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//===------- state-queuei.h - OpenMP GPU State Queue ------------- CUDA -*-===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file contains the implementation of a queue to hand out OpenMP state
// objects to teams of one or more kernels.
//
// Reference:
// Thomas R.W. Scogland and Wu-chun Feng. 2015.
// Design and Evaluation of Scalable Concurrent Queues for Many-Core
// Architectures. International Conference on Performance Engineering.
//
//===----------------------------------------------------------------------===//
#include "state-queue.h"
#include "common/target_atomic.h"
template <typename ElementType, uint32_t SIZE>
INLINE uint32_t omptarget_nvptx_Queue<ElementType, SIZE>::ENQUEUE_TICKET() {
return __kmpc_atomic_add((unsigned int *)&tail, 1u);
}
template <typename ElementType, uint32_t SIZE>
INLINE uint32_t omptarget_nvptx_Queue<ElementType, SIZE>::DEQUEUE_TICKET() {
return __kmpc_atomic_add((unsigned int *)&head, 1u);
}
template <typename ElementType, uint32_t SIZE>
INLINE uint32_t
omptarget_nvptx_Queue<ElementType, SIZE>::ID(uint32_t ticket) {
return (ticket / SIZE) * 2;
}
template <typename ElementType, uint32_t SIZE>
INLINE bool omptarget_nvptx_Queue<ElementType, SIZE>::IsServing(uint32_t slot,
uint32_t id) {
return __kmpc_atomic_add((unsigned int *)&ids[slot], 0u) == id;
}
template <typename ElementType, uint32_t SIZE>
INLINE void
omptarget_nvptx_Queue<ElementType, SIZE>::PushElement(uint32_t slot,
ElementType *element) {
__kmpc_atomic_exchange((unsigned long long *)&elementQueue[slot],
(unsigned long long)element);
}
template <typename ElementType, uint32_t SIZE>
INLINE ElementType *
omptarget_nvptx_Queue<ElementType, SIZE>::PopElement(uint32_t slot) {
return (ElementType *)__kmpc_atomic_add(
(unsigned long long *)&elementQueue[slot], (unsigned long long)0);
}
template <typename ElementType, uint32_t SIZE>
INLINE void omptarget_nvptx_Queue<ElementType, SIZE>::DoneServing(uint32_t slot,
uint32_t id) {
__kmpc_atomic_exchange((unsigned int *)&ids[slot], (id + 1) % MAX_ID);
}
template <typename ElementType, uint32_t SIZE>
INLINE void
omptarget_nvptx_Queue<ElementType, SIZE>::Enqueue(ElementType *element) {
uint32_t ticket = ENQUEUE_TICKET();
uint32_t slot = ticket % SIZE;
uint32_t id = ID(ticket) + 1;
while (!IsServing(slot, id))
;
PushElement(slot, element);
DoneServing(slot, id);
}
template <typename ElementType, uint32_t SIZE>
INLINE ElementType *omptarget_nvptx_Queue<ElementType, SIZE>::Dequeue() {
uint32_t ticket = DEQUEUE_TICKET();
uint32_t slot = ticket % SIZE;
uint32_t id = ID(ticket);
while (!IsServing(slot, id))
;
ElementType *element = PopElement(slot);
// This is to populate the queue because of the lack of GPU constructors.
if (element == 0)
element = &elements[slot];
DoneServing(slot, id);
return element;
}
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