[clang] [llvm] [clang] Initial frontend C-restrict support (PR #173394)

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AnastasiyaChernikova wrote:

> It is good to compare cases that should end up being equivalent in behavior (minus potential optimization misses), like observing how the code is handled today when restrict is introduced through inlining a function with restrict arguments and comparing that to the manual inlined version. I also recommend adding testcases that check the actual integration effect (aka, not just llvm-ir generation, but also optimization effects).

@dobbelaj-snps, thank you for your suggestion. I agree that writing these kinds of tests is an important part of the implementation. But I suppose writing these tests is more relevant to the backend implementation: https://github.com/llvm/llvm-project/pull/173395.
Regarding the first part of your 

> just adding and tracking a scope for restrict annotated pointers is not sufficient for correctness.

I don't understand why this implementation isn't sufficient. Could you please explain in more detail?

https://github.com/llvm/llvm-project/pull/173394