Take one more look, I think this option should work and integrate with --param=riscv-autovec-preference= since they have similar jobs but slightly different.
We have 3 value for --param=riscv-autovec-preference=: none, scalable and fixed-vlmax -mrvv-vector-bits=scalable is work like --param=riscv-autovec-preference=scalable and -mrvv-vector-bits=zvl is work like --param=riscv-autovec-preference=fixed-vlmax. So I think...we need to do some conflict check, like: -mrvv-vector-bits=zvl can't work with --param=riscv-autovec-preference=scalable -mrvv-vector-bits=scalable can't work with --param=riscv-autovec-preference=fixed-vlmax but it may not just alias since there is some useful combinations like: -mrvv-vector-bits=zvl with --param=riscv-autovec-preference=none: NO auto vectorization but intrinsic code still could benefit from the -mrvv-vector-bits=zvl option. -mrvv-vector-bits=scalable with --param=riscv-autovec-preference=none Should still work for VLS code gen, but just disable auto vectorization per the option semantic. However here is something we need some fix, since --param=riscv-autovec-preference=none still disable VLS code gen for now, you can see some example here: https://godbolt.org/z/fMTr3eW7K But I think it's really the right behavior here, this part might need to be fixed in vls_mode_valid_p and some other places. Anyway I think we need to check all use sites with RVV_FIXED_VLMAX and RVV_SCALABLE, and need to make sure all use site of RVV_FIXED_VLMAX also checked with RVV_VECTOR_BITS_ZVL. > -/* Return the VLEN value associated with -march. > +static int > +riscv_convert_vector_bits (int min_vlen) Not sure if we really need this function, it seems it always returns min_vlen? > +{ > + int rvv_bits = 0; > + > + switch (rvv_vector_bits) > + { > + case RVV_VECTOR_BITS_ZVL: > + case RVV_VECTOR_BITS_SCALABLE: > + rvv_bits = min_vlen; > + break; > + default: > + gcc_unreachable (); > + } > + > + return rvv_bits; > +} > + > +/* Return the VLEN value associated with -march and -mwrvv-vector-bits.
