What is an IELR(1)-parser? I try to teach myself the usage of bison. The manpage bison(1) says about bison:


  Generate a deterministic LR or generalized LR (GLR) parser employing LALR(1), IELR(1), or canonical LR(1) parser tables.


What is an IELR-parser? All relevant articles I found on the world wide web are paywalled.
An article that claims to introduce it: IELR(1): Practical LR(1) Parser Tables for
Non-LR(1) Grammars with Conflict Resolution (via archive.org) by Joel E. Denny and Brian A. Malloy, Clemson University, is freely available from Malloy's site.

What they are worth is something I can't answer. (Personally I don't understand the need for such crippled CFG parsing - why limit your expressive power when you can just use GLR?  What does make sense to me is something like TAG or PEG (they seem natural and add expressive power) or tree grammars (for languages such as XML, in which recognizing parse trees is unproblematic by design.)