State.cpp

//===------ State.cpp - OpenMP State & ICV interface ------------- C++ -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
//===----------------------------------------------------------------------===//

#include "Shared/Environment.h"

#include "Allocator.h"
#include "Configuration.h"
#include "Debug.h"
#include "DeviceTypes.h"
#include "DeviceUtils.h"
#include "Interface.h"
#include "LibC.h"
#include "Mapping.h"
#include "State.h"
#include "Synchronization.h"

using namespace ompx;

/// Memory implementation
///
///{

/// External symbol to access dynamic shared memory.
[[gnu::aligned(
    allocator::ALIGNMENT)]] extern Local<unsigned char> DynamicSharedBuffer[];

/// The kernel environment passed to the init method by the compiler.
[[clang::loader_uninitialized]] static Local<KernelEnvironmentTy *>
    KernelEnvironmentPtr;

/// The kernel launch environment passed as argument to the kernel by the
/// runtime.
[[clang::loader_uninitialized]] static Local<KernelLaunchEnvironmentTy *>
    KernelLaunchEnvironmentPtr;

///}

namespace {

/// Fallback implementations are missing to trigger a link time error.
/// Implementations for new devices, including the host, should go into a
/// dedicated begin/end declare variant.
///
///{
extern "C" {
#ifdef __AMDGPU__

[[gnu::weak]] void *malloc(size_t Size) { return allocator::alloc(Size); }
[[gnu::weak]] void free(void *Ptr) { allocator::free(Ptr); }

#else

[[gnu::weak, gnu::leaf]] void *malloc(size_t Size);
[[gnu::weak, gnu::leaf]] void free(void *Ptr);

#endif
}
///}

/// A "smart" stack in shared memory.
///
/// The stack exposes a malloc/free interface but works like a stack internally.
/// In fact, it is a separate stack *per warp*. That means, each warp must push
/// and pop symmetrically or this breaks, badly. The implementation will (aim
/// to) detect non-lock-step warps and fallback to malloc/free. The same will
/// happen if a warp runs out of memory. The master warp in generic memory is
/// special and is given more memory than the rest.
///
struct SharedMemorySmartStackTy {
  /// Initialize the stack. Must be called by all threads.
  void init(bool IsSPMD);

  /// Allocate \p Bytes on the stack for the encountering thread. Each thread
  /// can call this function.
  void *push(uint64_t Bytes);

  /// Deallocate the last allocation made by the encountering thread and pointed
  /// to by \p Ptr from the stack. Each thread can call this function.
  void pop(void *Ptr, uint64_t Bytes);

private:
  /// Compute the size of the storage space reserved for a thread.
  uint32_t computeThreadStorageTotal() {
    uint32_t NumLanesInBlock = mapping::getNumberOfThreadsInBlock();
    return __builtin_align_down(state::SharedScratchpadSize / NumLanesInBlock,
                                allocator::ALIGNMENT);
  }

  /// Return the top address of the warp data stack, that is the first address
  /// this warp will allocate memory at next.
  void *getThreadDataTop(uint32_t TId) {
    return &Data[computeThreadStorageTotal() * TId + Usage[TId]];
  }

  /// The actual storage, shared among all warps.
  [[gnu::aligned(
      allocator::ALIGNMENT)]] unsigned char Data[state::SharedScratchpadSize];
  [[gnu::aligned(
      allocator::ALIGNMENT)]] unsigned char Usage[mapping::MaxThreadsPerTeam];
};

static_assert(state::SharedScratchpadSize / mapping::MaxThreadsPerTeam <= 256,
              "Shared scratchpad of this size not supported yet.");

/// The allocation of a single shared memory scratchpad.
[[clang::loader_uninitialized]] static Local<SharedMemorySmartStackTy>
    SharedMemorySmartStack;

void SharedMemorySmartStackTy::init(bool IsSPMD) {
  Usage[mapping::getThreadIdInBlock()] = 0;
}

void *SharedMemorySmartStackTy::push(uint64_t Bytes) {
  // First align the number of requested bytes.
  /// FIXME: The stack shouldn't require worst-case padding. Alignment needs to
  /// be passed in as an argument and the stack rewritten to support it.
  uint64_t AlignedBytes = __builtin_align_up(Bytes, allocator::ALIGNMENT);

  uint32_t StorageTotal = computeThreadStorageTotal();

