[Support] Move LLD parallel algorithms to LLVM.

[zturner]

Summary

NFC, this is just a straight code move along with header / namespace fixups.

[chandlerc]

Maybe I'm stuck with an old diff or something?

lld/COFF/Writer.cpp

748

I find the fact that for_each is now getting looked up via ADL on the llvm::parallel::par type ... disturbing.

llvm/include/llvm/Support/TaskGroup.h

51–53

I thought all of this was being moved to be implementation details of the algorithms?

Also, all the code appears to still be LLD style?

[zturner]

lld/COFF/Writer.cpp

748

I can certainly qualify the function call, but I don't know of a way to disable ADL if that's what you're suggesting.

llvm/include/llvm/Support/TaskGroup.h

51–53

The executor stuff was all moved to an anonymous namespace inside of TaskGroup.cpp. TaskGroup cannot enjoy the same level of hiding because it needs to be usable from within a header file. Namely, Parallel.h. I can, however, move it to a detail namespace inside of Parallel.h if you prefer that.

also: Yes rui pointed out the names in a previous patch and I forgot to update them. All of them have been fixed except for the few instances in this file.

[chandlerc]

lld/COFF/Writer.cpp

748

It's "easy": foo(a, b, c) uses ADL and (foo)(a, b, c) doesn't use ADL. ;]

I'm not suggesting using (for_each) though. That seems a bit crazy.

Writing llvm::foo will also disable ADL. ADL only fires for unqualified names. But then writing the code gets super ugly:

llvm::for_each(llvm::parallel::par, ...);

Yuck. I guess I mildly prefer that? The standard sure chose an API that ends up requiring a lot of characters to type.

What do you or Rui think? I don't have strong feelings about which way you go here, so would generally defer to your or Rui's judgement.

llvm/include/llvm/Support/TaskGroup.h

51–53

I see, thanks.

I think a detail namespace is a touch cleaner. I'm happy for you to do that in this patch, same with any name cleanup.

[zturner]

• Changed naming conventions on the leftover LLD-style variables.
• Deleted TaskGroup.h and TaskGroup.cpp and moved corresponding code to Parallel.h and Parallel.cpp inside of the detail namespace.

[zturner]

lld/COFF/Writer.cpp

748

It's worse than that, because it's going to be llvm::parallel::for_each(llvm::parallel::par, ...). We could nuke the intermediate parallel namespace and go with llvm::for_each(llvm::par, ...), or we could do using llvm::parallel at the top of a file. The namespace is sufficiently scoped that bringing it in shouldn't be too onerous.

Personally I'm fine with any approach, including the ADL-based approach. That said, I don't think there's anything we can do to the API itself to alleviate this, so perhaps we don't need to do anything. Just leave it up to the users.

[zturner]

Rebased after renaming variables on the LLD side.

[ruiu]

lld/COFF/Writer.cpp

748

Because we have using namespace llvm at beginning of this file, you don't need to qualify it with llvm::, no?

[chandlerc]

LGTM on the LLVM side. Feel free to submit when you and Rui are happy with the usage pattern for this in LLD.

llvm/include/llvm/Support/Parallel.h

67

closing namespace comment?

[ruiu]

I'm happy as long as you remove unnecessary llvm:: specifier. LGTM.

lld/COFF/ICF.cpp

 //
 // See ELF/ICF.cpp for the details about the algortihm.
 //
 //===----------------------------------------------------------------------===//
 
 #include "Chunks.h"
 #include "Error.h"
 #include "Symbols.h"
-#include "lld/Core/Parallel.h"
 #include "llvm/ADT/Hashing.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/Parallel.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 #include <atomic>
 #include <vector>
 
 using namespace llvm;
 
 namespace lld {

lld/COFF/MapFile.cpp

 //===----------------------------------------------------------------------===//
 
 #include "MapFile.h"
 #include "Error.h"
 #include "SymbolTable.h"
 #include "Symbols.h"
 #include "Writer.h"
 
