std::move(*E);
}
// Checks that only one of OpcodeNames, OpcodeIndex or SnippetsFile is provided,
// and returns the opcode indices or {} if snippets should be read from
// `SnippetsFile`.
static std::vector<unsigned> getOpcodesOrDie(const MCInstrInfo &MCInstrInfo) {
const size_t NumSetFlags = (OpcodeNames.empty() ? 0 : 1) +
(OpcodeIndex == 0 ? 0 : 1) +
(SnippetsFile.empty() ? 0 : 1);
if (NumSetFlags != 1) {
ExitOnErr.setBanner("llvm-exegesis: ");
ExitWithError("please provide one and only one of 'opcode-index', "
"'opcode-name' or 'snippets-file'");
}
if (!SnippetsFile.empty())
return {};
if (OpcodeIndex > 0)
return {static_cast<unsigned>(OpcodeIndex)};
if (OpcodeIndex < 0) {
std::vector<unsigned> Result;
for (unsigned I = 1, E = MCInstrInfo.getNumOpcodes(); I < E; ++I)
Result.push_back(I);
return Result;
}
// Resolve opcode name -> opcode.
const auto ResolveName = [&MCInstrInfo](StringRef OpcodeName) -> unsigned {
for (unsigned I = 1, E = MCInstrInfo.getNumOpcodes(); I < E; ++I)
if (MCInstrInfo.getName(I) == OpcodeName)
return I;
return 0u;
};
SmallVector<StringRef, 2> Pieces;
StringRef(OpcodeNames.getValue())
.split(Pieces, ",", /* MaxSplit */ -1, /* KeepEmpty */ false);
std::vector<unsigned> Result;
for (const StringRef &OpcodeName : Pieces) {
if (unsigned Opcode = ResolveName(OpcodeName))
Result.push_back(Opcode);
else
ExitWithError(Twine("unknown opcode ").concat(OpcodeName));
}
return Result;
}
// Generates code snippets for opcode `Opcode`.
static Expected<std::vector<BenchmarkCode>>
generateSnippets(const LLVMState &State, unsigned Opcode,
const BitVector &ForbiddenRegs) {
const Instruction &Instr = State.getIC().getInstr(Opcode);
const MCInstrDesc &InstrDesc = Instr.Description;
// Ignore instructions that we cannot run.
if (InstrDesc.isPseudo())
return make_error<Failure>("Unsupported opcode: isPseudo");
if (InstrDesc.isBranch() || InstrDesc.isIndirectBranch())
return make_error<Failure>("Unsupported opcode: isBranch/isIndirectBranch");
if (InstrDesc.isCall() || InstrDesc.isReturn())
return make_error<Failure>("Unsupported opcode: isCall/isReturn");
const std::vector<InstructionTemplate> InstructionVariants =
State.getExegesisTarget().generateInstructionVariants(
Instr, MaxConfigsPerOpcode);
SnippetGenerator::Options SnippetOptions;
SnippetOptions.MaxConfigsPerOpcode = MaxConfigsPerOpcode;
const std::unique_ptr<SnippetGenerator> Generator =
State.getExegesisTarget().createSnippetGenerator(BenchmarkMode, State,
SnippetOptions);
if (!Generator)
ExitWithError("cannot create snippet generator");
std::vector<BenchmarkCode> Benchmarks;
for (const InstructionTemplate &Variant : InstructionVariants) {
if (Benchmarks.size() >= MaxConfigsPerOpcode)
break;
if (auto Err = Generator->generateConfigurations(Variant, Benchmarks,
ForbiddenRegs))
return std::move(Err);
}
return Benchmarks;
}
void benchmarkMain() {
#ifndef HAVE_LIBPFM
ExitWithError("benchmarking unavailable, LLVM was built without libpfm.");
#endif
if (exegesis::pfm::pfmInitialize())
ExitWithError("cannot initialize libpfm");
InitializeNativeTarget();
InitializeNativeTargetAsmPrinter();
InitializeNativeTargetAsmParser();
InitializeNativeExegesisTarget();
const LLVMState State(CpuName);
// Preliminary check to ensure features needed for requested
// benchmark mode are present on target CPU and/or OS.
ExitOnErr(State.getExegesisTarget().checkFeatureSupport());
const std::unique_ptr<BenchmarkRunner> Runner =
ExitOnErr(State.getExegesisTarget().createBenchmarkRunner(
BenchmarkMode, State, ResultAggMode));
if (!Runner) {
ExitWithError("cannot create benchmark runner");
}
const auto Opcodes = getOpcodesOrDie(State.getInstrInfo());
SmallVector<std::unique_ptr<const SnippetRepetitor>, 2> Repetitors;
if (RepetitionMode != InstructionBenchmark::RepetitionModeE::AggregateMin)
Repetitors.emplace_back(SnippetRepetitor::Create(RepetitionMode, State));
else {
for (InstructionBenchmark::RepetitionModeE RepMode :
{InstructionBenchmark::RepetitionModeE::Duplicate,
InstructionBenchmark::RepetitionModeE::Loop})
Repetitors.emplace_back(SnippetRepetitor::Create(RepMode, State));
}
BitVector AllReservedRegs;
llvm::for_each(Repetitors,
[&AllReservedRegs](
const std::unique_ptr<const SnippetRepetitor> &Repetitor) {
AllReservedRegs |= Repetitor->getReservedRegs();
});
std::vector<BenchmarkCode> Configurations;
if (!Opcodes.empty()) {
for (const unsigned Opcode : Opcodes) {
// Ignore instructions without a sched class if
// -ignore-invalid-sched-class is passed.
