projects / thirdparty / gcc.git / blame
| Commit | Line | Data |
|---|---|---|
| c63539ff ML |
1 | .. |
| 2 | Copyright 1988-2022 Free Software Foundation, Inc. | |
| 3 | This is part of the GCC manual. | |
| 4 | For copying conditions, see the copyright.rst file. | |
| 5 | ||
| 6 | .. _nvptx: | |
| 7 | ||
| 8 | nvptx | |
| 9 | ***** | |
| 10 | ||
| 11 | On the hardware side, there is the hierarchy (fine to coarse): | |
| 12 | ||
| 13 | * thread | |
| 14 | ||
| 15 | * warp | |
| 16 | ||
| 17 | * thread block | |
| 18 | ||
| 19 | * streaming multiprocessor | |
| 20 | ||
| 21 | All OpenMP and OpenACC levels are used, i.e. | |
| 22 | ||
| 23 | * OpenMP's simd and OpenACC's vector map to threads | |
| 24 | ||
| 25 | * OpenMP's threads ('parallel') and OpenACC's workers map to warps | |
| 26 | ||
| 27 | * OpenMP's teams and OpenACC's gang use a threadpool with the | |
| 28 | size of the number of teams or gangs, respectively. | |
| 29 | ||
| 30 | The used sizes are | |
| 31 | ||
| 32 | * The ``warp_size`` is always 32 | |
| 33 | ||
| 34 | * CUDA kernel launched: ``dim={#teams,1,1}, blocks={#threads,warp_size,1}``. | |
| 35 | ||
| 36 | Additional information can be obtained by setting the environment variable to | |
| 37 | ``GOMP_DEBUG=1`` (very verbose; grep for ``kernel.*launch`` for launch | |
| 38 | parameters). | |
| 39 | ||
| 40 | GCC generates generic PTX ISA code, which is just-in-time compiled by CUDA, | |
| 41 | which caches the JIT in the user's directory (see CUDA documentation; can be | |
| 42 | tuned by the environment variables ``CUDA_CACHE_{DISABLE,MAXSIZE,PATH}``. | |
| 43 | ||
| 44 | Note: While PTX ISA is generic, the ``-mptx=`` and ``-march=`` commandline | |
| 45 | options still affect the used PTX ISA code and, thus, the requirments on | |
| 46 | CUDA version and hardware. | |
| 47 | ||
| 48 | The implementation remark: | |
| 49 | ||
| 50 | * I/O within OpenMP target regions and OpenACC parallel/kernels is supported | |
| 51 | using the C library ``printf`` functions. Note that the Fortran | |
| 52 | ``print`` / ``write`` statements are not supported, yet. | |
| 53 | ||
| 54 | * Compilation OpenMP code that contains ``requires reverse_offload`` | |
| 55 | requires at least ``-march=sm_35``, compiling for ``-march=sm_30`` | |
| 56 | is not supported. | |
| 57 | ||
| 58 | .. - | |
| 59 | The libgomp ABI | |
| 3ed1b4ce | 60 | - |