llvm/docs
Ahmed Bougacha 868b1fe194 [AArch64][GlobalISel] Legalize narrow scalar ops again.
Since r279760, we've been marking as legal operations on narrow integer
types that have wider legal equivalents (for instance, G_ADD s8).
Compared to legalizing these operations, this reduced the amount of
extends/truncates required, but was always a weird legalization decision
made at selection time.

So far, we haven't been able to formalize it in a way that permits the
selector generated from SelectionDAG patterns to be sufficient.

Using a wide instruction (say, s64), when a narrower instruction exists
(s32) would introduce register class incompatibilities (when one narrow
generic instruction is selected to the wider variant, but another is
selected to the narrower variant).

It's also impractical to limit which narrow operations are matched for
which instruction, as restricting "narrow selection" to ranges of types
clashes with potentially incompatible instruction predicates.

Concerns were also raised regarding  MIPS64's sign-extended register
assumptions, as well as wrapping behavior.
See discussions in https://reviews.llvm.org/D26878.

Instead, legalize the operations.

Should we ever revert to selecting these narrow operations, we should
try to represent this more accurately: for instance, by separating
a "concrete" type on operations, and an "underlying" type on vregs, we
could move the "this narrow-looking op is really legal" decision to the
legalizer, and let the selector use the "underlying" vreg type only,
which would be guaranteed to map to a register class.

