// which automatically provides functionality for the entire suite of client
// APIs.
//
-// This API represents memory as a (Pointer, Size) pair. The Pointer component
-// specifies the base memory address of the region, the Size specifies how large
-// of an area is being queried, or UnknownSize if the size is not known.
-// Pointers that point to two completely different objects in memory never
-// alias, regardless of the value of the Size component.
+// This API identifies memory regions with the Location class. The pointer
+// component specifies the base memory address of the region. The Size specifies
+// the maximum size (in address units) of the memory region, or UnknownSize if
+// the size is not known. The TBAA tag identifies the "type" of the memory
+// reference; see the TypeBasedAliasAnalysis class for details.
+//
+// Some non-obvious details include:
+// - Pointers that point to two completely different objects in memory never
+// alias, regardless of the value of the Size component.
+// - NoAlias doesn't imply inequal pointers. The most obvious example of this
+// is two pointers to constant memory. Even if they are equal, constant
+// memory is never stored to, so there will never be any dependencies.
+// In this and other situations, the pointers may be both NoAlias and
+// MustAlias at the same time. The current API can only return one result,
+// though this is rarely a problem in practice.
//
//===----------------------------------------------------------------------===//
#define LLVM_ANALYSIS_ALIAS_ANALYSIS_H
#include "llvm/Support/CallSite.h"
-#include <vector>
+#include "llvm/ADT/DenseMap.h"
namespace llvm {
class TargetData;
class Pass;
class AnalysisUsage;
+class MemTransferInst;
+class MemIntrinsic;
class AliasAnalysis {
protected:
/// getTypeStoreSize - Return the TargetData store size for the given type,
/// if known, or a conservative value otherwise.
///
- uint64_t getTypeStoreSize(const Type *Ty);
+ uint64_t getTypeStoreSize(Type *Ty);
//===--------------------------------------------------------------------===//
/// Alias Queries...
struct Location {
/// Ptr - The address of the start of the location.
const Value *Ptr;
- /// Size - The maximum size of the location, or UnknownSize if the size is
- /// not known. Note that an unknown size does not mean the pointer aliases
- /// the entire virtual address space, because there are restrictions on
- /// stepping out of one object and into another.
+ /// Size - The maximum size of the location, in address-units, or
+ /// UnknownSize if the size is not known. Note that an unknown size does
+ /// not mean the pointer aliases the entire virtual address space, because
+ /// there are restrictions on stepping out of one object and into another.
/// See http://llvm.org/docs/LangRef.html#pointeraliasing
uint64_t Size;
/// TBAATag - The metadata node which describes the TBAA type of
/// the location, or null if there is no known unique tag.
const MDNode *TBAATag;
- explicit Location(const Value *P = 0,
- uint64_t S = UnknownSize,
+ explicit Location(const Value *P = 0, uint64_t S = UnknownSize,
const MDNode *N = 0)
: Ptr(P), Size(S), TBAATag(N) {}
return Copy;
}
+ Location getWithNewSize(uint64_t NewSize) const {
+ Location Copy(*this);
+ Copy.Size = NewSize;
+ return Copy;
+ }
+
Location getWithoutTBAATag() const {
Location Copy(*this);
Copy.TBAATag = 0;
}
};
+ /// getLocation - Fill in Loc with information about the memory reference by
+ /// the given instruction.
+ Location getLocation(const LoadInst *LI);
+ Location getLocation(const StoreInst *SI);
+ Location getLocation(const VAArgInst *VI);
+ static Location getLocationForSource(const MemTransferInst *MTI);
+ static Location getLocationForDest(const MemIntrinsic *MI);
+
/// Alias analysis result - Either we know for sure that it does not alias, we
/// know for sure it must alias, or we don't know anything: The two pointers
/// _might_ alias. This enum is designed so you can do things like:
/// See docs/AliasAnalysis.html for more information on the specific meanings
/// of these values.
///
- enum AliasResult { NoAlias = 0, MayAlias = 1, MustAlias = 2 };
+ enum AliasResult {
+ NoAlias = 0, ///< No dependencies.
+ MayAlias, ///< Anything goes.
