llvm-project/llvm/lib/Analysis
Manoj Gupta 77eeac3d9e llvm: Add support for "-fno-delete-null-pointer-checks"
Summary:
Support for this option is needed for building Linux kernel.
This is a very frequently requested feature by kernel developers.

More details : https://lkml.org/lkml/2018/4/4/601

GCC option description for -fdelete-null-pointer-checks:
This Assume that programs cannot safely dereference null pointers,
and that no code or data element resides at address zero.

-fno-delete-null-pointer-checks is the inverse of this implying that
null pointer dereferencing is not undefined.

This feature is implemented in LLVM IR in this CL as the function attribute
"null-pointer-is-valid"="true" in IR (Under review at D47894).
The CL updates several passes that assumed null pointer dereferencing is
undefined to not optimize when the "null-pointer-is-valid"="true"
attribute is present.

Reviewers: t.p.northover, efriedma, jyknight, chandlerc, rnk, srhines, void, george.burgess.iv

Reviewed By: efriedma, george.burgess.iv

Subscribers: eraman, haicheng, george.burgess.iv, drinkcat, theraven, reames, sanjoy, xbolva00, llvm-commits

Differential Revision: https://reviews.llvm.org/D47895

llvm-svn: 336613
2018-07-09 22:27:23 +00:00
..
AliasAnalysis.cpp [MSSA] Print more optimization information 2018-06-14 19:55:53 +00:00
AliasAnalysisEvaluator.cpp [MSSA] Print more optimization information 2018-06-14 19:55:53 +00:00
AliasAnalysisSummary.cpp
AliasAnalysisSummary.h Revert r332657: "[AA] cfl-anders-aa with field sensitivity" 2018-05-17 21:56:39 +00:00
AliasSetTracker.cpp [AliasSet] Fix UnknownInstructions printing 2018-06-27 16:34:30 +00:00
Analysis.cpp Add a PhiValuesAnalysis pass to calculate the underlying values of phis 2018-06-28 14:13:06 +00:00
AssumptionCache.cpp [Analysis, Transforms] Fix some Clang-tidy modernize and Include What You Use warnings; other minor fixes (NFC). 2017-09-01 21:37:29 +00:00
BasicAliasAnalysis.cpp llvm: Add support for "-fno-delete-null-pointer-checks" 2018-07-09 22:27:23 +00:00
BlockFrequencyInfo.cpp Revert r320104: infinite loop profiling bug fix 2017-12-08 19:38:07 +00:00
BlockFrequencyInfoImpl.cpp Rename DEBUG macro to LLVM_DEBUG. 2018-05-14 12:53:11 +00:00
BranchProbabilityInfo.cpp [BPI] Remove unnecessary std::list 2018-06-15 21:06:43 +00:00
CFG.cpp
CFGPrinter.cpp Revert "Extend CFGPrinter and CallPrinter with Heat Colors" 2018-06-29 17:48:58 +00:00
CFLAndersAliasAnalysis.cpp Replace AA's uses of uint64_t with LocationSize; NFC. 2018-05-25 21:16:58 +00:00
CFLGraph.h [CFLAA] Reflow comments; NFC 2018-05-26 02:17:43 +00:00
CFLSteensAliasAnalysis.cpp Rename DEBUG macro to LLVM_DEBUG. 2018-05-14 12:53:11 +00:00
CGSCCPassManager.cpp Rename DEBUG macro to LLVM_DEBUG. 2018-05-14 12:53:11 +00:00
CMakeLists.txt Revert "Extend CFGPrinter and CallPrinter with Heat Colors" 2018-06-29 17:48:58 +00:00
CallGraph.cpp IWYU for llvm-config.h in llvm, additions. 2018-04-30 14:59:11 +00:00
CallGraphSCCPass.cpp CallGraphSCCPass: iterate over all functions. 2018-07-06 08:04:47 +00:00
CallPrinter.cpp Revert "Extend CFGPrinter and CallPrinter with Heat Colors" 2018-06-29 17:48:58 +00:00
CaptureTracking.cpp Fix aliasing of launder.invariant.group 2018-05-23 09:16:44 +00:00
CmpInstAnalysis.cpp [InstCombine][InstSimplify] Teach decomposeBitTestICmp to look through truncate instructions 2017-09-01 21:27:34 +00:00
CodeMetrics.cpp Rename DEBUG macro to LLVM_DEBUG. 2018-05-14 12:53:11 +00:00
ConstantFolding.cpp llvm: Add support for "-fno-delete-null-pointer-checks" 2018-07-09 22:27:23 +00:00
CostModel.cpp Remove redundant includes from lib/Analysis. 2017-12-13 21:30:41 +00:00
Delinearization.cpp [NFC] Consolidate six getPointerOperand() utility functions into one place 2018-03-09 21:05:58 +00:00
DemandedBits.cpp Rename DEBUG macro to LLVM_DEBUG. 2018-05-14 12:53:11 +00:00
DependenceAnalysis.cpp [DA] Delinearise AddRecs if we can prove they don't wrap 2018-06-25 15:13:26 +00:00
