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This caused miscompiles of Chromium tests for iOS due clobbering of live registers. See discussion on the code review for details. > Background: > > This fixes a longstanding problem where llvm breaks ARC's autorelease > optimization (see the link below) by separating calls from the marker > instructions or retainRV/claimRV calls. The backend changes are in > https://reviews.llvm.org/D92569. > > https://clang.llvm.org/docs/AutomaticReferenceCounting.html#arc-runtime-objc-autoreleasereturnvalue > > What this patch does to fix the problem: > > - The front-end adds operand bundle "clang.arc.attachedcall" to calls, > which indicates the call is implicitly followed by a marker > instruction and an implicit retainRV/claimRV call that consumes the > call result. In addition, it emits a call to > @llvm.objc.clang.arc.noop.use, which consumes the call result, to > prevent the middle-end passes from changing the return type of the > called function. This is currently done only when the target is arm64 > and the optimization level is higher than -O0. > > - ARC optimizer temporarily emits retainRV/claimRV calls after the calls > with the operand bundle in the IR and removes the inserted calls after > processing the function. > > - ARC contract pass emits retainRV/claimRV calls after the call with the > operand bundle. It doesn't remove the operand bundle on the call since > the backend needs it to emit the marker instruction. The retainRV and > claimRV calls are emitted late in the pipeline to prevent optimization > passes from transforming the IR in a way that makes it harder for the > ARC middle-end passes to figure out the def-use relationship between > the call and the retainRV/claimRV calls (which is the cause of > PR31925). > > - The function inliner removes an autoreleaseRV call in the callee if > nothing in the callee prevents it from being paired up with the > retainRV/claimRV call in the caller. It then inserts a release call if > claimRV is attached to the call since autoreleaseRV+claimRV is > equivalent to a release. If it cannot find an autoreleaseRV call, it > tries to transfer the operand bundle to a function call in the callee. > This is important since the ARC optimizer can remove the autoreleaseRV > returning the callee result, which makes it impossible to pair it up > with the retainRV/claimRV call in the caller. If that fails, it simply > emits a retain call in the IR if retainRV is attached to the call and > does nothing if claimRV is attached to it. > > - SCCP refrains from replacing the return value of a call with a > constant value if the call has the operand bundle. This ensures the > call always has at least one user (the call to > @llvm.objc.clang.arc.noop.use). > > - This patch also fixes a bug in replaceUsesOfNonProtoConstant where > multiple operand bundles of the same kind were being added to a call. > > Future work: > > - Use the operand bundle on x86-64. > > - Fix the auto upgrader to convert call+retainRV/claimRV pairs into > calls with the operand bundles. > > rdar://71443534 > > Differential Revision: https://reviews.llvm.org/D92808 This reverts commit ed4718eccb12bd42214ca4fb17d196d49561c0c7. |
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AMDGPU | ||
CommandGuide | ||
DependenceGraphs | ||
Frontend | ||
GlobalISel | ||
HistoricalNotes | ||
PDB | ||
Proposals | ||
TableGen | ||
tutorial | ||
AddingConstrainedIntrinsics.rst | ||
AdvancedBuilds.rst | ||
AliasAnalysis.rst | ||
AMDGPUDwarfExtensionsForHeterogeneousDebugging.rst | ||
AMDGPUInstructionNotation.rst | ||
AMDGPUInstructionSyntax.rst | ||
