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llvm-mirror/docs
Bill Wendling ffaf238dd0 Allow "callbr" to return non-void values
Summary:
Terminators in LLVM aren't prohibited from returning values. This means that
the "callbr" instruction, which is used for "asm goto", can support "asm goto
with outputs."

This patch removes all restrictions against "callbr" returning values. The
heavy lifting is done by the code generator. The "INLINEASM_BR" instruction's
a terminator, and the code generator doesn't allow non-terminator instructions
after a terminator. In order to correctly model the feature, we need to copy
outputs from "INLINEASM_BR" into virtual registers. Of course, those copies
aren't terminators.

To get around this issue, we split the block containing the "INLINEASM_BR"
right before the "COPY" instructions. This results in two cheats:

  - Any physical registers defined by "INLINEASM_BR" need to be marked as
    live-in into the block with the "COPY" instructions. This violates an
    assumption that physical registers aren't marked as "live-in" until after
    register allocation. But it seems as if the live-in information only
    needs to be correct after register allocation. So we're able to get away
    with this.

  - The indirect branches from the "INLINEASM_BR" are moved to the "COPY"
    block. This is to satisfy PHI nodes.

I've been told that MLIR can support this handily, but until we're able to
use it, we'll have to stick with the above.

Reviewers: jyknight, nickdesaulniers, hfinkel, MaskRay, lattner

Reviewed By: nickdesaulniers, MaskRay, lattner

Subscribers: rriddle, qcolombet, jdoerfert, MatzeB, echristo, MaskRay, xbolva00, aaron.ballman, cfe-commits, JonChesterfield, hiraditya, llvm-commits, rnk, craig.topper

