Originally @lizhengxing's PR. Retargeting main.
This PR pulls 2 upstream changes, Add a new WeakVH value handle; NFC
(f1c0eafd5b)
and Use a 2 bit pointer in ValueHandleBase::PrevPair; NFC
(b297bff1cc),
into DXC.
Here's the summary of the changes:
Add a new WeakVH value handle; NFC
> WeakVH nulls itself out if the value it was tracking gets deleted, but
it does not track RAUW.
>
> Reviewers: dblaikie, davide
>
> Subscribers: mcrosier, llvm-commits
>
> Differential Revision: https://reviews.llvm.org/D32267
Use a 2 bit pointer in ValueHandleBase::PrevPair; NFC
> This was an omission in r301813. I had made the supporting changes to
make this happen, but I forgot to actually update the
>
> PrevPair declaration.
This is part 4 and 5 of the fix for #6659.
b197bec653