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History

Chandler Carruth aea315a631 [LoopInfo] Add helper methods to compute two useful orderings of the loops in a function. These are relatively confusing to talk about and compute correctly so it seems really good to write down their implementation in one place. I've replaced one place we needed this in the loop PM infrastructure and I have another place in a pending patch that wants it. We can't quite use this for the core loop PM walk because there we're sometimes working on a sub-forest. I'll add the expected unittests before committing this but wanted to make sure folks were happy with these names / comments. Credit goes to Richard Smith for the idea for naming the order where siblings are in reverse program order but the tree traversal remains preorder. Differential Revision: https://reviews.llvm.org/D28932 llvm-svn: 292569		2017-01-20 02:41:20 +00:00
..
AliasAnalysis.cpp	[AliasAnalysis] Fences do not modify constant memory location	2017-01-20 00:21:33 +00:00
AliasAnalysisEvaluator.cpp	Consistently use FunctionAnalysisManager	2016-08-09 00:28:15 +00:00
AliasAnalysisSummary.cpp	Update a comment.	2016-08-25 01:29:55 +00:00
AliasAnalysisSummary.h	Make some LLVM_CONSTEXPR variables const. NFC.	2016-08-25 01:05:08 +00:00
AliasSetTracker.cpp	[AliasSetTracker] Make AST smarter about assume intrinsics that don't actually affect memory.	2016-11-07 14:11:45 +00:00
Analysis.cpp	[LCSSA] Perform LCSSA verification only for the current loop nest.	2016-10-28 12:57:20 +00:00
AssumptionCache.cpp	[ValueTracking] recognize a 'not' of an assumed condition as false	2017-01-17 18:15:49 +00:00
BasicAliasAnalysis.cpp	[PM] Remove a pointless optimization.	2016-12-27 18:04:11 +00:00
BlockFrequencyInfo.cpp	Add an interface to scale the frequencies of a set of blocks.	2017-01-19 18:53:16 +00:00
BlockFrequencyInfoImpl.cpp	[GraphTraits] Replace all NodeType usage with NodeRef	2016-08-22 21:09:30 +00:00
BranchProbabilityInfo.cpp	Retry: [BPI] Use a safer constructor to calculate branch probabilities	2016-12-17 01:02:08 +00:00
CallGraph.cpp	[PM] Change the static object whose address is used to uniquely identify	2016-11-23 17:53:26 +00:00
CallGraphSCCPass.cpp	Improve the `-filter-print-funcs` option to skip the banner for CGSCC pass when nothing is to be printed	2017-01-18 21:37:11 +00:00
CallPrinter.cpp
CaptureTracking.cpp	[CaptureTracking] Volatile operations capture their memory location	2016-05-26 17:36:22 +00:00
CFG.cpp
CFGPrinter.cpp	[PM] Port CFGViewer and CFGPrinter to the new Pass Manager	2016-09-15 18:35:27 +00:00
CFLAndersAliasAnalysis.cpp	Apply clang-tidy's performance-unnecessary-value-param to LLVM.	2017-01-13 14:39:03 +00:00
CFLGraph.h	[CFLAA] Check for pointer types in more places.	2016-07-29 01:23:45 +00:00
CFLSteensAliasAnalysis.cpp	[PM] Change the static object whose address is used to uniquely identify	2016-11-23 17:53:26 +00:00
CGSCCPassManager.cpp	[PM] Teach the CGSCC's CG update utility to more carefully invalidate	2016-12-28 10:34:50 +00:00
