[clang] [llvm] Extend MemoryEffects to Support Target-Specific Memory Locations (PR #148650)

[via llvm-commits]

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CarolineConcatto wrote:

@paulwalker-arm  let me know if that is the behaviour we would like for the target_mem.
If so then we will need to change as well for MLIR.
This test is failing:
mlir/test/Target/LLVMIR/llvmir.mlir
I was looking at this commit:

```
commit 9b9cfe77a50abccc4b82a497e17566a454b699bd
Author: Christian Ulmann <christian.ulmann at nextsilicon.com>
Date:   Thu Jan 12 16:48:19 2023 +0100
 
     [mlir][LLVM] Replace readnone with memory effects]
```
MLIR has its own attributes, a mirror from llvm-ir,  and it maps to memory effects.


https://github.com/llvm/llvm-project/pull/148650