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[PM/AA] Clean up and homogenize comments throughout basic-aa. 

llvm-svn: 244200
This commit is contained in:
Chandler Carruth 2015-08-06 08:17:06 +00:00
parent 051eeca08e
commit c5d811253a
2 changed files with 76 additions and 86 deletions
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51
llvm/include/llvm/Analysis/BasicAliasAnalysis.h
View File

@ -28,7 +28,7 @@
namespace llvm {
/// BasicAliasAnalysis - This is the primary alias analysis implementation.
/// This is the primary alias analysis implementation.
struct BasicAliasAnalysis : public ImmutablePass, public AliasAnalysis {
static char ID; // Class identification, replacement for typeinfo
@ -86,25 +86,22 @@ struct BasicAliasAnalysis : public ImmutablePass, public AliasAnalysis {
ModRefInfo getModRefInfo(ImmutableCallSite CS1,
ImmutableCallSite CS2) override;
/// pointsToConstantMemory - Chase pointers until we find a (constant
/// global) or not.
/// Chases pointers until we find a (constant global) or not.
bool pointsToConstantMemory(const MemoryLocation &Loc, bool OrLocal) override;
/// Get the location associated with a pointer argument of a callsite.
ModRefInfo getArgModRefInfo(ImmutableCallSite CS, unsigned ArgIdx) override;
/// getModRefBehavior - Return the behavior when calling the given
/// call site.
/// Returns the behavior when calling the given call site.
FunctionModRefBehavior getModRefBehavior(ImmutableCallSite CS) override;
/// getModRefBehavior - Return the behavior when calling the given function.
/// For use when the call site is not known.
/// Returns the behavior when calling the given function. For use when the
/// call site is not known.
FunctionModRefBehavior getModRefBehavior(const Function *F) override;
/// getAdjustedAnalysisPointer - This method is used when a pass implements
/// an analysis interface through multiple inheritance. If needed, it
/// should override this to adjust the this pointer as needed for the
/// specified pass info.
/// This method is used when a pass implements an analysis interface through
/// multiple inheritance. If needed, it should override this to adjust the
/// this pointer as needed for the specified pass info.
void *getAdjustedAnalysisPointer(const void *ID) override {
if (ID == &AliasAnalysis::ID)
return (AliasAnalysis *)this;
@ -129,16 +126,18 @@ private:
}
};
// AliasCache - Track alias queries to guard against recursion.
/// Track alias queries to guard against recursion.
typedef std::pair<MemoryLocation, MemoryLocation> LocPair;
typedef SmallDenseMap<LocPair, AliasResult, 8> AliasCacheTy;
AliasCacheTy AliasCache;
/// \brief Track phi nodes we have visited. When interpret "Value" pointer
/// equality as value equality we need to make sure that the "Value" is not
/// part of a cycle. Otherwise, two uses could come from different
/// "iterations" of a cycle and see different values for the same "Value"
/// pointer.
/// Tracks phi nodes we have visited.
///
/// When interpret "Value" pointer equality as value equality we need to make
/// sure that the "Value" is not part of a cycle. Otherwise, two uses could
/// come from different "iterations" of a cycle and see different values for
/// the same "Value" pointer.
///
/// The following example shows the problem:
/// %p = phi(%alloca1, %addr2)
/// %l = load %ptr
@ -148,7 +147,7 @@ private:
/// store %l, ...
SmallPtrSet<const BasicBlock *, 8> VisitedPhiBBs;
// Visited - Track instructions visited by pointsToConstantMemory.
/// Tracks instructions visited by pointsToConstantMemory.
SmallPtrSet<const Value *, 16> Visited;
static Value *GetLinearExpression(Value *V, APInt &Scale, APInt &Offset,
@ -162,36 +161,20 @@ private:
bool &MaxLookupReached, const DataLayout &DL,
AssumptionCache *AC, DominatorTree *DT);
/// \brief Check whether two Values can be considered equivalent.
///
/// In addition to pointer equivalence of \p V1 and \p V2 this checks
/// whether they can not be part of a cycle in the value graph by looking at
/// all visited phi nodes an making sure that the phis cannot reach the
/// value. We have to do this because we are looking through phi nodes (That
/// is we say noalias(V, phi(VA, VB)) if noalias(V, VA) and noalias(V, VB).
bool isValueEqualInPotentialCycles(const Value *V1, const Value *V2);
/// \brief Dest and Src are the variable indices from two decomposed
/// GetElementPtr instructions GEP1 and GEP2 which have common base
/// pointers. Subtract the GEP2 indices from GEP1 to find the symbolic
/// difference between the two pointers.
void GetIndexDifference(SmallVectorImpl<VariableGEPIndex> &Dest,
const SmallVectorImpl<VariableGEPIndex> &Src);
// aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP
// instruction against another.
