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History

Roman Lebedev c8b6177910 Reland "[ScalarEvolution] createSCEV(): recognize `udiv`/`urem` disguised as an `sdiv`/`srem`" This reverts commit d3e3f36ff1151f565730977ac4f663a2ccee48ae, which reverter the original commit 2c16100e6f72075564ea1f67fa5a82c269dafcd3, but with polly tests now actually passing.		2020-07-06 18:00:22 +03:00
..
models/inliner
AliasAnalysis.cpp
AliasAnalysisEvaluator.cpp
AliasAnalysisSummary.cpp
AliasAnalysisSummary.h
AliasSetTracker.cpp
Analysis.cpp
AssumeBundleQueries.cpp
AssumptionCache.cpp
BasicAliasAnalysis.cpp
BlockFrequencyInfo.cpp
BlockFrequencyInfoImpl.cpp
BranchProbabilityInfo.cpp
CallGraph.cpp
CallGraphSCCPass.cpp
CallPrinter.cpp
CaptureTracking.cpp
CFG.cpp
CFGPrinter.cpp
CFLAndersAliasAnalysis.cpp
CFLGraph.h
CFLSteensAliasAnalysis.cpp
CGSCCPassManager.cpp
CMakeLists.txt
CmpInstAnalysis.cpp
CodeMetrics.cpp
ConstantFolding.cpp
CostModel.cpp
DDG.cpp
Delinearization.cpp
DemandedBits.cpp
DependenceAnalysis.cpp
DependenceGraphBuilder.cpp
DivergenceAnalysis.cpp
DominanceFrontier.cpp
DomPrinter.cpp
DomTreeUpdater.cpp
EHPersonalities.cpp
GlobalsModRef.cpp
GuardUtils.cpp
HeatUtils.cpp
IndirectCallPromotionAnalysis.cpp
InlineAdvisor.cpp
InlineCost.cpp
InlineFeaturesAnalysis.cpp
InstCount.cpp
InstructionPrecedenceTracking.cpp
InstructionSimplify.cpp
Interval.cpp
IntervalPartition.cpp
IVDescriptors.cpp
IVUsers.cpp
LazyBlockFrequencyInfo.cpp
LazyBranchProbabilityInfo.cpp
LazyCallGraph.cpp
LazyValueInfo.cpp
LegacyDivergenceAnalysis.cpp
Lint.cpp
LLVMBuild.txt
Loads.cpp
LoopAccessAnalysis.cpp
LoopAnalysisManager.cpp
LoopCacheAnalysis.cpp
LoopInfo.cpp
LoopNestAnalysis.cpp
LoopPass.cpp
LoopUnrollAnalyzer.cpp
MemDepPrinter.cpp
MemDerefPrinter.cpp
MemoryBuiltins.cpp
MemoryDependenceAnalysis.cpp
MemoryLocation.cpp
MemorySSA.cpp
MemorySSAUpdater.cpp
MLInlineAdvisor.cpp
ModuleDebugInfoPrinter.cpp
ModuleSummaryAnalysis.cpp
MustExecute.cpp
ObjCARCAliasAnalysis.cpp
ObjCARCAnalysisUtils.cpp
ObjCARCInstKind.cpp
OptimizationRemarkEmitter.cpp
OrderedInstructions.cpp
PHITransAddr.cpp
PhiValues.cpp
PostDominators.cpp
ProfileSummaryInfo.cpp
PtrUseVisitor.cpp
README.txt
RegionInfo.cpp
RegionPass.cpp
RegionPrinter.cpp
ReleaseModeModelRunner.cpp
ScalarEvolution.cpp
ScalarEvolutionAliasAnalysis.cpp
ScalarEvolutionDivision.cpp
ScalarEvolutionNormalization.cpp
ScopedNoAliasAA.cpp
StackLifetime.cpp
StackSafetyAnalysis.cpp
StratifiedSets.h
SyncDependenceAnalysis.cpp
SyntheticCountsUtils.cpp
TargetLibraryInfo.cpp
TargetTransformInfo.cpp
Trace.cpp
TypeBasedAliasAnalysis.cpp
TypeMetadataUtils.cpp
ValueLattice.cpp
ValueLatticeUtils.cpp
ValueTracking.cpp
VectorUtils.cpp
VFABIDemangling.cpp

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))

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