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

[Simon Pilgrim via cfe-commits]

RKSimon wrote:

@kimyounhoex1 are you able to get this finished soon please? the patch is starting to bit rot due to all the other constexpr work

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