[PATCH] D64128: [CodeGen] Generate llvm.ptrmask instead of inttoptr(and(ptrtoint, C)) if possible.

[Florian Hahn via Phabricator via cfe-commits]

fhahn abandoned this revision.
fhahn added a comment.

In D64128#1578916 <https://reviews.llvm.org/D64128#1578916>, @fhahn wrote:

> In D64128#1576391 <https://reviews.llvm.org/D64128#1576391>, @rjmccall wrote:
>
> > I wouldn't favor adding something really obscure that was only useful for clang, but I think builtins to set and clear mask bits while promising to preserve object-reference identity would be more generally useful for libraries.  For example, there might be somewhere in libc++ that could take advantage of this.
>
>
> Yep, I think for this to be generally useful we would also need an intrinsic to set bits as well. I'll commit the LLVM patches and improvements to ValueTracking in the next few days for ptrmask and will put up a patch for builtins once I know more about how libcxx could use them.


Thanks for all the comments! I checked with a few contributors to libcxx and there seem to be no very obvious places where this would help a lot. IUUC for now the patch is not really worth pursuing further.


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