Register names Register ABI Description 0 zero Constant 0 1 ra Return address 2 sp Stack pointer 3 gp Global pointer 4 tp Thread pointer 5 to 7 t0 to t2 Temporary register 8 s0/fp Save register, frame pointer 9 s1 Save register 10 to 17 a0 to a7 Function arguments or return value 18 to 27 s2 to s11 Save register 28 to 31 t3 to t6 Temporary register Assembly Manual SEW ("V" Spec 6.1) Assembly Bits SEW vsew e8 000 (0) 8bit 0 e16 001 (1) 16bit 1 e32 010 (2) 32bit 2 e64 011 (3) 64bit 3 e128 100 (4) 128bit 4 e256 101 (5) 256bit 5 e512 110 (6) 512bit 6 e1024 111 (7) 1024bit 7 LMUL ("V" Spec 6.1) Assembly vlmul LMUL m1 000 (0) 1 m2 001 (1) 2 m4 010 (2) 4 m8 011 (3) 8 mf8 101 (-3) 1/8 mf4 110 (-2) 1/4 mf2 111 (-1) 1/2