Green’s Dictionary of Slang

1. badly injured [whack v.¹ (1)].

1977		(con. 1940s) O. Manning Danger Tree 90: His company had been ‘whacked up’ giving covering fire during the evacuation.
1997		L. Pettiway Workin’ It 200: My brains were all wacked up. I was like a zombie. I mean it was like I was brain dead.

2. see whacked adj. (4)