llvm-6502

mirror of https://github.com/c64scene-ar/llvm-6502.git synced 2024-12-13 20:32:21 +00:00

History

Mark Heffernan b10837d169 Clarify HowFarToZero computation when the step is a positive power of two. Functionally this should be identical to the existing code except for the case where Step is maximally negative (eg, INT_MIN). We now punt in that one corner case to make reasoning about the code easier. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224274 91177308-0d34-0410-b5e6-96231b3b80d8		2014-12-15 21:19:53 +00:00
..
IPA	Remove the unused FindUsedTypes pass.	2014-11-24 20:53:26 +00:00
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	ConstantFold, InstSimplify: undef >>a x can be either -1 or 0, choose 0	2014-12-10 21:58:15 +00:00
Interval.cpp
IntervalPartition.cpp
IVUsers.cpp
JumpInstrTableInfo.cpp
LazyCallGraph.cpp
LazyValueInfo.cpp	LazyValueInfo: Actually re-visit partially solved block-values in solveBlockValue()	2014-11-25 17:23:05 +00:00
LibCallAliasAnalysis.cpp
LibCallSemantics.cpp
Lint.cpp
LLVMBuild.txt
Loads.cpp	Revert r220349 to re-instate r220277 with a fix for PR21330 -- quite	2014-11-25 08:20:27 +00:00
LoopInfo.cpp
LoopPass.cpp
Makefile
MemDepPrinter.cpp
MemoryBuiltins.cpp
MemoryDependenceAnalysis.cpp	Relax an assert a bit to avoid a crash on unreachable code.	2014-12-01 02:55:24 +00:00
ModuleDebugInfoPrinter.cpp
NoAliasAnalysis.cpp
PHITransAddr.cpp
PostDominators.cpp
PtrUseVisitor.cpp
README.txt
RegionInfo.cpp
RegionPass.cpp
RegionPrinter.cpp
ScalarEvolution.cpp	Clarify HowFarToZero computation when the step is a positive power of two. Functionally this should be identical to the existing code except for the case where Step is maximally negative (eg, INT_MIN). We now punt in that one corner case to make reasoning about the code easier.	2014-12-15 21:19:53 +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: Don't recurse too deeply in computeKnownBitsFromAssume	2014-12-12 23:59:29 +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))

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