[LTO] Add stats-file option to LTO/Config.h.

[fhahn]

Summary

This patch adds a StatsFile option to LTO/Config.h and updates both
LLVMGold and llvm-lto2 to set it.

[tejohnson]

A few thoughts/suggestions:

It would be better to add the calls to EnableStatistics and PrintStatisticsJSON to the LTO library, specifically inside LTO::run in LTO.cpp, so that all LTO clients can get the support with just an lto::Config change. E.g. the llvm-lto2 tool, lld.

What about -save-stats=cwd? It seems that both "obj" and "cwd" should be supported. But better than that:

• The -save-stats clang Driver option causes the -stats-file= cc1 option to be set. Better to support a -stats-file= option in gold-plugin and corresponding Config setting LTO, which is more generic than -save-stats.
• Once that is done, you can automatically set the gold-plugin option when -save-stats is passed to the cc1 invocation, in tools::AddGoldPlugin in clang. That simplifies the user model, and the option you need to pass in your corresponding CMake change, which can just be -save-stats=cwd.

Needs a test (assuming it is added to the LTO code, add both a gold and an llvm-lto2 based test).

[fhahn]

Thank you very much for your suggestions Teresa! I've updated the patch to handle a new StatsFile config option in LTO::run. And added stats-file support to LLVMgold.so and llvm-lto2. I will link the patch that updated AddGoldPlugin.

[tejohnson]

tools/gold/gold-plugin.cpp

206

document

1069

I think there is going to be a strange interaction with this code. I added this so that we still get the stats printed to stderr under the -stats llvm internal option when we exit early because we are only doing the ThinLTO indexing step (for distrubuted ThinLTO builds), since we don't execute ~StatisticInfo() in that case. The problem is that AreStatisticsEnabled() returns "Enabled || Stats", and Enabled will be true with this patch if the new stats-file plugin option is specified. So I think what would happen for distributed builds, when we exit early here, if the new plugin option is passed we will incorrectly dump stats to stderr as well.

Hmm, looks like we should probably just call llvm_shutdown() here before we exit, which would take care of destructing StatisticInfo. Let me try that and get back...

[tejohnson]

LGTM but please wait until after D45820 goes in.

tools/gold/gold-plugin.cpp

1069

Just mailed you D45820 that fixes this.

[fhahn]

Add comment to option in gold-plugin.cpp

include/llvm/LTO/Config.h

struct Config {
   std::string RemarksFilename = "";
 
   /// Whether to emit optimization remarks with hotness informations.
   bool RemarksWithHotness = false;
 
   /// Whether to emit the pass manager debuggging informations.
   bool DebugPassManager = false;
 
+  /// Statistics output file path.
+  std::string StatsFile;
+
   bool ShouldDiscardValueNames = true;
   DiagnosticHandlerFunction DiagHandler;
 
   /// If this field is set, LTO will write input file paths and symbol
   /// resolutions here in llvm-lto2 command line flag format. This can be
   /// used for testing and for running the LTO pipeline outside of the linker
   /// with llvm-lto2.
   std::unique_ptr<raw_ostream> ResolutionFile;

lib/LTO/LTO.cpp

 //===-LTO.cpp - LLVM Link Time Optimizer ----------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file implements functions and classes used to support LTO.
 //
 //===----------------------------------------------------------------------===//
 
 #include "llvm/LTO/LTO.h"
+#include "llvm/ADT/Statistic.h"
 #include "llvm/Analysis/TargetLibraryInfo.h"
 #include "llvm/Analysis/TargetTransformInfo.h"
 #include "llvm/Bitcode/BitcodeReader.h"
 #include "llvm/Bitcode/BitcodeWriter.h"
 #include "llvm/CodeGen/Analysis.h"
 #include "llvm/IR/AutoUpgrade.h"
 #include "llvm/IR/DiagnosticPrinter.h"
 #include "llvm/IR/LegacyPassManager.h"
Error LTO::run(AddStreamFn AddStream, NativeObjectCache Cache) {
   auto isPrevailing = [&](GlobalValue::GUID G) {
     auto It = GUIDPrevailingResolutions.find(G);
     if (It == GUIDPrevailingResolutions.end())
       return PrevailingType::Unknown;
     return It->second;
   };
   computeDeadSymbols(ThinLTO.CombinedIndex, GUIDPreservedSymbols, isPrevailing);
 
