class TargetData;
class AliasAnalysis {
- const TargetData *TD;
protected:
+ const TargetData *TD;
+ AliasAnalysis *AA; // Previous Alias Analysis to chain to.
+
/// InitializeAliasAnalysis - Subclasses must call this method to initialize
/// the AliasAnalysis interface before any other methods are called. This is
/// typically called by the run* methods of these subclasses. This may be
virtual void getAnalysisUsage(AnalysisUsage &AU) const;
public:
- AliasAnalysis() : TD(0) {}
+ AliasAnalysis() : TD(0), AA(0) {}
virtual ~AliasAnalysis(); // We want to be subclassed
/// getTargetData - Every alias analysis implementation depends on the size of
/// analysis implementations.
///
virtual AliasResult alias(const Value *V1, unsigned V1Size,
- const Value *V2, unsigned V2Size) {
- return MayAlias;
- }
+ const Value *V2, unsigned V2Size);
/// getMustAliases - If there are any pointers known that must alias this
/// pointer, return them now. This allows alias-set based alias analyses to
/// alias analysis supports this, it should ADD any must aliased pointers to
/// the specified vector.
///
- virtual void getMustAliases(Value *P, std::vector<Value*> &RetVals) {}
+ virtual void getMustAliases(Value *P, std::vector<Value*> &RetVals);
/// pointsToConstantMemory - If the specified pointer is known to point into
/// constant global memory, return true. This allows disambiguation of store
/// instructions from constant pointers.
///
- virtual bool pointsToConstantMemory(const Value *P) { return false; }
+ virtual bool pointsToConstantMemory(const Value *P);
+
+ /// doesNotAccessMemory - If the specified function is known to never read or
+ /// write memory, return true. If the function only reads from known-constant
+ /// memory, it is also legal to return true. Functions that unwind the stack
+ /// are not legal for this predicate.
+ ///
+ /// Many optimizations (such as CSE and LICM) can be performed on calls to it,
+ /// without worrying about aliasing properties, and many functions have this
+ /// property (e.g. 'sin' and 'cos').
+ ///
+ /// This property corresponds to the GCC 'const' attribute.
+ ///
+ virtual bool doesNotAccessMemory(Function *F);
+
+ /// onlyReadsMemory - If the specified function is known to only read from
+ /// non-volatile memory (or not access memory at all), return true. Functions
+ /// that unwind the stack are not legal for this predicate.
+ ///
+ /// This property allows many common optimizations to be performed in the
+ /// absence of interfering store instructions, such as CSE of strlen calls.
+ ///
+ /// This property corresponds to the GCC 'pure' attribute.
+ ///
+ virtual bool onlyReadsMemory(Function *F);
+
//===--------------------------------------------------------------------===//
/// Simple mod/ref information...
/// a particular call site modifies or reads the memory specified by the
/// pointer.
///
- virtual ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size) {
- // If P points to a constant memory location, the call definitely could not
- // modify the memory location.
- return pointsToConstantMemory(P) ? Ref : ModRef;
- }
+ virtual ModRefResult getModRefInfo(CallSite CS, Value *P, unsigned Size);
/// getModRefInfo - Return information about whether two call sites may refer
/// to the same set of memory locations. This function returns NoModRef if
- /// the two calls refer to disjoint memory locations, Ref if they both read
- /// some of the same memory, Mod if they both write to some of the same
- /// memory, and ModRef if they read and write to the same memory.
+ /// the two calls refer to disjoint memory locations, Ref if CS1 reads memory
+ /// written by CS2, Mod if CS1 writes to memory read or written by CS2, or
+ /// ModRef if CS1 might read or write memory accessed by CS2.
///
- virtual ModRefResult getModRefInfo(CallSite CS1, CallSite CS2) {
- return ModRef;
- }
+ virtual ModRefResult getModRefInfo(CallSite CS1, CallSite CS2);
+
+ /// hasNoModRefInfoForCalls - Return true if the analysis has no mod/ref
+ /// information for pairs of function calls (other than "pure" and "const"
+ /// functions). This can be used by clients to avoid many pointless queries.
+ /// Remember that if you override this and chain to another analysis, you must
+ /// make sure that it doesn't have mod/ref info either.
+ ///
+ virtual bool hasNoModRefInfoForCalls() const;
/// Convenience functions...
ModRefResult getModRefInfo(LoadInst *L, Value *P, unsigned Size);
- ModRefResult getModRefInfo(StoreInst*S, Value *P, unsigned Size);
- ModRefResult getModRefInfo(CallInst *C, Value *P, unsigned Size) {
+ ModRefResult getModRefInfo(StoreInst *S, Value *P, unsigned Size);
+ ModRefResult getModRefInfo(CallInst *C, Value *P, unsigned Size) {
return getModRefInfo(CallSite(C), P, Size);
}
- ModRefResult getModRefInfo(InvokeInst*I, Value *P, unsigned Size) {
+ ModRefResult getModRefInfo(InvokeInst *I, Value *P, unsigned Size) {
return getModRefInfo(CallSite(I), P, Size);
}
ModRefResult getModRefInfo(Instruction *I, Value *P, unsigned Size) {
}
}
+ //===--------------------------------------------------------------------===//
+ /// Higher level methods for querying mod/ref information.
+ ///
+
/// canBasicBlockModify - Return true if it is possible for execution of the
/// specified basic block to modify the value pointed to by Ptr.
///
///
bool canInstructionRangeModify(const Instruction &I1, const Instruction &I2,
const Value *Ptr, unsigned Size);
+
+ //===--------------------------------------------------------------------===//
+ /// Methods that clients should call when they transform the program to allow
+ /// alias analyses to update their internal data structures. Note that these
+ /// methods may be called on any instruction, regardless of whether or not
+ /// they have pointer-analysis implications.
+ ///
+
+ /// deleteValue - This method should be called whenever an LLVM Value is
+ /// deleted from the program, for example when an instruction is found to be
+ /// redundant and is eliminated.
+ ///
+ virtual void deleteValue(Value *V);
+
+ /// copyValue - This method should be used whenever a preexisting value in the
+ /// program is copied or cloned, introducing a new value. Note that analysis
+ /// implementations should tolerate clients that use this method to introduce
+ /// the same value multiple times: if the analysis already knows about a
+ /// value, it should ignore the request.
+ ///
+ virtual void copyValue(Value *From, Value *To);
+
+ /// replaceWithNewValue - This method is the obvious combination of the two
+ /// above, and it provided as a helper to simplify client code.
+ ///
+ void replaceWithNewValue(Value *Old, Value *New) {
+ copyValue(Old, New);
+ deleteValue(Old);
+ }
};
// Because of the way .a files work, we must force the BasicAA implementation to
projects / oota-llvm.git / blobdiff