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/ADT/Optional.h" 16 #include "llvm/Config/config.h" 17 #include "llvm/Support/Host.h" 18 #include "llvm/Support/thread.h" 19 20 #include <cassert> 21 #include <errno.h> 22 #include <stdlib.h> 23 #include <string.h> 24 25 using namespace llvm; 26 27 //===----------------------------------------------------------------------===// 28 //=== WARNING: Implementation here must contain only TRULY operating system 29 //=== independent code. 30 //===----------------------------------------------------------------------===// 31 32 bool llvm::llvm_is_multithreaded() { 33 #if LLVM_ENABLE_THREADS != 0 34 return true; 35 #else 36 return false; 37 #endif 38 } 39 40 #if LLVM_ENABLE_THREADS == 0 || \ 41 (!defined(_WIN32) && !defined(HAVE_PTHREAD_H)) 42 uint64_t llvm::get_threadid() { return 0; } 43 44 uint32_t llvm::get_max_thread_name_length() { return 0; } 45 46 void llvm::set_thread_name(const Twine &Name) {} 47 48 void llvm::get_thread_name(SmallVectorImpl<char> &Name) { Name.clear(); } 49 50 llvm::BitVector llvm::get_thread_affinity_mask() { return {}; } 51 52 unsigned llvm::ThreadPoolStrategy::compute_thread_count() const { 53 // When threads are disabled, ensure clients will loop at least once. 54 return 1; 55 } 56 57 #else 58 59 int computeHostNumHardwareThreads(); 60 61 unsigned llvm::ThreadPoolStrategy::compute_thread_count() const { 62 int MaxThreadCount = UseHyperThreads ? computeHostNumHardwareThreads() 63 : sys::getHostNumPhysicalCores(); 64 if (MaxThreadCount <= 0) 65 MaxThreadCount = 1; 66 if (ThreadsRequested == 0) 67 return MaxThreadCount; 68 if (!Limit) 69 return ThreadsRequested; 70 return std::min((unsigned)MaxThreadCount, ThreadsRequested); 71 } 72 73 // Include the platform-specific parts of this class. 74 #ifdef LLVM_ON_UNIX 75 #include "Unix/Threading.inc" 76 #endif 77 #ifdef _WIN32 78 #include "Windows/Threading.inc" 79 #endif 80 81 #if defined(__APPLE__) 82 // Darwin's default stack size for threads except the main one is only 512KB, 83 // which is not enough for some/many normal LLVM compilations. This implements 84 // the same interface as std::thread but requests the same stack size as the 85 // main thread (8MB) before creation. 86 const llvm::Optional<unsigned> llvm::thread::DefaultStackSize = 8 * 1024 * 1024; 87 #else 88 const llvm::Optional<unsigned> llvm::thread::DefaultStackSize = None; 89 #endif 90 91 92 #endif 93 94 Optional<ThreadPoolStrategy> 95 llvm::get_threadpool_strategy(StringRef Num, ThreadPoolStrategy Default) { 96 if (Num == "all") 97 return llvm::hardware_concurrency(); 98 if (Num.empty()) 99 return Default; 100 unsigned V; 101 if (Num.getAsInteger(10, V)) 102 return None; // malformed 'Num' value 103 if (V == 0) 104 return Default; 105 106 // Do not take the Default into account. This effectively disables 107 // heavyweight_hardware_concurrency() if the user asks for any number of 108 // threads on the cmd-line. 109 ThreadPoolStrategy S = llvm::hardware_concurrency(); 110 S.ThreadsRequested = V; 111 return S; 112 } 113