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//===-- llvm/Support/Threading.cpp- Control multithreading mode --*- C++ -*-==//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file defines helper functions for running LLVM in a multi-threaded
// environment.
//
//===----------------------------------------------------------------------===//
#include "llvm/Support/Threading.h"
#include "llvm/Config/config.h"
#include "llvm/Support/Atomic.h"
#include "llvm/Support/Mutex.h"
#include "llvm/Support/thread.h"
#include <cassert>
using namespace llvm;
bool llvm::llvm_is_multithreaded() {
#if LLVM_ENABLE_THREADS != 0
return true;
#else
return false;
#endif
}
#if LLVM_ENABLE_THREADS != 0 && defined(HAVE_PTHREAD_H)
#include <pthread.h>
struct ThreadInfo {
void (*UserFn)(void *);
void *UserData;
};
static void *ExecuteOnThread_Dispatch(void *Arg) {
ThreadInfo *TI = reinterpret_cast<ThreadInfo*>(Arg);
TI->UserFn(TI->UserData);
return nullptr;
}
void llvm::llvm_execute_on_thread(void (*Fn)(void*), void *UserData,
unsigned RequestedStackSize) {
ThreadInfo Info = { Fn, UserData };
pthread_attr_t Attr;
pthread_t Thread;
// Construct the attributes object.
if (::pthread_attr_init(&Attr) != 0)
return;
// Set the requested stack size, if given.
if (RequestedStackSize != 0) {
if (::pthread_attr_setstacksize(&Attr, RequestedStackSize) != 0)
goto error;
}
// Construct and execute the thread.
if (::pthread_create(&Thread, &Attr, ExecuteOnThread_Dispatch, &Info) != 0)
goto error;
// Wait for the thread and clean up.
::pthread_join(Thread, nullptr);
error:
::pthread_attr_destroy(&Attr);
}
#elif LLVM_ENABLE_THREADS!=0 && defined(LLVM_ON_WIN32)
#include "Windows/WindowsSupport.h"
#include <process.h>
// Windows will at times define MemoryFence.
#ifdef MemoryFence
#undef MemoryFence
#endif
struct ThreadInfo {
void (*func)(void*);
void *param;
};
static unsigned __stdcall ThreadCallback(void *param) {
struct ThreadInfo *info = reinterpret_cast<struct ThreadInfo *>(param);
info->func(info->param);
return 0;
}
void llvm::llvm_execute_on_thread(void (*Fn)(void*), void *UserData,
unsigned RequestedStackSize) {
struct ThreadInfo param = { Fn, UserData };
HANDLE hThread = (HANDLE)::_beginthreadex(NULL,
RequestedStackSize, ThreadCallback,
¶m, 0, NULL);
if (hThread) {
// We actually don't care whether the wait succeeds or fails, in
// the same way we don't care whether the pthread_join call succeeds
// or fails. There's not much we could do if this were to fail. But
// on success, this call will wait until the thread finishes executing
// before returning.
(void)::WaitForSingleObject(hThread, INFINITE);
::CloseHandle(hThread);
}
}
#else
// Support for non-Win32, non-pthread implementation.
void llvm::llvm_execute_on_thread(void (*Fn)(void*), void *UserData,
unsigned RequestedStackSize) {
(void) RequestedStackSize;
Fn(UserData);
}
#endif
void llvm::call_once(once_flag &flag, void (*fptr)(void)) {
#if LLVM_THREADING_USE_STD_CALL_ONCE
std::call_once(flag, fptr);
#else
// For other platforms we use a generic (if brittle) version based on our
// atomics.
sys::cas_flag old_val = sys::CompareAndSwap(&flag, Wait, Uninitialized);
if (old_val == Uninitialized) {
fptr();
sys::MemoryFence();
TsanIgnoreWritesBegin();
TsanHappensBefore(&flag);
flag = Done;
TsanIgnoreWritesEnd();
} else {
// Wait until any thread doing the call has finished.
sys::cas_flag tmp = flag;
sys::MemoryFence();
while (tmp != Done) {
tmp = flag;
sys::MemoryFence();
}
}
TsanHappensAfter(&flag);
#endif
}
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