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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/IR/Verifier.h"
#include "llvm/Support/ToolOutputFile.h"
#include "llvm/Transforms/Utils/Cloning.h"
#include <fstream>
#include <set>
using namespace llvm;
void writeOutput(llvm::Module *M, llvm::StringRef Message);
bool IsReduced(Module &M, TestRunner &Test, SmallString<128> &CurrentFilepath) {
// Write Module to tmp file
int FD;
std::error_code EC =
sys::fs::createTemporaryFile("llvm-reduce", "ll", FD, CurrentFilepath);
if (EC) {
errs() << "Error making unique filename: " << EC.message() << "!\n";
exit(1);
}
ToolOutputFile Out(CurrentFilepath, FD);
M.print(Out.os(), /*AnnotationWriter=*/nullptr);
Out.os().close();
if (Out.os().has_error()) {
errs() << "Error emitting bitcode to file '" << CurrentFilepath << "'!\n";
exit(1);
}
// Current Chunks aren't interesting
return Test.run(CurrentFilepath);
}
/// Counts the amount of lines for a given file
static int getLines(StringRef Filepath) {
int Lines = 0;
std::string CurrLine;
std::ifstream FileStream{std::string(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 {
int 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, int Targets,
std::function<void(const std::vector<Chunk> &, Module *)>
ExtractChunksFromModule) {
assert(Targets >= 0);
if (!Targets) {
errs() << "\nNothing to reduce\n";
return;
}
if (Module *Program = Test.getProgram()) {
SmallString<128> CurrentFilepath;
if (!IsReduced(*Program, Test, CurrentFilepath)) {
errs() << "\nInput isn't interesting! Verify interesting-ness test\n";
exit(1);
}
assert(!verifyModule(*Program, &errs()) &&
"input module is broken before making changes");
}
std::vector<Chunk> ChunksStillConsideredInteresting = {{1, Targets}};
std::unique_ptr<Module> ReducedProgram;
bool FoundAtLeastOneNewUninterestingChunkWithCurrentGranularity;
do {
FoundAtLeastOneNewUninterestingChunkWithCurrentGranularity = false;
std::set<Chunk> UninterestingChunks;
for (Chunk &ChunkToCheckForUninterestingness :
reverse(ChunksStillConsideredInteresting)) {
// Take all of ChunksStillConsideredInteresting chunks, except those we've
// already deemed uninteresting (UninterestingChunks) but didn't remove
// from ChunksStillConsideredInteresting yet, and additionally ignore
// ChunkToCheckForUninterestingness chunk.
std::vector<Chunk> CurrentChunks;
CurrentChunks.reserve(ChunksStillConsideredInteresting.size() -
UninterestingChunks.size() - 1);
copy_if(ChunksStillConsideredInteresting,
std::back_inserter(CurrentChunks), [&](const Chunk &C) {
return !UninterestingChunks.count(C) &&
C != ChunkToCheckForUninterestingness;
});
// 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());
// Some reductions may result in invalid IR. Skip such reductions.
if (verifyModule(*Clone.get(), &errs())) {
errs() << " **** WARNING | reduction resulted in invalid module, "
"skipping\n";
continue;
}
errs() << "Ignoring: ";
ChunkToCheckForUninterestingness.print();
for (const Chunk &C : UninterestingChunks)
C.print();
SmallString<128> CurrentFilepath;
if (!IsReduced(*Clone, Test, CurrentFilepath)) {
// Program became non-reduced, so this chunk appears to be interesting.
errs() << "\n";
continue;
}
FoundAtLeastOneNewUninterestingChunkWithCurrentGranularity = true;
UninterestingChunks.insert(ChunkToCheckForUninterestingness);
ReducedProgram = std::move(Clone);
errs() << " **** SUCCESS | lines: " << getLines(CurrentFilepath) << "\n";
writeOutput(ReducedProgram.get(), "Saved new best reduction to ");
}
// Delete uninteresting chunks
erase_if(ChunksStillConsideredInteresting,
[&UninterestingChunks](const Chunk &C) {
return UninterestingChunks.count(C);
});
} while (!ChunksStillConsideredInteresting.empty() &&
(FoundAtLeastOneNewUninterestingChunkWithCurrentGranularity ||
increaseGranularity(ChunksStillConsideredInteresting)));
// If we reduced the testcase replace it
if (ReducedProgram)
Test.setProgram(std::move(ReducedProgram));
errs() << "Couldn't increase anymore.\n";
}
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