llvm-mirror

mirror of https://github.com/RPCS3/llvm-mirror.git synced 2025-02-28 16:28:58 +00:00

History

Hans Wennborg 173103be2a Revert f0c2a5a "[LV] Generalize conditions for sinking instrs for first order recurrences."

It broke Chromium, causing "Instruction does not dominate all uses!" errors.
See https://bugs.chromium.org/p/chromium/issues/detail?id=1022297#c1 for a
reproducer.

> If the recurrence PHI node has a single user, we can sink any
> instruction without side effects, given that all users are dominated by
> the instruction computing the incoming value of the next iteration
> ('Previous'). We can sink instructions that may cause traps, because
> that only causes the trap to occur later, but not on any new paths.
>
> With the relaxed check, we also have to make sure that we do not have a
> direct cycle (meaning PHI user == 'Previous), which indicates a
> reduction relation, which potentially gets missed by
> ReductionDescriptor.
>
> As follow-ups, we can also sink stores, iff they do not alias with
> other instructions we move them across and we could also support sinking
> chains of instructions and multiple users of the PHI.
>
> Fixes PR43398.
>
> Reviewers: hsaito, dcaballe, Ayal, rengolin
>
> Reviewed By: Ayal
>
> Differential Revision: https://reviews.llvm.org/D69228

2019-11-07 11:00:02 +01:00

AliasAnalysis.cpp

…

AliasAnalysisEvaluator.cpp

…

AliasAnalysisSummary.cpp

…

AliasAnalysisSummary.h

…

AliasSetTracker.cpp

…

Analysis.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

[WC] Fix a subtle bug in our definition of widenable branch

2019-11-06 14:16:34 -08:00

IndirectCallPromotionAnalysis.cpp

…

InlineCost.cpp

…

InstCount.cpp

…

InstructionPrecedenceTracking.cpp

…

InstructionSimplify.cpp

…

Interval.cpp

…

IntervalPartition.cpp

…

IVDescriptors.cpp

Revert f0c2a5a "[LV] Generalize conditions for sinking instrs for first order recurrences."

2019-11-07 11:00:02 +01:00

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

…

LoopPass.cpp

…

LoopUnrollAnalyzer.cpp

…

MemDepPrinter.cpp

…

MemDerefPrinter.cpp

…

MemoryBuiltins.cpp

…

MemoryDependenceAnalysis.cpp

…

MemoryLocation.cpp

…

MemorySSA.cpp

…

MemorySSAUpdater.cpp

…

ModuleDebugInfoPrinter.cpp

…

ModuleSummaryAnalysis.cpp

…

MustExecute.cpp

…

ObjCARCAliasAnalysis.cpp

…

ObjCARCAnalysisUtils.cpp

…

ObjCARCInstKind.cpp

…

OptimizationRemarkEmitter.cpp

…

OrderedBasicBlock.cpp

…

OrderedInstructions.cpp

…

PHITransAddr.cpp

…

PhiValues.cpp

…

PostDominators.cpp

…

ProfileSummaryInfo.cpp

…

PtrUseVisitor.cpp

…

README.txt

…

RegionInfo.cpp

…

RegionPass.cpp

…

RegionPrinter.cpp

…

ScalarEvolution.cpp

…

ScalarEvolutionAliasAnalysis.cpp

…

ScalarEvolutionExpander.cpp

…

ScalarEvolutionNormalization.cpp

…

ScopedNoAliasAA.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))

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