[PATCH] D52164: [InstSimplify] Fold ne/eq comparison of a pointer produced by a noalias function

[Hal Finkel via Phabricator via llvm-commits]

hfinkel requested changes to this revision.
hfinkel added a comment.
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Unfortunately, I don't think that we can do this. noalias semantics only provide information about the overlap of memory accesses using the resulting pointers, in the context of other necessary constraints, and does not strongly constrain the pointer values. For example, it might be that:

  int *x = malloc(n);
  free(x);
  int *y = malloc(n);
  if (y == x) // should we always fold this to false?
    printf("malloc reused memory");

Also, what happens if the result is null, and you're comparing to a value which also happens to be null?


Repository:
  rL LLVM

https://reviews.llvm.org/D52164