[PATCH] D59065: [BasicAA] Simplify inttoptr(and(ptrtoint(X), C)) to X, if C preserves all significant bits.

[Sanjoy Das via Phabricator via llvm-commits]

sanjoy added a comment.

In D59065#1448178 <https://reviews.llvm.org/D59065#1448178>, @hfinkel wrote:

> > I am also not entirely sure how control dependencies could add new underlying objects with this patch
>
> Please read this https://bugs.llvm.org/show_bug.cgi?id=34548
>
> I *think* that this is okay if the ptrtoint and the and have only one user, and they're in the same basic block, and there's nothing that can throw, etc. in between?


I'm not sure about this.  You could have:

  int32* ptr0 = malloc(4);
  int32* ptr1 = malloc(4);
  
  if (ptr0+1 != ptr1) return;
  
  int32* ptr = (int*)(int64)(ptr0+1);

in which `ptr` would alias `ptr1`.  But if you transform `ptr` to `ptr0+1` then it would not alias `ptr1`.  That IR ^ could have resulted from:

  int32* ptr0 = malloc(4);
  int32* ptr1 = malloc(4);
  
  if (ptr0+1 != ptr1) return;
  
  int64 ptr0_i = (int64)(ptr0+1);
  int64 ptr1_i = (int64)(ptr1);
  
  int32* ptr = (int*)ptr1_i;


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