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https://github.com/c64scene-ar/llvm-6502.git
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8744520b53
Summary: This patch adds an llvm_call_once which is a wrapper around std::call_once on platforms where it is available and devoid of bugs. The patch also migrates the ManagedStatic mutex to be allocated using llvm_call_once. These changes are philosophically equivalent to the changes added in r219638, which were reverted due to a hang on Win32 which was the result of a bug in the Windows implementation of std::call_once. Reviewers: aaron.ballman, chapuni, chandlerc, rnk Reviewed By: rnk Subscribers: majnemer, llvm-commits Differential Revision: http://reviews.llvm.org/D5922 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@220932 91177308-0d34-0410-b5e6-96231b3b80d8
98 lines
2.8 KiB
C++
98 lines
2.8 KiB
C++
//===-- ManagedStatic.cpp - Static Global wrapper -------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the ManagedStatic class and llvm_shutdown().
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Support/ManagedStatic.h"
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#include "llvm/Config/config.h"
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#include "llvm/Support/Atomic.h"
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#include "llvm/Support/Mutex.h"
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#include "llvm/Support/MutexGuard.h"
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#include "llvm/Support/Threading.h"
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#include <cassert>
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using namespace llvm;
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static const ManagedStaticBase *StaticList = nullptr;
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static sys::Mutex *ManagedStaticMutex = nullptr;
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LLVM_DEFINE_ONCE_FLAG(mutex_init_flag);
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static void initializeMutex() {
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ManagedStaticMutex = new sys::Mutex();
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}
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static sys::Mutex* getManagedStaticMutex() {
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// We need to use a function local static here, since this can get called
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// during a static constructor and we need to guarantee that it's initialized
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// correctly.
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call_once(mutex_init_flag, initializeMutex);
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return ManagedStaticMutex;
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}
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void ManagedStaticBase::RegisterManagedStatic(void *(*Creator)(),
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void (*Deleter)(void*)) const {
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assert(Creator);
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if (llvm_is_multithreaded()) {
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MutexGuard Lock(*getManagedStaticMutex());
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if (!Ptr) {
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void* tmp = Creator();
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TsanHappensBefore(this);
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sys::MemoryFence();
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// This write is racy against the first read in the ManagedStatic
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// accessors. The race is benign because it does a second read after a
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// memory fence, at which point it isn't possible to get a partial value.
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TsanIgnoreWritesBegin();
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Ptr = tmp;
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TsanIgnoreWritesEnd();
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DeleterFn = Deleter;
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// Add to list of managed statics.
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Next = StaticList;
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StaticList = this;
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}
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} else {
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assert(!Ptr && !DeleterFn && !Next &&
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"Partially initialized ManagedStatic!?");
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Ptr = Creator();
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DeleterFn = Deleter;
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// Add to list of managed statics.
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Next = StaticList;
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StaticList = this;
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}
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}
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void ManagedStaticBase::destroy() const {
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assert(DeleterFn && "ManagedStatic not initialized correctly!");
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assert(StaticList == this &&
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"Not destroyed in reverse order of construction?");
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// Unlink from list.
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StaticList = Next;
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Next = nullptr;
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// Destroy memory.
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DeleterFn(Ptr);
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// Cleanup.
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Ptr = nullptr;
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DeleterFn = nullptr;
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}
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/// llvm_shutdown - Deallocate and destroy all ManagedStatic variables.
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void llvm::llvm_shutdown() {
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MutexGuard Lock(*getManagedStaticMutex());
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while (StaticList)
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StaticList->destroy();
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}
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