-#include "lld/Core/Parallel.h"
+#include "llvm/Support/Parallel.h"
 #include "llvm/Support/raw_ostream.h"
 
 using namespace llvm;
 using namespace llvm::object;
 
 using namespace lld;
 using namespace lld::coff;
 
static SymbolMapTy getSectionSyms(ArrayRef<DefinedRegular *> Syms) {
   }
   return Ret;
 }
 
 // Construct a map from symbols to their stringified representations.
 static DenseMap<DefinedRegular *, std::string>
 getSymbolStrings(ArrayRef<DefinedRegular *> Syms) {
   std::vector<std::string> Str(Syms.size());
-  for_each_n(parallel::par, (size_t)0, Syms.size(), [&](size_t I) {
+  for_each_n(llvm::parallel::par, (size_t)0, Syms.size(), [&](size_t I) {
     raw_string_ostream OS(Str[I]);
     writeHeader(OS, Syms[I]->getRVA(), 0, 0);
     OS << indent(2) << toString(*Syms[I]);
   });
 
   DenseMap<DefinedRegular *, std::string> Ret;
   for (size_t I = 0, E = Syms.size(); I < E; ++I)
     Ret[Syms[I]] = std::move(Str[I]);

lld/COFF/Writer.cpp

 #include "DLL.h"
 #include "Error.h"
 #include "InputFiles.h"
 #include "MapFile.h"
 #include "Memory.h"
 #include "PDB.h"
 #include "SymbolTable.h"
 #include "Symbols.h"
-#include "lld/Core/Parallel.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/StringSwitch.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/Support/Endian.h"
 #include "llvm/Support/FileOutputBuffer.h"
+#include "llvm/Support/Parallel.h"
 #include "llvm/Support/RandomNumberGenerator.h"
 #include "llvm/Support/raw_ostream.h"
 #include <algorithm>
 #include <cstdio>
 #include <map>
 #include <memory>
 #include <utility>
 
void Writer::writeSections() {
   uint8_t *Buf = Buffer->getBufferStart();
   for (OutputSection *Sec : OutputSections) {
     uint8_t *SecBuf = Buf + Sec->getFileOff();
     // Fill gaps between functions in .text with INT3 instructions
     // instead of leaving as NUL bytes (which can be interpreted as
     // ADD instructions).
     if (Sec->getPermissions() & IMAGE_SCN_CNT_CODE)
       memset(SecBuf, 0xCC, Sec->getRawSize());
-    for_each(parallel::par, Sec->getChunks().begin(), Sec->getChunks().end(),
-             [&](Chunk *C) { C->writeTo(SecBuf); });
+    for_each(llvm::parallel::par, Sec->getChunks().begin(),
+             Sec->getChunks().end(), [&](Chunk *C) { C->writeTo(SecBuf); });
   }
 }
 
 // Sort .pdata section contents according to PE/COFF spec 5.5.
 void Writer::sortExceptionTable() {
   OutputSection *Sec = findSection(".pdata");
   if (!Sec)
     return;
   // We assume .pdata contains function table entries only.
   uint8_t *Begin = Buffer->getBufferStart() + Sec->getFileOff();
   uint8_t *End = Begin + Sec->getVirtualSize();
   if (Config->Machine == AMD64) {
     struct Entry { ulittle32_t Begin, End, Unwind; };
-    sort(parallel::par, (Entry *)Begin, (Entry *)End,
+    sort(llvm::parallel::par, (Entry *)Begin, (Entry *)End,
          [](const Entry &A, const Entry &B) { return A.Begin < B.Begin; });
     return;
   }
   if (Config->Machine == ARMNT) {
     struct Entry { ulittle32_t Begin, Unwind; };
-    sort(parallel::par, (Entry *)Begin, (Entry *)End,
+    sort(llvm::parallel::par, (Entry *)Begin, (Entry *)End,
          [](const Entry &A, const Entry &B) { return A.Begin < B.Begin; });
     return;
   }
   errs() << "warning: don't know how to handle .pdata.\n";
 }
 
 // Backfill the CVSignature in a PDB70 Debug Record.  This backfilling allows us
 // to get reproducible builds.

lld/ELF/Threads.h

 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLD_ELF_THREADS_H
 #define LLD_ELF_THREADS_H
 