AliasResult aliasGEP(const GEPOperator *V1, uint64_t V1Size,
const AAMDNodes &V1AAInfo, const Value *V2,
uint64_t V2Size, const AAMDNodes &V2AAInfo,
const Value *UnderlyingV1, const Value *UnderlyingV2);
// aliasPHI - Provide a bunch of ad-hoc rules to disambiguate a PHI
// instruction against another.
AliasResult aliasPHI(const PHINode *PN, uint64_t PNSize,
const AAMDNodes &PNAAInfo, const Value *V2,
uint64_t V2Size, const AAMDNodes &V2AAInfo);
/// aliasSelect - Disambiguate a Select instruction against another value.
AliasResult aliasSelect(const SelectInst *SI, uint64_t SISize,
const AAMDNodes &SIAAInfo, const Value *V2,
uint64_t V2Size, const AAMDNodes &V2AAInfo);

111
llvm/lib/Analysis/BasicAliasAnalysis.cpp
View File

@ -65,8 +65,8 @@ static const unsigned MaxLookupSearchDepth = 6;
// Useful predicates
//===----------------------------------------------------------------------===//
/// isNonEscapingLocalObject - Return true if the pointer is to a function-local
/// object that never escapes from the function.
/// Returns true if the pointer is to a function-local object that never
/// escapes from the function.
static bool isNonEscapingLocalObject(const Value *V) {
// If this is a local allocation, check to see if it escapes.
if (isa<AllocaInst>(V) || isNoAliasCall(V))
@ -90,8 +90,8 @@ static bool isNonEscapingLocalObject(const Value *V) {
return false;
}
/// isEscapeSource - Return true if the pointer is one which would have
/// been considered an escape by isNonEscapingLocalObject.
/// Returns true if the pointer is one which would have been considered an
/// escape by isNonEscapingLocalObject.
static bool isEscapeSource(const Value *V) {
if (isa<CallInst>(V) || isa<InvokeInst>(V) || isa<Argument>(V))
return true;
@ -105,8 +105,7 @@ static bool isEscapeSource(const Value *V) {
return false;
}
/// getObjectSize - Return the size of the object specified by V, or
/// UnknownSize if unknown.
/// Returns the size of the object specified by V, or UnknownSize if unknown.
static uint64_t getObjectSize(const Value *V, const DataLayout &DL,
const TargetLibraryInfo &TLI,
bool RoundToAlign = false) {
@ -116,8 +115,8 @@ static uint64_t getObjectSize(const Value *V, const DataLayout &DL,
return MemoryLocation::UnknownSize;
}
/// isObjectSmallerThan - Return true if we can prove that the object specified
/// by V is smaller than Size.
/// Returns true if we can prove that the object specified by V is smaller than
/// Size.
static bool isObjectSmallerThan(const Value *V, uint64_t Size,
const DataLayout &DL,
const TargetLibraryInfo &TLI) {
@ -157,8 +156,7 @@ static bool isObjectSmallerThan(const Value *V, uint64_t Size,
return ObjectSize != MemoryLocation::UnknownSize && ObjectSize < Size;
}
/// isObjectSize - Return true if we can prove that the object specified
/// by V has size Size.
/// Returns true if we can prove that the object specified by V has size Size.
static bool isObjectSize(const Value *V, uint64_t Size, const DataLayout &DL,
const TargetLibraryInfo &TLI) {
uint64_t ObjectSize = getObjectSize(V, DL, TLI);
@ -169,11 +167,13 @@ static bool isObjectSize(const Value *V, uint64_t Size, const DataLayout &DL,
// GetElementPtr Instruction Decomposition and Analysis
//===----------------------------------------------------------------------===//
/// GetLinearExpression - Analyze the specified value as a linear expression:
/// "A*V + B", where A and B are constant integers. Return the scale and offset
/// values as APInts and return V as a Value*, and return whether we looked
/// through any sign or zero extends. The incoming Value is known to have
/// IntegerType and it may already be sign or zero extended.
/// Analyzes the specified value as a linear expression: "A*V + B", where A and
/// B are constant integers.
