Re: [PATCH 29/56] disas/riscv: Handle aliases of csrrwi during decode

On Sun, 2026-08-09 at 15:35 -0700, Richard Henderson wrote:
> Signed-off-by: Richard Henderson <[email protected]>

Reviewed-by: Alistair Francis <[email protected]>

Alistair

> ---
>  disas/riscv.h |  2 --
>  disas/riscv.c | 28 ++++++++--------------------
>  2 files changed, 8 insertions(+), 22 deletions(-)
> 
> diff --git a/disas/riscv.h b/disas/riscv.h
> index d8c5acd969..3bbcbf10fb 100644
> --- a/disas/riscv.h
> +++ b/disas/riscv.h
> @@ -84,8 +84,6 @@ typedef enum {
>      rvc_imm_eq_zero,
>      rvc_imm_eq_n1,
>      rvc_imm_eq_p1,
> -    rvc_csr_eq_0x001,
> -    rvc_csr_eq_0x002,
>  } rvc_constraint;
>  
>  typedef enum {
> diff --git a/disas/riscv.c b/disas/riscv.c
> index 9ec79baf4d..d3cbfb86ac 100644
> --- a/disas/riscv.c
> +++ b/disas/riscv.c
> @@ -1063,8 +1063,6 @@ static const rvc_constraint rvcc_ret[] = {
> rvc_rd_eq_x0, rvc_rs1_eq_ra,
>                                             rvc_end };
>  static const rvc_constraint rvcc_jr[] = { rvc_rd_eq_x0,
> rvc_imm_eq_zero,
>                                            rvc_end };
> -static const rvc_constraint rvcc_fsrmi[] = { rvc_csr_eq_0x002,
> rvc_end };
> -static const rvc_constraint rvcc_fsflagsi[] = { rvc_csr_eq_0x001,
> rvc_end };
>  
>  /* pseudo-instruction metadata */
>  
> @@ -1145,12 +1143,6 @@ static const rv_comp_data rvcp_subw[] = {
>      { rv_op_illegal, NULL }
>  };
>  
> -static const rv_comp_data rvcp_csrrwi[] = {
> -    { rv_op_fsrmi, rvcc_fsrmi },
> -    { rv_op_fsflagsi, rvcc_fsflagsi },
> -    { rv_op_illegal, NULL }
> -};
> -
>  static const rv_comp_data rvcp_fsgnj_s[] = {
>      { rv_op_fmv_s, rvcc_fmv_s },
>      { rv_op_illegal, NULL }
> @@ -1722,7 +1714,7 @@ static const rv_opcode_data rvi_opcode_data[] =
> {
>      { "csrrw", rv_codec_i_csr, rv_fmt_rd_csr_rs1 },
>      { "csrrs", rv_codec_i_csr, rv_fmt_rd_csr_rs1 },
>      { "csrrc", rv_codec_i_csr, rv_fmt_rd_csr_rs1 },
> -    { "csrrwi", rv_codec_i_csr, rv_fmt_rd_csr_zimm, rvcp_csrrwi },
> +    { "csrrwi", rv_codec_i_csr, rv_fmt_rd_csr_zimm },
>      { "csrrsi", rv_codec_i_csr, rv_fmt_rd_csr_zimm },
>      { "csrrci", rv_codec_i_csr, rv_fmt_rd_csr_zimm },
>      { "flw", rv_codec_i, rv_fmt_frd_offset_rs1 },
> @@ -4469,7 +4461,13 @@ static void decode_inst_opcode(rv_decode *dec,
> rv_isa isa)
>                      }
>                  }
>                  break;
> -            case 5: op = rv_op_csrrwi; break;
> +            case 5:
> +                switch (operand_csr12(inst)) {
> +                case 1: op = rv_op_fsflagsi; break;
> +                case 2: op = rv_op_fsrmi; break;
> +                default: op = rv_op_csrrwi; break;
> +                }
> +                break;
>              case 6: op = rv_op_csrrsi; break;
>              case 7: op = rv_op_csrrci; break;
>              }
> @@ -4991,16 +4989,6 @@ static bool check_constraints(rv_decode *dec,
> const rvc_constraint *c)
>                  return false;
>              }
>              break;
> -        case rvc_csr_eq_0x001:
> -            if (!(imm == 0x001)) {
> -                return false;
> -            }
> -            break;
> -        case rvc_csr_eq_0x002:
> -            if (!(imm == 0x002)) {
> -                return false;
> -            }
> -            break;
>          default: break;
>          }
>          c++;