///
virtual bool pointsToConstantMemory(const Value *P) { return false; }
+ /// 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.
+ ///
+ /// 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) { return false; }
+
+ /// onlyReadsMemory - If the specified function is known to only read from
+ /// non-volatile memory (or not access memory at all), return true.
+ ///
+ /// 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) { return doesNotAccessMemory(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
/// 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.
///
- virtual ModRefResult getModRefInfo(CallSite CS1, CallSite CS2) {
- return ModRef;
- }
+ virtual ModRefResult getModRefInfo(CallSite CS1, CallSite CS2);
/// 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) {