[PATCH] D74935: [LangRef][AliasAnalysis] Clarify `noalias` affects only modified objects

Johannes Doerfert via Phabricator via llvm-commits llvm-commits at lists.llvm.org
Thu Mar 5 09:51:06 PST 2020


jdoerfert added a comment.

In D74935#1907100 <https://reviews.llvm.org/D74935#1907100>, @jeroen.dobbelaere wrote:

> Just to give an example:
>
>   int foo(int* restrict *pA, int* restrict *pB) {
>     int tmp=**pB;
>     **pA=42;
>     return tmp - **pB; // **pA and **pB can refer to the same objects
>   }
>    
>
> [...]


`*pA` and `*pB` are both restrict qualified pointers, are they not?
If so, why can they point to the same location?

I mean, w/o the side channel stuff the two `int *` values may alias
even if you have `noalias` on the arguments (https://godbolt.org/z/J9v_gK).


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