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
22using 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))
31uint64_t llvm::get_threadid() { return 0; }
32
33uint32_t llvm::get_max_thread_name_length() { return 0; }
34
35void llvm::set_thread_name(const Twine &Name) {}
36
37void llvm::get_thread_name(SmallVectorImpl<char> &Name) { Name.clear(); }
38
39llvm::BitVector llvm::get_thread_affinity_mask() { return {}; }
40
41unsigned 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
47int llvm::get_physical_cores() { return -1; }
48
49#else
50
51static int computeHostNumHardwareThreads();
52
53unsigned 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(a: (unsigned)MaxThreadCount, b: 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.
83const 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.
88const std::optional<unsigned> llvm::thread::DefaultStackSize = 4 * 1024 * 1024;
89#else
90const std::optional<unsigned> llvm::thread::DefaultStackSize;
91#endif
92
93
94#endif
95
96std::optional<ThreadPoolStrategy>
97llvm::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(Radix: 10, Result&: 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