DivergenceAnalysis.cpp Remove redundant includes from lib/Analysis. 2017-12-13 21:30:41 +00:00
DomPrinter.cpp Revert "Extend CFGPrinter and CallPrinter with Heat Colors" 2018-06-29 17:48:58 +00:00
DominanceFrontier.cpp IWYU for llvm-config.h in llvm, additions. 2018-04-30 14:59:11 +00:00
EHPersonalities.cpp [WebAssembly] Add Wasm personality and isScopedEHPersonality() 2018-05-17 20:52:03 +00:00
GlobalsModRef.cpp [GlobalsAA] Fix a pretty terrible bug that has been in GlobalsAA for 2018-03-16 23:51:33 +00:00
IVUsers.cpp Rename DEBUG macro to LLVM_DEBUG. 2018-05-14 12:53:11 +00:00
IndirectCallPromotionAnalysis.cpp Rename DEBUG macro to LLVM_DEBUG. 2018-05-14 12:53:11 +00:00
InlineCost.cpp llvm: Add support for "-fno-delete-null-pointer-checks" 2018-07-09 22:27:23 +00:00
InstCount.cpp [Analysis] RemoveTotalMemInst counting in InstCount to avoid reading back other Statistic variables 2017-07-18 02:41:12 +00:00
InstructionSimplify.cpp llvm: Add support for "-fno-delete-null-pointer-checks" 2018-07-09 22:27:23 +00:00
Interval.cpp [Analysis] Fix some Clang-tidy modernize-use-using and Include What You Use warnings; other minor fixes (NFC). 2017-07-24 23:16:33 +00:00
IntervalPartition.cpp [Analysis] Fix some Clang-tidy modernize-use-using and Include What You Use warnings; other minor fixes (NFC). 2017-07-24 23:16:33 +00:00
IteratedDominanceFrontier.cpp [IDF] Enforce the returned blocks to be sorted. 2018-05-12 01:44:32 +00:00
LLVMBuild.txt Update libdeps to add BinaryFormat, introduced in r304864. 2017-06-07 04:48:49 +00:00
LazyBlockFrequencyInfo.cpp Require DominatorTree when requiring/preserving LoopInfo in the old pass manager 2018-05-17 09:05:40 +00:00
LazyBranchProbabilityInfo.cpp Require DominatorTree when requiring/preserving LoopInfo in the old pass manager 2018-05-17 09:05:40 +00:00
LazyCallGraph.cpp [STLExtras] Add size() for ranges, and remove distance() 2018-05-16 23:20:42 +00:00
LazyValueInfo.cpp llvm: Add support for "-fno-delete-null-pointer-checks" 2018-07-09 22:27:23 +00:00
Lint.cpp Remove \brief commands from doxygen comments. 2018-05-01 15:54:18 +00:00
Loads.cpp Fix aliasing of launder.invariant.group 2018-05-23 09:16:44 +00:00
LoopAccessAnalysis.cpp llvm: Add support for "-fno-delete-null-pointer-checks" 2018-07-09 22:27:23 +00:00
LoopAnalysisManager.cpp Fixed spelling mistake in comments of LLVM Analysis passes 2018-02-28 19:08:52 +00:00
LoopInfo.cpp [LoopInfo] Port loop exit interfaces from Loop to LoopBase 2018-07-09 17:52:49 +00:00
LoopPass.cpp [LegacyPM] Fix PR37888 by teaching the legacy loop pass manager how to 2018-06-22 02:43:41 +00:00
LoopUnrollAnalyzer.cpp Remove \brief commands from doxygen comments. 2018-05-01 15:54:18 +00:00
MemDepPrinter.cpp Sort the remaining #include lines in include/... and lib/.... 2017-06-06 11:49:48 +00:00
MemDerefPrinter.cpp Remove redundant includes from lib/Analysis. 2017-12-13 21:30:41 +00:00
MemoryBuiltins.cpp Make llvm.objectsize more conservative with null 2018-07-09 22:21:16 +00:00
MemoryDependenceAnalysis.cpp Dissallow non-empty metadata for invariant.group 2018-05-18 23:53:46 +00:00
MemoryLocation.cpp [DSE] Teach the pass that atomic memory intrinsics are stores. 2018-04-23 19:06:49 +00:00
MemorySSA.cpp [MemorySSA] Add APIs to MemoryPhis to delete incoming blocks/values, and an updater API to remove blocks. 2018-06-29 20:46:16 +00:00
MemorySSAUpdater.cpp [MemorySSA] Add APIs to MemoryPhis to delete incoming blocks/values, and an updater API to remove blocks. 2018-06-29 20:46:16 +00:00
ModuleDebugInfoPrinter.cpp Remove redundant includes from lib/Analysis. 2017-12-13 21:30:41 +00:00
ModuleSummaryAnalysis.cpp [ThinLTO] Add string saver onto index for value names 2018-06-26 02:29:08 +00:00
MustExecute.cpp [MustExecute] Fix a debug invariant issue in isGuaranteedToExecute() 2018-05-25 13:02:59 +00:00
