Revert "[llvm-profdata] Speed up merging by using a thread pool"

This reverts commit r275921. It broke the ppc64be bot:

  http://lab.llvm.org:8011/builders/clang-ppc64be-linux-multistage/builds/3537

I'm not sure why it broke, but based on the output, it looks like an
off-by-one (one profile left un-merged).

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@275937 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 23 insertions, 115 deletions

diff --git a/tools/llvm-profdata/llvm-profdata.cpp b/tools/llvm-profdata/llvm-profdata.cpp
index e57b19f5a06..8e4b4c3d4ed 100644
--- a/tools/llvm-profdata/llvm-profdata.cpp
+++ b/tools/llvm-profdata/llvm-profdata.cpp
@@ -29,7 +29,6 @@
 #include "llvm/Support/Path.h"
 #include "llvm/Support/PrettyStackTrace.h"
 #include "llvm/Support/Signals.h"
-#include "llvm/Support/ThreadPool.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 
@@ -118,68 +117,9 @@ struct WeightedFile {
 };
 typedef SmallVector<WeightedFile, 5> WeightedFileVector;
 
-/// Keep track of merged data and reported errors.
-struct WriterContext {
-  std::mutex Lock;
-  InstrProfWriter Writer;
-  Error Err;
-  StringRef ErrWhence;
-  std::mutex &ErrLock;
-  SmallSet<instrprof_error, 4> &WriterErrorCodes;
-
-  WriterContext(bool IsSparse, std::mutex &ErrLock,
-                SmallSet<instrprof_error, 4> &WriterErrorCodes)
-      : Lock(), Writer(IsSparse), Err(Error::success()), ErrWhence(""),
-        ErrLock(ErrLock), WriterErrorCodes(WriterErrorCodes) {}
-};
-
-/// Load an input into a writer context.
-static void loadInput(const WeightedFile &Input, WriterContext *WC) {
-  std::unique_lock<std::mutex> CtxGuard{WC->Lock};
-
-  // If there's a pending hard error, don't do more work.
-  if (WC->Err)
-    return;
-
-  WC->ErrWhence = Input.Filename;
-
-  auto ReaderOrErr = InstrProfReader::create(Input.Filename);
-  if ((WC->Err = ReaderOrErr.takeError()))
-    return;
-
-  auto Reader = std::move(ReaderOrErr.get());
-  bool IsIRProfile = Reader->isIRLevelProfile();
-  if (WC->Writer.setIsIRLevelProfile(IsIRProfile)) {
-    WC->Err = make_error<StringError>(
-        "Merge IR generated profile with Clang generated profile.",
-        std::error_code());
-    return;
-  }
-
-  for (auto &I : *Reader) {
-    if (Error E = WC->Writer.addRecord(std::move(I), Input.Weight)) {
-      // Only show hint the first time an error occurs.
-      instrprof_error IPE = InstrProfError::take(std::move(E));
-      std::unique_lock<std::mutex> ErrGuard{WC->ErrLock};
-      bool firstTime = WC->WriterErrorCodes.insert(IPE).second;
-      handleMergeWriterError(make_error<InstrProfError>(IPE), Input.Filename,
-                             I.Name, firstTime);
-    }
-  }
-  if (Reader->hasError())
-    WC->Err = Reader->getError();
-}
-
-/// Merge the \p Src writer context into \p Dst.
-static void mergeWriterContexts(WriterContext *Dst, WriterContext *Src) {
-  if (Error E = Dst->Writer.mergeRecordsFromWriter(std::move(Src->Writer)))
-    Dst->Err = std::move(E);
-}
-
 static void mergeInstrProfile(const WeightedFileVector &Inputs,
                               StringRef OutputFilename,
-                              ProfileFormat OutputFormat, bool OutputSparse,
-                              unsigned NumThreads) {
+                              ProfileFormat OutputFormat, bool OutputSparse) {
   if (OutputFilename.compare("-") == 0)
     exitWithError("Cannot write indexed profdata format to stdout.");
 
@@ -191,57 +131,30 @@ static void mergeInstrProfile(const WeightedFileVector &Inputs,
   if (EC)
     exitWithErrorCode(EC, OutputFilename);
 
