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bc37be1855
This is stricter than the default "ieee", and should probably be the default. This patch leaves the default alone. I can change this in a future patch. There are non-reversible transforms I would like to perform which are legal under IEEE denormal handling, but illegal with flushing zero behavior. Namely, conversions between llvm.is.fpclass and fcmp with zeroes. Under "ieee" handling, it is legal to translate between llvm.is.fpclass(x, fcZero) and fcmp x, 0. Under "preserve-sign" handling, it is legal to translate between llvm.is.fpclass(x, fcSubnormal|fcZero) and fcmp x, 0. I would like to compile and distribute some math library functions in a mode where it's callable from code with and without denormals enabled, which requires not changing the compares with denormals or zeroes. If an IEEE function transforms an llvm.is.fpclass call into an fcmp 0, it is no longer possible to call the function from code with denormals enabled, or write an optimization to move the function into a denormal flushing mode. For the original function, if x was a denormal, the class would evaluate to false. If the function compiled with denormal handling was converted to or called from a preserve-sign function, the fcmp now evaluates to true. This could also be of use for strictfp handling, where code may be changing the denormal mode. Alternative name could be "unknown". Replaces the old AMDGPU custom inlining logic with more conservative logic which tries to permit inlining for callees with dynamic handling and avoids inlining other mismatched modes.
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