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This is similar to the existing alloca and program address spaces (D37052) and should be used when creating/accessing global variables. We need this in our CHERI fork of LLVM to place all globals in address space 200. This ensures that values are accessed using CHERI load/store instructions instead of the normal MIPS/RISC-V ones. The problem this is trying to fix is that most of the time the type of globals is created using a simple PointerType::getUnqual() (or ::get() with the default address-space value of 0). This does not work for us and we get assertion/compilation/instruction selection failures whenever a new call is added that uses the default value of zero. In our fork we have removed the default parameter value of zero for most address space arguments and use DL.getProgramAddressSpace() or DL.getGlobalsAddressSpace() whenever possible. If this change is accepted, I will upstream follow-up patches to use DL.getGlobalsAddressSpace() instead of relying on the default value of 0 for PointerType::get(), etc. This patch and the follow-up changes will not have any functional changes for existing backends with the default globals address space of zero. A follow-up commit will change the default globals address space for AMDGPU to 1. Reviewed By: dylanmckay Differential Revision: https://reviews.llvm.org/D70947
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 docs/
make -f Makefile.sphinx linkcheck
Doxygen page Output
==============
Install doxygen <http://www.stack.nl/~dimitri/doxygen/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