[llvm] replace many GlobalValue->getValueType calls with more specific queries (PR #177039)

[Jameson Nash via llvm-commits]

vtjnash wrote:

Split into 2 PRs, dropping the contentious commit. Upon reflection, I think that one needs a more wholistic redesign anyways: https://github.com/llvm/llvm-project/pull/176996#issuecomment-3778809210

https://github.com/llvm/llvm-project/pull/177039