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/Config/llvm-config.h" 17 18 #include <cassert> 19 #include <optional> 20 #include <stdlib.h> 21 22 using namespace llvm; 23 24 //===----------------------------------------------------------------------===// 25 //=== WARNING: Implementation here must contain only TRULY operating system 26 //=== independent code. 27 //===----------------------------------------------------------------------===// 28 29 #if LLVM_ENABLE_THREADS == 0 || \ 30 (!defined(_WIN32) && !defined(HAVE_PTHREAD_H)) 31 uint64_t llvm::get_threadid() { return 0; } 32 33 uint32_t llvm::get_max_thread_name_length() { return 0; } 34 35 void llvm::set_thread_name(const Twine &Name) {} 36 37 void llvm::get_thread_name(SmallVectorImpl<char> &Name) { Name.clear(); } 38 39 llvm::BitVector llvm::get_thread_affinity_mask() { return {}; } 40 41 unsigned llvm::ThreadPoolStrategy::compute_thread_count() const { 42 // When threads are disabled, ensure clients will loop at least once. 43 return 1; 44 } 45 46 // Unknown if threading turned off 47 int llvm::get_physical_cores() { return -1; } 48 49 #else 50 51 static int computeHostNumHardwareThreads(); 52 53 unsigned llvm::ThreadPoolStrategy::compute_thread_count() const { 54 int MaxThreadCount = 55 UseHyperThreads ? computeHostNumHardwareThreads() : get_physical_cores(); 56 if (MaxThreadCount <= 0) 57 MaxThreadCount = 1; 58 if (ThreadsRequested == 0) 59 return MaxThreadCount; 60 if (!Limit) 61 return ThreadsRequested; 62 return std::min((unsigned)MaxThreadCount, ThreadsRequested); 63 } 64 65 // Include the platform-specific parts of this class. 66 #ifdef LLVM_ON_UNIX 67 #include "Unix/Threading.inc" 68 #endif 69 #ifdef _WIN32 70 #include "Windows/Threading.inc" 71 #endif 72 73 // Must be included after Threading.inc to provide definition for llvm::thread 74 // because FreeBSD's condvar.h (included by user.h) misuses the "thread" 75 // keyword. 76 #include "llvm/Support/thread.h" 77 78 #if defined(__APPLE__) 79 // Darwin's default stack size for threads except the main one is only 512KB, 80 // which is not enough for some/many normal LLVM compilations. This implements 81 // the same interface as std::thread but requests the same stack size as the 82 // main thread (8MB) before creation. 83 const std::optional<unsigned> llvm::thread::DefaultStackSize = 8 * 1024 * 1024; 84 #elif defined(_AIX) 85 // On AIX, the default pthread stack size limit is ~192k for 64-bit programs. 86 // This limit is easily reached when doing link-time thinLTO. AIX library 87 // developers have used 4MB, so we'll do the same. 88 const std::optional<unsigned> llvm::thread::DefaultStackSize = 4 * 1024 * 1024; 89 #else 90 const std::optional<unsigned> llvm::thread::DefaultStackSize; 91 #endif 92 93 94 #endif 95 96 std::optional<ThreadPoolStrategy> 97 llvm::get_threadpool_strategy(StringRef Num, ThreadPoolStrategy Default) { 98 if (Num == "all") 99 return llvm::hardware_concurrency(); 100 if (Num.empty()) 101 return Default; 102 unsigned V; 103 if (Num.getAsInteger(10, V)) 104 return std::nullopt; // malformed 'Num' value 105 if (V == 0) 106 return Default; 107 108 // Do not take the Default into account. This effectively disables 109 // heavyweight_hardware_concurrency() if the user asks for any number of 110 // threads on the cmd-line. 111 ThreadPoolStrategy S = llvm::hardware_concurrency(); 112 S.ThreadsRequested = V; 113 return S; 114 } 115