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Make ManagedStatic threadsafe by using atomic operations.

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git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@71796 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Owen Anderson 2009-05-14 21:26:50 +00:00
parent 9693813080
commit 87ba22dc67
1 changed files with 36 additions and 4 deletions
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40
include/llvm/Support/ManagedStatic.h
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@ -14,6 +14,8 @@
#ifndef LLVM_SUPPORT_MANAGED_STATIC_H
#define LLVM_SUPPORT_MANAGED_STATIC_H
#include "llvm/System/Atomic.h"
namespace llvm {
/// object_deleter - Helper method for ManagedStatic.
@ -26,6 +28,8 @@ void object_deleter(void *Ptr) {
/// ManagedStaticBase - Common base class for ManagedStatic instances.
class ManagedStaticBase {
protected:
sys::cas_flag InitFlag;
// This should only be used as a static variable, which guarantees that this
// will be zero initialized.
mutable void *Ptr;
@ -51,19 +55,47 @@ public:
// Accessors.
C &operator*() {
if (!Ptr) LazyInit();
sys::cas_flag OldFlag = sys::CompareAndSwap(&InitFlag, 1, 0);
if (OldFlag == 0) {
LazyInit();
sys::MemoryFence();
InitFlag = 2;
} else if (OldFlag == 1)
while (OldFlag == 1) ;
return *static_cast<C*>(Ptr);
}
C *operator->() {
if (!Ptr) LazyInit();
sys::cas_flag OldFlag = sys::CompareAndSwap(&InitFlag, 1, 0);
if (OldFlag == 0) {
LazyInit();
sys::MemoryFence();
InitFlag = 2;
} else if (OldFlag == 1)
while (OldFlag == 1) ;
return static_cast<C*>(Ptr);
}
const C &operator*() const {
if (!Ptr) LazyInit();
sys::cas_flag OldFlag = sys::CompareAndSwap(&InitFlag, 1, 0);
if (OldFlag == 0) {
LazyInit();
sys::MemoryFence();
InitFlag = 2;
} else if (OldFlag == 1)
while (OldFlag == 1) ;
return *static_cast<C*>(Ptr);
}
const C *operator->() const {
if (!Ptr) LazyInit();
sys::cas_flag OldFlag = sys::CompareAndSwap(&InitFlag, 1, 0);
if (OldFlag == 0) {
LazyInit();
sys::MemoryFence();
InitFlag = 2;
} else if (OldFlag == 1)
while (OldFlag == 1) ;
return static_cast<C*>(Ptr);
}