llvm-6502/lib/Analysis
Dan Gohman 655b5a48b9 Delete code for folding undefs in ScalarEvolution. It's invalid in
obscure ways, and it isn't actually important in the real world.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@159969 91177308-0d34-0410-b5e6-96231b3b80d8
2012-07-09 23:51:20 +00:00
..
IPA RefreshCallGraph: ignore 'invoke intrinsic'. IntrinsicInst doesnt not recognize invoke, and shouldnt at this point, since the rest of LLVM codebase doesnt expect invoke of intrinsics 2012-06-29 17:49:32 +00:00
AliasAnalysis.cpp Move the capture analysis from MemoryDependencyAnalysis to a more general place 2012-05-14 20:35:04 +00:00
AliasAnalysisCounter.cpp
AliasAnalysisEvaluator.cpp
AliasDebugger.cpp
AliasSetTracker.cpp Reduce use list thrashing by using DenseMap's find_as for maps with ValueHandle keys. 2012-06-30 22:37:15 +00:00
Analysis.cpp
BasicAliasAnalysis.cpp refactor the MemoryBuiltin analysis: 2012-06-21 15:45:28 +00:00
BlockFrequencyInfo.cpp
BranchProbabilityInfo.cpp
CaptureTracking.cpp Fix intendation. 2012-05-10 23:38:07 +00:00
CFGPrinter.cpp
CMakeLists.txt Update the CMake files. 2012-06-29 09:01:47 +00:00
CodeMetrics.cpp A pile of long over-due refactorings here. There are some very, *very* 2012-05-04 00:58:03 +00:00
ConstantFolding.cpp Reapply r155682, making constant folding more consistent, with a fix to work 2012-04-27 17:50:22 +00:00
DbgInfoPrinter.cpp Move lib/Analysis/DebugInfo.cpp to lib/VMCore/DebugInfo.cpp and 2012-06-28 00:05:13 +00:00
DominanceFrontier.cpp
DomPrinter.cpp
InlineCost.cpp Fix typos found by http://github.com/lyda/misspell-check 2012-06-02 10:20:22 +00:00
InstCount.cpp
InstructionSimplify.cpp Remove extraneous ';'. 2012-05-17 20:27:58 +00:00
Interval.cpp
IntervalPartition.cpp
IVUsers.cpp
LazyValueInfo.cpp make LazyValueInfo analyze the default case of switch statements (we know that in the default branch the value cannot be any of the switch cases) 2012-06-28 16:13:37 +00:00
LibCallAliasAnalysis.cpp
LibCallSemantics.cpp
Lint.cpp Always compute all the bits in ComputeMaskedBits. 2012-04-04 12:51:34 +00:00
LLVMBuild.txt
Loads.cpp
LoopDependenceAnalysis.cpp
LoopInfo.cpp Enable the new LoopInfo algorithm by default. 2012-06-26 04:11:38 +00:00
LoopPass.cpp Enable the new LoopInfo algorithm by default. 2012-06-26 04:11:38 +00:00
Makefile
MemDepPrinter.cpp Mark some static arrays as const. 2012-05-24 06:35:32 +00:00
MemoryBuiltins.cpp fold PHI nodes in SizeOffsetEvaluator whenever possible. 2012-07-03 17:13:25 +00:00
MemoryDependenceAnalysis.cpp refactor the MemoryBuiltin analysis: 2012-06-21 15:45:28 +00:00
ModuleDebugInfoPrinter.cpp Move lib/Analysis/DebugInfo.cpp to lib/VMCore/DebugInfo.cpp and 2012-06-28 00:05:13 +00:00
NoAliasAnalysis.cpp
PathNumbering.cpp
PathProfileInfo.cpp
PathProfileVerifier.cpp
PHITransAddr.cpp
PostDominators.cpp
ProfileEstimatorPass.cpp
ProfileInfo.cpp
ProfileInfoLoader.cpp Round 2 of dead private variable removal. 2012-06-06 19:47:08 +00:00
ProfileInfoLoaderPass.cpp Round 2 of dead private variable removal. 2012-06-06 19:47:08 +00:00
ProfileVerifierPass.cpp
README.txt
RegionInfo.cpp Rename the Region::block_iterator to Region::block_node_iterator, and 2012-05-04 20:55:23 +00:00
RegionPass.cpp Rename the Region::block_iterator to Region::block_node_iterator, and 2012-05-04 20:55:23 +00:00
RegionPrinter.cpp Rename the Region::block_iterator to Region::block_node_iterator, and 2012-05-04 20:55:23 +00:00
ScalarEvolution.cpp Delete code for folding undefs in ScalarEvolution. It's invalid in 2012-07-09 23:51:20 +00:00
ScalarEvolutionAliasAnalysis.cpp
ScalarEvolutionExpander.cpp LSR fix: add a missing phi check during IV hoisting. 2012-05-22 17:39:59 +00:00
ScalarEvolutionNormalization.cpp
SparsePropagation.cpp
Trace.cpp
TypeBasedAliasAnalysis.cpp
ValueTracking.cpp PHINode::hasConstantValue(): return undef if the PHI is fully recursive. 2012-07-03 21:15:40 +00:00

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))

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