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llvm-mirror/docs
Andres Freund 7602e1153a Add PerfJITEventListener for perf profiling support.
This new JIT event listener supports generating profiling data for
the linux 'perf' profiling tool, allowing it to generate function and
instruction level profiles.

Currently this functionality is not enabled by default, but must be
enabled with LLVM_USE_PERF=yes.  Given that the listener has no
dependencies, it might be sensible to enable by default once the
initial issues have been shaken out.

I followed existing precedent in registering the listener by default
in lli. Should there be a decision to enable this by default on linux,
that should probably be changed.

Please note that until https://reviews.llvm.org/D47343 is resolved,
using this functionality with mcjit rather than orcjit will not
reliably work.

Disregarding the previous comment, here's an example:

$ cat /tmp/expensive_loop.c

bool stupid_isprime(uint64_t num)
{
        if (num == 2)
                return true;
        if (num < 1 || num % 2 == 0)
                return false;
        for(uint64_t i = 3; i < num / 2; i+= 2) {
                if (num % i == 0)
                        return false;
        }
        return true;
}

int main(int argc, char **argv)
{
        int numprimes = 0;

        for (uint64_t num = argc; num < 100000; num++)
        {
                if (stupid_isprime(num))
                        numprimes++;
        }

        return numprimes;
}

$ clang -ggdb -S -c -emit-llvm /tmp/expensive_loop.c -o
/tmp/expensive_loop.ll

$ perf record -o perf.data -g -k 1 ./bin/lli -jit-kind=mcjit /tmp/expensive_loop.ll 1

$ perf inject --jit -i perf.data -o perf.jit.data

$ perf report -i perf.jit.data
-   92.59%  lli      jitted-5881-2.so                   [.] stupid_isprime
     stupid_isprime
     main
     llvm::MCJIT::runFunction
     llvm::ExecutionEngine::runFunctionAsMain
     main
     __libc_start_main
     0x4bf6258d4c544155
+    0.85%  lli      ld-2.27.so                         [.] do_lookup_x

And line-level annotations also work:
       │              for(uint64_t i = 3; i < num / 2; i+= 2) {
       │1 30:   movq   $0x3,-0x18(%rbp)
  0.03 │1 38:   mov    -0x18(%rbp),%rax
  0.03 │        mov    -0x10(%rbp),%rcx
       │        shr    $0x1,%rcx
  3.63 │     ┌──cmp    %rcx,%rax
       │     ├──jae    6f
       │     │                if (num % i == 0)
  0.03 │     │  mov    -0x10(%rbp),%rax
       │     │  xor    %edx,%edx
 89.00 │     │  divq   -0x18(%rbp)
       │     │  cmp    $0x0,%rdx
  0.22 │     │↓ jne    5f
       │     │                        return false;
       │     │  movb   $0x0,-0x1(%rbp)
       │     │↓ jmp    73
       │     │        }
  3.22 │1 5f:│↓ jmp    61
       │     │        for(uint64_t i = 3; i < num / 2; i+= 2) {

