LLVM  14.0.0git
Threading.cpp
Go to the documentation of this file.
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/ADT/Optional.h"
16 #include "llvm/Config/config.h"
17 #include "llvm/Support/Host.h"
18 
19 #include <cassert>
20 #include <errno.h>
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 
32 #if LLVM_ENABLE_THREADS != 0
33  return true;
34 #else
35  return false;
36 #endif
37 }
38 
39 #if LLVM_ENABLE_THREADS == 0 || \
40  (!defined(_WIN32) && !defined(HAVE_PTHREAD_H))
41 uint64_t llvm::get_threadid() { return 0; }
42 
44 
45 void llvm::set_thread_name(const Twine &Name) {}
46 
48 
50 
52  // When threads are disabled, ensure clients will loop at least once.
53  return 1;
54 }
55 
56 #else
57 
59 
61  int MaxThreadCount = UseHyperThreads ? computeHostNumHardwareThreads()
63  if (MaxThreadCount <= 0)
64  MaxThreadCount = 1;
65  if (ThreadsRequested == 0)
66  return MaxThreadCount;
67  if (!Limit)
68  return ThreadsRequested;
69  return std::min((unsigned)MaxThreadCount, ThreadsRequested);
70 }
71 
72 // Include the platform-specific parts of this class.
73 #ifdef LLVM_ON_UNIX
74 #include "Unix/Threading.inc"
75 #endif
76 #ifdef _WIN32
77 #include "Windows/Threading.inc"
78 #endif
79 
80 // Must be included after Threading.inc to provide definition for llvm::thread
81 // because FreeBSD's condvar.h (included by user.h) misuses the "thread"
82 // keyword.
83 #include "llvm/Support/thread.h"
84 
85 #if defined(__APPLE__)
86  // Darwin's default stack size for threads except the main one is only 512KB,
87  // which is not enough for some/many normal LLVM compilations. This implements
88  // the same interface as std::thread but requests the same stack size as the
89  // main thread (8MB) before creation.
91 #else
93 #endif
94 
95 
96 #endif
97 
100  if (Num == "all")
102  if (Num.empty())
103  return Default;
104  unsigned V;
105  if (Num.getAsInteger(10, V))
106  return None; // malformed 'Num' value
107  if (V == 0)
108  return Default;
109 
110  // Do not take the Default into account. This effectively disables
111  // heavyweight_hardware_concurrency() if the user asks for any number of
112  // threads on the cmd-line.
114  S.ThreadsRequested = V;
115  return S;
116 }
Threading.inc
llvm::ThreadPoolStrategy::compute_thread_count
unsigned compute_thread_count() const
Retrieves the max available threads for the current strategy.
Definition: Threading.cpp:60
llvm::hardware_concurrency
ThreadPoolStrategy hardware_concurrency(unsigned ThreadCount=0)
Returns a default thread strategy where all available hardware resources are to be used,...
Definition: Threading.h:188
llvm
---------------------— PointerInfo ------------------------------------—
Definition: AllocatorList.h:23
llvm::StringRef::empty
LLVM_NODISCARD bool empty() const
empty - Check if the string is empty.
Definition: StringRef.h:153
Optional.h
Host.h
llvm::ThreadPoolStrategy
This tells how a thread pool will be used.
Definition: Threading.h:119
llvm::Optional< unsigned >
computeHostNumHardwareThreads
int computeHostNumHardwareThreads()
llvm::get_threadid
uint64_t get_threadid()
Return the current thread id, as used in various OS system calls.
llvm::get_max_thread_name_length
uint32_t get_max_thread_name_length()
Get the maximum length of a thread name on this platform.
llvm::get_thread_name
void get_thread_name(SmallVectorImpl< char > &Name)
Get the name of the current thread.
llvm::BitVector
Definition: BitVector.h:74
llvm::StringRef::getAsInteger
std::enable_if_t< std::numeric_limits< T >::is_signed, bool > getAsInteger(unsigned Radix, T &Result) const
Parse the current string as an integer of the specified radix.
Definition: StringRef.h:510
llvm::None
const NoneType None
Definition: None.h:23
Threading.h
uint64_t
llvm::get_threadpool_strategy
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:99
Threading.inc
llvm::sys::getHostNumPhysicalCores
int getHostNumPhysicalCores()
Get the number of physical cores (as opposed to logical cores returned from thread::hardware_concurre...
Definition: Host.cpp:1494
llvm::min
Expected< ExpressionValue > min(const ExpressionValue &Lhs, const ExpressionValue &Rhs)
Definition: FileCheck.cpp:357
llvm::StringRef
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:58
uint32_t
S
add sub stmia L5 ldr r0 bl L_printf $stub Instead of a and a wouldn t it be better to do three moves *Return an aggregate type is even return S
Definition: README.txt:210
llvm::thread::DefaultStackSize
static const llvm::Optional< unsigned > DefaultStackSize
Definition: thread.h:75
llvm::Twine
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:83
llvm::GraphProgram::Name
Name
Definition: GraphWriter.h:52
llvm::set_thread_name
void set_thread_name(const Twine &Name)
Set the name of the current thread.
llvm::llvm_is_multithreaded
bool llvm_is_multithreaded()
Returns true if LLVM is compiled with support for multi-threading, and false otherwise.
Definition: Threading.cpp:31
llvm::get_thread_affinity_mask
llvm::BitVector get_thread_affinity_mask()
Returns a mask that represents on which hardware thread, core, CPU, NUMA group, the calling thread ca...
llvm::SmallVectorImpl< char >
thread.h