[Support] Add -polly-dump-module pass.

This pass allows writing the LLVM-IR just before and after the Polly
passes to a file.

Dumping the IR before Polly helps reproducing bugs that occur in code
generated by clang. It is the only reliable way to get the IR that
triggers a bug. The alternative is to emit the IR with

    clang -c -emit-llvm -S -o dump.ll

then pass it through all optimization passes

    opt dump.ll -basicaa -sroa ... -S -o optdump.ll

to then reproduce the error with

    opt optdump.ll -polly-opt-isl -polly-codegen -analyze

However, the IR is not the same. -O3 uses a PassBuilder than creates passes
with different parameters than the default.

Dumping the IR after Polly is useful to compare a miscompilation with
a known-good configuration.

Differential Revision: https://reviews.llvm.org/D30788

llvm-svn: 297415

1 files changed, 95 insertions, 0 deletions

diff --git a/polly/lib/Support/DumpModulePass.cpp b/polly/lib/Support/DumpModulePass.cpp
new file mode 100644
index 00000000000..558088cf898
--- /dev/null
+++ b/polly/lib/Support/DumpModulePass.cpp
@@ -0,0 +1,95 @@
+//===------ DumpModulePass.cpp ----------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Write a module to a file.
+//
+//===----------------------------------------------------------------------===//
+
+#include "polly/Support/DumpModulePass.h"
+
+#include "polly/Options.h"
+#include "llvm/IR/LegacyPassManagers.h"
+#include "llvm/IR/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/ToolOutputFile.h"
+#include <string.h>
+#define DEBUG_TYPE "polly-dump-module"
+
+using namespace llvm;
+using namespace polly;
+
+namespace {
+
+class DumpModule : public ModulePass {
+private:
+  DumpModule(const DumpModule &) = delete;
+  const DumpModule &operator=(const DumpModule &) = delete;
+
+  std::string Filename;
+  bool IsSuffix;
+
+public:
+  static char ID;
+
+  /// This constructor is used e.g. if using opt -polly-dump-module.
+  ///
+  /// Provide a default suffix to not overwrite the original file.
+  explicit DumpModule() : ModulePass(ID), Filename("-dump"), IsSuffix(true) {}
+
+  explicit DumpModule(llvm::StringRef Filename, bool IsSuffix)
+      : ModulePass(ID), Filename(Filename), IsSuffix(IsSuffix) {}
+
+  /// @name ModulePass interface
+  //@{
+  virtual void getAnalysisUsage(llvm::AnalysisUsage &AU) const override {
+    AU.setPreservesAll();
+  }
+
+  virtual bool runOnModule(llvm::Module &M) override {
+    std::string Dumpfile;
+    if (IsSuffix) {
+      auto ModuleName = M.getName();
+      auto Stem = sys::path::stem(ModuleName);
+      Dumpfile = (Twine(Stem) + Filename + ".ll").str();
+    } else {
+      Dumpfile = Filename;
+    }
+    DEBUG(dbgs() << "Dumping module to " << Dumpfile << '\n');
+
+    std::unique_ptr<tool_output_file> Out;
+    std::error_code EC;
+    Out.reset(new tool_output_file(Dumpfile, EC, sys::fs::F_None));
+    if (EC) {
+      errs() << EC.message() << '\n';
+      return false;
+    }
+
+    M.print(Out->os(), nullptr);
+    Out->keep();
+
+    return false;
+  }
+  //@}
+};
+
+char DumpModule::ID;
+} // namespace
+
+ModulePass *polly::createDumpModulePass(llvm::StringRef Filename,
+                                        bool IsSuffix) {
+  return new DumpModule(Filename, IsSuffix);
+}
+
+INITIALIZE_PASS_BEGIN(DumpModule, "polly-dump-module", "Polly - Dump Module",
+                      false, false)
+INITIALIZE_PASS_END(DumpModule, "polly-dump-module", "Polly - Dump Module",
+                    false, false)