In any case, we eventually should mitigate:
- the performance impact by selecting no-op extract/truncates to COPYs
  (which we currently do), and the COPYs to register reuses (which we
  don't do yet).
- the compile-time impact by optimizing away extract/truncate sequences
  in the legalizer.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@292827 91177308-0d34-0410-b5e6-96231b3b80d8
2017-01-23 21:10:05 +00:00
..
_ocamldoc
_static Fix some typos in the doc 2016-08-28 20:29:18 +00:00
_templates
_themes/llvm-theme
CommandGuide [lit] Support sharding testsuites, for parallel execution. 2017-01-18 18:12:20 +00:00
Frontend
HistoricalNotes
PDB Add documentation for the PDB Module Info stream. 2016-11-29 22:14:56 +00:00
Proposals fix some typos in the doc 2017-01-14 11:37:01 +00:00
TableGen [Docs][TableGen] Remove reference to tablegen supporting octal integers. It doesn't and hasn't for at least 9 years. 2016-11-18 02:28:50 +00:00
tutorial [Docs] Fix a broken link in the Kaleidoscope tutorial. 2016-09-13 06:31:37 +00:00
AdvancedBuilds.rst
AliasAnalysis.rst [Docs] Add initial MemorySSA documentation. 2016-08-17 00:17:29 +00:00
AMDGPUUsage.rst fix some typos in the doc 2017-01-14 11:37:01 +00:00
ARM-BE-bitcastfail.png
ARM-BE-bitcastsuccess.png
ARM-BE-ld1.png
ARM-BE-ldr.png
Atomics.rst fix some various typos in the doc 2016-07-02 19:28:40 +00:00
BigEndianNEON.rst
BitCodeFormat.rst [docs] Update some obsolete information in BitCodeFormat docs. 2016-10-14 16:23:09 +00:00
BlockFrequencyTerminology.rst
BranchWeightMetadata.rst This code block breaks the docs build (http://lab.llvm.org:8011/builders/llvm-sphinx-docs/builds/11925/steps/docs-llvm-html/logs/stdio). Setting the code highlighting to none instead of llvm. 2016-07-19 23:50:11 +00:00
Bugpoint.rst
CMake.rst [docs] Point to upstream Sphinx install instructions. 2017-01-22 03:47:49 +00:00
CMakeLists.txt [cmake] Support overriding remaining HTML doc install directories 2016-09-27 19:52:29 +00:00
CMakePrimer.rst [docs] fix cmake code-block warning 2016-07-20 09:47:09 +00:00
CodeGenerator.rst [Support/ELF/AMDGPU] Add 32-bit lo/hi got and pc relative relocations 2016-10-14 04:03:49 +00:00
CodeOfConduct.rst [Conduct] Refine what "rare cases" means wrt violations outside our spaces. 2016-07-06 19:32:41 +00:00
CodingStandards.rst Fix some remaining documentation references to MSVC 2013 2016-12-15 19:08:02 +00:00
CommandLine.rst Update CommandLine.rst getRegisteredOptions example 2016-11-07 02:43:01 +00:00
CompileCudaWithLLVM.rst [Docs] Update docs to indicate that CUDA compilation is supported on Windows. 2017-01-05 16:54:28 +00:00
CompilerWriterInfo.rst [docs] fix link to AMD manuals (PR30946) 2016-11-08 16:49:24 +00:00
conf.py Bump trunk version to 5.0.0svn 2017-01-12 21:22:36 +00:00
Coroutines.rst Changing a code block to text because Sphinx does not like it on the builder (http://lab.llvm.org:8011/builders/llvm-sphinx-docs/builds/12517/steps/docs-llvm-html/logs/stdio) 2016-08-31 14:37:20 +00:00
CoverageMappingFormat.rst fix some typos in the doc 2017-01-14 11:37:01 +00:00
DebuggingJITedCode.rst
DeveloperPolicy.rst wordsmith the "new targets" section a bit. 2016-08-17 22:17:03 +00:00
doxygen-mainpage.dox
doxygen.cfg.in [docs] Tell Doxygen to expand LLVM_ALIGNAS to nothing 2017-01-19 13:37:42 +00:00
Dummy.html
ExceptionHandling.rst [docs] Fixing Sphinx warnings to unclog the buildbot 2016-07-20 12:16:38 +00:00
ExtendedIntegerResults.txt
ExtendingLLVM.rst
Extensions.rst Silence some Sphinx diagnostics in an attempt to get the documentation builder back to green (http://lab.llvm.org:8011/builders/llvm-sphinx-docs/builds/1895). 2017-01-17 21:48:31 +00:00
FAQ.rst fix some typos in the doc 2016-07-28 09:28:58 +00:00
FaultMaps.rst
GarbageCollection.rst Tidy up example of getting the pointer size. 2016-10-14 05:45:46 +00:00
gcc-loops.png
GetElementPtr.rst [docs] Fixing Sphinx warnings to unclog the buildbot 2016-07-20 12:16:38 +00:00
