virtual bool pointsToConstantMemory(const Value *P) { return false; }
/// doesNotAccessMemory - If the specified function is known to never read or
- /// write memory, return true.
+ /// 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
virtual bool doesNotAccessMemory(Function *F) { return false; }
/// onlyReadsMemory - If the specified function is known to only read from
- /// non-volatile memory (or not access memory at all), return true.
+ /// 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.
/// 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 { return false; }
+
/// 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) {