Files
clang-p2996/llvm/docs
Serge Pavlov 6862f0fab1 [FPEnv] Intrinsics for access to FP control modes
The change introduces intrinsics 'get_fpmode', 'set_fpmode' and
'reset_fpmode'. They manage all target dynamic floating-point control
modes, which include, for instance, rounding direction, precision,
treatment of denormals and so on. The intrinsics do the same
operations as the C library functions 'fegetmode' and 'fesetmode'. By
default they are lowered to calls to these functions.

Two main use cases are supported by this implementation.

1. Local modification of the control modes. In this case the code
usually has a pattern (in pseudocode):

    saved_modes = get_fpmode()
    set_fpmode(<new_modes>)
    ...
    <do operations under the new modes>
    ...
    set_fpmode(saved_modes)

In the case when it is known that the current FP environment is default,
the code may be shorter:

    set_fpmode(<new_modes>)
    ...
    <do operations under the new modes>
    ...
    reset_fpmode()

Such patterns appear not only in user code but also in implementations
of various FP controlling pragmas. In particular, the implementation of
`#pragma STDC FENV_ROUND` requires similar code if the target does not
support static rounding mode.

2. Portable control of FP modes. Usually FP control modes are set by
writing to some control register. Different targets have different
layout of this register, the way the register is accessed also may be
different. Using set of target-specific definitions for the control
register bits together with these intrinsic functions provides enough
portable way to handle control modes across wide range of hardware.

This change defines only llvm intrinsic function, which implement the
access required for the aforementioned use cases.

Differential Revision: https://reviews.llvm.org/D82525
2023-08-24 15:52:19 +07:00
..
2023-08-18 13:15:38 -04:00
2023-08-13 23:46:44 -07:00
2023-06-28 08:27:41 -07:00
2023-08-14 10:10:10 -07:00

LLVM Documentation
==================

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 -j3 docs-llvm-html
    $BROWSER <build-dir>/docs/html/index.html

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

If you are interested in writing new documentation, you will want to read
`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 -j3 docs-llvm-man
    man -l <build-dir>/docs/man/FileCheck.1

The correspondence between .rst files and man pages is
`docs/CommandGuide/Foo.rst` <-> `<build-dir>/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://llvm.org/docs/CommandGuide/Foo.html`.

Checking links
==============

The reachability of external links in the documentation can be checked by
running:

    cd llvm/docs/
    sphinx-build -b linkcheck . _build/lintcheck/
    # report will be generated in _build/lintcheck/output.txt

Doxygen page Output
==============

Install doxygen <https://www.doxygen.nl/download.html> and dot2tex <https://dot2tex.readthedocs.io/en/latest>.

    cd <build-dir>
    cmake -DLLVM_ENABLE_DOXYGEN=On <llvm-top-src-dir>
    make doxygen-llvm # for LLVM docs
    make doxygen-clang # for clang docs

It will generate html in

    <build-dir>/docs/doxygen/html # for LLVM docs
    <build-dir>/tools/clang/docs/doxygen/html # for clang docs