core/ir/riscv64/isl/zifencei.txt

# "Zifencei" Instruction-Fetch Fence.
# Version 2.0

# imm[11:0], rs1, and rd, are reserved for finer-grain fences in future extensions.
# Standard software shall zero these fields.
fence.i | i | | 00000000000000000001000000001111