[PATCH] D75285: Mark restrict pointer or reference to const as invariant

[Hal Finkel via Phabricator via cfe-commits]

hfinkel requested changes to this revision.
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Unfortunately, we cannot do this kind of thing just because it seems to make sense. The language semantics must be exactly satisfied by the IR-level semantics. I certainly agree that it would make sense for users to be able to mark invariant loads, but this mechanism simply might not be the right one.

One problem here is that, with something like:

  char test2(X *x) {
    const char* __restrict p = &(x->b);
    return *p;
  }

what happens when the function is inlined? Does the "invariantness" only still apply to accesses within the scope of the local restrict pointer? I believe that it would not, and that would be a problem because later code might legally modify the relevant data.


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https://reviews.llvm.org/D75285