[CodeGen] Add space-optimized EmitMergeInputChains1_2 to the DAG isel matching tables. Shaves about 5100 bytes from the X86 matcher table. NFC

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@262815 91177308-0d34-0410-b5e6-96231b3b80d8
3 files changed