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llvm-mirror/docs
Adrian Prantl f625c157a1 PR32382: Fix emitting complex DWARF expressions.
The DWARF specification knows 3 kinds of non-empty simple location
descriptions:
1. Register location descriptions
  - describe a variable in a register
  - consist of only a DW_OP_reg
2. Memory location descriptions
  - describe the address of a variable
3. Implicit location descriptions
  - describe the value of a variable
  - end with DW_OP_stack_value & friends

The existing DwarfExpression code is pretty much ignorant of these
restrictions. This used to not matter because we only emitted very
short expressions that we happened to get right by accident.  This
patch makes DwarfExpression aware of the rules defined by the DWARF
standard and now chooses the right kind of location description for
each expression being emitted.

This would have been an NFC commit (for the existing testsuite) if not
for the way that clang describes captured block variables. Based on
how the previous code in LLVM emitted locations, DW_OP_deref
operations that should have come at the end of the expression are put
at its beginning. Fixing this means changing the semantics of
DIExpression, so this patch bumps the version number of DIExpression
and implements a bitcode upgrade.

There are two major changes in this patch:

I had to fix the semantics of dbg.declare for describing function
arguments. After this patch a dbg.declare always takes the *address*
of a variable as the first argument, even if the argument is not an
alloca.

When lowering a DBG_VALUE, the decision of whether to emit a register
location description or a memory location description depends on the
MachineLocation — register machine locations may get promoted to
memory locations based on their DIExpression. (Future) optimization
passes that want to salvage implicit debug location for variables may
do so by appending a DW_OP_stack_value. For example:
  DBG_VALUE, [RBP-8]                        --> DW_OP_fbreg -8
  DBG_VALUE, RAX                            --> DW_OP_reg0 +0
  DBG_VALUE, RAX, DIExpression(DW_OP_deref) --> DW_OP_reg0 +0

All testcases that were modified were regenerated from clang. I also
added source-based testcases for each of these to the debuginfo-tests
repository over the last week to make sure that no synchronized bugs
slip in. The debuginfo-tests compile from source and run the debugger.

https://bugs.llvm.org/show_bug.cgi?id=32382
<rdar://problem/31205000>

Differential Revision: https://reviews.llvm.org/D31439

llvm-svn: 300522
2017-04-18 01:21:53 +00:00
..
_ocamldoc
_static Fix some typos in the doc 2016-08-28 20:29:18 +00:00
_templates
_themes/llvm-theme
CommandGuide Resubmit r297897: [PGO] Value profile for size of memory intrinsic calls 2017-03-16 21:15:48 +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 [X86][AVX512] Adding new LLVM TableGen backend which generates the EVEX2VEX compressing tables. 2017-03-07 08:11:19 +00:00
tutorial Remove redundant code block and update comment. 2017-03-04 14:00:44 +00:00
AdvancedBuilds.rst
AliasAnalysis.rst Invariant.group and mustalias docs fixes 2017-04-12 07:59:35 +00:00
AMDGPUUsage.rst [DebugInfo] Emit address space with DW_AT_address_class attribute for pointer and reference types 2017-03-08 23:55:44 +00:00
ARM-BE-bitcastfail.png
ARM-BE-bitcastsuccess.png
ARM-BE-ld1.png
ARM-BE-ldr.png
Atomics.rst
BigEndianNEON.rst
BitCodeFormat.rst Bitcode: Add a string table to the bitcode format. 2017-04-17 17:51:36 +00:00
BlockFrequencyTerminology.rst
BranchWeightMetadata.rst Add function importing info from samplepgo profile to the module summary. 2017-02-28 18:09:44 +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 [docs] Fix typo 2017-02-09 23:02:37 +00:00
CodeOfConduct.rst
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 docs/conf.py: Suppress sphinx highlighting failure warnings 2017-02-10 00:00:22 +00:00
Coroutines.rst [coroutines] Add syntax coloring to examples in Coroutines.rst 2017-04-05 05:26:26 +00:00
CoverageMappingFormat.rst fix some typos in the doc 2017-01-14 11:37:01 +00:00
DebuggingJITedCode.rst
DeveloperPolicy.rst Update Bugzilla URLs in docs 2017-02-17 08:26:11 +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 Change section flag character for SHF_LINK_ORDER to "o". 2017-04-04 22:35:08 +00:00
FAQ.rst fix some typos in the doc 2016-07-28 09:28:58 +00:00
FaultMaps.rst Fix the docs build 2017-02-07 20:36:03 +00:00
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.rst statement. 2017-03-29 14:27:38 +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] Document the staging buildbot 2017-02-05 21:21:23 +00:00
HowToBuildOnARM.rst
HowToCrossCompileLLVM.rst
HowToReleaseLLVM.rst Adding RELEASE_TESTERS.TXT 2016-07-21 16:46:44 +00:00
HowToSetUpLLVMStyleRTTI.rst
HowToSubmitABug.rst Update Bugzilla URLs in docs 2017-02-17 08:26:11 +00:00
HowToUseAttributes.rst Fix RST docs AttributeList heading underline 2017-03-21 17:05:00 +00:00
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 [XRay][docs] Add XRayExample to docindex. 2017-03-31 02:51:19 +00:00
LangRef.rst PR32382: Fix emitting complex DWARF expressions. 2017-04-18 01:21:53 +00:00
Lexicon.rst Update Bugzilla URLs in docs 2017-02-17 08:26:11 +00:00
LibFuzzer.rst [libFuzzer] more trophies 2017-04-14 20:11:16 +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 Fix LLVMBuild.txt typo. NFC 2017-04-03 18:21:50 +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 MIRLangRef: Add a section on simplifying .mir tests 2017-04-13 23:45:14 +00:00
NVPTXUsage.rst Update NVVMReflect usage doc to new idiom for adding target-specific early passes. 2017-01-27 19:44:24 +00:00
OptBisect.rst Remove opt-bisect support for "cases" in favor of debug counters 2017-03-11 01:41:03 +00:00
Packaging.rst
Passes.rst
Phabricator.rst [doc] Fix minor grammatical error in Phabricator.rst 2017-01-05 13:08:14 +00:00
ProgrammersManual.rst Update stale doxygen links in ProgrammersManual.rst 2017-04-03 22:24:32 +00:00
Projects.rst
re_format.7
README.txt
ReleaseNotes.rst Don't try to link to the 4.0 release notes 2017-02-09 23:03:34 +00:00
ReleaseProcess.rst
ReportingGuide.rst
ScudoHardenedAllocator.rst [docs] Documentation update for Scudo 2017-02-09 16:07:52 +00:00
SegmentedStacks.rst [docs] Fixing Sphinx warnings to unclog the buildbot 2016-07-20 12:16:38 +00:00
SourceLevelDebugging.rst PR32382: Fix emitting complex DWARF expressions. 2017-04-18 01:21:53 +00:00
SphinxQuickstartTemplate.rst
StackMaps.rst [Stackmap] Added callsite counts to emitted function information. 2016-09-14 20:22:03 +00:00
Statepoints.rst Update Bugzilla URLs in docs 2017-02-17 08:26:11 +00:00
SystemLibrary.rst
TableGenFundamentals.rst
TestingGuide.rst [docs] cleanup documentation on lit substitutions 2017-02-09 14:12:30 +00:00
TestSuiteMakefileGuide.rst
TypeMetadata.rst
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] Update the XRay documentation 2017-02-28 22:01:26 +00:00
XRayExample.rst [XRay][docs] Fix hyperlink to XRay doc 2017-04-06 04:26:26 +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