llvm/docs
James Y Knight 36720c565c Add __atomic_* lowering to AtomicExpandPass.
AtomicExpandPass can now lower atomic load, atomic store, atomicrmw, and
cmpxchg instructions to __atomic_* library calls, when the target
doesn't support atomics of a given size.

This is the first step towards moving all atomic lowering from clang
into llvm. When all is done, the behavior of __sync_* builtins,
__atomic_* builtins, and C11 atomics will be unified.

Previously LLVM would pass everything through to the ISelLowering
code. There, unsupported atomic instructions would turn into __sync_*
library calls. Because of that behavior, Clang currently avoids emitting
llvm IR atomic instructions when this would happen, and emits __atomic_*
library functions itself, in the frontend.

This change makes LLVM able to emit __atomic_* libcalls, and thus will
eventually allow clang to depend on LLVM to do the right thing.

It is advantageous to do the new lowering to atomic libcalls in
AtomicExpandPass, before ISel time, because it's important that all
atomic operations for a given size either lower to __atomic_*
libcalls (which may use locks), or native instructions which won't. No
mixing and matching.

At the moment, this code is enabled only for SPARC, as a
demonstration. The next commit will expand support to all of the other
targets.

Differential Revision: http://reviews.llvm.org/D18200

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@266002 91177308-0d34-0410-b5e6-96231b3b80d8
2016-04-11 22:22:33 +00:00
..
_ocamldoc
_static
_templates
_themes/llvm-theme
CommandGuide Document standard substitutions defined by lit. 2016-04-04 17:14:45 +00:00
Frontend
HistoricalNotes
TableGen
tutorial [Kaleidoscope] Rename Error -> LogError in Chapters 2-5. 2016-03-25 17:41:26 +00:00
AdvancedBuilds.rst Fixing autocorrect changing cmake->make 2016-03-18 22:11:51 +00:00
AliasAnalysis.rst fix typo 2016-01-13 16:46:41 +00:00
AMDGPUUsage.rst AMDGPU: Document address space mapping 2016-04-06 01:29:19 +00:00
ARM-BE-bitcastfail.png
ARM-BE-bitcastsuccess.png
ARM-BE-ld1.png
ARM-BE-ldr.png
Atomics.rst Add __atomic_* lowering to AtomicExpandPass. 2016-04-11 22:22:33 +00:00
BigEndianNEON.rst
BitCodeFormat.rst Swift Calling Convention: add swiftcc. 2016-04-05 22:41:47 +00:00
BitSets.rst docs: Document how bitsets may be used to encode type information. 2016-02-03 02:01:08 +00:00
BlockFrequencyTerminology.rst
BranchWeightMetadata.rst
Bugpoint.rst
CMake.rst [Docs] Updating CMake docs to include LLVM_OPTIMIZED_TABLEGEN 2016-03-24 18:46:43 +00:00
CMakeLists.txt
CodeGenerator.rst [docs] "Straightforward" is one word. 2016-03-14 20:18:51 +00:00
CodingStandards.rst
CommandLine.rst
CompileCudaWithLLVM.rst [docs] Add gpucc publication and tutorial. 2016-03-30 05:05:40 +00:00
CompilerWriterInfo.rst ARM: improve documentation slightly. 2016-02-09 23:55:48 +00:00
conf.py Update version to 3.9. 2016-01-13 17:32:32 +00:00
CoverageMappingFormat.rst [docs] Corrections w.r.t V2 of the coverage mapping format 2016-03-28 22:16:01 +00:00
DebuggingJITedCode.rst
DeveloperPolicy.rst Fix a spurious if. 2015-12-11 00:51:59 +00:00
doxygen-mainpage.dox [docs] Updated docs to work with Doxygen 1.8.11 2016-03-06 03:50:08 +00:00
doxygen.cfg.in [docs] Updated docs to work with Doxygen 1.8.11 2016-03-06 03:50:08 +00:00
Dummy.html