Subscribers: mgorny, llvm-commits

Differential Revision: https://reviews.llvm.org/D44892

llvm-svn: 337789
2018-07-24 00:54:06 +00:00
..
_ocamldoc
_static
_templates
_themes/llvm-theme
CommandGuide [llvm-mca][docs] Define IPC where it is first mentioned. NFC. 2018-07-23 21:10:50 +00:00
Frontend
HistoricalNotes
PDB Update MSF File Documentation. 2018-01-12 21:42:39 +00:00
Proposals remove unreferenced footnotes 2018-01-05 00:24:55 +00:00
TableGen [TableGen] Add a general-purpose JSON backend. 2018-07-11 08:40:19 +00:00
tutorial [docs] Fix a typo in KaleidoscopeJIT tutorial 2018-05-08 18:43:27 +00:00
AdvancedBuilds.rst [NFC] Remove apostrophe to use 'it' in the possessive form. 2018-01-26 18:43:57 +00:00
AliasAnalysis.rst [doc] Removed obsolete -count-aa from AliasAnalysis documentation 2018-04-23 13:45:28 +00:00
AMDGPUAsmGFX7.rst [AMDGPU][MC][DOC] Updated AMD GPU assembler description 2018-03-12 15:55:08 +00:00
AMDGPUAsmGFX8.rst [AMDGPU][MC][DOC] Updated AMD GPU assembler description 2018-03-12 15:55:08 +00:00
AMDGPUAsmGFX9.rst [AMDGPU][MC][DOC] Updated AMD GPU assembler description 2018-03-12 15:55:08 +00:00
AMDGPUOperandSyntax.rst [AMDGPU][MC][DOC] Updated AMD GPU assembler description 2018-03-12 15:55:08 +00:00
AMDGPUUsage.rst AMDHSA: Put old assembler docs back 2018-06-22 19:23:18 +00:00
ARM-BE-bitcastfail.png
ARM-BE-bitcastsuccess.png
ARM-BE-ld1.png
ARM-BE-ldr.png
Atomics.rst
Benchmarking.rst
BigEndianNEON.rst
BitCodeFormat.rst Add the ShadowCallStack attribute 2018-04-03 20:10:40 +00:00
BlockFrequencyTerminology.rst
BranchWeightMetadata.rst
Bugpoint.rst Rename DEBUG macro to LLVM_DEBUG. 2018-05-14 12:53:11 +00:00
CFIVerify.rst [cfi-verify] Abort on unsupported targets 2018-07-16 15:26:44 +00:00
CMake.rst Add PerfJITEventListener for perf profiling support. 2018-07-24 00:54:06 +00:00
CMakeLists.txt
CMakePrimer.rst
CodeGenerator.rst [NFC] fix trivial typos in documents 2018-06-15 05:10:09 +00:00
CodeOfConduct.rst
CodingStandards.rst [NFC] update coding standard links to HTTPS 2018-05-18 16:44:13 +00:00
CommandLine.rst Rename DEBUG macro to LLVM_DEBUG. 2018-05-14 12:53:11 +00:00
CompileCudaWithLLVM.rst
CompilerWriterInfo.rst [docs] Update CompilerWriterInfo.rst for MIPS 2018-06-14 15:16:37 +00:00
conf.py Revert "[docs] Add support for Markdown documentation in Sphinx" 2018-07-23 20:00:32 +00:00
Contributing.rst [Docs] Add LLVM for Grad Students to Contributing page. 2018-03-02 14:35:02 +00:00
Coroutines.rst [coroutines] Add support for llvm.coro.noop intrinsics 2018-04-02 16:55:12 +00:00
CoverageMappingFormat.rst
DebuggingJITedCode.rst
DeveloperPolicy.rst
Docker.rst Migrate dockerfiles to use multi-stage builds. 2018-03-26 15:12:30 +00:00
doxygen-mainpage.dox
doxygen.cfg.in [NFC] fix trivial typos in comments and documents 2018-01-26 08:15:29 +00:00
ExceptionHandling.rst [NFC] fix trivial typos in documents and comments 2018-04-12 05:53:20 +00:00
ExtendedIntegerResults.txt
ExtendingLLVM.rst
Extensions.rst MC: Implement support for new .addrsig and .addrsig_sym directives. 2018-07-17 22:17:18 +00:00
FAQ.rst
FaultMaps.rst
FuzzingLLVM.rst
GarbageCollection.rst Remove @brief commands from doxygen comments, too. 2018-05-01 16:10:38 +00:00
gcc-loops.png
GetElementPtr.rst
