| commit | 8e478e819e1e8a3f2a5d941b80b3d4b686cf860a | [log] [tgz] |
|---|---|---|
| author | agozillon <Andrew.Gozillon@amd.com> | Mon Feb 05 18:45:07 2024 +0100 |
| committer | Copybara-Service <copybara-worker@google.com> | Mon Feb 05 09:47:34 2024 -0800 |
| tree | e91eecefecdc54a39fe0702e17b41de34a0f1e90 | |
| parent | 7ef658a1904d28ddd57f2649f8914cfc0ff0f0d8 [diff] |
[Flang][OpenMP] Initial mapping of Fortran pointers and allocatables for target devices (#71766) This patch seeks to add an initial lowering for pointers and allocatable variables captured by implicit and explicit map in Flang OpenMP for Target operations that take map clauses e.g. Target, Target Update. Target Exit/Enter etc. Currently this is done by treating the type that lowers to a descriptor (allocatable/pointer/assumed shape) as a map of a record type (e.g. a structure) as that's effectively what descriptor types lower to in LLVM-IR and what they're represented as in the Fortran runtime (written in C/C++). The descriptor effectively lowers to a structure containing scalar and array elements that represent various aspects of the underlying data being mapped (lower bound, upper bound, extent being the main ones of interest in most cases) and a pointer to the allocated data. In this current iteration of the mapping we map the structure in it's entirety and then attach the underlying data pointer and map the data to the device, this allows most of the required data to be resident on the device for use. Currently we do not support the addendum (another block of pointer data), but it shouldn't be too difficult to extend this to support it. The MapInfoOp generation for descriptor types is primarily handled in an optimization pass, where it expands BoxType (descriptor types) map captures into two maps, one for the structure (scalar elements) and the other for the pointer data (base address) and links them in a Parent <-> Child relationship. The later lowering processes will then treat them as a conjoined structure with a pointer member map. GitOrigin-RevId: 95fe47ca7e99d999108705640e49075f4c5f39a7
Flang is a ground-up implementation of a Fortran front end written in modern C++. It started off as the f18 project (https://github.com/flang-compiler/f18) with an aim to replace the previous flang project (https://github.com/flang-compiler/flang) and address its various deficiencies. F18 was subsequently accepted into the LLVM project and rechristened as Flang.
Please note that flang is not ready yet for production usage.
Read more about flang in the docs directory. Start with the compiler overview.
To better understand Fortran as a language and the specific grammar accepted by flang, read Fortran For C Programmers and flang's specifications of the Fortran grammar and the OpenMP grammar.
Treatment of language extensions is covered in this document.
To understand the compilers handling of intrinsics, see the discussion of intrinsics.
To understand how a flang program communicates with libraries at runtime, see the discussion of runtime descriptors.
If you're interested in contributing to the compiler, read the style guide and also review how flang uses modern C++ features.
If you are interested in writing new documentation, follow LLVM's Markdown style guide.
Consult the Getting Started with Flang for information on building and running flang.