CMakeLists.txt	[PM] Separate the LoopAnalysisManager from the LoopPassManager and move	2017-01-11 09:43:56 +00:00
CodeMetrics.cpp	Revert @llvm.assume with operator bundles (r289755-r289757)	2016-12-19 08:22:17 +00:00
ConstantFolding.cpp	[InstCombiner] Simplify lib calls to `round{,f}`	2016-12-26 14:29:29 +00:00
CostModel.cpp	[X86] updating TTI costs for arithmetic instructions on X86\SLM arch.	2017-01-11 08:23:37 +00:00
Delinearization.cpp
DemandedBits.cpp	Revert @llvm.assume with operator bundles (r289755-r289757)	2016-12-19 08:22:17 +00:00
DependenceAnalysis.cpp	[PM] Change the static object whose address is used to uniquely identify	2016-11-23 17:53:26 +00:00
DivergenceAnalysis.cpp
DominanceFrontier.cpp	[PM] Introduce an analysis set used to preserve all analyses over	2017-01-15 06:32:49 +00:00
DomPrinter.cpp
EHPersonalities.cpp	[tsan] Add support for C++ exceptions into TSan (call __tsan_func_exit during unwinding), LLVM part	2016-11-14 21:41:13 +00:00
GlobalsModRef.cpp	[PM] Change the static object whose address is used to uniquely identify	2016-11-23 17:53:26 +00:00
IndirectCallPromotionAnalysis.cpp	Remove another unused variable from r275216	2016-07-12 23:49:17 +00:00
InlineCost.cpp	Revert "[InlineCost] Use TTI to check if GEP is free."	2017-01-19 22:51:03 +00:00
InstCount.cpp
InstructionSimplify.cpp	Removing potentially error-prone fallthrough. NFC	2017-01-14 07:28:47 +00:00
Interval.cpp	Apply clang-tidy's modernize-loop-convert to lib/Analysis.	2016-06-26 17:27:42 +00:00
IntervalPartition.cpp	Apply clang-tidy's modernize-loop-convert to lib/Analysis.	2016-06-26 17:27:42 +00:00
IteratedDominanceFrontier.cpp	Normalize file docs. NFC.	2016-07-21 20:52:35 +00:00
IVUsers.cpp	[PM] Separate the LoopAnalysisManager from the LoopPassManager and move	2017-01-11 09:43:56 +00:00
LazyBlockFrequencyInfo.cpp	[BPI] Add new LazyBPI analysis	2016-07-28 23:31:12 +00:00
LazyBranchProbabilityInfo.cpp	[BPI] Add new LazyBPI analysis	2016-07-28 23:31:12 +00:00
LazyCallGraph.cpp	[PM] Teach the CGSCC's CG update utility to more carefully invalidate	2016-12-28 10:34:50 +00:00
LazyValueInfo.cpp	Make processing @llvm.assume more efficient - Add affected values to the assumption cache	2017-01-11 13:24:24 +00:00
Lint.cpp	Revert @llvm.assume with operator bundles (r289755-r289757)	2016-12-19 08:22:17 +00:00
LLVMBuild.txt	Restore "[ThinLTO] Prevent exporting of locals used/defined in module level asm"	2016-11-14 17:12:32 +00:00
Loads.cpp	[Loads] Fix crash in is isDereferenceableAndAlignedPointer()	2016-10-28 15:32:28 +00:00
LoopAccessAnalysis.cpp	[PM] Separate the LoopAnalysisManager from the LoopPassManager and move	2017-01-11 09:43:56 +00:00
LoopAnalysisManager.cpp	[LoopInfo] Add helper methods to compute two useful orderings of the	2017-01-20 02:41:20 +00:00
LoopInfo.cpp	Use getLoopLatch in place of isLoopSimplifyForm	2017-01-15 21:17:52 +00:00
LoopPass.cpp	Reverted: Track validity of pass results	2017-01-15 10:23:18 +00:00
LoopUnrollAnalyzer.cpp	[LoopUnrollAnalyzer] Handle out of bounds accesses in visitLoad	2016-07-23 02:56:49 +00:00
