mirror of
https://github.com/RPCS3/llvm-mirror.git
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ecad339479
----------------------------------------
define i32 @src(i32 %x, i32 %y) {
%0:
%r = uadd_sat i32 %x, %y
ret i32 %r
}
=>
define i32 @tgt(i32 %x, i32 %y) {
%0:
%t0 = sub nsw nuw i32 4294967295, %y
%t1 = umin i32 %x, %t0
%r = add nuw i32 %t1, %y
ret i32 %r
}
Transformation seems to be correct!
The alternative, naive, lowering could be the following,
although i don't think it's better,
thought it will likely be needed for sadd/ssub/*shl:
----------------------------------------
define i32 @src(i32 %x, i32 %y) {
%0:
%r = uadd_sat i32 %x, %y
ret i32 %r
}
=>
define i32 @tgt(i32 %x, i32 %y) {
%0:
%t0 = zext i32 %x to i33
%t1 = zext i32 %y to i33
%t2 = add nuw i33 %t0, %t1
%t3 = zext i32 4294967295 to i33
%t4 = umin i33 %t2, %t3
%r = trunc i33 %t4 to i32
ret i32 %r
}
Transformation seems to be correct!
|
||
|---|---|---|
| .. | ||
| 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 | ||
| ConstraintSystem.cpp | ||
| CostModel.cpp | ||
| DDG.cpp | ||
| Delinearization.cpp | ||
| DemandedBits.cpp | ||
| DependenceAnalysis.cpp | ||
| DependenceGraphBuilder.cpp | ||
| DevelopmentModeInlineAdvisor.cpp | ||
| DivergenceAnalysis.cpp | ||
| DominanceFrontier.cpp | ||
| DomPrinter.cpp | ||
| DomTreeUpdater.cpp | ||
| EHPersonalities.cpp | ||
| FunctionPropertiesAnalysis.cpp | ||
| GlobalsModRef.cpp | ||
| GuardUtils.cpp | ||
| HeatUtils.cpp | ||
| IndirectCallPromotionAnalysis.cpp | ||
| InlineAdvisor.cpp | ||
| InlineCost.cpp | ||
| InlineSizeEstimatorAnalysis.cpp | ||
| InstCount.cpp | ||
| InstructionPrecedenceTracking.cpp | ||
| InstructionSimplify.cpp | ||
| Interval.cpp | ||
| IntervalPartition.cpp | ||
| IRSimilarityIdentifier.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 | ||
| PHITransAddr.cpp | ||
| PhiValues.cpp | ||
| PostDominators.cpp | ||
| ProfileSummaryInfo.cpp | ||
| PtrUseVisitor.cpp | ||
| README.txt | ||
| RegionInfo.cpp | ||
| RegionPass.cpp | ||
| RegionPrinter.cpp | ||
| ReleaseModeModelRunner.cpp | ||
| ReplayInlineAdvisor.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 | ||
| TFUtils.cpp | ||
| Trace.cpp | ||
| TypeBasedAliasAnalysis.cpp | ||
| TypeMetadataUtils.cpp | ||
| ValueLattice.cpp | ||
| ValueLatticeUtils.cpp | ||
| ValueTracking.cpp | ||
| VectorUtils.cpp | ||
| VFABIDemangling.cpp | ||
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))
//===---------------------------------------------------------------------===//