[llvm] [RuntimeDyld][ELF][AArch64] Fix resolveAArch64ShortBranch. (PR #92245)

[Alastair Houghton via llvm-commits]

al45tair wrote:

OK, I've reproduce the sign extension problem. Just trying to work out why it's happening. (It's an existing bug, nothing to do with the code I added…)

https://github.com/llvm/llvm-project/pull/92245