MemDepPrinter.cpp	Apply clang-tidy's modernize-loop-convert to lib/Analysis.	2016-06-26 17:27:42 +00:00
MemDerefPrinter.cpp
MemoryBuiltins.cpp	[Analysis] Ignore `nobuiltin` on `allocsize` function calls.	2016-12-27 06:32:14 +00:00
MemoryDependenceAnalysis.cpp	[Devirtualization] MemDep returns non-local !invariant.group dependencies	2017-01-12 11:33:58 +00:00
MemoryLocation.cpp
ModuleDebugInfoPrinter.cpp	[IR] Remove the DIExpression field from DIGlobalVariable.	2016-12-20 02:09:43 +00:00
ModuleSummaryAnalysis.cpp	ThinLTO: add early "dead-stripping" on the Index	2017-01-05 21:34:18 +00:00
ObjCARCAliasAnalysis.cpp	Consistently use FunctionAnalysisManager	2016-08-09 00:28:15 +00:00
ObjCARCAnalysisUtils.cpp
ObjCARCInstKind.cpp	Create llvm.addressofreturnaddress intrinsic	2016-10-12 22:13:19 +00:00
OptimizationDiagnosticInfo.cpp	[PM] Teach the optimization remarks emitter to handle invalidation	2017-01-15 08:20:50 +00:00
OrderedBasicBlock.cpp
PHITransAddr.cpp	Revert @llvm.assume with operator bundles (r289755-r289757)	2016-12-19 08:22:17 +00:00
PostDominators.cpp	[PM] Introduce an analysis set used to preserve all analyses over	2017-01-15 06:32:49 +00:00
ProfileSummaryInfo.cpp	Compute summary before calling extractProfTotalWeight	2017-01-14 00:32:37 +00:00
PtrUseVisitor.cpp
README.txt
RegionInfo.cpp	[PM] Introduce an analysis set used to preserve all analyses over	2017-01-15 06:32:49 +00:00
RegionPass.cpp	Reverted: Track validity of pass results	2017-01-15 10:23:18 +00:00
RegionPrinter.cpp	Apply clang-tidy's modernize-loop-convert to lib/Analysis.	2016-06-26 17:27:42 +00:00
ScalarEvolution.cpp	[SCEV] Make getUDivExactExpr handle non-nuw multiplies correctly.	2017-01-18 23:56:42 +00:00
ScalarEvolutionAliasAnalysis.cpp	[PM] Change the static object whose address is used to uniquely identify	2016-11-23 17:53:26 +00:00
ScalarEvolutionExpander.cpp	Revert @llvm.assume with operator bundles (r289755-r289757)	2016-12-19 08:22:17 +00:00
ScalarEvolutionNormalization.cpp
ScopedNoAliasAA.cpp	[PM] Change the static object whose address is used to uniquely identify	2016-11-23 17:53:26 +00:00
SparsePropagation.cpp	Apply clang-tidy's modernize-loop-convert to lib/Analysis.	2016-06-26 17:27:42 +00:00
StratifiedSets.h	Do a sweep over move ctors and remove those that are identical to the default.	2016-10-20 12:20:28 +00:00
TargetLibraryInfo.cpp	[TLI] Appease spurious MSVC warning using llvm_unreachable. NFC.	2017-01-17 19:54:18 +00:00
TargetTransformInfo.cpp	[X86] updating TTI costs for arithmetic instructions on X86\SLM arch.	2017-01-11 08:23:37 +00:00
Trace.cpp
TypeBasedAliasAnalysis.cpp	[TBAA] Don't generate invalid TBAA when merging nodes	2016-12-11 20:07:25 +00:00
TypeMetadataUtils.cpp	TypeMetadataUtils: Simplify; spotted by Mehdi.	2016-12-21 19:00:47 +00:00
ValueTracking.cpp	[ValueTracking] recognize a 'not' of an assumed condition as false	2017-01-17 18:15:49 +00:00
VectorUtils.cpp	IR: Change the gep_type_iterator API to avoid always exposing the "current" type.	2016-12-02 02:24:42 +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))

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