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 96