[clang] [clang] VectorExprEvaluator::VisitCallExpr - add constant folding for X86 pslldqi/psrldqi intrinsics (PR #157403)

[Simon Pilgrim via cfe-commits]

https://github.com/RKSimon requested changes to this pull request.

Thanks - this is looking correct now, please can you resolve the merge conflict and add equivalent handling to InterpBuiltin.cpp (we currently have 2 constexpr handlers so this needs to be duplicated).

https://github.com/llvm/llvm-project/pull/157403