llvm dev - May 2018 - [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
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