GettingStarted.rst Document the git config for Windows to do line-endings correctly. 2018-06-27 19:58:28 +00:00
GettingStartedVS.rst
GlobalISel.rst
GoldPlugin.rst [docs] Update GoldPlugin documentation 2018-07-18 17:10:17 +00:00
HowToAddABuilder.rst
HowToBuildOnARM.rst
HowToCrossCompileBuiltinsOnArm.rst
HowToCrossCompileLLVM.rst
HowToReleaseLLVM.rst
HowToSetUpLLVMStyleRTTI.rst
HowToSubmitABug.rst [docs] Fix mention of GCC frontend 2018-01-15 17:11:22 +00:00
HowToUseAttributes.rst
HowToUseInstrMappings.rst
InAlloca.rst
index.rst Revert "[docs] Add support for Markdown documentation in Sphinx" 2018-07-23 20:00:32 +00:00
LangRef.rst [UnJ] Document unroll and jam pass and loop metadata 2018-07-19 12:37:00 +00:00
Lexicon.rst [Lexicon] Add "ICE", internal compiler error 2018-04-05 14:08:16 +00:00
LibFuzzer.rst [libFuzzer] Update documentation regarding MSan. 2018-07-19 17:59:11 +00:00
LinkTimeOptimization.rst
linpack-pc.png
LLVMBuild.rst
LLVMBuild.txt
make.bat
Makefile.sphinx
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
MemorySSA.rst [NFC] fix trivial typos in comments and documents 2018-01-26 08:15:29 +00:00
MergeFunctions.rst
MIRLangRef.rst [NFC] fix trivial typos in documents 2018-06-15 05:10:09 +00:00
NVPTXUsage.rst
OptBisect.rst
Packaging.rst
Passes.rst [UnJ] Document unroll and jam pass and loop metadata 2018-07-19 12:37:00 +00:00
Phabricator.rst [docs] Tweak update to Phabricator docs about setting repository for diffs uploaded via web 2018-01-12 15:44:35 +00:00
ProgrammersManual.rst [NFC] fix trivial typos in documents 2018-06-15 05:10:09 +00:00
Projects.rst
re_format.7
README.txt
ReleaseNotes.rst [docs] add various sanitisers support for FreeBSD/OpenBSD 2018-06-07 16:33:48 +00:00
ReleaseProcess.rst [docs] Make ReleaseProcess.rst 80 column. NFCI 2018-01-18 14:57:55 +00:00
ReportingGuide.rst
ScudoHardenedAllocator.rst [docs] Scudo documentation minor update 2018-05-18 17:02:35 +00:00
SegmentedStacks.rst
SourceLevelDebugging.rst [Docs] Testing Debug Info Preservation in Optimizations 2018-07-19 14:08:54 +00:00
speculative_load_hardening_microbenchmarks.png [x86/SLH] Add the design document for Speculative Load Hardening, 2018-07-18 14:05:14 +00:00
SpeculativeLoadHardening.md [x86/SLH] Add the design document for Speculative Load Hardening, 2018-07-18 14:05:14 +00:00
SphinxQuickstartTemplate.rst
StackMaps.rst
Statepoints.rst
SystemLibrary.rst s/LLVM_ON_WIN32/_WIN32/, llvm 2018-04-29 00:45:03 +00:00
TableGenFundamentals.rst
TestingGuide.rst [llvm] Document "%T" as deprecated in TestingGuide.rst 2018-06-19 22:22:48 +00:00
TestSuiteMakefileGuide.rst
TypeMetadata.rst
Vectorizers.rst docs: Remove reference to a deprecated flag 2018-01-23 20:22:37 +00:00
WritingAnLLVMBackend.rst
WritingAnLLVMPass.rst
XRay.rst [XRay][compiler-rt+docs] Introduce __xray_log_init_mode(...). 2018-05-04 06:01:12 +00:00
XRayExample.rst Tidy some language in the xray documentation. 2018-05-27 09:19:03 +00:00
XRayFDRFormat.rst Tidy some language in the xray documentation. 2018-05-27 09:19:03 +00:00
yaml2obj.rst
YamlIO.rst [Docs] Fix LLVM_YAML_IS_DOCUMENT_LIST_VECTOR 2018-07-23 14:17:43 +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

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