When one mistakenly specifies 'def' instead of using 'defm',
the error message is quite misleading: 'Couldn't find class..'
Instead, it should recommend using defm if the multiclass of
same name exists.
Reviewed By: hfinkel
Differential Revision: https://reviews.llvm.org/D59294
llvm-svn: 356985
Javed Absar