TableGen: Add !foldl operation

Change-Id: I63d67bf6e0b315e2d3360e47e3b62c9517f38987

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@326790 91177308-0d34-0410-b5e6-96231b3b80d8
8 files changed