[RFC] Adding 2 functions to the ALiasAnalysis interface (getAddressesDistance + ModRefSameBuffer)

Hi,
RFC

Im adding 2 new functions to the AliasAnalysis interface:

1) ModRefSameBufferCheck:
this function will receive 2 memoryLocation as parameters, and returns true if the parameters are modifying or refering the same buffer or same memory block, false otherwise.
2) getAddressesDistance:
the function will recieve 2 memoryLocation, if they are mod/ref-ing the same buffer/memory block, the function will return the distance between those locations at the memory. None otherwise (Optional<int64_t>)

interface change:https://reviews.llvm.org/D46864

those 2 function can be impelemented easly in AlisAnalysis and can help alot of users, a usage example is for detecting bank conflicts (using the distance between memoryLoc and the number and size of the banks you can know if you have a conflict).

implementation and usage example (with code duplication for a first implementation, lets discuss the idea first):
https://reviews.llvm.org/D46928

I saw one bad implemntation for detecting bank conflicts in Hexagon open-source, but it wont realy work for most of examples, they only check if the registers are equal… in my implamentation I check the real distance between locations…

thanks,
Atheel Massalha
Compiler Engineer