1 files changed, 72 insertions, 0 deletions
diff --git a/compiler-rt/lib/sanitizer_common/sanitizer_lfstack.h b/compiler-rt/lib/sanitizer_common/sanitizer_lfstack.h
new file mode 100644
index 000000000000..af2ca55ec3f6
--- /dev/null
+++ b/compiler-rt/lib/sanitizer_common/sanitizer_lfstack.h
@@ -0,0 +1,72 @@
+//===-- sanitizer_lfstack.h -=-----------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// Lock-free stack.
+// Uses 32/17 bits as ABA-counter on 32/64-bit platforms.
+// The memory passed to Push() must not be ever munmap'ed.
+// The type T must contain T *next field.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SANITIZER_LFSTACK_H
+#define SANITIZER_LFSTACK_H
+
+#include "sanitizer_internal_defs.h"
+#include "sanitizer_common.h"
+#include "sanitizer_atomic.h"
+
+namespace __sanitizer {
+
+template<typename T>
+struct LFStack {
+  void Clear() {
+    atomic_store(&head_, 0, memory_order_relaxed);
+  }
+
+  bool Empty() const {
+    return (atomic_load(&head_, memory_order_relaxed) & kPtrMask) == 0;
+  }
+
+  void Push(T *p) {
+    u64 cmp = atomic_load(&head_, memory_order_relaxed);
+    for (;;) {
+      u64 cnt = (cmp & kCounterMask) + kCounterInc;
+      u64 xch = (u64)(uptr)p | cnt;
+      p->next = (T*)(uptr)(cmp & kPtrMask);
+      if (atomic_compare_exchange_weak(&head_, &cmp, xch,
+                                       memory_order_release))
+        break;
+    }
+  }
+
+  T *Pop() {
+    u64 cmp = atomic_load(&head_, memory_order_acquire);
+    for (;;) {
+      T *cur = (T*)(uptr)(cmp & kPtrMask);
+      if (!cur)
+        return nullptr;
+      T *nxt = cur->next;
+      u64 cnt = (cmp & kCounterMask);
+      u64 xch = (u64)(uptr)nxt | cnt;
+      if (atomic_compare_exchange_weak(&head_, &cmp, xch,
+                                       memory_order_acquire))
+        return cur;
+    }
+  }
+
+  // private:
+  static const int kCounterBits = FIRST_32_SECOND_64(32, 17);
+  static const u64 kPtrMask = ((u64)-1) >> kCounterBits;
+  static const u64 kCounterMask = ~kPtrMask;
+  static const u64 kCounterInc = kPtrMask + 1;
+
+  atomic_uint64_t head_;
+};
+} // namespace __sanitizer
+
+#endif // SANITIZER_LFSTACK_H