 #include "Config.h"
 
-#include "lld/Core/Parallel.h"
+#include "llvm/Support/Parallel.h"
 #include <algorithm>
 #include <functional>
 
 namespace lld {
 namespace elf {
 
 template <class IterTy, class FuncTy>
 void parallelForEach(IterTy Begin, IterTy End, FuncTy Fn) {
   if (Config->Threads)
-    for_each(parallel::par, Begin, End, Fn);
+    for_each(llvm::parallel::par, Begin, End, Fn);
   else
-    for_each(parallel::seq, Begin, End, Fn);
+    for_each(llvm::parallel::seq, Begin, End, Fn);
 }
 
 inline void parallelFor(size_t Begin, size_t End,
                         std::function<void(size_t)> Fn) {
   if (Config->Threads)
-    for_each_n(parallel::par, Begin, End, Fn);
+    for_each_n(llvm::parallel::par, Begin, End, Fn);
   else
-    for_each_n(parallel::seq, Begin, End, Fn);
+    for_each_n(llvm::parallel::seq, Begin, End, Fn);
 }
 }
 }
 
 #endif

lld/lib/Core/CMakeLists.txt

 if(NOT LLD_BUILT_STANDALONE)
   set(tablegen_deps intrinsics_gen)
 endif()
 
 add_lld_library(lldCore
   DefinedAtom.cpp
   Error.cpp
   File.cpp
   LinkingContext.cpp
   Reader.cpp
   Reproduce.cpp
   Resolver.cpp
   SymbolTable.cpp
   TargetOptionsCommandFlags.cpp
-  TaskGroup.cpp
   Writer.cpp
 
   ADDITIONAL_HEADER_DIRS
   ${LLD_INCLUDE_DIR}/lld/Core
 
   LINK_COMPONENTS
     MC
     Support
   
   LINK_LIBS
   ${LLVM_PTHREAD_LIB}
 
   DEPENDS
   ${tablegen_deps}
   )

lld/lib/ReaderWriter/MachO/LayoutPass.cpp

 //===-- ReaderWriter/MachO/LayoutPass.cpp - Layout atoms ------------------===//
 //
 //                             The LLVM Linker
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #include "LayoutPass.h"
 #include "lld/Core/Instrumentation.h"
-#include "lld/Core/Parallel.h"
 #include "lld/Core/PassManager.h"
 #include "lld/ReaderWriter/MachOLinkingContext.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/Twine.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/Parallel.h"
 #include <algorithm>
 #include <set>
 #include <utility>
 
 using namespace lld;
 
 #define DEBUG_TYPE "LayoutPass"
 
llvm::Error LayoutPass::perform(SimpleFile &mergedFile) {
   buildOrdinalOverrideMap(atomRange);
 
   DEBUG({
     llvm::dbgs() << "unsorted atoms:\n";
     printDefinedAtoms(atomRange);
   });
 
   std::vector<LayoutPass::SortKey> vec = decorate(atomRange);
-  sort(parallel::par, vec.begin(), vec.end(),
+  sort(llvm::parallel::par, vec.begin(), vec.end(),
        [&](const LayoutPass::SortKey &l, const LayoutPass::SortKey &r) -> bool {
          return compareAtoms(l, r, _customSorter);
        });
   DEBUG(checkTransitivity(vec, _customSorter));
   undecorate(atomRange, vec);
 
   DEBUG({
     llvm::dbgs() << "sorted atoms:\n";

lld/unittests/CMakeLists.txt

 add_custom_target(LLDUnitTests)
 set_target_properties(LLDUnitTests PROPERTIES FOLDER "lld tests")
 
 set(CMAKE_BUILD_WITH_INSTALL_RPATH OFF)
 
 # add_lld_unittest(test_dirname file1.cpp file2.cpp)
 #
 # Will compile the list of files together and link against lld
 # Produces a binary named 'basename(test_dirname)'.
 function(add_lld_unittest test_dirname)
   add_unittest(LLDUnitTests ${test_dirname} ${ARGN})
   target_link_libraries(${test_dirname} ${LLVM_COMMON_LIBS})
 endfunction()
 
