Reapply "[OpenACC] Sema changes for +*&|^ reduction combiner recipes (… (https://github.com/llvm/llvm-project/pull/162920)#163246

erichkeane merged 2 commits intollvm:mainllvm/llvm-project:mainfrom

erichkeane:ReaddReductionSemaWithFlattenedASTerichkeane/llvm-project:ReaddReductionSemaWithFlattenedASTCopy head branch name to clipboard