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Basic: use std::atomic instead of home-grown synch #3006

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Merged
merged 1 commit into from
Jun 20, 2016
Merged

Basic: use std::atomic instead of home-grown synch #3006

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16 changes: 9 additions & 7 deletions include/swift/Basic/ThreadSafeRefCounted.h
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,7 @@
#ifndef SWIFT_BASIC_THREADSAFEREFCOUNTED_H
#define SWIFT_BASIC_THREADSAFEREFCOUNTED_H

#include "llvm/Support/Atomic.h"
#include <atomic>
#include <cassert>

namespace swift {
Expand All @@ -28,18 +28,19 @@ namespace swift {
/// FIXME: This should eventually move to llvm.
template <class Derived>
class ThreadSafeRefCountedBase {
mutable llvm::sys::cas_flag ref_cnt;
mutable std::atomic<unsigned> ref_cnt;

protected:
ThreadSafeRefCountedBase() : ref_cnt(0) {}

public:
void Retain() const {
llvm::sys::AtomicIncrement(&ref_cnt);
ref_cnt.fetch_add(1, std::memory_order_acq_rel);
}

void Release() const {
int refCount = static_cast<int>(llvm::sys::AtomicDecrement(&ref_cnt));
int refCount =
static_cast<int>(ref_cnt.fetch_sub(1, std::memory_order_acq_rel));
assert(refCount >= 0 && "Reference count was already zero.");
if (refCount == 0) delete static_cast<const Derived*>(this);
}
Expand All @@ -52,7 +53,7 @@ class ThreadSafeRefCountedBase {
/// already have virtual methods to enforce dynamic allocation via 'new'.
/// FIXME: This should eventually move to llvm.
class ThreadSafeRefCountedBaseVPTR {
mutable llvm::sys::cas_flag ref_cnt;
mutable std::atomic<unsigned> ref_cnt;
virtual void anchor();

protected:
Expand All @@ -61,11 +62,12 @@ class ThreadSafeRefCountedBaseVPTR {

public:
void Retain() const {
llvm::sys::AtomicIncrement(&ref_cnt);
ref_cnt.fetch_add(1, std::memory_order_acq_rel);
}

void Release() const {
int refCount = static_cast<int>(llvm::sys::AtomicDecrement(&ref_cnt));
int refCount =
static_cast<int>(ref_cnt.fetch_sub(1, std::memory_order_acq_rel));
assert(refCount >= 0 && "Reference count was already zero.");
if (refCount == 0) delete this;
}
Expand Down