llvm-6502/lib/Analysis
Benjamin Kramer e574246489 ConstantFolding: Add a missing folding that leads to a miscompile.
We use constant folding to see if an intrinsic evaluates to the same value as a
constant that we know. If we don't take the undefinedness into account we get a
value that doesn't match the actual implementation, and miscompiled code.

This was uncovered by Chandler's simplifycfg changes.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@173356 91177308-0d34-0410-b5e6-96231b3b80d8
2013-01-24 16:28:28 +00:00
..
IPA Begin fleshing out an interface in TTI for modelling the costs of 2013-01-22 11:26:02 +00:00
AliasAnalysis.cpp Memory Dependence Analysis: fix a miscompile that uses DT to approxmiate the 2013-01-04 19:19:47 +00:00
AliasAnalysisCounter.cpp Use the new script to sort the includes of every file under lib. 2012-12-03 16:50:05 +00:00
AliasAnalysisEvaluator.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
AliasDebugger.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
AliasSetTracker.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
Analysis.cpp Move the initialization to the Analysis library as well as the pass. 2013-01-07 03:33:08 +00:00
BasicAliasAnalysis.cpp Actually update the CMake and Makefile builds correctly, and update the 2013-01-02 12:09:16 +00:00
BlockFrequencyInfo.cpp Use the new script to sort the includes of every file under lib. 2012-12-03 16:50:05 +00:00
BranchProbabilityInfo.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
CaptureTracking.cpp Give CaptureTracker::shouldExplore a base implementation. Most users want to do 2012-10-08 22:12:48 +00:00
CFGPrinter.cpp Use the new script to sort the includes of every file under lib. 2012-12-03 16:50:05 +00:00
CMakeLists.txt Sink InlineCost.cpp into IPA -- it is now officially an interprocedural 2013-01-21 12:09:41 +00:00
CodeMetrics.cpp Begin fleshing out an interface in TTI for modelling the costs of 2013-01-22 11:26:02 +00:00
ConstantFolding.cpp ConstantFolding: Add a missing folding that leads to a miscompile. 2013-01-24 16:28:28 +00:00
CostModel.cpp Move TargetTransformInfo to live under the Analysis library. This no 2013-01-07 03:08:10 +00:00
DbgInfoPrinter.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
DependenceAnalysis.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
DominanceFrontier.cpp Use the new script to sort the includes of every file under lib. 2012-12-03 16:50:05 +00:00
DomPrinter.cpp
InstCount.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
InstructionSimplify.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
Interval.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
IntervalPartition.cpp
IVUsers.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
LazyValueInfo.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
LibCallAliasAnalysis.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
LibCallSemantics.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
Lint.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
LLVMBuild.txt
Loads.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
LoopInfo.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
LoopPass.cpp
Makefile
MemDepPrinter.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
MemoryBuiltins.cpp Reverting r171325 & r172363. This was causing a mis-compile on the self-hosted LTO build bots. 2013-01-17 21:28:46 +00:00
MemoryDependenceAnalysis.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
ModuleDebugInfoPrinter.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
NoAliasAnalysis.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
PathNumbering.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
PathProfileInfo.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
PathProfileVerifier.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
PHITransAddr.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
PostDominators.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
ProfileDataLoader.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
ProfileDataLoaderPass.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
ProfileEstimatorPass.cpp Use the new script to sort the includes of every file under lib. 2012-12-03 16:50:05 +00:00
ProfileInfo.cpp Use the new script to sort the includes of every file under lib. 2012-12-03 16:50:05 +00:00
ProfileInfoLoader.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
ProfileInfoLoaderPass.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
ProfileVerifierPass.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
PtrUseVisitor.cpp Hoist the GEP constant address offset computation to a common home on 2012-12-11 10:29:10 +00:00
README.txt
RegionInfo.cpp Use the new script to sort the includes of every file under lib. 2012-12-03 16:50:05 +00:00
RegionPass.cpp
RegionPrinter.cpp Use the new script to sort the includes of every file under lib. 2012-12-03 16:50:05 +00:00
ScalarEvolution.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
ScalarEvolutionAliasAnalysis.cpp Use the new script to sort the includes of every file under lib. 2012-12-03 16:50:05 +00:00
ScalarEvolutionExpander.cpp SCEVExpander fix. RAUW needs to update the InsertedExpressions cache. 2013-01-14 21:00:37 +00:00
ScalarEvolutionNormalization.cpp
SparsePropagation.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
TargetTransformInfo.cpp Begin fleshing out an interface in TTI for modelling the costs of 2013-01-22 11:26:02 +00:00
Trace.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
TypeBasedAliasAnalysis.cpp Move all of the header files which are involved in modelling the LLVM IR 2013-01-02 11:36:10 +00:00
ValueTracking.cpp Remove redundant 'llvm::' qualifications 2013-01-13 16:01:15 +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))

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