///
/// Returns the scale and offset values as APInts and return V as a Value*, and
/// return whether we looked through any sign or zero extends. The incoming
/// Value is known to have IntegerType and it may already be sign or zero
/// extended.
///
/// Note that this looks through extends, so the high bits may not be
/// represented in the result.
@ -259,21 +259,19 @@ static bool isObjectSize(const Value *V, uint64_t Size, const DataLayout &DL,
return V;
}
/// DecomposeGEPExpression - If V is a symbolic pointer expression, decompose it
/// into a base pointer with a constant offset and a number of scaled symbolic
/// offsets.
/// If V is a symbolic pointer expression, decompose it into a base pointer
/// with a constant offset and a number of scaled symbolic offsets.
///
/// The scaled symbolic offsets (represented by pairs of a Value* and a scale in
/// the VarIndices vector) are Value*'s that are known to be scaled by the
/// specified amount, but which may have other unrepresented high bits. As such,
/// the gep cannot necessarily be reconstructed from its decomposed form.
/// The scaled symbolic offsets (represented by pairs of a Value* and a scale
/// in the VarIndices vector) are Value*'s that are known to be scaled by the
/// specified amount, but which may have other unrepresented high bits. As
/// such, the gep cannot necessarily be reconstructed from its decomposed form.
///
/// When DataLayout is around, this function is capable of analyzing everything
/// that GetUnderlyingObject can look through. To be able to do that
/// GetUnderlyingObject and DecomposeGEPExpression must use the same search
/// depth (MaxLookupSearchDepth).
/// When DataLayout not is around, it just looks through pointer casts.
///
/// depth (MaxLookupSearchDepth). When DataLayout not is around, it just looks
/// through pointer casts.
/*static*/ const Value *BasicAliasAnalysis::DecomposeGEPExpression(
const Value *V, int64_t &BaseOffs,
SmallVectorImpl<VariableGEPIndex> &VarIndices, bool &MaxLookupReached,
@ -425,9 +423,9 @@ ImmutablePass *llvm::createBasicAliasAnalysisPass() {
return new BasicAliasAnalysis();
}
/// pointsToConstantMemory - Returns whether the given pointer value
/// points to memory that is local to the function, with global constants being
/// considered local to all functions.
/// Returns whether the given pointer value points to memory that is local to
/// the function, with global constants being considered local to all
/// functions.
bool BasicAliasAnalysis::pointsToConstantMemory(const MemoryLocation &Loc,
bool OrLocal) {
assert(Visited.empty() && "Visited must be cleared after use!");
@ -505,7 +503,7 @@ static bool isMemsetPattern16(const Function *MS,
return false;
}
/// getModRefBehavior - Return the behavior when calling the given call site.
/// Returns the behavior when calling the given call site.
FunctionModRefBehavior
BasicAliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
if (CS.doesNotAccessMemory())
@ -526,8 +524,8 @@ BasicAliasAnalysis::getModRefBehavior(ImmutableCallSite CS) {
return FunctionModRefBehavior(AliasAnalysis::getModRefBehavior(CS) & Min);
}
/// getModRefBehavior - Return the behavior when calling the given function.
/// For use when the call site is not known.
/// Returns the behavior when calling the given function. For use when the call
/// site is not known.
FunctionModRefBehavior
BasicAliasAnalysis::getModRefBehavior(const Function *F) {
// If the function declares it doesn't access memory, we can't do better.
@ -601,10 +599,12 @@ bool BasicAliasAnalysis::doInitialization(Module &M) {
return true;
}
/// getModRefInfo - Check to see if the specified callsite can clobber the
/// specified memory object. Since we only look at local properties of this
/// function, we really can't say much about this query. We do, however, use
/// simple "address taken" analysis on local objects.
/// Checks to see if the specified callsite can clobber the specified memory
/// object.
///
/// Since we only look at local properties of this function, we really can't
/// say much about this query. We do, however, use simple "address taken"
/// analysis on local objects.
ModRefInfo BasicAliasAnalysis::getModRefInfo(ImmutableCallSite CS,
const MemoryLocation &Loc) {
assert(notDifferentParent(CS.getInstruction(), Loc.Ptr) &&
@ -674,8 +674,8 @@ ModRefInfo BasicAliasAnalysis::getModRefInfo(ImmutableCallSite CS1,
return AliasAnalysis::getModRefInfo(CS1, CS2);
}
/// \brief Provide ad-hoc rules to disambiguate accesses through two GEP
/// operators, both having the exact same pointer operand.
