lib/Support/Threading.cpp

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