ObjCARCAliasAnalysis.cpp [ModRefInfo] Make enum ModRefInfo an enum class [NFC]. 2017-12-07 22:41:34 +00:00
ObjCARCAnalysisUtils.cpp Remove \brief commands from doxygen comments. 2018-05-01 15:54:18 +00:00
ObjCARCInstKind.cpp [DebugInfo] Add DILabel metadata and intrinsic llvm.dbg.label. 2018-05-09 02:40:45 +00:00
OptimizationRemarkEmitter.cpp Remove redundant includes from lib/Analysis. 2017-12-13 21:30:41 +00:00
OrderedBasicBlock.cpp Remove \brief commands from doxygen comments. 2018-05-01 15:54:18 +00:00
PHITransAddr.cpp IWYU for llvm-config.h in llvm, additions. 2018-04-30 14:59:11 +00:00
PhiValues.cpp Add a PhiValuesAnalysis pass to calculate the underlying values of phis 2018-06-28 14:13:06 +00:00
PostDominators.cpp [Dominators] Add PDT constructor from Function 2018-05-23 17:29:21 +00:00
ProfileSummaryInfo.cpp [SampleFDO] Don't treat warm callsite with inline instance in the profile as cold 2018-05-10 23:02:27 +00:00
PtrUseVisitor.cpp [Analysis] Fix some Clang-tidy modernize and Include What You Use warnings; other minor fixes (NFC). 2017-08-18 23:51:26 +00:00
README.txt
RegionInfo.cpp IWYU for llvm-config.h in llvm, additions. 2018-04-30 14:59:11 +00:00
RegionPass.cpp Rename DEBUG macro to LLVM_DEBUG. 2018-05-14 12:53:11 +00:00
RegionPrinter.cpp Revert "Extend CFGPrinter and CallPrinter with Heat Colors" 2018-06-29 17:48:58 +00:00
ScalarEvolution.cpp Revert "[SCEV] Strengthen StrengthenNoWrapFlags (reapply r334428)." 2018-07-06 23:20:35 +00:00
ScalarEvolutionAliasAnalysis.cpp
ScalarEvolutionExpander.cpp SCEVExpander::expandAddRecExprLiterally(): check before casting as Instruction 2018-06-29 07:44:20 +00:00
ScalarEvolutionNormalization.cpp Sort the remaining #include lines in include/... and lib/.... 2017-06-06 11:49:48 +00:00
ScopedNoAliasAA.cpp [ModRefInfo] Make enum ModRefInfo an enum class [NFC]. 2017-12-07 22:41:34 +00:00
StratifiedSets.h Remove \brief commands from doxygen comments. 2018-05-01 15:54:18 +00:00
SyntheticCountsUtils.cpp Remove CallGraphTraits and use equivalent methods in GraphTraits 2018-02-01 19:40:35 +00:00
TargetLibraryInfo.cpp Add Triple::isMIPS()/isMIPS32()/isMIPS64(). NFC 2018-06-25 16:49:20 +00:00
TargetTransformInfo.cpp [IR] move shuffle mask queries from TTI to ShuffleVectorInst 2018-06-19 18:44:00 +00:00
Trace.cpp IWYU for llvm-config.h in llvm, additions. 2018-04-30 14:59:11 +00:00
TypeBasedAliasAnalysis.cpp Fix more spelling mistakes in comments of LLVM Analysis passes 2018-03-02 18:57:02 +00:00
TypeMetadataUtils.cpp
ValueLattice.cpp [LVI] Move LVILatticeVal class to separate header file (NFC). 2017-09-28 11:09:22 +00:00
ValueLatticeUtils.cpp [IPSCCP] Move common functions to ValueLatticeUtils (NFC) 2017-10-13 17:53:44 +00:00
ValueTracking.cpp llvm: Add support for "-fno-delete-null-pointer-checks" 2018-07-09 22:27:23 +00:00
VectorUtils.cpp Remove \brief commands from doxygen comments. 2018-05-01 15:54:18 +00:00

README.txt

Analysis Opportunities:

//===---------------------------------------------------------------------===//

In test/Transforms/LoopStrengthReduce/quadradic-exit-value.ll, the
ScalarEvolution expression for %r is this:

  {1,+,3,+,2}<loop>

Outside the loop, this could be evaluated simply as (%n * %n), however
ScalarEvolution currently evaluates it as

  (-2 + (2 * (trunc i65 (((zext i64 (-2 + %n) to i65) * (zext i64 (-1 + %n) to i65)) /u 2) to i64)) + (3 * %n))

In addition to being much more complicated, it involves i65 arithmetic,
which is very inefficient when expanded into code.

//===---------------------------------------------------------------------===//

In formatValue in test/CodeGen/X86/lsr-delayed-fold.ll,

ScalarEvolution is forming this expression:

((trunc i64 (-1 * %arg5) to i32) + (trunc i64 %arg5 to i32) + (-1 * (trunc i64 undef to i32)))

This could be folded to

(-1 * (trunc i64 undef to i32))

//===---------------------------------------------------------------------===//