lib/Support/Threading.cpp

   1 //===-- llvm/Support/Threading.cpp- Control multithreading mode --*- C++ -*-==//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This file defines helper functions for running LLVM in a multi-threaded
  10 // environment.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "llvm/Support/Threading.h"
  15 #include "llvm/Config/config.h"
  16 #include "llvm/Support/Host.h"
  17
  18 #include <cassert>
  19 #include <errno.h>
  20 #include <stdlib.h>
  21 #include <string.h>
  22
  23 using namespace llvm;
  24
  25 //===----------------------------------------------------------------------===//
  26 //=== WARNING: Implementation here must contain only TRULY operating system
  27 //===          independent code.
  28 //===----------------------------------------------------------------------===//
  29
  30 bool llvm::llvm_is_multithreaded() {
  31 #if LLVM_ENABLE_THREADS != 0
  32   return true;
  33 #else
  34   return false;
  35 #endif
  36 }
  37
  38 #if LLVM_ENABLE_THREADS == 0 ||                                                \
  39     (!defined(_WIN32) && !defined(HAVE_PTHREAD_H))
  40 // Support for non-Win32, non-pthread implementation.
  41 void llvm::llvm_execute_on_thread(void (*Fn)(void *), void *UserData,
  42                                   unsigned RequestedStackSize) {
  43   (void)RequestedStackSize;
  44   Fn(UserData);
  45 }
  46
  47 unsigned llvm::heavyweight_hardware_concurrency() { return 1; }
  48
  49 unsigned llvm::hardware_concurrency() { return 1; }
  50
  51 uint64_t llvm::get_threadid() { return 0; }
  52
  53 uint32_t llvm::get_max_thread_name_length() { return 0; }
  54
  55 void llvm::set_thread_name(const Twine &Name) {}
  56
  57 void llvm::get_thread_name(SmallVectorImpl<char> &Name) { Name.clear(); }
  58
  59 #else
  60
  61 #include <thread>
  62 unsigned llvm::heavyweight_hardware_concurrency() {
  63   // Since we can't get here unless LLVM_ENABLE_THREADS == 1, it is safe to use
  64   // `std::thread` directly instead of `llvm::thread` (and indeed, doing so
  65   // allows us to not define `thread` in the llvm namespace, which conflicts
  66   // with some platforms such as FreeBSD whose headers also define a struct
  67   // called `thread` in the global namespace which can cause ambiguity due to
  68   // ADL.
  69   int NumPhysical = sys::getHostNumPhysicalCores();
  70   if (NumPhysical == -1)
  71     return std::thread::hardware_concurrency();
  72   return NumPhysical;
  73 }
  74
  75 unsigned llvm::hardware_concurrency() {
  76 #if defined(HAVE_SCHED_GETAFFINITY) && defined(HAVE_CPU_COUNT)
  77   cpu_set_t Set;
  78   if (sched_getaffinity(0, sizeof(Set), &Set))
  79     return CPU_COUNT(&Set);
  80 #endif
  81   // Guard against std::thread::hardware_concurrency() returning 0.
  82   if (unsigned Val = std::thread::hardware_concurrency())
  83     return Val;
  84   return 1;
  85 }
  86
  87 // Include the platform-specific parts of this class.
  88 #ifdef LLVM_ON_UNIX
  89 #include "Unix/Threading.inc"
  90 #endif
  91 #ifdef _WIN32
  92 #include "Windows/Threading.inc"
  93 #endif
  94
  95 #endif