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: 368358
diff --git a/llvm/tools/llvm-reduce/deltas/Delta.cpp b/llvm/tools/llvm-reduce/deltas/Delta.cpp
new file mode 100644
index 0000000..cf8d884
--- /dev/null
+++ b/llvm/tools/llvm-reduce/deltas/Delta.cpp
@@ -0,0 +1,179 @@
+//===- 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"
+
+/// 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;
+}
+
+/// Prints the Chunk Indexes with the following format: [start, end], if
+/// chunk is at minimum size (1), then it just displays [start].
+static void printChunks(std::vector<Chunk> Chunks, bool Oneline = false) {
+ if (Chunks.empty()) {
+ outs() << "No Chunks";
+ return;
+ }
+
+ for (auto C : Chunks) {
+ if (!Oneline)
+ outs() << '\t';
+ C.print();
+ if (!Oneline)
+ outs() << '\n';
+ }
+}
+
+/// 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) {
+ 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 {
+ 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;
+ outs() << "Success! New Chunks:\n";
+ printChunks(Chunks);
+ }
+ 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) {
+ outs() << "\nNothing to reduce\n";
+ return;
+ }
+
+ std::vector<Chunk> Chunks = {{1, Targets}};
+ std::set<Chunk> UninterestingChunks;
+ std::unique_ptr<Module> ReducedProgram;
+
+ if (!Test.run(Test.getReducedFilepath())) {
+ outs() << "\nInput isn't interesting! Verify interesting-ness test\n";
+ return;
+ }
+
+ if (!increaseGranularity(Chunks)) {
+ outs() << "\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());
+
+ outs() << "Testing with: ";
+ printChunks(CurrentChunks, /*Oneline=*/true);
+ outs() << " | " << sys::path::filename(CurrentFilepath);
+
+ // Current Chunks aren't interesting
+ if (!Test.run(CurrentFilepath)) {
+ outs() << "\n";
+ continue;
+ }
+
+ UninterestingChunks.insert(Chunks[I]);
+ Test.setReducedFilepath(CurrentFilepath);
+ ReducedProgram = std::move(Clone);
+ outs() << " **** 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));
+ outs() << "Couldn't increase anymore.\n";
+}
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