llvm-6502/lib/Analysis
David Majnemer c3e70ca886 InstSimplify: Simplify trivial and/or of icmps
Some ICmpInsts when anded/ored with another ICmpInst trivially reduces
to true or false depending on whether or not all integers or no integers
satisfy the intersected/unioned range.

This sort of trivial looking code can come about when InstCombine
performs a range reduction-type operation on sdiv and the like.

This fixes PR20916.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@217750 91177308-0d34-0410-b5e6-96231b3b80d8
2014-09-15 08:15:28 +00:00
..
IPA Add functions for finding ephemeral values 2014-09-07 13:49:57 +00:00
AliasAnalysis.cpp
AliasAnalysisCounter.cpp
AliasAnalysisEvaluator.cpp
AliasDebugger.cpp
AliasSetTracker.cpp
Analysis.cpp Add a CFL Alias Analysis implementation 2014-09-02 21:43:13 +00:00
AssumptionTracker.cpp Add an Assumption-Tracking Pass 2014-09-07 12:44:26 +00:00
BasicAliasAnalysis.cpp Make use of @llvm.assume in ValueTracking (computeKnownBits, etc.) 2014-09-07 18:57:58 +00:00
BlockFrequencyInfo.cpp
BlockFrequencyInfoImpl.cpp
BranchProbabilityInfo.cpp
CaptureTracking.cpp
CFG.cpp
CFGPrinter.cpp
CFLAliasAnalysis.cpp [CFLAA] Remove one final initializer list 2014-09-03 00:06:47 +00:00
CGSCCPassManager.cpp
CMakeLists.txt Add an Assumption-Tracking Pass 2014-09-07 12:44:26 +00:00
CodeMetrics.cpp Add functions for finding ephemeral values 2014-09-07 13:49:57 +00:00
ConstantFolding.cpp
CostModel.cpp
Delinearization.cpp
DependenceAnalysis.cpp
DominanceFrontier.cpp
DomPrinter.cpp
InstCount.cpp
InstructionSimplify.cpp InstSimplify: Simplify trivial and/or of icmps 2014-09-15 08:15:28 +00:00
Interval.cpp
IntervalPartition.cpp
IVUsers.cpp
JumpInstrTableInfo.cpp
LazyCallGraph.cpp
LazyValueInfo.cpp Make use of @llvm.assume from LazyValueInfo 2014-09-07 20:29:59 +00:00
LibCallAliasAnalysis.cpp
LibCallSemantics.cpp
Lint.cpp Make use of @llvm.assume in ValueTracking (computeKnownBits, etc.) 2014-09-07 18:57:58 +00:00
LLVMBuild.txt
Loads.cpp
LoopInfo.cpp
LoopPass.cpp
Makefile
MemDepPrinter.cpp
MemoryBuiltins.cpp
MemoryDependenceAnalysis.cpp Make use of @llvm.assume in ValueTracking (computeKnownBits, etc.) 2014-09-07 18:57:58 +00:00
ModuleDebugInfoPrinter.cpp
NoAliasAnalysis.cpp
PHITransAddr.cpp Make use of @llvm.assume in ValueTracking (computeKnownBits, etc.) 2014-09-07 18:57:58 +00:00
PostDominators.cpp
PtrUseVisitor.cpp
README.txt
RegionInfo.cpp
RegionPass.cpp
RegionPrinter.cpp
ScalarEvolution.cpp Make use @llvm.assume for loop guards in ScalarEvolution 2014-09-07 21:37:59 +00:00
ScalarEvolutionAliasAnalysis.cpp
ScalarEvolutionExpander.cpp Make use of @llvm.assume in ValueTracking (computeKnownBits, etc.) 2014-09-07 18:57:58 +00:00
ScalarEvolutionNormalization.cpp
ScopedNoAliasAA.cpp Add override to overriden virtual methods, remove virtual keywords. 2014-09-03 11:41:21 +00:00
SparsePropagation.cpp
StratifiedSets.h [CFLAA] And even more MSVC fixes 2014-09-02 23:50:01 +00:00
TargetTransformInfo.cpp Rename getMaximumUnrollFactor -> getMaxInterleaveFactor; also rename option names controlling this variable. 2014-09-10 17:58:16 +00:00
Trace.cpp
TypeBasedAliasAnalysis.cpp
ValueTracking.cpp Fix an ODR violation consisting of two 'struct Query' in the global namespace. 2014-09-12 08:56:53 +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))

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