/// Provide ad-hoc rules to disambiguate accesses through two GEP operators,
/// both having the exact same pointer operand.
static AliasResult aliasSameBasePointerGEPs(const GEPOperator *GEP1,
uint64_t V1Size,
const GEPOperator *GEP2,
@ -768,11 +768,12 @@ static AliasResult aliasSameBasePointerGEPs(const GEPOperator *GEP1,
return MayAlias;
}
/// aliasGEP - Provide a bunch of ad-hoc rules to disambiguate a GEP instruction
/// against another pointer. We know that V1 is a GEP, but we don't know
/// anything about V2. UnderlyingV1 is GetUnderlyingObject(GEP1, DL),
/// UnderlyingV2 is the same for V2.
/// Provides a bunch of ad-hoc rules to disambiguate a GEP instruction against
/// another pointer.
///
/// We know that V1 is a GEP, but we don't know anything about V2.
/// UnderlyingV1 is GetUnderlyingObject(GEP1, DL), UnderlyingV2 is the same for
/// V2.
AliasResult BasicAliasAnalysis::aliasGEP(
const GEPOperator *GEP1, uint64_t V1Size, const AAMDNodes &V1AAInfo,
const Value *V2, uint64_t V2Size, const AAMDNodes &V2AAInfo,
@ -1041,8 +1042,8 @@ static AliasResult MergeAliasResults(AliasResult A, AliasResult B) {
return MayAlias;
}
/// aliasSelect - Provide a bunch of ad-hoc rules to disambiguate a Select
/// instruction against another.
/// Provides a bunch of ad-hoc rules to disambiguate a Select instruction
/// against another.
AliasResult BasicAliasAnalysis::aliasSelect(const SelectInst *SI,
uint64_t SISize,
const AAMDNodes &SIAAInfo,
@ -1074,8 +1075,8 @@ AliasResult BasicAliasAnalysis::aliasSelect(const SelectInst *SI,
return MergeAliasResults(ThisAlias, Alias);
}
// aliasPHI - Provide a bunch of ad-hoc rules to disambiguate a PHI instruction
// against another.
/// Provide a bunch of ad-hoc rules to disambiguate a PHI instruction against
/// another.
AliasResult BasicAliasAnalysis::aliasPHI(const PHINode *PN, uint64_t PNSize,
const AAMDNodes &PNAAInfo,
const Value *V2, uint64_t V2Size,
@ -1180,9 +1181,8 @@ AliasResult BasicAliasAnalysis::aliasPHI(const PHINode *PN, uint64_t PNSize,
return Alias;
}
// aliasCheck - Provide a bunch of ad-hoc rules to disambiguate in common cases,
// such as array references.
//
/// Provideis a bunch of ad-hoc rules to disambiguate in common cases, such as
/// array references.
AliasResult BasicAliasAnalysis::aliasCheck(const Value *V1, uint64_t V1Size,
AAMDNodes V1AAInfo, const Value *V2,
uint64_t V2Size,
@ -1336,6 +1336,13 @@ AliasResult BasicAliasAnalysis::aliasCheck(const Value *V1, uint64_t V1Size,
return AliasCache[Locs] = Result;
}
/// Check whether two Values can be considered equivalent.
///
/// In addition to pointer equivalence of \p V1 and \p V2 this checks whether
/// they can not be part of a cycle in the value graph by looking at all
/// visited phi nodes an making sure that the phis cannot reach the value. We
/// have to do this because we are looking through phi nodes (That is we say
/// noalias(V, phi(VA, VB)) if noalias(V, VA) and noalias(V, VB).
bool BasicAliasAnalysis::isValueEqualInPotentialCycles(const Value *V,
const Value *V2) {
if (V != V2)
@ -1368,10 +1375,10 @@ bool BasicAliasAnalysis::isValueEqualInPotentialCycles(const Value *V,
return true;
}
/// GetIndexDifference - Dest and Src are the variable indices from two
/// decomposed GetElementPtr instructions GEP1 and GEP2 which have common base
/// pointers. Subtract the GEP2 indices from GEP1 to find the symbolic
/// difference between the two pointers.
/// Computes the symbolic difference between two de-composed GEPs.
///
/// Dest and Src are the variable indices from two decomposed GetElementPtr
/// instructions GEP1 and GEP2 which have common base pointers.
void BasicAliasAnalysis::GetIndexDifference(
SmallVectorImpl<VariableGEPIndex> &Dest,
const SmallVectorImpl<VariableGEPIndex> &Src) {