  // The main thread in generic mode gets the space of its entire warp as the
  // other threads do not participate in any computation at all.
  if (mapping::isMainThreadInGenericMode())
    StorageTotal *= mapping::getWarpSize();

  int TId = mapping::getThreadIdInBlock();
  if (Usage[TId] + AlignedBytes <= StorageTotal) {
    void *Ptr = getThreadDataTop(TId);
    Usage[TId] += AlignedBytes;
    return Ptr;
  }

  if (config::isDebugMode(DeviceDebugKind::CommonIssues))
    printf("Shared memory stack full, fallback to dynamic allocation of global "
           "memory will negatively impact performance.\n");
  void *GlobalMemory = memory::allocGlobal(
      AlignedBytes, "Slow path shared memory allocation, insufficient "
                    "shared memory stack memory!");
  ASSERT(GlobalMemory != nullptr, "nullptr returned by malloc!");

  return GlobalMemory;
}

void SharedMemorySmartStackTy::pop(void *Ptr, uint64_t Bytes) {
  uint64_t AlignedBytes = __builtin_align_up(Bytes, allocator::ALIGNMENT);
  if (utils::isSharedMemPtr(Ptr)) {
    int TId = mapping::getThreadIdInBlock();
    Usage[TId] -= AlignedBytes;
    return;
  }
  memory::freeGlobal(Ptr, "Slow path shared memory deallocation");
}

} // namespace

void *memory::getDynamicBuffer() { return DynamicSharedBuffer; }

void *memory::allocShared(uint64_t Bytes, const char *Reason) {
  return SharedMemorySmartStack.push(Bytes);
}

void memory::freeShared(void *Ptr, uint64_t Bytes, const char *Reason) {
  SharedMemorySmartStack.pop(Ptr, Bytes);
}

void *memory::allocGlobal(uint64_t Bytes, const char *Reason) {
  void *Ptr = malloc(Bytes);
  if (config::isDebugMode(DeviceDebugKind::CommonIssues) && Ptr == nullptr)
    printf("nullptr returned by malloc!\n");
  return Ptr;
}

void memory::freeGlobal(void *Ptr, const char *Reason) { free(Ptr); }

///}

bool state::ICVStateTy::operator==(const ICVStateTy &Other) const {
  return (NThreadsVar == Other.NThreadsVar) & (LevelVar == Other.LevelVar) &
         (ActiveLevelVar == Other.ActiveLevelVar) &
         (MaxActiveLevelsVar == Other.MaxActiveLevelsVar) &
         (RunSchedVar == Other.RunSchedVar) &
         (RunSchedChunkVar == Other.RunSchedChunkVar);
}

void state::ICVStateTy::assertEqual(const ICVStateTy &Other) const {
  ASSERT(NThreadsVar == Other.NThreadsVar, nullptr);
  ASSERT(LevelVar == Other.LevelVar, nullptr);
  ASSERT(ActiveLevelVar == Other.ActiveLevelVar, nullptr);
  ASSERT(MaxActiveLevelsVar == Other.MaxActiveLevelsVar, nullptr);
  ASSERT(RunSchedVar == Other.RunSchedVar, nullptr);
  ASSERT(RunSchedChunkVar == Other.RunSchedChunkVar, nullptr);
}

void state::TeamStateTy::init(bool IsSPMD) {
  ICVState.NThreadsVar = 0;
  ICVState.LevelVar = 0;
  ICVState.ActiveLevelVar = 0;
  ICVState.Padding0Val = 0;
  ICVState.MaxActiveLevelsVar = 1;
  ICVState.RunSchedVar = omp_sched_static;
  ICVState.RunSchedChunkVar = 1;
  ParallelTeamSize = 1;
  HasThreadState = false;
  ParallelRegionFnVar = nullptr;
}

bool state::TeamStateTy::operator==(const TeamStateTy &Other) const {
  return (ICVState == Other.ICVState) &
         (HasThreadState == Other.HasThreadState) &
         (ParallelTeamSize == Other.ParallelTeamSize);
}

void state::TeamStateTy::assertEqual(TeamStateTy &Other) const {
  ICVState.assertEqual(Other.ICVState);
  ASSERT(ParallelTeamSize == Other.ParallelTeamSize, nullptr);
  ASSERT(HasThreadState == Other.HasThreadState, nullptr);
}

[[clang::loader_uninitialized]] Local<state::TeamStateTy>
    ompx::state::TeamState;
[[clang::loader_uninitialized]] Local<state::ThreadStateTy **>
    ompx::state::ThreadStates;

namespace {

int returnValIfLevelIsActive(int Level, int Val, int DefaultVal,
                             int OutOfBoundsVal = -1) {
  if (Level == 0)
    return DefaultVal;
  int LevelVar = omp_get_level();
  if (OMP_UNLIKELY(Level < 0 || Level > LevelVar))
    return OutOfBoundsVal;
  int ActiveLevel = icv::ActiveLevel;
  if (OMP_UNLIKELY(Level != ActiveLevel))
    return DefaultVal;
  return Val;
}

