[PATCH] D71787: [Attributor] UB Attribute now handles all instructions that access memory through a pointer

[Stefanos Baziotis via Phabricator via llvm-commits]

baziotis created this revision.
baziotis added a reviewer: jdoerfert.
Herald added subscribers: llvm-commits, jfb, hiraditya.
Herald added a reviewer: sstefan1.
Herald added a project: LLVM.

Follow-up on: https://reviews.llvm.org/D71435
We basically use `checkForAllInstructions` to loop through all the instructions in a function that access memory through a pointer: load, store, atomicrmw, atomiccmpxchg
Note that we can now use the `getPointerOperand()` that gets us the pointer operand for an instruction that belongs to the aforementioned set.

Question: This function returns `nullptr` if the instruction is `volatile`. Why?
Guess:  Because if it is volatile, we don't want to do any transformation to it.

Another subtle point is that I had to add AtomicRMW, AtomicCmpXchg to `initializeInformationCache()`. Following `checkAllInstructions()` path, that
seemed the most reasonable place to add it and correct the fact that these instructions were ignored (they were not in `OpcodeInstMap` etc.). Is that ok?


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D71787

Files:
  llvm/lib/Transforms/IPO/Attributor.cpp
  llvm/test/Transforms/Attributor/undefined_behavior.ll

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