X-Git-Url: http://plrg.eecs.uci.edu/git/?p=oota-llvm.git;a=blobdiff_plain;f=lib%2FAnalysis%2FBasicAliasAnalysis.cpp;h=c2a530a44be9a9b7494f395f9366553149c8d625;hp=78b2e7e9ca64e65e00b6612ca4fbc8a0ff1a3145;hb=e29d3ef447f8c4c0dac37d6e89797bc9e075eda8;hpb=940e92b1932585802cf0fcde51ece95bb5083b49 diff --git a/lib/Analysis/BasicAliasAnalysis.cpp b/lib/Analysis/BasicAliasAnalysis.cpp index 78b2e7e9ca6..c2a530a44be 100644 --- a/lib/Analysis/BasicAliasAnalysis.cpp +++ b/lib/Analysis/BasicAliasAnalysis.cpp @@ -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(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(V) || isa(V) || isa(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 &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 &Dest, const SmallVectorImpl &Src) {