Added Delta IR Reduction Tool

Summary: Tool parses input IR file, and runs the delta debugging algorithm to reduce the functions inside the input file.

Reviewers: alexshap, chandlerc

Subscribers: mgorny, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D63672

> llvm-svn: 368071

llvm-svn: 368112

1 files changed, 222 insertions, 0 deletions

diff --git a/llvm/tools/llvm-reduce/deltas/Delta.h b/llvm/tools/llvm-reduce/deltas/Delta.h
new file mode 100644
index 00000000000..60b212832c2
--- /dev/null
+++ b/llvm/tools/llvm-reduce/deltas/Delta.h
@@ -0,0 +1,222 @@
+//===- llvm-reduce.cpp - The LLVM Delta Reduction utility -----------------===//
+//
+// 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.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TOOLS_LLVMREDUCE_LLVMREDUCE_DELTA_H
+#define LLVM_TOOLS_LLVMREDUCE_LLVMREDUCE_DELTA_H
+
+#include "../TestRunner.h"
+#include "llvm/IR/Verifier.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/ScopedPrinter.h"
+#include "llvm/Support/ToolOutputFile.h"
+#include <fstream>
+#include <set>
+#include <vector>
+
+using namespace llvm;
+
+struct Chunk {
+  int begin;
+  int end;
+
+  /// Operator when populating CurrentChunks in Generic Delta Pass
+  friend bool operator!=(const Chunk &C1, const Chunk &C2) {
+    return C1.begin != C2.begin && C1.end != C2.end;
+  }
+
+  /// Operator used for sets
+  friend bool operator<(const Chunk &C1, const Chunk &C2) {
+    return C1.begin < C2.begin;
+  }
+};
+
+/// Writes IR code to the given Filepath
+inline 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 outputs
+/// the module inside it.
+inline SmallString<128> createTmpFile(Module *M, StringRef TmpDir) {
+  SmallString<128> UniqueFilepath;
+  int UniqueFD;
+
+  std::error_code EC = sys::fs::createUniqueFile(TmpDir + "/tmp-%%%.ll",
+                                                 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;
+}
+
+/// Prints the Chunk Indexes with the following format: [start, end], if
+/// chunk is at minimum size (1), then it just displays [start].
+inline void printChunks(std::vector<Chunk> Chunks, bool Oneline = false) {
+  for (auto C : Chunks) {
+    if (!Oneline)
+      outs() << '\t';
+    outs() << "[" << C.begin;
+    if (C.end - C.begin != 0)
+      outs() << "," << C.end;
+    outs() << "]";
+    if (!Oneline)
+      outs() << '\n';
+  }
+}
+
+/// Counts the amount of lines for a given file
+inline 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.
+inline bool increaseGranularity(std::vector<Chunk> &Chunks) {
+  outs() << "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;
+    outs() << "Success! New Chunks:\n";
+    printChunks(Chunks);
+  }
+  return SplitOne;
+}
+
+namespace llvm {
+
+/// This class implements the Delta Debugging algorithm, it receives a set of
+/// Targets (e.g. Functions, Instructions, Basic Blocks, etc.) and splits them
+/// in half; these chunks of targets are then tested while ignoring one chunk,
+/// if a chunk is proven to be uninteresting (i.e. fails the test) it is
+/// removed from consideration. Otherwise, the algorithm will attempt to split
+/// the Chunks in half and start the process again, until it can't split chunks
+/// anymore.
+///
+/// The class is intended to be called statically by the DeltaManager class
+/// alongside a specialized delta pass (e.g. RemoveFunctions) passed as a
+/// template.
+/// This specialized pass implements two functions:
+///   * getTargetCount, which returns the amount of targets (e.g. Functions)
+///     there are in the Module.
+///   * extractChunksFromModule, which clones the given Module and modifies it
+///     so it only contains Chunk Targets.
+///
+/// Other implementations of the Delta Debugging algorithm can be found in the
+/// CReduce, Delta, and Lithium projects.
+template <class P> class Delta {
+public:
+  /// Runs the Delta Debugging algorithm, splits the code into chunks and
+  /// reduces the amount of chunks that are considered interesting by the
+  /// given test.
+  static void run(TestRunner &Test) {
+    int TargetCount = P::getTargetCount(Test.getProgram());
+    std::vector<Chunk> Chunks = {{1, TargetCount}};
+    std::set<Chunk> UninterestingChunks;
+    std::unique_ptr<Module> ReducedProgram;
+
+    if (Test.run(Test.getReducedFilepath()))
+      increaseGranularity(Chunks);
+    else {
+      outs() << "Error: input file isnt interesting\n";
+      exit(1);
+    }
+
+    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);
+
+        // Generate Module with only Targets inside Current Chunks
+        std::unique_ptr<Module> CurrentProgram =
+            P::extractChunksFromModule(CurrentChunks, Test.getProgram());
+        // Write Module to tmp file
+        SmallString<128> CurrentFilepath =
+            createTmpFile(CurrentProgram.get(), Test.getTmpDir());
+
+        outs() << "Testing with: ";
+        printChunks(CurrentChunks, /*Oneline=*/true);
+        outs() << " | " << sys::path::filename(CurrentFilepath);
+
+        // Current Chunks aren't interesting
+        if (!Test.run(CurrentFilepath)) {
+          outs() << "\n";
+          continue;
+        }
+
+        // We only care about interesting chunks if they reduce the testcase
+        if (getLines(CurrentFilepath) < getLines(Test.getReducedFilepath())) {
+          UninterestingChunks.insert(Chunks[I]);
+          Test.setReducedFilepath(CurrentFilepath);
+          ReducedProgram = std::move(CurrentProgram);
+          outs() << " **** SUCCESS | lines: " << getLines(CurrentFilepath);
+        }
+        outs() << "\n";
+      }
+      // Delete uninteresting chunks
+      auto UnwantedChunks = Chunks.end();
+      UnwantedChunks = std::remove_if(Chunks.begin(), Chunks.end(),
+                                      [UninterestingChunks](const Chunk &C) {
+                                        return UninterestingChunks.count(C);
+                                      });
+      Chunks.erase(UnwantedChunks, Chunks.end());
+    } while (!UninterestingChunks.empty() || increaseGranularity(Chunks));
+
+    // If we reduced the testcase replace it
+    if (ReducedProgram)
+      Test.setProgram(std::move(ReducedProgram));
+    outs() << "Couldn't increase anymore.\n";
+  }
+};
+
+} // namespace llvm
+
+#endif