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//===- Delta.cpp - Delta Debugging Algorithm Implementation ---------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file contains the implementation for the Delta Debugging Algorithm:
// it splits a given set of Targets (i.e. Functions, Instructions, BBs, etc.)
// into chunks and tries to reduce the number chunks that are interesting.
//
//===----------------------------------------------------------------------===//
#include "Delta.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/ToolOutputFile.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include <fstream>
#include <set>
using namespace llvm;
/// Writes IR code to the given Filepath
static bool writeProgramToFile(StringRef Filepath, int FD, const Module &M) {
ToolOutputFile Out(Filepath, FD);
M.print(Out.os(), /*AnnotationWriter=*/nullptr);
Out.os().close();
if (!Out.os().has_error()) {
Out.keep();
return false;
}
return true;
}
/// Creates a temporary (and unique) file inside the tmp folder and writes
/// the given module IR.
static SmallString<128> createTmpFile(Module *M, StringRef TmpDir) {
SmallString<128> UniqueFilepath;
int UniqueFD;
SmallString<128> TmpFilepath;
sys::path::append(TmpFilepath, TmpDir, "tmp-%%%.ll");
std::error_code EC =
sys::fs::createUniqueFile(TmpFilepath, UniqueFD, UniqueFilepath);
if (EC) {
errs() << "Error making unique filename: " << EC.message() << "!\n";
exit(1);
}
if (writeProgramToFile(UniqueFilepath, UniqueFD, *M)) {
errs() << "Error emitting bitcode to file '" << UniqueFilepath << "'!\n";
exit(1);
}
return UniqueFilepath;
}
/// Counts the amount of lines for a given file
static unsigned getLines(StringRef Filepath) {
unsigned Lines = 0;
std::string CurrLine;
std::ifstream FileStream(Filepath);
while (std::getline(FileStream, CurrLine))
++Lines;
return Lines;
}
/// Splits Chunks in half and prints them.
/// If unable to split (when chunk size is 1) returns false.
static bool increaseGranularity(std::vector<Chunk> &Chunks) {
errs() << "Increasing granularity...";
std::vector<Chunk> NewChunks;
bool SplitOne = false;
for (auto &C : Chunks) {
if (C.end - C.begin == 0)
NewChunks.push_back(C);
else {
unsigned Half = (C.begin + C.end) / 2;
NewChunks.push_back({C.begin, Half});
NewChunks.push_back({Half + 1, C.end});
SplitOne = true;
}
}
if (SplitOne) {
Chunks = NewChunks;
errs() << "Success! New Chunks:\n";
for (auto C : Chunks) {
errs() << '\t';
C.print();
errs() << '\n';
}
}
return SplitOne;
}
/// Runs the Delta Debugging algorithm, splits the code into chunks and
/// reduces the amount of chunks that are considered interesting by the
/// given test.
void llvm::runDeltaPass(
TestRunner &Test, unsigned Targets,
std::function<void(const std::vector<Chunk> &, Module *)>
ExtractChunksFromModule) {
if (!Targets) {
errs() << "\nNothing to reduce\n";
return;
}
if (!Test.run(Test.getReducedFilepath())) {
errs() << "\nInput isn't interesting! Verify interesting-ness test\n";
exit(1);
}
std::vector<Chunk> Chunks = {{1, Targets}};
std::set<Chunk> UninterestingChunks;
std::unique_ptr<Module> ReducedProgram;
if (!increaseGranularity(Chunks)) {
errs() << "\nAlready at minimum size. Cannot reduce anymore.\n";
return;
}
do {
UninterestingChunks = {};
for (int I = Chunks.size() - 1; I >= 0; --I) {
std::vector<Chunk> CurrentChunks;
for (auto C : Chunks)
if (!UninterestingChunks.count(C) && C != Chunks[I])
CurrentChunks.push_back(C);
if (CurrentChunks.empty())
continue;
// Clone module before hacking it up..
std::unique_ptr<Module> Clone = CloneModule(*Test.getProgram());
// Generate Module with only Targets inside Current Chunks
ExtractChunksFromModule(CurrentChunks, Clone.get());
// Write Module to tmp file
SmallString<128> CurrentFilepath =
createTmpFile(Clone.get(), Test.getTmpDir());
errs() << "Ignoring: ";
Chunks[I].print();
for (auto C : UninterestingChunks)
C.print();
errs() << " | " << sys::path::filename(CurrentFilepath);
// Current Chunks aren't interesting
if (!Test.run(CurrentFilepath)) {
errs() << "\n";
continue;
}
UninterestingChunks.insert(Chunks[I]);
Test.setReducedFilepath(CurrentFilepath);
ReducedProgram = std::move(Clone);
errs() << " **** SUCCESS | lines: " << getLines(CurrentFilepath) << "\n";
}
// Delete uninteresting chunks
erase_if(Chunks, [&UninterestingChunks](const Chunk &C) {
return UninterestingChunks.count(C);
});
} while (!UninterestingChunks.empty() || increaseGranularity(Chunks));
// If we reduced the testcase replace it
if (ReducedProgram)
Test.setProgram(std::move(ReducedProgram));
errs() << "Couldn't increase anymore.\n";
}
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