} // namespace

void state::init(bool IsSPMD, KernelEnvironmentTy &KernelEnvironment,
                 KernelLaunchEnvironmentTy &KernelLaunchEnvironment) {
  SharedMemorySmartStack.init(IsSPMD);
  if (mapping::isInitialThreadInLevel0(IsSPMD)) {
    TeamState.init(IsSPMD);
    ThreadStates = nullptr;
    KernelEnvironmentPtr = &KernelEnvironment;
    KernelLaunchEnvironmentPtr = &KernelLaunchEnvironment;
  }
}

KernelEnvironmentTy &state::getKernelEnvironment() {
  return *KernelEnvironmentPtr;
}

KernelLaunchEnvironmentTy &state::getKernelLaunchEnvironment() {
  return *KernelLaunchEnvironmentPtr;
}

void state::enterDataEnvironment(IdentTy *Ident) {
  ASSERT(config::mayUseThreadStates(),
         "Thread state modified while explicitly disabled!");
  if (!config::mayUseThreadStates())
    return;

  unsigned TId = mapping::getThreadIdInBlock();
  ThreadStateTy *NewThreadState = static_cast<ThreadStateTy *>(
      memory::allocGlobal(sizeof(ThreadStateTy), "ThreadStates alloc"));
  uintptr_t *ThreadStatesBitsPtr = reinterpret_cast<uintptr_t *>(&ThreadStates);
  if (!atomic::load(ThreadStatesBitsPtr, atomic::seq_cst)) {
    uint32_t Bytes =
        sizeof(ThreadStates[0]) * mapping::getNumberOfThreadsInBlock();
    void *ThreadStatesPtr =
        memory::allocGlobal(Bytes, "Thread state array allocation");
    __builtin_memset(ThreadStatesPtr, 0, Bytes);
    if (!atomic::cas(ThreadStatesBitsPtr, uintptr_t(0),
                     reinterpret_cast<uintptr_t>(ThreadStatesPtr),
                     atomic::seq_cst, atomic::seq_cst))
      memory::freeGlobal(ThreadStatesPtr,
                         "Thread state array allocated multiple times");
    ASSERT(atomic::load(ThreadStatesBitsPtr, atomic::seq_cst),
           "Expected valid thread states bit!");
  }
  NewThreadState->init(ThreadStates[TId]);
  TeamState.HasThreadState = true;
  ThreadStates[TId] = NewThreadState;
}

void state::exitDataEnvironment() {
  ASSERT(config::mayUseThreadStates(),
         "Thread state modified while explicitly disabled!");

  unsigned TId = mapping::getThreadIdInBlock();
  resetStateForThread(TId);
}

void state::resetStateForThread(uint32_t TId) {
  if (!config::mayUseThreadStates())
    return;
  if (OMP_LIKELY(!TeamState.HasThreadState || !ThreadStates[TId]))
    return;

  ThreadStateTy *PreviousThreadState = ThreadStates[TId]->PreviousThreadState;
  memory::freeGlobal(ThreadStates[TId], "ThreadStates dealloc");
  ThreadStates[TId] = PreviousThreadState;
}

void state::runAndCheckState(void(Func(void))) {
  TeamStateTy OldTeamState = TeamState;
  OldTeamState.assertEqual(TeamState);

  Func();

  OldTeamState.assertEqual(TeamState);
}

void state::assumeInitialState(bool IsSPMD) {
  TeamStateTy InitialTeamState;
  InitialTeamState.init(IsSPMD);
  InitialTeamState.assertEqual(TeamState);
  ASSERT(mapping::isSPMDMode() == IsSPMD, nullptr);
}

int state::getEffectivePTeamSize() {
  int PTeamSize = state::ParallelTeamSize;
  return PTeamSize ? PTeamSize : mapping::getMaxTeamThreads();
}

extern "C" {
void omp_set_dynamic(int V) {}

int omp_get_dynamic(void) { return 0; }

void omp_set_num_threads(int V) { icv::NThreads = V; }

int omp_get_max_threads(void) {
  int NT = icv::NThreads;
  return NT > 0 ? NT : mapping::getMaxTeamThreads();
}

int omp_get_level(void) {
  int LevelVar = icv::Level;
  ASSERT(LevelVar >= 0, nullptr);
  return LevelVar;
}

int omp_get_active_level(void) { return !!icv::ActiveLevel; }

int omp_in_parallel(void) { return !!icv::ActiveLevel; }

void omp_get_schedule(omp_sched_t *ScheduleKind, int *ChunkSize) {
  *ScheduleKind = static_cast<omp_sched_t>((int)icv::RunSched);
  *ChunkSize = state::RunSchedChunk;
}