+ PartialAlias, ///< Pointers differ, but pointees overlap.
+ MustAlias ///< Pointers are equal.
+ };
/// alias - The main low level interface to the alias analysis implementation.
/// Returns an AliasResult indicating whether the two pointers are aliased to
const Value *V2, uint64_t V2Size) {
return isNoAlias(Location(V1, V1Size), Location(V2, V2Size));
}
+
+ /// isMustAlias - A convenience wrapper.
+ bool isMustAlias(const Location &LocA, const Location &LocB) {
+ return alias(LocA, LocB) == MustAlias;
+ }
- /// pointsToConstantMemory - If the specified memory location is known to be
- /// constant, return true. This allows disambiguation of store
- /// instructions from constant pointers.
- ///
- virtual bool pointsToConstantMemory(const Location &Loc);
+ /// isMustAlias - A convenience wrapper.
+ bool isMustAlias(const Value *V1, const Value *V2) {
+ return alias(V1, 1, V2, 1) == MustAlias;
+ }
+
+ /// pointsToConstantMemory - If the specified memory location is
+ /// known to be constant, return true. If OrLocal is true and the
+ /// specified memory location is known to be "local" (derived from
+ /// an alloca), return true. Otherwise return false.
+ virtual bool pointsToConstantMemory(const Location &Loc,
+ bool OrLocal = false);
/// pointsToConstantMemory - A convenient wrapper.
- bool pointsToConstantMemory(const Value *P) {
- return pointsToConstantMemory(Location(P));
+ bool pointsToConstantMemory(const Value *P, bool OrLocal = false) {
+ return pointsToConstantMemory(Location(P), OrLocal);
}
//===--------------------------------------------------------------------===//
///
enum ModRefResult { NoModRef = 0, Ref = 1, Mod = 2, ModRef = 3 };
+ /// These values define additional bits used to define the
+ /// ModRefBehavior values.
+ enum { Nowhere = 0, ArgumentPointees = 4, Anywhere = 8 | ArgumentPointees };
/// ModRefBehavior - Summary of how a function affects memory in the program.
/// Loads from constant globals are not considered memory accesses for this
/// interface. Also, functions may freely modify stack space local to their
/// invocation without having to report it through these interfaces.
enum ModRefBehavior {
- // DoesNotAccessMemory - This function does not perform any non-local loads
- // or stores to memory.
- //
- // This property corresponds to the GCC 'const' attribute.
- DoesNotAccessMemory,
-
- // AccessesArguments - This function accesses function arguments in well
- // known (possibly volatile) ways, but does not access any other memory.
- AccessesArguments,
-
- // AccessesArgumentsAndGlobals - This function has accesses function
- // arguments and global variables well known (possibly volatile) ways, but
- // does not access any other memory.
- AccessesArgumentsAndGlobals,
-
- // OnlyReadsMemory - This function does not perform any non-local stores or
- // volatile loads, but may read from any memory location.
- //
- // This property corresponds to the GCC 'pure' attribute.
- OnlyReadsMemory,
-
- // UnknownModRefBehavior - This indicates that the function could not be
- // classified into one of the behaviors above.
- UnknownModRefBehavior
+ /// DoesNotAccessMemory - This function does not perform any non-local loads
+ /// or stores to memory.
+ ///
+ /// This property corresponds to the GCC 'const' attribute.
+ /// This property corresponds to the LLVM IR 'readnone' attribute.
+ /// This property corresponds to the IntrNoMem LLVM intrinsic flag.
+ DoesNotAccessMemory = Nowhere | NoModRef,
+
+ /// OnlyReadsArgumentPointees - The only memory references in this function
+ /// (if it has any) are non-volatile loads from objects pointed to by its
+ /// pointer-typed arguments, with arbitrary offsets.
+ ///
+ /// This property corresponds to the IntrReadArgMem LLVM intrinsic flag.
+ OnlyReadsArgumentPointees = ArgumentPointees | Ref,
+
+ /// OnlyAccessesArgumentPointees - The only memory references in this
+ /// function (if it has any) are non-volatile loads and stores from objects
+ /// pointed to by its pointer-typed arguments, with arbitrary offsets.