if (IgnoreInvalidSchedClass &&
State.getInstrInfo().get(Opcode).getSchedClass() == 0) {
errs() << State.getInstrInfo().getName(Opcode)
<< ": ignoring instruction without sched class\n";
continue;
}
auto ConfigsForInstr = generateSnippets(State, Opcode, AllReservedRegs);
if (!ConfigsForInstr) {
logAllUnhandledErrors(
ConfigsForInstr.takeError(), errs(),
Twine(State.getInstrInfo().getName(Opcode)).concat(": "));
continue;
}
std::move(ConfigsForInstr->begin(), ConfigsForInstr->end(),
std::back_inserter(Configurations));
}
} else {
Configurations = ExitOnErr(readSnippets(State, SnippetsFile));
}
if (NumRepetitions == 0) {
ExitOnErr.setBanner("llvm-exegesis: ");
ExitWithError("--num-repetitions must be greater than zero");
}
// Write to standard output if file is not set.
if (BenchmarkFile.empty())
BenchmarkFile = "-";
for (const BenchmarkCode &Conf : Configurations) {
InstructionBenchmark Result = ExitOnErr(Runner->runConfiguration(
Conf, NumRepetitions, Repetitors, DumpObjectToDisk));
ExitOnFileError(BenchmarkFile, Result.writeYaml(State, BenchmarkFile));
}
exegesis::pfm::pfmTerminate();
}
// Prints the results of running analysis pass `Pass` to file `OutputFilename`
// if OutputFilename is non-empty.
template <typename Pass>
static void maybeRunAnalysis(const Analysis &Analyzer, const std::string &Name,
const std::string &OutputFilename) {
if (OutputFilename.empty())
return;
if (OutputFilename != "-") {
errs() << "Printing " << Name << " results to file '" << OutputFilename
<< "'\n";
}
std::error_code ErrorCode;
raw_fd_ostream ClustersOS(OutputFilename, ErrorCode,
sys::fs::FA_Read | sys::fs::FA_Write);
if (ErrorCode)
ExitOnFileError(OutputFilename, errorCodeToError(ErrorCode));
if (auto Err = Analyzer.run<Pass>(ClustersOS))
ExitOnFileError(OutputFilename, std::move(Err));
}
static void analysisMain() {
ExitOnErr.setBanner("llvm-exegesis: ");
if (BenchmarkFile.empty())
ExitWithError("--benchmarks-file must be set");
if (AnalysisClustersOutputFile.empty() &&
AnalysisInconsistenciesOutputFile.empty()) {
ExitWithError(
"for --mode=analysis: At least one of --analysis-clusters-output-file "
"and --analysis-inconsistencies-output-file must be specified");
}
InitializeNativeTarget();
InitializeNativeTargetAsmPrinter();
InitializeNativeTargetDisassembler();
// Read benchmarks.
const LLVMState State("");
const std::vector<InstructionBenchmark> Points = ExitOnFileError(
BenchmarkFile, InstructionBenchmark::readYamls(State, BenchmarkFile));
outs() << "Parsed " << Points.size() << " benchmark points\n";
if (Points.empty()) {
errs() << "no benchmarks to analyze\n";
return;
}
// FIXME: Check that all points have the same triple/cpu.
// FIXME: Merge points from several runs (latency and uops).
std::string Error;
const auto *TheTarget =
TargetRegistry::lookupTarget(Points[0].LLVMTriple, Error);
if (!TheTarget) {
errs() << "unknown target '" << Points[0].LLVMTriple << "'\n";
return;
}
std::unique_ptr<MCInstrInfo> InstrInfo(TheTarget->createMCInstrInfo());
assert(InstrInfo && "Unable to create instruction info!");
const auto Clustering = ExitOnErr(InstructionBenchmarkClustering::create(
Points, AnalysisClusteringAlgorithm, AnalysisDbscanNumPoints,
AnalysisClusteringEpsilon, InstrInfo->getNumOpcodes()));
const Analysis Analyzer(*TheTarget, std::move(InstrInfo), Clustering,
AnalysisInconsistencyEpsilon,
AnalysisDisplayUnstableOpcodes);
maybeRunAnalysis<Analysis::PrintClusters>(Analyzer, "analysis clusters",
AnalysisClustersOutputFile);
maybeRunAnalysis<Analysis::PrintSchedClassInconsistencies>(
Analyzer, "sched class consistency analysis",
AnalysisInconsistenciesOutputFile);
}
} // namespace exegesis
} // namespace llvm
int main(int Argc, char **Argv) {
using namespace llvm;
cl::ParseCommandLineOptions(Argc, Argv, "");
exegesis::ExitOnErr.setExitCodeMapper([](const Error &Err) {
if (Err.isA<exegesis::ClusteringError>())
return EXIT_SUCCESS;
return EXIT_FAILURE;
});
if (exegesis::BenchmarkMode == exegesis::InstructionBenchmark::Unknown) {
exegesis::analysisMain();
} else {
exegesis::benchmarkMain();
}
return EXIT_SUCCESS;
}
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