LLVM: lib/Support/Threading.cpp Source File

LLVM 22.0.0git
Threading.cpp
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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
23using namespace llvm;
24
25//===----------------------------------------------------------------------===//
26//=== WARNING: Implementation here must contain only TRULY operating system
27//=== independent code.
28//===----------------------------------------------------------------------===//
29
30#if LLVM_ENABLE_THREADS == 0 || \
31 (!defined(_WIN32) && !defined(HAVE_PTHREAD_H))
32 uint64_t llvm::get_threadid() { return 0; }
33
34 uint32_t llvm::get_max_thread_name_length() { return 0; }
35
36 void llvm::set_thread_name(const Twine &Name) {}
37
38 void llvm::get_thread_name(SmallVectorImpl<char> &Name) { Name.clear(); }
39
40 llvm::BitVector llvm::get_thread_affinity_mask() { return {}; }
41
43 // When threads are disabled, ensure clients will loop at least once.
44 return 1;
45}
46
47// Unknown if threading turned off
48 int llvm::get_physical_cores() { return -1; }
49
50#else
51
52static int computeHostNumHardwareThreads();
53
54unsigned llvm::ThreadPoolStrategy::compute_thread_count() const {
55 if (UseJobserver)
56 if (auto JS = JobserverClient::getInstance())
57 return JS->getNumJobs();
58
59 int MaxThreadCount =
60 UseHyperThreads ? computeHostNumHardwareThreads() : get_physical_cores();
61 if (MaxThreadCount <= 0)
62 MaxThreadCount = 1;
63 if (ThreadsRequested == 0)
64 return MaxThreadCount;
65 if (!Limit)
66 return ThreadsRequested;
67 return std::min((unsigned)MaxThreadCount, ThreadsRequested);
68}
69
70// Include the platform-specific parts of this class.
71#ifdef LLVM_ON_UNIX
72#include "Unix/Threading.inc"
73#endif
74#ifdef _WIN32
75#include "Windows/Threading.inc"
76#endif
77
78// Must be included after Threading.inc to provide definition for llvm::thread
79// because FreeBSD's condvar.h (included by user.h) misuses the "thread"
80// keyword.
81#include "llvm/Support/thread.h"
82
83#if defined(__APPLE__)
84 // Darwin's default stack size for threads except the main one is only 512KB,
85 // which is not enough for some/many normal LLVM compilations. This implements
86 // the same interface as std::thread but requests the same stack size as the
87 // main thread (8MB) before creation.
88const std::optional<unsigned> llvm::thread::DefaultStackSize = 8 * 1024 * 1024;
89#elif defined(_AIX)
90 // On AIX, the default pthread stack size limit is ~192k for 64-bit programs.
91 // This limit is easily reached when doing link-time thinLTO. AIX library
92 // developers have used 4MB, so we'll do the same.
93const std::optional<unsigned> llvm::thread::DefaultStackSize = 4 * 1024 * 1024;
94#else
95const std::optional<unsigned> llvm::thread::DefaultStackSize;
96#endif
97
98
99#endif
100
101std::optional<ThreadPoolStrategy>
103 if (Num == "all")
105 if (Num.empty())
106 return Default;
107 unsigned V;
108 if (Num.getAsInteger(10, V))
109 return std::nullopt; // malformed 'Num' value
110 if (V == 0)
111 return Default;
112
113 // Do not take the Default into account. This effectively disables
114 // heavyweight_hardware_concurrency() if the user asks for any number of
115 // threads on the cmd-line.
117 S.ThreadsRequested = V;
118 return S;
119}
static JobserverClient * getInstance()
Returns the singleton instance of the JobserverClient.
Definition Jobserver.cpp:200
This class consists of common code factored out of the SmallVector class to reduce code duplication b...
Definition SmallVector.h:574
StringRef - Represent a constant reference to a string, i.e.
Definition StringRef.h:55
bool getAsInteger(unsigned Radix, T &Result) const
Parse the current string as an integer of the specified radix.
Definition StringRef.h:472
constexpr bool empty() const
empty - Check if the string is empty.
Definition StringRef.h:143
This tells how a thread pool will be used.
Definition Threading.h:115
unsigned ThreadsRequested
Definition Threading.h:121
LLVM_ABI unsigned compute_thread_count() const
Retrieves the max available threads for the current strategy.
Definition Threading.cpp:42
bool UseJobserver
If true, the thread pool will attempt to coordinate with a GNU Make jobserver, acquiring a job slot b...
Definition Threading.h:149
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition Twine.h:82
This is an optimization pass for GlobalISel generic memory operations.
Definition AddressRanges.h:18
ThreadPoolStrategy hardware_concurrency(unsigned ThreadCount=0)
Returns a default thread strategy where all available hardware resources are to be used,...
Definition Threading.h:190
LLVM_ABI llvm::BitVector get_thread_affinity_mask()
Returns a mask that represents on which hardware thread, core, CPU, NUMA group, the calling thread ca...
Definition Threading.cpp:40
LLVM_ABI uint32_t get_max_thread_name_length()
Get the maximum length of a thread name on this platform.
Definition Threading.cpp:34
LLVM_ABI void set_thread_name(const Twine &Name)
Set the name of the current thread.
Definition Threading.cpp:36
LLVM_ABI void get_thread_name(SmallVectorImpl< char > &Name)
Get the name of the current thread.
Definition Threading.cpp:38
LLVM_ABI int get_physical_cores()
Returns how many physical cores (as opposed to logical cores returned from thread::hardware_concurren...
Definition Threading.cpp:48
LLVM_ABI std::optional< ThreadPoolStrategy > get_threadpool_strategy(StringRef Num, ThreadPoolStrategy Default={})
Build a strategy from a number of threads as a string provided in Num.
Definition Threading.cpp:102
LLVM_ABI uint64_t get_threadid()
Return the current thread id, as used in various OS system calls.
Definition Threading.cpp:32
@ Default
The result values are uniform if and only if all operands are uniform.
Definition Uniformity.h:20
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