-add_subdirectory(CoreTests)
 add_subdirectory(DriverTests)
 add_subdirectory(MachOTests)

lld/unittests/CoreTests/CMakeLists.txt

-add_lld_unittest(CoreTests
-  ParallelTest.cpp
-  )
-
-target_link_libraries(CoreTests
-  lldCore ${LLVM_PTHREAD_LIB}
-  )

llvm/include/llvm/Support/Parallel.h

-//===- lld/Core/Parallel.h - Parallel utilities ---------------------------===//
+//===- llvm/Support/Parallel.h - Parallel algorithms ----------------------===//
 //
 //                             The LLVM Linker
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef LLD_CORE_PARALLEL_H
-#define LLD_CORE_PARALLEL_H
+#ifndef LLVM_SUPPORT_PARALLEL_H
+#define LLVM_SUPPORT_PARALLEL_H
 
-#include "lld/Core/LLVM.h"
-#include "lld/Core/TaskGroup.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/Config/llvm-config.h"
 #include "llvm/Support/MathExtras.h"
+#include "llvm/Support/TaskGroup.h"
 
 #include <algorithm>
 
 #if defined(_MSC_VER) && LLVM_ENABLE_THREADS
 #include <concrt.h>
 #include <ppl.h>
 #endif
 
-namespace lld {
+namespace llvm {
 
 namespace parallel {
 struct sequential_execution_policy {};
 struct parallel_execution_policy {};
 
 template <typename T>
 struct is_execution_policy
     : public std::integral_constant<

 
 #else
 const ptrdiff_t MinParallelSize = 1024;
 
 /// \brief Inclusive median.
 template <class RandomAccessIterator, class Comparator>
 RandomAccessIterator medianOf3(RandomAccessIterator Start,
                                RandomAccessIterator End,
                                const Comparator &Comp) {
   RandomAccessIterator Mid = Start + (std::distance(Start, End) / 2);
   return Comp(*Start, *(End - 1))
              ? (Comp(*Mid, *(End - 1)) ? (Comp(*Start, *Mid) ? Mid : Start)
                                        : End - 1)
              : (Comp(*Mid, *Start) ? (Comp(*(End - 1), *Mid) ? Mid : End - 1)
                                    : Start);
 }
 

 template <class IndexTy, class FuncTy>
 void for_each_n(parallel_execution_policy policy, IndexTy Begin, IndexTy End,
                 FuncTy Fn) {
   detail::parallel_for_each_n(Begin, End, Fn);
 }
 #endif
 
 } // namespace parallel
-} // End namespace lld
+} // End namespace llvm
 
-#endif // LLD_CORE_PARALLEL_H
+#endif // LLVM_SUPPORT_PARALLEL_H

llvm/include/llvm/Support/TaskGroup.h

-//===- lld/Core/TaskGroup.h - Task Group ----------------------------------===//
+//===- llvm/Support/TaskGroup.h - Task Group ------------------------------===//
 //
 //                             The LLVM Linker
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef LLD_CORE_TASKGROUP_H
-#define LLD_CORE_TASKGROUP_H
-
-#include "lld/Core/LLVM.h"
+#ifndef LLVM_SUPPORT_TASKGROUP_H
+#define LLVM_SUPPORT_TASKGROUP_H
 
 #include <condition_variable>
 #include <functional>
 #include <mutex>
 
-namespace lld {
+namespace llvm {
 /// \brief Allows one or more threads to wait on a potentially unknown number of
 ///   events.
 ///
 /// A latch starts at \p count. inc() increments this, and dec() decrements it.
 /// All calls to sync() will block while the count is not 0.
 ///
 /// Calling dec() on a Latch with a count of 0 has undefined behaivor.
 class Latch {
public:
   }
 
   void sync() const {
     std::unique_lock<std::mutex> lock(_condMut);
     _cond.wait(lock, [&] { return _count == 0; });
   }
 };
 