void omp_set_schedule(omp_sched_t ScheduleKind, int ChunkSize) {
  icv::RunSched = (int)ScheduleKind;
  state::RunSchedChunk = ChunkSize;
}

int omp_get_ancestor_thread_num(int Level) {
  return returnValIfLevelIsActive(Level, mapping::getThreadIdInBlock(), 0);
}

int omp_get_thread_num(void) {
  return omp_get_ancestor_thread_num(omp_get_level());
}

int omp_get_team_size(int Level) {
  return returnValIfLevelIsActive(Level, state::getEffectivePTeamSize(), 1);
}

int omp_get_num_threads(void) {
  return omp_get_level() != 1 ? 1 : state::getEffectivePTeamSize();
}

int omp_get_thread_limit(void) { return mapping::getMaxTeamThreads(); }

int omp_get_num_procs(void) { return mapping::getNumberOfProcessorElements(); }

void omp_set_nested(int) {}

int omp_get_nested(void) { return false; }

void omp_set_max_active_levels(int Levels) {
  icv::MaxActiveLevels = Levels > 0 ? 1 : 0;
}

int omp_get_max_active_levels(void) { return icv::MaxActiveLevels; }

omp_proc_bind_t omp_get_proc_bind(void) { return omp_proc_bind_false; }

int omp_get_num_places(void) { return 0; }

int omp_get_place_num_procs(int) { return omp_get_num_procs(); }

void omp_get_place_proc_ids(int, int *) {
  // TODO
}

int omp_get_place_num(void) { return 0; }

int omp_get_partition_num_places(void) { return 0; }

void omp_get_partition_place_nums(int *) {
  // TODO
}

int omp_get_cancellation(void) { return 0; }

void omp_set_default_device(int) {}

int omp_get_default_device(void) { return -1; }

int omp_get_num_devices(void) { return config::getNumDevices(); }

int omp_get_device_num(void) { return config::getDeviceNum(); }

int omp_get_num_teams(void) { return mapping::getNumberOfBlocksInKernel(); }

int omp_get_team_num() { return mapping::getBlockIdInKernel(); }

int omp_get_initial_device(void) { return -1; }

int omp_is_initial_device(void) { return 0; }
}

extern "C" {
[[clang::noinline]] void *__kmpc_alloc_shared(uint64_t Bytes) {
  return memory::allocShared(Bytes, "Frontend alloc shared");
}

[[clang::noinline]] void __kmpc_free_shared(void *Ptr, uint64_t Bytes) {
  memory::freeShared(Ptr, Bytes, "Frontend free shared");
}

void *__kmpc_get_dynamic_shared() { return memory::getDynamicBuffer(); }

void *llvm_omp_target_dynamic_shared_alloc() {
  return __kmpc_get_dynamic_shared();
}

void *llvm_omp_get_dynamic_shared() { return __kmpc_get_dynamic_shared(); }

/// Allocate storage in shared memory to communicate arguments from the main
/// thread to the workers in generic mode. If we exceed
/// NUM_SHARED_VARIABLES_IN_SHARED_MEM we will malloc space for communication.
constexpr uint64_t NUM_SHARED_VARIABLES_IN_SHARED_MEM = 64;

[[clang::loader_uninitialized]] static Local<void *>
    SharedMemVariableSharingSpace[NUM_SHARED_VARIABLES_IN_SHARED_MEM];
[[clang::loader_uninitialized]] static Local<void **>
    SharedMemVariableSharingSpacePtr;

void __kmpc_begin_sharing_variables(void ***GlobalArgs, uint64_t nArgs) {
  if (nArgs <= NUM_SHARED_VARIABLES_IN_SHARED_MEM) {
    SharedMemVariableSharingSpacePtr = &SharedMemVariableSharingSpace[0];
  } else {
    SharedMemVariableSharingSpacePtr = (void **)memory::allocGlobal(
        nArgs * sizeof(void *), "new extended args");
    ASSERT(SharedMemVariableSharingSpacePtr != nullptr,
           "Nullptr returned by malloc!");
  }
  *GlobalArgs = SharedMemVariableSharingSpacePtr;
}

void __kmpc_end_sharing_variables() {
  if (SharedMemVariableSharingSpacePtr != &SharedMemVariableSharingSpace[0])
    memory::freeGlobal(SharedMemVariableSharingSpacePtr, "new extended args");
}

void __kmpc_get_shared_variables(void ***GlobalArgs) {
  *GlobalArgs = SharedMemVariableSharingSpacePtr;
}
}