-  if (auto E = runRegularLTO(AddStream))
-    return E;
-  return runThinLTO(AddStream, Cache);
+  // Setup output file to emit statistics.
+  std::unique_ptr<ToolOutputFile> StatsFile = nullptr;
+  if (!Conf.StatsFile.empty()) {
+    EnableStatistics(false);
+    std::error_code EC;
+    StatsFile =
+        llvm::make_unique<ToolOutputFile>(Conf.StatsFile, EC, sys::fs::F_None);
+    if (EC)
+      return errorCodeToError(EC);
+    StatsFile->keep();
+  }
+
+  Error Result = runRegularLTO(AddStream);
+  if (!Result)
+    Result = runThinLTO(AddStream, Cache);
+
+  if (StatsFile)
+    PrintStatisticsJSON(StatsFile->os());
+
+  return Result;
 }
 
 Error LTO::runRegularLTO(AddStreamFn AddStream) {
   for (auto &M : RegularLTO.ModsWithSummaries)
     if (Error Err = linkRegularLTO(std::move(M),
                                    /*LivenessFromIndex=*/true))
       return Err;
 

test/tools/gold/X86/stats-file-option.ll

+; RUN: llvm-as -o %t.bc %s
+
+; Try to save statistics to file.
+; RUN: %gold -plugin %llvmshlibdir/LLVMgold%shlibext -plugin-opt=stats-file=%t2.stats \
+; RUN:    -m elf_x86_64 -r -o %t.o %t.bc
+; RUN: FileCheck --input-file=%t2.stats %s
+
+; CHECK: {
+; CHECK: "asm-printer.EmittedInsts":
+; CHECK: }
+
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define i32 @foo() {
+  ret i32 10
+}
+
+; Try to save statistics to an invalid file.
+; RUN: not %gold -plugin %llvmshlibdir/LLVMgold%shlibext -plugin-opt=stats-file=%t2/foo.stats \
+; RUN:    -m elf_x86_64 -r -o %t.o %t.bc 2>&1 | FileCheck --check-prefix=ERROR %s
+; ERROR: LLVM gold plugin: No such file or directory

test/tools/llvm-lto2/X86/stats-file-option.ll

+; RUN: llvm-as < %s > %t1.bc
+
+; Try to save statistics to file.
+; RUN: llvm-lto2 run %t1.bc -o %t.o -r %t1.bc,patatino,px -stats-file=%t2.stats
+; RUN: FileCheck --input-file=%t2.stats %s
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @patatino() {
+  fence seq_cst
+  ret void
+}
+
+; CHECK: {
+; CHECK: "asm-printer.EmittedInsts":
+; CHECK: }
+
+
+; Try to save statistics to an invalid file.
+; RUN: not llvm-lto2 run %t1.bc -o %t.o -r %t1.bc,patatino,px \
+; RUN:     -stats-file=%t2/foo.stats 2>&1 | FileCheck --check-prefix=ERROR %s
+; ERROR: LTO::run failed: No such file or directory

tools/gold/gold-plugin.cpp

#endif
   // New pass manager
   static bool new_pass_manager = false;
   // Debug new pass manager
   static bool debug_pass_manager = false;
   // Objcopy for debug fission.
   static std::string objcopy;
   // Directory to store the .dwo files.
   static std::string dwo_dir;
+  /// Statistics output filename.
+  static std::string stats_file;
 
