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#include "llvm/Support/Jobserver.h"
18
19#include <cassert>
20#include <optional>
21#include <stdlib.h>
22
23//===----------------------------------------------------------------------===//
24//=== WARNING: Implementation here must contain only TRULY operating system
25//=== independent code.
26//===----------------------------------------------------------------------===//
27
28#if LLVM_ENABLE_THREADS == 0 || \
29 (!defined(_WIN32) && !defined(HAVE_PTHREAD_H))
30
31using namespace llvm;
32
33uint64_t llvm::get_threadid() { return 0; }
34
35uint32_t llvm::get_max_thread_name_length() { return 0; }
36
37void llvm::set_thread_name(const Twine &Name) {}
38
39void llvm::get_thread_name(SmallVectorImpl<char> &Name) { Name.clear(); }
40
41llvm::BitVector llvm::get_thread_affinity_mask() { return {}; }
42
43unsigned 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
49int llvm::get_physical_cores() { return -1; }
50
51#else
52
53static int computeHostNumHardwareThreads();
54
55// Include the platform-specific parts of this class.
56#ifdef LLVM_ON_UNIX
57#include "Unix/Threading.inc"
58#endif
59#ifdef _WIN32
60#include "Windows/Threading.inc"
61#endif
62
63using namespace llvm;
64
65unsigned llvm::ThreadPoolStrategy::compute_thread_count() const {
66 if (UseJobserver)
67 if (auto JS = JobserverClient::getInstance())
68 return JS->getNumJobs();
69
70 int MaxThreadCount =
71 UseHyperThreads ? computeHostNumHardwareThreads() : get_physical_cores();
72 if (MaxThreadCount <= 0)
73 MaxThreadCount = 1;
74 if (ThreadsRequested == 0)
75 return MaxThreadCount;
76 if (!Limit)
77 return ThreadsRequested;
78 return std::min(a: (unsigned)MaxThreadCount, b: ThreadsRequested);
79}
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.
86const std::optional<unsigned> llvm::thread::DefaultStackSize = 8 * 1024 * 1024;
87#elif defined(_AIX)
88 // On AIX, the default pthread stack size limit is ~192k for 64-bit programs.
89 // This limit is easily reached when doing link-time thinLTO. AIX library
90 // developers have used 4MB, so we'll do the same.
91const std::optional<unsigned> llvm::thread::DefaultStackSize = 4 * 1024 * 1024;
92#else
93const std::optional<unsigned> llvm::thread::DefaultStackSize;
94#endif
95
96
97#endif
98
99std::optional<ThreadPoolStrategy>
100llvm::get_threadpool_strategy(StringRef Num, ThreadPoolStrategy Default) {
101 if (Num == "all")
102 return llvm::hardware_concurrency();
103 if (Num.empty())
104 return Default;
105 unsigned V;
106 if (Num.getAsInteger(Radix: 10, Result&: V))
107 return std::nullopt; // malformed 'Num' value
108 if (V == 0)
109 return Default;
110
111 // Do not take the Default into account. This effectively disables
112 // heavyweight_hardware_concurrency() if the user asks for any number of
113 // threads on the cmd-line.
114 ThreadPoolStrategy S = llvm::hardware_concurrency();
115 S.ThreadsRequested = V;
116 return S;
117}
118