AMDGPUModifierSyntax.rst | ||
AMDGPUOperandSyntax.rst | ||
AMDGPUUsage.rst | ||
ARM-BE-bitcastfail.png | ||
ARM-BE-bitcastsuccess.png | ||
ARM-BE-ld1.png | ||
ARM-BE-ldr.png | ||
Atomics.rst | ||
Benchmarking.rst | ||
BigEndianNEON.rst | ||
BitCodeFormat.rst | ||
BlockFrequencyTerminology.rst | ||
BranchWeightMetadata.rst | ||
BugLifeCycle.rst | ||
Bugpoint.rst | ||
BugpointRedesign.md | ||
BuildingADistribution.rst | ||
CFIVerify.rst | ||
CMake.rst | ||
CMakeLists.txt | ||
CMakePrimer.rst | ||
CodeGenerator.rst | ||
CodeOfConduct.rst | ||
CodeReview.rst | ||
CodingStandards.rst | ||
CommandLine.rst | ||
CompileCudaWithLLVM.rst | ||
CompilerWriterInfo.rst | ||
conf.py | ||
Contributing.rst | ||
Coroutines.rst | ||
CoverageMappingFormat.rst | ||
DebuggingJITedCode.rst | ||
DeveloperPolicy.rst | ||
Docker.rst | ||
doxygen-mainpage.dox | ||
doxygen.cfg.in | ||
epilogue-vectorization-cfg.png | ||
ExceptionHandling.rst | ||
ExtendedIntegerResults.txt | ||
ExtendingLLVM.rst | ||
Extensions.rst | ||
FAQ.rst | ||
FaultMaps.rst | ||
FuzzingLLVM.rst | ||
GarbageCollection.rst | ||
gcc-loops.png | ||
GetElementPtr.rst | ||
GettingInvolved.rst | ||
GettingStarted.rst | ||
GettingStartedTutorials.rst | ||
GettingStartedVS.rst | ||
GitBisecting.rst | ||
GoldPlugin.rst | ||
GwpAsan.rst | ||
HowToAddABuilder.rst | ||
HowToBuildOnARM.rst | ||
HowToBuildWithPGO.rst | ||
HowToCrossCompileBuiltinsOnArm.rst | ||
HowToCrossCompileLLVM.rst | ||
HowToReleaseLLVM.rst | ||
HowToSetUpLLVMStyleRTTI.rst | ||
HowToSubmitABug.rst | ||
HowToUpdateDebugInfo.rst | ||
HowToUseAttributes.rst | ||
HowToUseInstrMappings.rst | ||
InAlloca.rst | ||
index.rst | ||
JITLink.rst | ||
LangRef.rst | ||
Lexicon.rst | ||
LibFuzzer.rst | ||
LinkTimeOptimization.rst | ||
linpack-pc.png | ||
llvm-objdump.1 | ||
loop-guard.svg | ||
loop-irreducible.svg | ||
loop-merge.svg | ||
loop-nested.svg | ||
loop-nonmaximal.svg | ||
loop-separate.svg | ||
loop-single.svg | ||
loop-terminology-guarded-loop.png | ||
loop-terminology-initial-loop.png | ||
loop-terminology-rotated-loop.png | ||
loop-terminology.svg | ||
LoopTerminology.rst | ||
make.bat | ||
Makefile.sphinx | ||
MarkdownQuickstartTemplate.md | ||
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 | ||
MeetupGuidelines.rst | ||
MemorySSA.rst | ||
MemTagSanitizer.rst | ||
MergeFunctions.rst | ||
MIRLangRef.rst | ||
NewPassManager.rst | ||
NVPTXUsage.rst | ||
OptBisect.rst | ||
ORCv2.rst | ||
Packaging.rst | ||
Passes.rst | ||
Phabricator.rst | ||
ProgrammersManual.rst | ||
Projects.rst | ||
re_format.7 | ||
README.txt | ||
Reference.rst | ||
ReleaseNotes.rst | ||
ReleaseProcess.rst | ||
Remarks.rst | ||
ReportingGuide.rst | ||
ScudoHardenedAllocator.rst | ||
Security.rst | ||
SegmentedStacks.rst | ||
SourceLevelDebugging.rst | ||
speculative_load_hardening_microbenchmarks.png | ||
SpeculativeLoadHardening.md | ||
SphinxQuickstartTemplate.rst | ||
StackMaps.rst | ||
StackSafetyAnalysis.rst | ||
Statepoints.rst | ||
SupportLibrary.rst | ||
SupportPolicy.rst | ||
SystemLibrary.rst | ||
TableGenFundamentals.rst | ||
TestingGuide.rst | ||
TestSuiteGuide.md | ||
TestSuiteMakefileGuide.rst | ||
TransformMetadata.rst | ||
TypeMetadata.rst | ||
UserGuides.rst | ||
Vectorizers.rst | ||
WritingAnLLVMBackend.rst | ||
WritingAnLLVMNewPMPass.rst | ||
WritingAnLLVMPass.rst | ||
XRay.rst | ||
XRayExample.rst | ||
XRayFDRFormat.rst | ||
yaml2obj.rst | ||
YamlIO.rst |
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 <https://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` <-> `https://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. `https://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