llvm-6502/docs
Hal Finkel 16fd27b2c3 Add scoped-noalias metadata
This commit adds scoped noalias metadata. The primary motivations for this
feature are:
  1. To preserve noalias function attribute information when inlining
  2. To provide the ability to model block-scope C99 restrict pointers

Neither of these two abilities are added here, only the necessary
infrastructure. In fact, there should be no change to existing functionality,
only the addition of new features. The logic that converts noalias function
parameters into this metadata during inlining will come in a follow-up commit.

What is added here is the ability to generally specify noalias memory-access
sets. Regarding the metadata, alias-analysis scopes are defined similar to TBAA
nodes:

!scope0 = metadata !{ metadata !"scope of foo()" }
!scope1 = metadata !{ metadata !"scope 1", metadata !scope0 }
!scope2 = metadata !{ metadata !"scope 2", metadata !scope0 }
!scope3 = metadata !{ metadata !"scope 2.1", metadata !scope2 }
!scope4 = metadata !{ metadata !"scope 2.2", metadata !scope2 }

Loads and stores can be tagged with an alias-analysis scope, and also, with a
noalias tag for a specific scope:

... = load %ptr1, !alias.scope !{ !scope1 }
... = load %ptr2, !alias.scope !{ !scope1, !scope2 }, !noalias !{ !scope1 }

When evaluating an aliasing query, if one of the instructions is associated
with an alias.scope id that is identical to the noalias scope associated with
the other instruction, or is a descendant (in the scope hierarchy) of the
noalias scope associated with the other instruction, then the two memory
accesses are assumed not to alias.

Note that is the first element of the scope metadata is a string, then it can
be combined accross functions and translation units. The string can be replaced
by a self-reference to create globally unqiue scope identifiers.

[Note: This overview is slightly stylized, since the metadata nodes really need
to just be numbers (!0 instead of !scope0), and the scope lists are also global
unnamed metadata.]

