74 lines · cpp
1//===-- GPU implementation of the nanosleep function ----------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9#include "src/time/nanosleep.h"10 11#include "src/__support/common.h"12#include "src/__support/macros/config.h"13#include "src/__support/time/gpu/time_utils.h"14 15namespace LIBC_NAMESPACE_DECL {16 17LLVM_LIBC_FUNCTION(int, nanosleep,18 (const struct timespec *req, struct timespec *rem)) {19 if (!GPU_CLOCKS_PER_SEC || !req)20 return -1;21 22 uint64_t nsecs = req->tv_nsec + req->tv_sec * TICKS_PER_SEC;23 uint64_t tick_rate = TICKS_PER_SEC / GPU_CLOCKS_PER_SEC;24 25 uint64_t start = gpu::fixed_frequency_clock();26#if defined(LIBC_TARGET_ARCH_IS_NVPTX)27 uint64_t end = start + (nsecs + tick_rate - 1) / tick_rate;28 uint64_t cur = gpu::fixed_frequency_clock();29 // The NVPTX architecture supports sleeping and guaruntees the actual time30 // slept will be somewhere between zero and twice the requested amount. Here31 // we will sleep again if we undershot the time.32 while (cur < end) {33 if (__nvvm_reflect("__CUDA_ARCH") >= 700)34 LIBC_INLINE_ASM("nanosleep.u32 %0;" ::"r"(nsecs));35 cur = gpu::fixed_frequency_clock();36 nsecs -= nsecs > cur - start ? cur - start : 0;37 }38#elif defined(LIBC_TARGET_ARCH_IS_AMDGPU)39 uint64_t end = start + (nsecs + tick_rate - 1) / tick_rate;40 uint64_t cur = gpu::fixed_frequency_clock();41 // The AMDGPU architecture does not provide a sleep implementation with a42 // known delay so we simply repeatedly sleep with a large value of ~960 clock43 // cycles and check until we've passed the time using the known frequency.44 __builtin_amdgcn_s_sleep(2);45 while (cur < end) {46 __builtin_amdgcn_s_sleep(15);47 cur = gpu::fixed_frequency_clock();48 }49#else50 // Sleeping is not supported.51 if (rem) {52 rem->tv_sec = req->tv_sec;53 rem->tv_nsec = req->tv_nsec;54 }55 return -1;56#endif57 uint64_t stop = gpu::fixed_frequency_clock();58 59 // Check to make sure we slept for at least the desired duration and set the60 // remaining time if not.61 uint64_t elapsed = (stop - start) * tick_rate;62 if (elapsed < nsecs) {63 if (rem) {64 rem->tv_sec = (nsecs - elapsed) / TICKS_PER_SEC;65 rem->tv_nsec = (nsecs - elapsed) % TICKS_PER_SEC;66 }67 return -1;68 }69 70 return 0;71}72 73} // namespace LIBC_NAMESPACE_DECL74