Ilsh is an internet slang word that means "I'm laughing so hard." Ilsh can be used for the past (I laughed so hard), present (I'm laughing so hard), and for the future (I'll/I'd laugh so hard). Ilsh has been around for a while but people seem to have forgotten this term.
Use for past-tense - Dude ilsh when you did that yesterday
Use for present-tense - Now that you did that, ilsh!
Use for future-tense - If you pull that little stunt off, ilsh!