Tags: #llvm, #clang

Differential Revision: https://reviews.llvm.org/D69868
2020-02-24 18:29:06 -08:00
..
_ocamldoc
_static
_templates [www] More HTTPS and outdated link fixes. 2019-11-08 14:41:27 -08:00
_themes/llvm-theme [Docs] Updates sidebar links and sets max-width property for div.body 2019-10-15 21:27:20 +00:00
AMDGPU [AMDGPU][MC][DOC] Updated AMD GPU assembler syntax description. 2020-02-07 16:23:46 +03:00
CommandGuide [NFC][llvm-exegesis] Docs/help: opcode-index=-1 means measure everything 2020-02-13 12:46:12 +03:00
DependenceGraphs [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
Frontend Fix you->your typo. 2020-02-10 15:07:06 -08:00
GlobalISel [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
HistoricalNotes
PDB Fix a few spellos in docs. 2019-09-13 14:58:24 +00:00
Proposals [Doc] Proposal for vector predication 2020-02-10 10:35:50 +01:00
TableGen [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
tutorial [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
AddingConstrainedIntrinsics.rst [FEnv] Fix AddingConstrainedIntrinsics.rst after llvmorg-10-init-10282-g0c50c0b0552 2019-11-19 23:09:13 -08:00
AdvancedBuilds.rst
AliasAnalysis.rst
AMDGPUInstructionNotation.rst
AMDGPUInstructionSyntax.rst [AMDGPU][MC][DOC] Updated AMD GPU assembler syntax description. 2019-07-08 16:50:11 +00:00
AMDGPUModifierSyntax.rst [AMDGPU][MC][DOC] Updated AMD GPU assembler syntax description. 2019-12-25 17:51:53 +03:00
AMDGPUOperandSyntax.rst [AMDGPU][MC][DOC] Updated AMD GPU assembler syntax description. 2019-12-25 17:51:53 +03:00
AMDGPUUsage.rst [AMDGPU] AMDGPUUsage define call convention ABI 2020-02-19 15:56:19 -05:00
ARM-BE-bitcastfail.png
ARM-BE-bitcastsuccess.png
ARM-BE-ld1.png
ARM-BE-ldr.png
Atomics.rst [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
Benchmarking.rst
BigEndianNEON.rst [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
BitCodeFormat.rst [X86] Add new calling convention that guarantees tail call optimization 2019-10-07 22:28:58 +00:00
BlockFrequencyTerminology.rst [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
BranchWeightMetadata.rst
BugLifeCycle.rst
Bugpoint.rst [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
BugpointRedesign.md [Bugpoint redesign] Fix nonlocal URI link in doc 2019-08-09 21:48:47 +00:00
BuildingADistribution.rst Remove AllTargetsAsmPrinters 2020-01-17 19:04:06 -05:00
CFIVerify.rst
CMake.rst Continue removing llgo. 2020-02-10 10:33:58 -08:00
CMakeLists.txt
CMakePrimer.rst [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
CodeGenerator.rst [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
CodeOfConduct.rst
CodingStandards.rst Add coding standard recommending use of qualifiers in cpp files 2020-02-18 14:08:56 -08:00
CommandLine.rst [CommandLine] Add callbacks to Options 2019-12-06 15:16:45 -08:00
CompileCudaWithLLVM.rst [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
CompilerWriterInfo.rst [PowerPC][docs] Update Embedded PowerPC docs in Compiler Writers Info page 2019-12-30 20:22:37 +00:00
conf.py [Docs] Add a custom sidebar to doc pages 2019-09-20 22:16:39 +00:00
Contributing.rst Add discussion of git-format-patch to Phabricator.html 2019-12-03 18:54:46 -05:00
Coroutines.rst fix another doc typo to cycle bots 2019-12-20 21:59:51 -05:00
CoverageMappingFormat.rst [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
DebuggingJITedCode.rst [docs] Fix references to a renamed flag. 2019-11-06 14:42:57 -08:00
DeveloperPolicy.rst [doc] Clarify responsibility for fixing experimental target problems 2020-02-14 09:50:18 +00:00
Docker.rst
doxygen-mainpage.dox
doxygen.cfg.in [docs] update mathjax path in doxygen 2020-02-07 16:26:35 +00:00
ExceptionHandling.rst Remove extra "\01" prefix in EH docs 2020-01-19 08:20:17 -08:00
ExtendedIntegerResults.txt
ExtendingLLVM.rst
Extensions.rst [Frontend] Replace CC1 option -mcode-model with -mcmodel= 2020-02-21 23:10:50 -08:00
FAQ.rst [docs] Tiny rewording in the portability FAQ entry 2019-11-20 16:40:30 -08:00
FaultMaps.rst
FuzzingLLVM.rst [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
GarbageCollection.rst [AsmPrinter] De-capitalize all AsmPrinter::Emit* but EmitInstruction 2020-02-13 17:06:24 -08:00
gcc-loops.png
GetElementPtr.rst [DOC] Fix load instructions' syntax, function definition. 2019-06-12 11:24:22 +00:00
GettingInvolved.rst add GitBisecting to toctrees to try and placate the sphinx bot 2020-02-10 15:33:28 -05:00
GettingStarted.rst [docs] Add note on using cmake to perform the build 2020-02-14 13:44:56 -06:00
GettingStartedTutorials.rst [Docs] Adds Documentation links to sidebar 2019-10-09 20:26:13 +00:00