Existing noalias metadata in a callee is "cloned" for use by the inlined code.
This is necessary because the aliasing scopes are unique to each call site
(because of possible control dependencies on the aliasing properties). For
example, consider a function: foo(noalias a, noalias b) { *a = *b; } that gets
inlined into bar() { ... if (...) foo(a1, b1); ... if (...) foo(a2, b2); } --
now just because we know that a1 does not alias with b1 at the first call site,
and a2 does not alias with b2 at the second call site, we cannot let inlining
these functons have the metadata imply that a1 does not alias with b2.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213864 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-24 14:25:39 +00:00
..
_static
_templates
_themes/llvm-theme
CommandGuide Fix Sphinx warnings. 2014-07-21 16:39:00 +00:00
HistoricalNotes
TableGen Fix Sphinx warnings. 2014-07-21 16:39:00 +00:00
tutorial
AliasAnalysis.rst Update some AliasAnalysis pass docs for getAdjustedAnalysisPointer. 2014-05-22 19:38:25 +00:00
ARM-BE-bitcastfail.png [ARM64-BE] Add sphinx documentation for the ARM64 NEON implementation. 2014-05-12 15:13:39 +00:00
ARM-BE-bitcastsuccess.png [ARM64-BE] Add sphinx documentation for the ARM64 NEON implementation. 2014-05-12 15:13:39 +00:00
ARM-BE-ld1.png [ARM64-BE] Add sphinx documentation for the ARM64 NEON implementation. 2014-05-12 15:13:39 +00:00
ARM-BE-ldr.png [ARM64-BE] Add sphinx documentation for the ARM64 NEON implementation. 2014-05-12 15:13:39 +00:00
Atomics.rst IR: add "cmpxchg weak" variant to support permitted failure. 2014-06-13 14:24:07 +00:00
BigEndianNEON.rst Fix typos 2014-05-15 01:52:21 +00:00
BitCodeFormat.rst Revert "[ms-cxxabi] Add a new calling convention that swaps 'this' and 'sret'" 2014-05-09 22:56:42 +00:00
BlockFrequencyTerminology.rst Fix typos 2014-05-15 01:52:21 +00:00
BranchWeightMetadata.rst
Bugpoint.rst
CMake.rst Added LLVM_ENABLE_RTTI and LLVM_ENABLE_EH options that allow RTTI and EH 2014-07-22 15:41:18 +00:00
CMakeLists.txt
CodeGenerator.rst [docs] Fix a mangled sentence. 2014-07-01 18:22:32 +00:00
CodingStandards.rst Remove the recommendation against using std::function 2014-07-02 00:42:07 +00:00
CommandLine.rst
CompilerWriterInfo.rst
conf.py
DebuggingJITedCode.rst
DeveloperPolicy.rst Document what backwards compatibility we provide for bitcode. 2014-07-23 22:43:22 +00:00
doxygen.cfg.in
doxygen.css
doxygen.footer
doxygen.header
doxygen.intro
Dummy.html
ExceptionHandling.rst
ExtendedIntegerResults.txt
ExtendingLLVM.rst
Extensions.rst ARM: add VLA extension for WoA Itanium ABI 2014-06-09 20:18:42 +00:00
FAQ.rst
GarbageCollection.rst Fix 'platform-specific' hyphenations 2014-06-30 18:57:16 +00:00
gcc-loops.png
GetElementPtr.rst
GettingStarted.rst Drop the udis86 wrapper from llvm::sys 2014-07-17 20:05:29 +00:00
GettingStartedVS.rst Document how to select build configuration with Visual C++ IDE or command line. 2014-06-05 16:42:26 +00:00
GoldPlugin.rst
HowToAddABuilder.rst
HowToBuildOnARM.rst
HowToCrossCompileLLVM.rst
HowToReleaseLLVM.rst docs: Update relaease documents to include the patch number in the RELEASE tags 2014-07-21 14:28:31 +00:00
HowToSetUpLLVMStyleRTTI.rst
HowToSubmitABug.rst
HowToUseAttributes.rst
HowToUseInstrMappings.rst
InAlloca.rst
index.rst [ARM64-BE] Add sphinx documentation for the ARM64 NEON implementation. 2014-05-12 15:13:39 +00:00
LangRef.rst Add scoped-noalias metadata 2014-07-24 14:25:39 +00:00
Lexicon.rst fixed link 2014-07-14 19:52:36 +00:00
LinkTimeOptimization.rst
linpack-pc.png
LLVMBuild.rst
LLVMBuild.txt
make.bat
Makefile
Makefile.sphinx Revert "Treat warnings in Sphinx as errors. The reasons for doing this are..." 2014-07-22 18:09:17 +00:00
MakefileGuide.rst
MarkedUpDisassembly.rst undo test commit (whitespace only) 2014-06-30 08:09:35 +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
NVPTXUsage.rst
Packaging.rst
Passes.rst docs: Remove documentation for legacy PGO options 2014-06-04 06:29:38 +00:00
Phabricator.rst Phabricator doc: Explicit the fact that the patch needs to be there before the commit 2014-07-04 09:00:35 +00:00
ProgrammersManual.rst Revert "[C++11] Add predecessors(BasicBlock *) / successors(BasicBlock *) iterator ranges." 2014-07-21 17:06:51 +00:00
Projects.rst
re_format.7
README.txt
ReleaseNotes.rst Added release notes for MIPS. 2014-07-23 12:59:26 +00:00
ReleaseProcess.rst
SegmentedStacks.rst
SourceLevelDebugging.rst Debug info: split out complex DIVariable address expressions into a 2014-06-30 17:17:35 +00:00
SphinxQuickstartTemplate.rst
StackMaps.rst
SystemLibrary.rst
TableGenFundamentals.rst
TestingGuide.rst Reduce verbiage of lit.local.cfg files 2014-06-09 22:42:55 +00:00
TestSuiteMakefileGuide.rst
Vectorizers.rst Vectorization documentation for loop hint pragmas and Rpass diagnostics. 2014-06-27 18:30:08 +00:00
WritingAnLLVMBackend.rst
WritingAnLLVMPass.rst docs: Remove documentation for legacy PGO options 2014-06-04 06:29:38 +00:00
yaml2obj.rst
YamlIO.rst [YAML] Add an optional argument EnumMask to the yaml::IO::bitSetCase(). 2014-05-23 08:07:09 +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 docs/
    make -f Makefile.sphinx
    $BROWSER _build/html/index.html

The mapping between reStructuredText files and generated documentation is
`docs/Foo.rst` <-> `_build/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/man/`.

    cd docs/
    make -f Makefile.sphinx man
    man -l _build/man/FileCheck.1

The correspondence between .rst files and man pages is
`docs/CommandGuide/Foo.rst` <-> `_build/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 reachibility of external links in the documentation can be checked by
running:

    cd docs/
    make -f Makefile.sphinx linkcheck