Abhinav Gaba c62cd2877c
[OpenMP][Offload] Add LIBOMPTARGET_TREAT_ATTACH_AUTO_AS_ALWAYS to treat attach(auto) as attach(always). (#172382)
This is needed as a way to support older code that was expecting
unconditional attachment to happen for cases like:

```c
  int *p;
  int x;

  #pragma omp targret enter data map(p) // (A)
  #pragma omp target enter data map(x)  // (B)
  p = &x;

  // By default, this does NOT attach p and x
  #pragma omp target enter data map(p[0:0]) // (C)
```

When the environment variable is set, such maps, where both the pointer
and the pointee already have corresponding copies on the device, but are
not attached to one another, will be attached as-if OpenMP 6.1 TR14's
`attach(always)` map-type-modifier was specified on `(C)`.
2025-12-16 15:55:27 -08:00
..

OpenMP LLVM Documentation
==================

OpenMP LLVM's documentation is written in reStructuredText, a lightweight
plaintext markup language (file extension `.rst`). While the
reStructuredText documentation should be quite readable in source form, it
is mostly meant to be processed by the Sphinx documentation generation
system to create HTML pages which are hosted on <https://llvm.org/docs/> and
updated after every commit. Manpage output is also supported, see below.

If you instead would like to generate and view the HTML locally, install
Sphinx <http://sphinx-doc.org/> and then do:

    cd <build-dir>
    cmake -DLLVM_ENABLE_SPHINX=true -DSPHINX_OUTPUT_HTML=true -DCMAKE_MODULE_PATH=/path/to/llvm/cmake/modules <src-dir>
    make docs-openmp-html
    $BROWSER <build-dir>/docs/html/index.html

The mapping between reStructuredText files and generated documentation is
`docs/Foo.rst` <-> `<build-dir>/projects/openmp/docs//html/Foo.html` <->
`https://openmp.llvm.org/docs/Foo.html`.

If you are interested in writing new documentation, you will want to read
`llvm/docs/SphinxQuickstartTemplate.rst` which will get you writing
documentation very fast and includes examples of the most important
reStructuredText markup syntax.

Manpage Output
===============

Building the manpages is similar to building the HTML documentation. The
primary difference is to use the `man` makefile target, instead of the
default (which is `html`). Sphinx then produces the man pages in the
directory `<build-dir>/docs/man/`.

    cd <build-dir>
    cmake -DLLVM_ENABLE_SPHINX=true -DSPHINX_OUTPUT_MAN=true <src-dir>
    make
    man -l >build-dir>/docs/man/FileCheck.1

The correspondence between .rst files and man pages is
`docs/CommandGuide/Foo.rst` <-> `<build-dir>/projects/openmp/docs//man/Foo.1`.
These .rst files are also included during HTML generation so they are also
viewable online (as noted above) at e.g.
`https://openmp.llvm.org/docs/CommandGuide/Foo.html`.