forked from OSchip/llvm-project
0c1c70aef4
By enhancing value tracking, we allow an existing min/max canonicalization to kick in and improve codegen for several targets that have min/max instructions. Unfortunately, recognizing min/max in value tracking may cause us to hit a hack in InstCombiner::visitICmpInst() more often: http://lists.llvm.org/pipermail/llvm-dev/2017-January/109340.html ...but I'm hoping we can remove that soon. Correctness proofs based on Alive: Name: smaxmin Pre: C1 < C2 %cmp2 = icmp slt i8 %x, C2 %min = select i1 %cmp2, i8 %x, i8 C2 %cmp3 = icmp slt i8 %x, C1 %r = select i1 %cmp3, i8 C1, i8 %min => %cmp2 = icmp slt i8 %x, C2 %min = select i1 %cmp2, i8 %x, i8 C2 %cmp1 = icmp sgt i8 %min, C1 %r = select i1 %cmp1, i8 %min, i8 C1 Name: sminmax Pre: C1 > C2 %cmp2 = icmp sgt i8 %x, C2 %max = select i1 %cmp2, i8 %x, i8 C2 %cmp3 = icmp sgt i8 %x, C1 %r = select i1 %cmp3, i8 C1, i8 %max => %cmp2 = icmp sgt i8 %x, C2 %max = select i1 %cmp2, i8 %x, i8 C2 %cmp1 = icmp slt i8 %max, C1 %r = select i1 %cmp1, i8 %max, i8 C1 ---------------------------------------- Optimization: smaxmin Done: 1 Optimization is correct! ---------------------------------------- Optimization: sminmax Done: 1 Optimization is correct! Name: umaxmin Pre: C1 u< C2 %cmp2 = icmp ult i8 %x, C2 %min = select i1 %cmp2, i8 %x, i8 C2 %cmp3 = icmp ult i8 %x, C1 %r = select i1 %cmp3, i8 C1, i8 %min => %cmp2 = icmp ult i8 %x, C2 %min = select i1 %cmp2, i8 %x, i8 C2 %cmp1 = icmp ugt i8 %min, C1 %r = select i1 %cmp1, i8 %min, i8 C1 Name: uminmax Pre: C1 u> C2 %cmp2 = icmp ugt i8 %x, C2 %max = select i1 %cmp2, i8 %x, i8 C2 %cmp3 = icmp ugt i8 %x, C1 %r = select i1 %cmp3, i8 C1, i8 %max => %cmp2 = icmp ugt i8 %x, C2 %max = select i1 %cmp2, i8 %x, i8 C2 %cmp1 = icmp ult i8 %max, C1 %r = select i1 %cmp1, i8 %max, i8 C1 ---------------------------------------- Optimization: umaxmin Done: 1 Optimization is correct! ---------------------------------------- Optimization: uminmax Done: 1 Optimization is correct! llvm-svn: 292660 |
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| .. | ||
| AliasAnalysis.cpp | ||
| AliasAnalysisEvaluator.cpp | ||
| AliasAnalysisSummary.cpp | ||
| AliasAnalysisSummary.h | ||
| AliasSetTracker.cpp | ||
| Analysis.cpp | ||
| AssumptionCache.cpp | ||
| BasicAliasAnalysis.cpp | ||
| BlockFrequencyInfo.cpp | ||
| BlockFrequencyInfoImpl.cpp | ||
| BranchProbabilityInfo.cpp | ||
| CFG.cpp | ||
| CFGPrinter.cpp | ||
| CFLAndersAliasAnalysis.cpp | ||
| CFLGraph.h | ||
| CFLSteensAliasAnalysis.cpp | ||
| CGSCCPassManager.cpp | ||
| CMakeLists.txt | ||
| CallGraph.cpp | ||
| CallGraphSCCPass.cpp | ||
| CallPrinter.cpp | ||
| CaptureTracking.cpp | ||
| CodeMetrics.cpp | ||
| ConstantFolding.cpp | ||
| CostModel.cpp | ||
| Delinearization.cpp | ||
| DemandedBits.cpp | ||
| DependenceAnalysis.cpp | ||
| DivergenceAnalysis.cpp | ||
| DomPrinter.cpp | ||
| DominanceFrontier.cpp | ||
| EHPersonalities.cpp | ||
| GlobalsModRef.cpp | ||
| IVUsers.cpp | ||
| IndirectCallPromotionAnalysis.cpp | ||
| InlineCost.cpp | ||
| InstCount.cpp | ||
| InstructionSimplify.cpp | ||
| Interval.cpp | ||
| IntervalPartition.cpp | ||
| IteratedDominanceFrontier.cpp | ||
| LLVMBuild.txt | ||
| LazyBlockFrequencyInfo.cpp | ||
| LazyBranchProbabilityInfo.cpp | ||
| LazyCallGraph.cpp | ||
| LazyValueInfo.cpp | ||
| Lint.cpp | ||
| Loads.cpp | ||
| LoopAccessAnalysis.cpp | ||
| LoopAnalysisManager.cpp | ||
| LoopInfo.cpp | ||
| LoopPass.cpp | ||
| LoopUnrollAnalyzer.cpp | ||
| MemDepPrinter.cpp | ||
| MemDerefPrinter.cpp | ||
| MemoryBuiltins.cpp | ||
| MemoryDependenceAnalysis.cpp | ||
| MemoryLocation.cpp | ||
| ModuleDebugInfoPrinter.cpp | ||
| ModuleSummaryAnalysis.cpp | ||
| ObjCARCAliasAnalysis.cpp | ||
| ObjCARCAnalysisUtils.cpp | ||
| ObjCARCInstKind.cpp | ||
| OptimizationDiagnosticInfo.cpp | ||
| OrderedBasicBlock.cpp | ||
| PHITransAddr.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 | ||
| SparsePropagation.cpp | ||
| StratifiedSets.h | ||
| TargetLibraryInfo.cpp | ||
| TargetTransformInfo.cpp | ||
| Trace.cpp | ||
| TypeBasedAliasAnalysis.cpp | ||
| TypeMetadataUtils.cpp | ||
| ValueTracking.cpp | ||
| VectorUtils.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))
//===---------------------------------------------------------------------===//