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 <errno.h> 20 #include <optional> 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 #if LLVM_ENABLE_THREADS == 0 || \ 32 (!defined(_WIN32) && !defined(HAVE_PTHREAD_H)) get_threadid()33uint64_t llvm::get_threadid() { return 0; } 34 get_max_thread_name_length()35uint32_t llvm::get_max_thread_name_length() { return 0; } 36 set_thread_name(const Twine & Name)37void llvm::set_thread_name(const Twine &Name) {} 38 get_thread_name(SmallVectorImpl<char> & Name)39void llvm::get_thread_name(SmallVectorImpl<char> &Name) { Name.clear(); } 40 get_thread_affinity_mask()41llvm::BitVector llvm::get_thread_affinity_mask() { return {}; } 42 compute_thread_count() const43unsigned llvm::ThreadPoolStrategy::compute_thread_count() const { 44 // When threads are disabled, ensure clients will loop at least once. 45 return 1; 46 } 47 48 // Unknown if threading turned off get_physical_cores()49int llvm::get_physical_cores() { return -1; } 50 51 #else 52 53 static int computeHostNumHardwareThreads(); 54 compute_thread_count() const55unsigned llvm::ThreadPoolStrategy::compute_thread_count() const { 56 int MaxThreadCount = 57 UseHyperThreads ? computeHostNumHardwareThreads() : get_physical_cores(); 58 if (MaxThreadCount <= 0) 59 MaxThreadCount = 1; 60 if (ThreadsRequested == 0) 61 return MaxThreadCount; 62 if (!Limit) 63 return ThreadsRequested; 64 return std::min((unsigned)MaxThreadCount, ThreadsRequested); 65 } 66 67 // Include the platform-specific parts of this class. 68 #ifdef LLVM_ON_UNIX 69 #include "Unix/Threading.inc" 70 #endif 71 #ifdef _WIN32 72 #include "Windows/Threading.inc" 73 #endif 74 75 // Must be included after Threading.inc to provide definition for llvm::thread 76 // because FreeBSD's condvar.h (included by user.h) misuses the "thread" 77 // keyword. 78 #include "llvm/Support/thread.h" 79 80 #if defined(__APPLE__) 81 // Darwin's default stack size for threads except the main one is only 512KB, 82 // which is not enough for some/many normal LLVM compilations. This implements 83 // the same interface as std::thread but requests the same stack size as the 84 // main thread (8MB) before creation. 85 const std::optional<unsigned> llvm::thread::DefaultStackSize = 8 * 1024 * 1024; 86 #else 87 const std::optional<unsigned> llvm::thread::DefaultStackSize; 88 #endif 89 90 91 #endif 92 93 std::optional<ThreadPoolStrategy> get_threadpool_strategy(StringRef Num,ThreadPoolStrategy Default)94llvm::get_threadpool_strategy(StringRef Num, ThreadPoolStrategy Default) { 95 if (Num == "all") 96 return llvm::hardware_concurrency(); 97 if (Num.empty()) 98 return Default; 99 unsigned V; 100 if (Num.getAsInteger(10, V)) 101 return std::nullopt; // malformed 'Num' value 102 if (V == 0) 103 return Default; 104 105 // Do not take the Default into account. This effectively disables 106 // heavyweight_hardware_concurrency() if the user asks for any number of 107 // threads on the cmd-line. 108 ThreadPoolStrategy S = llvm::hardware_concurrency(); 109 S.ThreadsRequested = V; 110 return S; 111 } 112