Limitations and unsupported APIs

2026-10-07

2 min read time

Applies to Linux and Windows

Platform limitations

libhipcxx has the following platform limitations.

• libhipcxx does not support the CUDA backend or NVIDIA hardware.

• cuda::std::chrono::system_clock::now() does not return a UNIX timestamp. The host system clock and the device system clock are not synchronized and may run at different clock rates.

Important

Some APIs from libcudacxx may be missing or may not achieve the same performance on AMD GPUs due to fundamental hardware architecture differences between AMD and NVIDIA GPUs. APIs that rely on NVIDIA-specific hardware features (such as PTX instructions, tensor cores, or specific compute capabilities) may be unavailable, provide degraded functionality, or fall back to software implementations with reduced performance.

Unsupported APIs

The following APIs from libcudacxx are not supported in libhipcxx:

Group	API	Description
Synchronization Library	<cuda/std/latch>	Single-phase asynchronous thread-coordination mechanism.
Synchronization Library	<cuda/std/barrier>	Multi-phase asynchronous thread-coordination mechanism.
Synchronization Library	<cuda/std/semaphore>	Primitives for constraining concurrent access.
Extended Synchronization Library	<cuda/latch>	System-wide cuda::std::latch single-phase asynchronous thread coordination mechanism.
Extended Synchronization Library	<cuda/barrier>	System-wide cuda::std::barrier multi-phase asynchronous thread coordination mechanism.
Extended Synchronization Library	<cuda/semaphore>	System-wide primitives for constraining concurrent access.
Extended Synchronization Library	<cuda/pipeline>	Coordination mechanisms to sequence asynchronous operations.
Extended Memory Access Properties Library	<cuda/annotated_ptr>	Memory access properties for pointers.
Extended Memory Access Properties Library	<cuda/discard_memory>	Discards modified cache lines without writing them back. The header is available, but cuda::discard_memory has no effect on AMD GPUs.
Extended Warp Library	<cuda/warp>	Warp shuffle functions. The header is available, but cuda::device::warp_shuffle_* are only compiled for NVIDIA PTX targets.
Extended Work Stealing Library	<cuda/work_stealing>	cuda::for_each_canceled_block for cancelling and stealing thread blocks. On AMD GPUs it invokes the function once for the current block and does not cancel other blocks.
Device-Level APIs	cuda::device::*	Hardware-specific device functions including warp shuffles, barrier operations with transaction counts, and async memory operations. These require NVIDIA PTX instructions and SM-specific hardware features not available on AMD GPUs.
PTX API	<cuda/ptx>	The cuda::ptx namespace contains functions that map to NVIDIA PTX instructions.