+ ///
+ /// This property corresponds to the IntrReadWriteArgMem LLVM intrinsic flag.
+ OnlyAccessesArgumentPointees = ArgumentPointees | ModRef,
+
+ /// OnlyReadsMemory - This function does not perform any non-local stores or
+ /// volatile loads, but may read from any memory location.
+ ///
+ /// This property corresponds to the GCC 'pure' attribute.
+ /// This property corresponds to the LLVM IR 'readonly' attribute.
+ /// This property corresponds to the IntrReadMem LLVM intrinsic flag.
+ OnlyReadsMemory = Anywhere | Ref,
+
+ /// UnknownModRefBehavior - This indicates that the function could not be
+ /// classified into one of the behaviors above.
+ UnknownModRefBehavior = Anywhere | ModRef
};
/// getModRefBehavior - Return the behavior when calling the given call site.
/// This property corresponds to the GCC 'pure' attribute.
///
bool onlyReadsMemory(ImmutableCallSite CS) {
- ModRefBehavior MRB = getModRefBehavior(CS);
- return MRB == DoesNotAccessMemory || MRB == OnlyReadsMemory;
+ return onlyReadsMemory(getModRefBehavior(CS));
}
/// onlyReadsMemory - If the specified function is known to only read from
/// when the call site is not known.
///
bool onlyReadsMemory(const Function *F) {
- ModRefBehavior MRB = getModRefBehavior(F);
- return MRB == DoesNotAccessMemory || MRB == OnlyReadsMemory;
+ return onlyReadsMemory(getModRefBehavior(F));
}
+ /// onlyReadsMemory - Return true if functions with the specified behavior are
+ /// known to only read from non-volatile memory (or not access memory at all).
+ ///
+ static bool onlyReadsMemory(ModRefBehavior MRB) {
+ return !(MRB & Mod);
+ }
+
+ /// onlyAccessesArgPointees - Return true if functions with the specified
+ /// behavior are known to read and write at most from objects pointed to by
+ /// their pointer-typed arguments (with arbitrary offsets).
+ ///
+ static bool onlyAccessesArgPointees(ModRefBehavior MRB) {
+ return !(MRB & Anywhere & ~ArgumentPointees);
+ }
+
+ /// doesAccessArgPointees - Return true if functions with the specified
+ /// behavior are known to potentially read or write from objects pointed
+ /// to be their pointer-typed arguments (with arbitrary offsets).
+ ///
+ static bool doesAccessArgPointees(ModRefBehavior MRB) {
+ return (MRB & ModRef) && (MRB & ArgumentPointees);
+ }
/// getModRefInfo - Return information about whether or not an instruction may
/// read or write the specified memory location. An instruction
case Instruction::VAArg: return getModRefInfo((const VAArgInst*)I, Loc);
case Instruction::Load: return getModRefInfo((const LoadInst*)I, Loc);
case Instruction::Store: return getModRefInfo((const StoreInst*)I, Loc);
+ case Instruction::Fence: return getModRefInfo((const FenceInst*)I, Loc);
+ case Instruction::AtomicCmpXchg:
+ return getModRefInfo((const AtomicCmpXchgInst*)I, Loc);
+ case Instruction::AtomicRMW:
+ return getModRefInfo((const AtomicRMWInst*)I, Loc);
case Instruction::Call: return getModRefInfo((const CallInst*)I, Loc);
case Instruction::Invoke: return getModRefInfo((const InvokeInst*)I,Loc);
default: return NoModRef;
ModRefResult getModRefInfo(const StoreInst *S, const Location &Loc);
/// getModRefInfo (for stores) - A convenience wrapper.
- ModRefResult getModRefInfo(const StoreInst *S, const Value *P, uint64_t Size) {
+ ModRefResult getModRefInfo(const StoreInst *S, const Value *P, uint64_t Size){
+ return getModRefInfo(S, Location(P, Size));
+ }
+
+ /// getModRefInfo (for fences) - Return whether information about whether
+ /// a particular store modifies or reads the specified memory location.
+ ModRefResult getModRefInfo(const FenceInst *S, const Location &Loc) {
+ // Conservatively correct. (We could possibly be a bit smarter if
+ // Loc is a alloca that doesn't escape.)