GettingStartedVS.rst Retire VS2015 Support 2019-07-09 10:10:48 +00:00
GitBisecting.rst git bisect docs: formatting tweaks 2020-02-10 15:47:59 -05:00
GoldPlugin.rst
GwpAsan.rst [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
HowToAddABuilder.rst wrap an rst file to 80 cols, to cycle bots 2019-12-06 17:28:02 -05:00
HowToBuildOnARM.rst [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
HowToBuildWithPGO.rst [docs] NFC: Fix typos in documents 2020-01-07 16:06:14 +01:00
HowToCrossCompileBuiltinsOnArm.rst [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
HowToCrossCompileLLVM.rst
HowToReleaseLLVM.rst Remove some autoconf references from docs and comments 2019-07-03 09:57:59 +00:00
HowToSetUpLLVMStyleRTTI.rst
HowToSubmitABug.rst
HowToUseAttributes.rst
HowToUseInstrMappings.rst
InAlloca.rst
index.rst Make coding standards document more inclusive 2019-11-21 13:37:17 +01:00
LangRef.rst Allow "callbr" to return non-void values 2020-02-24 18:29:06 -08:00
Lexicon.rst [docs] fix typo in Lexicon.rst 2019-12-24 09:47:15 +01:00
LibFuzzer.rst [libFuzzer] Minor documentation fixes. 2020-02-03 14:41:06 -08:00
LinkTimeOptimization.rst
linpack-pc.png
llvm-objdump.1
LLVMBuild.rst
LLVMBuild.txt
LoopTerminology.rst [Analysis][Docs] Parents of loops documentation. 2020-02-21 17:11:53 -06:00
make.bat
Makefile.sphinx
MarkdownQuickstartTemplate.md
MarkedUpDisassembly.rst [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
MCJIT-creation.png
MCJIT-dyld-load.png
MCJIT-engine-builder.png
MCJIT-load-object.png
MCJIT-load.png
MCJIT-resolve-relocations.png
MCJITDesignAndImplementation.rst
MeetupGuidelines.rst Add guidelines/recommendations for organizers of LLVM Socials 2019-05-14 07:20:58 +00:00
MemorySSA.rst
MemTagSanitizer.rst [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
MergeFunctions.rst
MIRLangRef.rst [globalisel][docs] Rework GMIR documentation and add an early GenericOpcode reference 2019-11-05 15:16:43 -08:00
NVPTXUsage.rst
OptBisect.rst [LegacyPassManager] Delete BasicBlockPass/Manager. 2019-10-30 11:40:16 -07:00
ORCv2.rst [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
Packaging.rst
Passes.rst [docs] NFC: Fix typos in documents 2020-01-07 16:06:14 +01:00
Phabricator.rst phab doc: Replace or remove references to svn 2020-01-09 22:29:20 +01:00
ProgrammersManual.rst Revert "Revert "Reland "[Support] make report_fatal_error abort instead of exit""" 2020-02-13 10:16:06 -08:00
Projects.rst
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README.txt [NFC] Test commit, whitespace change 2019-06-06 22:07:14 +00:00
Reference.rst Add MemTagSanitizer documentation. 2019-11-01 10:46:04 -07:00
ReleaseNotes.rst [ReleaseNotes] Mention the vector-function-abi-variant attribute. 2020-02-24 17:39:31 +00:00
ReleaseProcess.rst [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
Remarks.rst [Remarks] Extend the RemarkStreamer to support other emitters 2020-02-04 17:16:02 -08:00
ReportingGuide.rst [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
ScudoHardenedAllocator.rst
SegmentedStacks.rst
SourceLevelDebugging.rst [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
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SpeculativeLoadHardening.md Fix a few spellos in docs. 2019-09-13 14:58:24 +00:00
SphinxQuickstartTemplate.rst Docs: Updates Sphinx Quickstart template for new contributors 2019-11-10 09:27:32 -07:00
StackMaps.rst
StackSafetyAnalysis.rst
Statepoints.rst
SupportLibrary.rst
SystemLibrary.rst
TableGenFundamentals.rst
TestingGuide.rst Change the googlemock link 2020-01-22 10:14:47 +01:00
TestSuiteGuide.md [Docs] Fix a typo 2019-12-18 15:19:01 -08:00
TestSuiteMakefileGuide.rst
TransformMetadata.rst [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
TypeMetadata.rst Reland: Dead Virtual Function Elimination 2019-10-17 09:58:57 +00:00
UserGuides.rst [Docs] Moves Control Flow Document to User Guides 2019-10-13 20:05:22 +00:00
Vectorizers.rst [doc] typo in optimisation remark example 2020-02-06 14:55:18 +00:00
WritingAnLLVMBackend.rst Update spelling of {analyze,insert,remove}Branch in strings and comments 2020-01-21 10:15:38 -06:00
WritingAnLLVMPass.rst Generalize the pass registration mechanism used by Polly to any third-party tool 2020-01-02 16:45:31 +01:00
XRay.rst
XRayExample.rst
XRayFDRFormat.rst [llvm] NFC: fix trivial typos in documents 2020-01-22 11:32:51 +08:00
yaml2obj.rst
YamlIO.rst remove a trailing space character (test commit) 2020-01-27 15:01:55 -08:00

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

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