The BPF virtual machine does not support neg nor neg32 instructions with
an immediate.
The erroneous instructions were removed from binutils:
https://sourceware.org/pipermail/binutils/2023-August/129135.html
Change the define_insn so that an immediate cannot be accepted.
From testing, a neg-immediate was probably never chosen over a
mov-immediate anyway.
gcc/
* config/bpf/bpf.md (neg): Second operand must be a register.
;;; Negation
(define_insn "neg<AM:mode>2"
- [(set (match_operand:AM 0 "register_operand" "=r,r")
- (neg:AM (match_operand:AM 1 "reg_or_imm_operand" " 0,I")))]
+ [(set (match_operand:AM 0 "register_operand" "=r")
+ (neg:AM (match_operand:AM 1 "register_operand" " 0")))]
""
"{neg<msuffix>\t%0|%w0 = -%w1}"
[(set_attr "type" "<mtype>")])