   // Optimization remarks filename and hotness options
   static std::string OptRemarksFilename;
   static bool OptRemarksWithHotness = false;
 
   static void process_plugin_option(const char *opt_)
   {
     if (opt_ == nullptr)
static void process_plugin_option(const char *opt_)
     } else if (opt.startswith("objcopy=")) {
       objcopy = opt.substr(strlen("objcopy="));
     } else if (opt.startswith("dwo_dir=")) {
       dwo_dir = opt.substr(strlen("dwo_dir="));
     } else if (opt.startswith("opt-remarks-filename=")) {
       OptRemarksFilename = opt.substr(strlen("opt-remarks-filename="));
     } else if (opt == "opt-remarks-with-hotness") {
       OptRemarksWithHotness = true;
+    } else if (opt.startswith("stats-file=")) {
+      stats_file = opt.substr(strlen("stats-file="));
     } else {
       // Save this option to pass to the code generator.
       // ParseCommandLineOptions() expects argv[0] to be program name. Lazily
       // add that.
       if (extra.empty())
         extra.push_back("LLVMgold");
 
       extra.push_back(opt_);
static std::unique_ptr<LTO> createLTO(IndexWriteCallback OnIndexWrite,
   Conf.RemarksFilename = options::OptRemarksFilename;
   Conf.RemarksWithHotness = options::OptRemarksWithHotness;
 
   // Use new pass manager if set in driver
   Conf.UseNewPM = options::new_pass_manager;
   // Debug new pass manager if requested
   Conf.DebugPassManager = options::debug_pass_manager;
 
+  Conf.StatsFile = options::stats_file;
   return llvm::make_unique<LTO>(std::move(Conf), Backend,
                                 options::ParallelCodeGenParallelismLevel);
 }
 
 // Write empty files that may be expected by a distributed build
 // system when invoked with thinlto_index_only. This is invoked when
 // the linker has decided not to include the given module in the
 // final link. Frequently the distributed build system will want to
static ld_plugin_status allSymbolsReadHook() {
 
   std::vector<std::pair<SmallString<128>, bool>> Files = runLTO();
 
   if (options::TheOutputType == options::OT_DISABLE ||
       options::TheOutputType == options::OT_BC_ONLY)
     return LDPS_OK;
 
   if (options::thinlto_index_only) {
     llvm_shutdown();
     cleanup_hook();
     exit(0);
   }
 
   for (const auto &F : Files)
     if (!F.first.empty())
       recordFile(F.first.str(), F.second);
 

tools/llvm-lto2/llvm-lto2.cpp

static cl::opt<bool>
     UseNewPM("use-new-pm",
              cl::desc("Run LTO passes using the new pass manager"),
              cl::init(false), cl::Hidden);
 
 static cl::opt<bool>
     DebugPassManager("debug-pass-manager", cl::init(false), cl::Hidden,
                      cl::desc("Print pass management debugging information"));
 
+static cl::opt<std::string>
+    StatsFile("stats-file", cl::desc("Filename to write statistics to"));
+
 static void check(Error E, std::string Msg) {
   if (!E)
     return;
   handleAllErrors(std::move(E), [&](ErrorInfoBase &EIB) {
     errs() << "llvm-lto2: " << Msg << ": " << EIB.message().c_str() << '\n';
   });
   exit(1);
 }
default:
     return 1;
   }
 
   if (FileType.getNumOccurrences())
     Conf.CGFileType = FileType;
 
   Conf.OverrideTriple = OverrideTriple;
   Conf.DefaultTriple = DefaultTriple;
+  Conf.StatsFile = StatsFile;
 
   ThinBackend Backend;
   if (ThinLTODistributedIndexes)
     Backend = createWriteIndexesThinBackend(/* OldPrefix */ "",
                                             /* NewPrefix */ "",
                                             /* ShouldEmitImportsFiles */ true,
                                             /* LinkedObjectsFile */ nullptr,
                                             /* OnWrite */ {});