Convert (CMP (srl/shl X, C), 0) to (CMP (and X, C'), 0) when only the zero flag is used.

This allows a TEST to be used and can be combined with any AND that may already exist as an input to the shift.

This was already done in EmitTest, but was easily tricked by multiple uses because the setcc might be used by multiple instructions. Once the SETCC and users are legalized then we can look for the shift to be used by a single CMP, but the CMP itself can have multiple users.

This appears to fix the case in PR39968.

llvm-svn: 349385