[llvm] [NFCI][BitcodeReader]Read real GUID from VI as opposed to storing it in map (PR #107735)

[Kazu Hirata via llvm-commits]

kazutakahirata wrote:

Nice finding!  Let me see if I understand things correctly.

- We always create an instance of `ValueInfo` with the same GUID as `std::get<2>`.
- Once an instance of `ValueInfo` is created, its pointer portion never changes.
- The pointer portion of `ValueInfo` points to an key-value pair of `GlobalValueSummaryMapTy`, so the key portion, `GUID`, shouldn't change.

So, `std::get<2>(VIAndOriginalGUID)` and `VIAndOriginalGUID.first.getGUID()` must be always the same.

Did I get this right?

https://github.com/llvm/llvm-project/pull/107735