The encoding of the X_PAR non standard RISCV extension
The RISCV base opcode map (riscv-spec-v2.2.pdf, page 103, Table 1) is completed with the place of the X_PAR instruction subset.
The X_PAR extension is a greenfield one (riscv-spec-v2.2.pdf, page 114).
The X_PAR extension fills custom-0 slot.
Any X_PAR instruction has bits 6-2 set as 00010.
The X_PAR encoding uses the funct3 (bits 14-12) and funct7 (bits 31-25) fields as opcode extensions. For p_lwcv/re and p_swcv/re instructions, only full words can be transferred.
