Mark de Wever cbaa3597aa Reland "[CMake] Bumps minimum version to 3.20.0.
This reverts commit d763c6e5e2d0a6b34097aa7dabca31e9aff9b0b6.

Adds the patch by @hans from
https://github.com/llvm/llvm-project/issues/62719
This patch fixes the Windows build.

d763c6e5e2d0a6b34097aa7dabca31e9aff9b0b6 reverted the reviews

D144509 [CMake] Bumps minimum version to 3.20.0.

This partly undoes D137724.

This change has been discussed on discourse
https://discourse.llvm.org/t/rfc-upgrading-llvms-minimum-required-cmake-version/66193

Note this does not remove work-arounds for older CMake versions, that
will be done in followup patches.

D150532 [OpenMP] Compile assembly files as ASM, not C

Since CMake 3.20, CMake explicitly passes "-x c" (or equivalent)
when compiling a file which has been set as having the language
C. This behaviour change only takes place if "cmake_minimum_required"
is set to 3.20 or newer, or if the policy CMP0119 is set to new.

Attempting to compile assembly files with "-x c" fails, however
this is workarounded in many cases, as OpenMP overrides this with
"-x assembler-with-cpp", however this is only added for non-Windows
targets.

Thus, after increasing cmake_minimum_required to 3.20, this breaks
compiling the GNU assembly for Windows targets; the GNU assembly is
used for ARM and AArch64 Windows targets when building with Clang.
This patch unbreaks that.

D150688 [cmake] Set CMP0091 to fix Windows builds after the cmake_minimum_required bump

The build uses other mechanism to select the runtime.

Fixes #62719

Reviewed By: #libc, Mordante

Differential Revision: https://reviews.llvm.org/D151344
2023-05-27 12:51:21 +02:00
..

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 <src-dir>
    make
    $BROWSER <build-dir>/projects/openmp/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`.