 /// \brief Allows launching a number of tasks and waiting for them to finish
 ///   either explicitly via sync() or implicitly on destruction.
 class TaskGroup {
   Latch _latch;
 
 public:
   void spawn(std::function<void()> f);
 
   void sync() const { _latch.sync(); }
 };
 }
 
 #endif

llvm/lib/Support/CMakeLists.txt

add_llvm_library(LLVMSupport
   StringExtras.cpp
   StringMap.cpp
   StringPool.cpp
   StringSaver.cpp
   StringRef.cpp
   SystemUtils.cpp
   TarWriter.cpp
   TargetParser.cpp
+  TaskGroup.cpp
   ThreadPool.cpp
   Timer.cpp
   ToolOutputFile.cpp
   TrigramIndex.cpp
   Triple.cpp
   Twine.cpp
   Unicode.cpp
   YAMLParser.cpp

llvm/lib/Support/TaskGroup.cpp

 //===- lld/Core/TaskGroup.cpp - Task Group --------------------------------===//
 //
 //                             The LLVM Linker
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
-#include "lld/Core/TaskGroup.h"
+#include "llvm/Support/TaskGroup.h"
 #include "llvm/Config/llvm-config.h"
 
 #include <atomic>
 #include <stack>
 #include <thread>
 
 #if defined(_MSC_VER) && LLVM_ENABLE_THREADS
+#pragma warning(push)
+#pragma warning(disable : 4530)
 #include <concrt.h>
 #include <ppl.h>
+#pragma warning(pop)
 #endif
 
-using namespace lld;
+using namespace llvm;
 
 namespace {
 
 /// \brief An abstract class that takes closures and runs them asynchronously.
 class Executor {
 public:
   virtual ~Executor() = default;
   virtual void add(std::function<void()> func) = 0;

llvm/unittests/Support/CMakeLists.txt

add_llvm_unittest(SupportTests
   LineIteratorTest.cpp
   LockFileManagerTest.cpp
   MD5Test.cpp
   ManagedStatic.cpp
   MathExtrasTest.cpp
   MemoryBufferTest.cpp
   MemoryTest.cpp
   NativeFormatTests.cpp
+  ParallelTest.cpp
   Path.cpp
   ProcessTest.cpp
   ProgramTest.cpp
   RegexTest.cpp
   ReplaceFileTest.cpp
   ScaledNumberTest.cpp
   SourceMgrTest.cpp
   SpecialCaseListTest.cpp

llvm/unittests/Support/ParallelTest.cpp

-//===- lld/unittest/ParallelTest.cpp --------------------------------------===//
+//===- llvm/unittest/Support/ParallelTest.cpp -----------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
 /// \brief Parallel.h unit tests.
 ///
 //===----------------------------------------------------------------------===//
 
+#include "llvm/Support/Parallel.h"
 #include "gtest/gtest.h"
-#include "lld/Core/Parallel.h"
 #include <array>
 #include <random>
 
 uint32_t array[1024 * 1024];
 
+using namespace llvm;
+
 TEST(Parallel, sort) {
   std::mt19937 randEngine;
   std::uniform_int_distribution<uint32_t> dist;
 
   for (auto &i : array)
     i = dist(randEngine);
 
-  sort(lld::parallel::par, std::begin(array), std::end(array));
+  sort(parallel::par, std::begin(array), std::end(array));
   ASSERT_TRUE(std::is_sorted(std::begin(array), std::end(array)));
 }
 
 TEST(Parallel, parallel_for) {
   // We need to test the case with a TaskSize > 1. We are white-box testing
   // here. The TaskSize is calculated as (End - Begin) / 1024 at the time of
   // writing.
   uint32_t range[2050];
   std::fill(range, range + 2050, 1);
-  for_each_n(lld::parallel::par, 0, 2049, [&range](size_t I) { ++range[I]; });
+  for_each_n(parallel::par, 0, 2049, [&range](size_t I) { ++range[I]; });
 
   uint32_t expected[2049];
   std::fill(expected, expected + 2049, 2);
   ASSERT_TRUE(std::equal(range, range + 2049, expected));
   // Check that we don't write past the end of the requested range.
   ASSERT_EQ(range[2049], 1u);
 }