ExceptionHandling.rst [WinEH] Disallow cyclic unwinds 2016-01-10 04:31:05 +00:00
ExtendedIntegerResults.txt
ExtendingLLVM.rst
Extensions.rst
FAQ.rst FAQ: Remove the entire Build Problems section 2016-03-23 06:54:42 +00:00
FaultMaps.rst
GarbageCollection.rst
gcc-loops.png
GetElementPtr.rst
GettingStarted.rst docs: Fix footnote after r260042. 2016-03-28 21:24:46 +00:00
GettingStartedVS.rst Clarifying some of the requirements for building with Visual Studio on Windows. Namely, we require the latest Update to be installed (for sanity purposes), and we require CMake 2.8.12.2 for building LLVM with Visual Studio. 2016-03-29 20:23:55 +00:00
GoldPlugin.rst [docs] Remove references to autotools build. 2016-01-30 01:10:15 +00:00
HowToAddABuilder.rst
HowToBuildOnARM.rst
HowToCrossCompileLLVM.rst
HowToReleaseLLVM.rst Fix some typos in the llvm doc 2016-02-14 20:16:22 +00:00
HowToSetUpLLVMStyleRTTI.rst
HowToSubmitABug.rst
HowToUseAttributes.rst
HowToUseInstrMappings.rst
InAlloca.rst
index.rst Updates based on post-commit review of r263834 2016-03-18 21:57:51 +00:00
LangRef.rst [SSP] Remove llvm.stackprotectorcheck. 2016-04-08 21:26:31 +00:00
Lexicon.rst
LibFuzzer.rst [libFuzzer] more trophies 2016-03-29 23:13:25 +00:00
LinkTimeOptimization.rst
linpack-pc.png
LLVMBuild.rst Fixing the documentation builds 2016-01-26 22:53:12 +00:00
LLVMBuild.txt
make.bat
Makefile.sphinx Bring back Makefile.sphinx 2016-03-23 00:30:57 +00:00
MarkedUpDisassembly.rst
MCJIT-creation.png
MCJIT-dyld-load.png
MCJIT-engine-builder.png
MCJIT-load-object.png
MCJIT-load.png
MCJIT-resolve-relocations.png
MCJITDesignAndImplementation.rst Fix several accidental DOS line endings in source files 2016-01-03 17:22:03 +00:00
MergeFunctions.rst Fix some typos in the llvm doc 2016-02-14 20:16:22 +00:00
MIRLangRef.rst
NVPTXUsage.rst [NVPTX] Make NVVMReflect a function pass. 2016-03-30 20:40:11 +00:00
Packaging.rst
Passes.rst
Phabricator.rst [docs] Improve the documentation on committing code reviewed on 2016-01-14 13:39:29 +00:00
ProgrammersManual.rst Try to fix ODR violation of ErrorInfo::ID 2016-03-24 23:49:34 +00:00
Projects.rst
re_format.7
README.txt [docs] Update the docs to describe how to build the docs with cmake 2016-02-07 15:42:12 +00:00
ReleaseNotes.rst [PPC] Added a note to release notes 2016-04-07 16:47:35 +00:00
ReleaseProcess.rst [OPENMP] Make -fopenmp to turn on OpenMP support by default. 2015-12-10 05:45:58 +00:00
SegmentedStacks.rst
SourceLevelDebugging.rst testcase gardening: update the emissionKind enum to the new syntax. (NFC) 2016-04-01 00:16:49 +00:00
SphinxQuickstartTemplate.rst
StackMaps.rst
Statepoints.rst [Statepoint docs] Delete trailing whitespace 2016-03-04 18:14:09 +00:00
SystemLibrary.rst
TableGenFundamentals.rst
TestingGuide.rst Fixing the documentation builds 2016-01-26 22:53:12 +00:00
TestSuiteMakefileGuide.rst Fix the docs I broke 2016-03-11 23:31:02 +00:00
Vectorizers.rst
WritingAnLLVMBackend.rst
WritingAnLLVMPass.rst Fix typo. 2016-03-06 12:37:34 +00:00
yaml2obj.rst
YamlIO.rst [docs] Fix typo in YamlIO.rst 2016-02-04 20:42:43 +00:00

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 <http://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` <-> `http://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.
`http://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