GettingStarted.rst Fix GettingStarted doc so that the example build command for cmake LLVM_ENABLE_PROJECTS works on linux 2017-01-17 23:23:08 +00:00
GettingStartedVS.rst [doc] Remove explicit CMake version requirement for MSVC 2016-11-09 01:44:42 +00:00
GlobalISel.rst [AArch64][GlobalISel] Legalize narrow scalar ops again. 2017-01-23 21:10:05 +00:00
GoldPlugin.rst Revert 'Test commit as per developer policy' 2016-11-30 08:24:43 +00:00
HowToAddABuilder.rst [docs] Fix a broken URL in 'HowToAddABuilder' 2016-09-29 13:29:49 +00:00
HowToBuildOnARM.rst
HowToCrossCompileLLVM.rst
HowToReleaseLLVM.rst Adding RELEASE_TESTERS.TXT 2016-07-21 16:46:44 +00:00
HowToSetUpLLVMStyleRTTI.rst
HowToSubmitABug.rst
HowToUseAttributes.rst
HowToUseInstrMappings.rst [docs] Fixing Sphinx warnings to unclog the buildbot 2016-07-20 12:16:38 +00:00
InAlloca.rst [docs] Fixing Sphinx warnings to unclog the buildbot 2016-07-20 12:16:38 +00:00
index.rst [PDB] Begin adding documentation for the PDB file format. 2016-11-10 19:24:21 +00:00
LangRef.rst docs: Document that !absolute_symbol { all-ones, all-ones } means the full set. 2017-01-20 21:56:37 +00:00
Lexicon.rst [docs] Add PR to Lexicon 2016-10-06 16:39:22 +00:00
LibFuzzer.rst [libFuzzer] better link for trophies 2017-01-18 00:45:02 +00:00
LinkTimeOptimization.rst [docs] Typos and whitespace fixed in LTO docs. 2016-11-29 18:00:31 +00:00
linpack-pc.png
LLVMBuild.rst Test commit. 2016-12-24 17:26:38 +00:00
LLVMBuild.txt
make.bat
Makefile.sphinx
MarkedUpDisassembly.rst [docs] Fixing Sphinx warnings to unclog the buildbot 2016-07-20 12:16:38 +00:00
MCJIT-creation.png
MCJIT-dyld-load.png
MCJIT-engine-builder.png
MCJIT-load-object.png
MCJIT-load.png
MCJIT-resolve-relocations.png
MCJITDesignAndImplementation.rst
MemorySSA.rst Fix some typos in the doc 2016-08-28 20:29:18 +00:00
MergeFunctions.rst [docs] Fixing Sphinx warnings to unclog the buildbot 2016-07-20 12:16:38 +00:00
MIRLangRef.rst [docs] Fixing Sphinx warnings to unclog the buildbot 2016-07-20 12:16:38 +00:00
NVPTXUsage.rst Silence some Sphinx diagnostics in an attempt to get the documentation builder back to green (http://lab.llvm.org:8011/builders/llvm-sphinx-docs/builds/1895). 2017-01-17 21:48:31 +00:00
OptBisect.rst Adding document describing the use of the -opt-bisect-limit option. 2016-08-26 23:11:48 +00:00
Packaging.rst
Passes.rst Remove the ScalarReplAggregates pass 2016-06-15 00:19:09 +00:00
Phabricator.rst [doc] Fix minor grammatical error in Phabricator.rst 2017-01-05 13:08:14 +00:00
ProgrammersManual.rst fix some typos in the doc 2017-01-14 11:37:01 +00:00
Projects.rst
re_format.7
README.txt
ReleaseNotes.rst Clear the release notes for 5.0.0 2017-01-12 21:50:22 +00:00
ReleaseProcess.rst
ReportingGuide.rst fix some various typos in the doc 2016-07-02 19:28:40 +00:00
ScudoHardenedAllocator.rst [scudo] Documentation update for Scudo, from https://reviews.llvm.org/D23332 2016-08-09 23:57:04 +00:00
SegmentedStacks.rst [docs] Fixing Sphinx warnings to unclog the buildbot 2016-07-20 12:16:38 +00:00
SourceLevelDebugging.rst [docs] Fix some typos. NFC. 2016-11-01 23:55:50 +00:00
SphinxQuickstartTemplate.rst
StackMaps.rst [Stackmap] Added callsite counts to emitted function information. 2016-09-14 20:22:03 +00:00
Statepoints.rst [docs] Fixing Sphinx warnings to unclog the buildbot 2016-07-20 12:16:38 +00:00
SystemLibrary.rst
TableGenFundamentals.rst
TestingGuide.rst fix some typos in the doc 2017-01-14 11:37:01 +00:00
TestSuiteMakefileGuide.rst
TypeMetadata.rst IR: New representation for CFI and virtual call optimization pass metadata. 2016-06-24 21:21:32 +00:00
Vectorizers.rst
WritingAnLLVMBackend.rst fix some typos in the doc 2017-01-14 11:37:01 +00:00
WritingAnLLVMPass.rst [docs] Make WritingAnLLVMPass.rst up-to-date with current state of things 2016-09-27 12:07:21 +00:00
XRay.rst [XRay][docs] Define requirements on installed log handlers. 2016-11-16 02:18:23 +00:00
yaml2obj.rst
YamlIO.rst fix some typos in the doc 2017-01-14 11:37:01 +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