+ return ModRef;
+ }
+
+ /// getModRefInfo (for fences) - A convenience wrapper.
+ ModRefResult getModRefInfo(const FenceInst *S, const Value *P, uint64_t Size){
return getModRefInfo(S, Location(P, Size));
}
+ /// getModRefInfo (for cmpxchges) - Return whether information about whether
+ /// a particular cmpxchg modifies or reads the specified memory location.
+ ModRefResult getModRefInfo(const AtomicCmpXchgInst *CX, const Location &Loc) {
+ // Conservatively correct. (But there are obvious ways to be smarter.)
+ return ModRef;
+ }
+
+ /// getModRefInfo (for cmpxchges) - A convenience wrapper.
+ ModRefResult getModRefInfo(const AtomicCmpXchgInst *CX,
+ const Value *P, unsigned Size) {
+ return getModRefInfo(CX, Location(P, Size));
+ }
+
+ /// getModRefInfo (for atomicrmws) - Return whether information about whether
+ /// a particular atomicrmw modifies or reads the specified memory location.
+ ModRefResult getModRefInfo(const AtomicRMWInst *RMW, const Location &Loc) {
+ // Conservatively correct. (But there are obvious ways to be smarter.)
+ return ModRef;
+ }
+
+ /// getModRefInfo (for atomicrmws) - A convenience wrapper.
+ ModRefResult getModRefInfo(const AtomicRMWInst *RMW,
+ const Value *P, unsigned Size) {
+ return getModRefInfo(RMW, Location(P, Size));
+ }
+
/// getModRefInfo (for va_args) - Return whether information about whether
/// a particular va_arg modifies or reads the specified memory location.
ModRefResult getModRefInfo(const VAArgInst* I, const Location &Loc);
/// getModRefInfo (for va_args) - A convenience wrapper.
- ModRefResult getModRefInfo(const VAArgInst* I, const Value* P, uint64_t Size) {
+ ModRefResult getModRefInfo(const VAArgInst* I, const Value* P, uint64_t Size){
return getModRefInfo(I, Location(P, Size));
}
///
virtual void copyValue(Value *From, Value *To);
+ /// addEscapingUse - This method should be used whenever an escaping use is
+ /// added to a pointer value. Analysis implementations may either return
+ /// conservative responses for that value in the future, or may recompute
+ /// some or all internal state to continue providing precise responses.
+ ///
+ /// Escaping uses are considered by anything _except_ the following:
+ /// - GEPs or bitcasts of the pointer
+ /// - Loads through the pointer
+ /// - Stores through (but not of) the pointer
+ virtual void addEscapingUse(Use &U);
+
/// replaceWithNewValue - This method is the obvious combination of the two
/// above, and it provided as a helper to simplify client code.
///
}
};
+// Specialize DenseMapInfo for Location.
+template<>
+struct DenseMapInfo<AliasAnalysis::Location> {
+ static inline AliasAnalysis::Location getEmptyKey() {
+ return
+ AliasAnalysis::Location(DenseMapInfo<const Value *>::getEmptyKey(),
+ 0, 0);
+ }
+ static inline AliasAnalysis::Location getTombstoneKey() {
+ return
+ AliasAnalysis::Location(DenseMapInfo<const Value *>::getTombstoneKey(),
+ 0, 0);
+ }
+ static unsigned getHashValue(const AliasAnalysis::Location &Val) {
+ return DenseMapInfo<const Value *>::getHashValue(Val.Ptr) ^
+ DenseMapInfo<uint64_t>::getHashValue(Val.Size) ^
+ DenseMapInfo<const MDNode *>::getHashValue(Val.TBAATag);
+ }
+ static bool isEqual(const AliasAnalysis::Location &LHS,
+ const AliasAnalysis::Location &RHS) {
+ return LHS.Ptr == RHS.Ptr &&
+ LHS.Size == RHS.Size &&
+ LHS.TBAATag == RHS.TBAATag;
+ }
+};
+
/// isNoAliasCall - Return true if this pointer is returned by a noalias
/// function.
bool isNoAliasCall(const Value *V);
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