llvm/lib/Analysis/CMakeLists.txt
Chandler Carruth ed90ed077a Add a new visitor for walking the uses of a pointer value.
This visitor provides infrastructure for recursively traversing the
use-graph of a pointer-producing instruction like an alloca or a malloc.
It maintains a worklist of uses to visit, so it can handle very deep
recursions. It automatically looks through instructions which simply
translate one pointer to another (bitcasts and GEPs). It tracks the
offset relative to the original pointer as long as that offset remains
constant and exposes it during the visit as an APInt offset. Finally, it
performs conservative escape analysis.

However, currently it has some limitations that should be addressed
going forward:
1) It doesn't handle vectors of pointers.
2) It doesn't provide a cheaper visitor when the constant offset
   tracking isn't needed.
3) It doesn't support non-instruction pointer values.

The current functionality is exactly what is required to implement the
SROA pointer-use visitors in terms of this one, rather than in terms of
their own ad-hoc base visitor, which was always very poorly specified.
SROA has been converted to use this, and the code there deleted which
this utility now provides.

Technically speaking, using this new visitor allows SROA to handle a few
more cases than it previously did. It is now more aggressive in ignoring
chains of instructions which look like they would defeat SROA, but in
fact do not because they never result in a read or write of memory.
While this is "neat", it shouldn't be interesting for real programs as
any such chains should have been removed by others passes long before we
get to SROA. As a consequence, I've not added any tests for these
features -- it shouldn't be part of SROA's contract to perform such
heroics.

The goal is to extend the functionality of this visitor going forward,
and re-use it from passes like ASan that can benefit from doing
a detailed walk of the uses of a pointer.

Thanks to Ben Kramer for the code review rounds and lots of help
reviewing and debugging this patch.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@169728 91177308-0d34-0410-b5e6-96231b3b80d8
2012-12-10 08:28:39 +00:00

67 lines
1.4 KiB
CMake

add_llvm_library(LLVMAnalysis
AliasAnalysis.cpp
AliasAnalysisCounter.cpp
AliasAnalysisEvaluator.cpp
AliasDebugger.cpp
AliasSetTracker.cpp
Analysis.cpp
BasicAliasAnalysis.cpp
BlockFrequencyInfo.cpp
BranchProbabilityInfo.cpp
CFGPrinter.cpp
CaptureTracking.cpp
CostModel.cpp
CodeMetrics.cpp
ConstantFolding.cpp
DbgInfoPrinter.cpp
DependenceAnalysis.cpp
DomPrinter.cpp
DominanceFrontier.cpp
IVUsers.cpp
InlineCost.cpp
InstCount.cpp
InstructionSimplify.cpp
Interval.cpp
IntervalPartition.cpp
LazyValueInfo.cpp
LibCallAliasAnalysis.cpp
LibCallSemantics.cpp
Lint.cpp
Loads.cpp
LoopInfo.cpp
LoopPass.cpp
MemDepPrinter.cpp
MemoryBuiltins.cpp
MemoryDependenceAnalysis.cpp
ModuleDebugInfoPrinter.cpp
NoAliasAnalysis.cpp
PHITransAddr.cpp
PathNumbering.cpp
PathProfileInfo.cpp
PathProfileVerifier.cpp
PostDominators.cpp
ProfileEstimatorPass.cpp
ProfileInfo.cpp
ProfileInfoLoader.cpp
ProfileInfoLoaderPass.cpp
ProfileVerifierPass.cpp
ProfileDataLoader.cpp
ProfileDataLoaderPass.cpp
PtrUseVisitor.cpp
RegionInfo.cpp
RegionPass.cpp
RegionPrinter.cpp
ScalarEvolution.cpp
ScalarEvolutionAliasAnalysis.cpp
ScalarEvolutionExpander.cpp
ScalarEvolutionNormalization.cpp
SparsePropagation.cpp
Trace.cpp
TypeBasedAliasAnalysis.cpp
ValueTracking.cpp
)
add_dependencies(LLVMAnalysis intrinsics_gen)
add_subdirectory(IPA)