llvm-6502

mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-11-03 14:08:57 +00:00

History

David Majnemer 77e22b7836 ValueTracking: ComputeNumSignBits should tolerate misshapen phi nodes PHI nodes can have zero operands in the middle of a transform. It is expected that utilities in Analysis don't freak out when this happens. Note that it is considered invalid to allow these misshapen phi nodes to make it to another pass. This fixes PR22086. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225126 91177308-0d34-0410-b5e6-96231b3b80d8		2015-01-04 07:06:53 +00:00
..
IPA
AliasAnalysis.cpp	Sink store based on alias analysis	2014-12-15 14:09:53 +00:00
AliasAnalysisCounter.cpp
AliasAnalysisEvaluator.cpp
AliasDebugger.cpp
AliasSetTracker.cpp
Analysis.cpp
AssumptionTracker.cpp
BasicAliasAnalysis.cpp
BlockFrequencyInfo.cpp
BlockFrequencyInfoImpl.cpp	BFI: Saturate when combining edges to a successor	2014-12-05 19:13:42 +00:00
BranchProbabilityInfo.cpp	IR: Split Metadata from Value	2014-12-09 18:38:53 +00:00
CaptureTracking.cpp
CFG.cpp
CFGPrinter.cpp
CFLAliasAnalysis.cpp
CGSCCPassManager.cpp
CMakeLists.txt
CodeMetrics.cpp
ConstantFolding.cpp
CostModel.cpp
Delinearization.cpp
DependenceAnalysis.cpp
DominanceFrontier.cpp
DomPrinter.cpp
FunctionTargetTransformInfo.cpp
InstCount.cpp
InstructionSimplify.cpp	InstSimplify: Don't bother if getScalarSizeInBits returns zero	2014-12-20 04:45:33 +00:00
Interval.cpp
IntervalPartition.cpp
IVUsers.cpp
JumpInstrTableInfo.cpp
LazyCallGraph.cpp
LazyValueInfo.cpp
LibCallAliasAnalysis.cpp
LibCallSemantics.cpp
Lint.cpp
LLVMBuild.txt
Loads.cpp
LoopInfo.cpp
LoopPass.cpp
Makefile
MemDepPrinter.cpp
MemoryBuiltins.cpp
MemoryDependenceAnalysis.cpp	Remove redundant assignment.	2014-12-19 11:29:34 +00:00
ModuleDebugInfoPrinter.cpp
NoAliasAnalysis.cpp
PHITransAddr.cpp
PostDominators.cpp
PtrUseVisitor.cpp
README.txt
RegionInfo.cpp
RegionPass.cpp
RegionPrinter.cpp
ScalarEvolution.cpp	Teach ScalarEvolution to exploit min and max expressions when proving	2014-12-15 22:50:15 +00:00
ScalarEvolutionAliasAnalysis.cpp
ScalarEvolutionExpander.cpp
ScalarEvolutionNormalization.cpp
ScopedNoAliasAA.cpp
SparsePropagation.cpp
StratifiedSets.h
TargetTransformInfo.cpp	Loop Vectorizer minor changes in the code -	2014-12-14 09:43:50 +00:00
Trace.cpp
TypeBasedAliasAnalysis.cpp	IR: Split Metadata from Value	2014-12-09 18:38:53 +00:00
ValueTracking.cpp	ValueTracking: ComputeNumSignBits should tolerate misshapen phi nodes	2015-01-04 07:06:53 +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))

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