[llvm] [SDAG] Don't allow implicit trunc in getConstant() (PR #117558)

[Björn Pettersson via llvm-commits]

bjope wrote:

Also started to see assertion failures (with big-endian targets) in relation to DAGCombiner::ReduceLoadOpStoreWidth -> getMemBasePlusOffset , when ending up adding negative offsets.

I actually consider that as a bug in ReduceLoadOpStoreWidth (that was exposed by this patch) and propose a fix in this pull request: https://github.com/llvm/llvm-project/pull/119203

https://github.com/llvm/llvm-project/pull/117558