-  std::mutex ErrorLock;
+  InstrProfWriter Writer(OutputSparse);
   SmallSet<instrprof_error, 4> WriterErrorCodes;
-
-  // If NumThreads is not specified, auto-detect a good default.
-  if (NumThreads == 0)
-    NumThreads = std::max(1U, std::min(std::thread::hardware_concurrency(),
-                                       unsigned(Inputs.size() / 2)));
-
-  // Initialize the writer contexts.
-  SmallVector<std::unique_ptr<WriterContext>, 4> Contexts;
-  for (unsigned I = 0; I < NumThreads; ++I)
-    Contexts.emplace_back(llvm::make_unique<WriterContext>(
-        OutputSparse, ErrorLock, WriterErrorCodes));
-
-  if (NumThreads == 1) {
-    for (const auto &Input : Inputs)
-      loadInput(Input, Contexts[0].get());
-  } else {
-    ThreadPool Pool(NumThreads);
-
-    // Load the inputs in parallel (N/NumThreads serial steps).
-    unsigned Ctx = 0;
-    for (const auto &Input : Inputs) {
-      Pool.async(loadInput, Input, Contexts[Ctx].get());
-      Ctx = (Ctx + 1) % NumThreads;
+  for (const auto &Input : Inputs) {
+    auto ReaderOrErr = InstrProfReader::create(Input.Filename);
+    if (Error E = ReaderOrErr.takeError())
+      exitWithError(std::move(E), Input.Filename);
+
+    auto Reader = std::move(ReaderOrErr.get());
+    bool IsIRProfile = Reader->isIRLevelProfile();
+    if (Writer.setIsIRLevelProfile(IsIRProfile))
+      exitWithError("Merge IR generated profile with Clang generated profile.");
+
+    for (auto &I : *Reader) {
+      if (Error E = Writer.addRecord(std::move(I), Input.Weight)) {
+        // Only show hint the first time an error occurs.
+        instrprof_error IPE = InstrProfError::take(std::move(E));
+        bool firstTime = WriterErrorCodes.insert(IPE).second;
+        handleMergeWriterError(make_error<InstrProfError>(IPE), Input.Filename,
+                               I.Name, firstTime);
+      }
     }
-    Pool.wait();
-
-    // Merge the writer contexts together (lg(NumThreads) serial steps).
-    unsigned Mid = Contexts.size() / 2;
-    unsigned End = Contexts.size();
-    assert(Mid > 0 && "Expected more than one context");
-    do {
-      for (unsigned I = 0; I < Mid; ++I)
-        Pool.async(mergeWriterContexts, Contexts[I].get(),
-                   Contexts[I + Mid].get());
-      if (End & 1)
-        Pool.async(mergeWriterContexts, Contexts[0].get(),
-                   Contexts[End - 1].get());
-      Pool.wait();
-      End = Mid;
-      Mid /= 2;
-    } while (Mid > 0);
+    if (Reader->hasError())
+      exitWithError(Reader->getError(), Input.Filename);
   }
-
-  // Handle deferred hard errors encountered during merging.
-  for (std::unique_ptr<WriterContext> &WC : Contexts)
-    if (WC->Err)
-      exitWithError(std::move(WC->Err), WC->ErrWhence);
-
-  InstrProfWriter &Writer = Contexts[0]->Writer;
   if (OutputFormat == PF_Text)
     Writer.writeText(Output);
   else
@@ -375,11 +288,6 @@ static int merge_main(int argc, const char *argv[]) {
                  clEnumValEnd));
   cl::opt<bool> OutputSparse("sparse", cl::init(false),
       cl::desc("Generate a sparse profile (only meaningful for -instr)"));
-  cl::opt<unsigned> NumThreads(
-      "num-threads", cl::init(0),
-      cl::desc("Number of merge threads to use (default: autodetect)"));
-  cl::alias NumThreadsA("j", cl::desc("Alias for --num-threads"),
-                        cl::aliasopt(NumThreads));
 
   cl::ParseCommandLineOptions(argc, argv, "LLVM profile data merger\n");
 
@@ -406,7 +314,7 @@ static int merge_main(int argc, const char *argv[]) {
 
   if (ProfileKind == instr)
     mergeInstrProfile(WeightedInputs, OutputFilename, OutputFormat,
-                      OutputSparse, NumThreads);
+                      OutputSparse);
   else
     mergeSampleProfile(WeightedInputs, OutputFilename, OutputFormat);