[PATCH v4] RISC-V: Add Zcmt instructions and csr.

[Nelson Chu]

Does this patch refer to the spec,
https://github.com/riscvarchive/riscv-code-size-reduction/releases?

On Wed, Sep 11, 2024 at 3:39 PM Jiawei <jiawei@iscas.ac.cn> wrote:

> @@ -3914,6 +3921,28 @@ riscv_ip (char *str, struct riscv_cl_insn *ip,
> expressionS *imm_expr,
>                         break;
>                       INSERT_OPERAND (SREG2, *ip, regno % 8);
>                       continue;
> +                   case 'I': /* index operand of cm.jt. The range is from
> 0 to 31.  */
> +                     my_getSmallExpression (imm_expr, imm_reloc, asarg,
> p);
> +                     if (imm_expr->X_op != O_constant
> +                         || imm_expr->X_add_number < 0
> +                         || imm_expr->X_add_number > 31)
> +                       {
> +                         as_bad ("bad index value for cm.jt, range: [0,
> 31]");
> +                         break;
> +                       }
> +                     ip->insn_opcode |= ENCODE_ZCMT_INDEX
> (imm_expr->X_add_number);
> +                     goto rvc_imm_done;
> +                   case 'i': /* index operand of cm.jalt. The range is
> from 32 to 255.  */
> +                     my_getSmallExpression (imm_expr, imm_reloc, asarg,
> p);
> +                     if (imm_expr->X_op != O_constant
> +                         || imm_expr->X_add_number < 32
> +                         || imm_expr->X_add_number > 255)
> +                       {
> +                         as_bad ("bad index value for cm.jalt, range:
> [32, 255]");
> +                         break;
> +                       }
> +                     ip->insn_opcode |= ENCODE_ZCMT_INDEX
> (imm_expr->X_add_number);
> +                     goto rvc_imm_done;
>

Since we already have the range check of the immediate field here, I think
we don't need to check them again in the match_cm_jt and match_cm_jalt.
That is - we don't need the match_cm* functions.


> diff --git a/include/opcode/riscv-opc.h b/include/opcode/riscv-opc.h
> index 73ee81158ae..5cc5e6e1eb5 100644
> --- a/include/opcode/riscv-opc.h
> +++ b/include/opcode/riscv-opc.h
> +/* Zcmt instructions.  */
> +#define MATCH_CM_JT 0xa002
> +#define MASK_CM_JT 0xff03
> +#define MATCH_CM_JALT 0xa002
> +#define MASK_CM_JALT 0xfc03


0xfc03 also for MASK_CM_JT?


> diff --git a/opcodes/riscv-dis.c b/opcodes/riscv-dis.c
> index 8ab138e45ce..ec12f488858 100644
> --- a/opcodes/riscv-dis.c
> +++ b/opcodes/riscv-dis.c
> @@ -61,6 +61,8 @@ struct riscv_private_data
>  {
>    bfd_vma gp;
>    bfd_vma print_addr;
> +  bfd_vma jvt_base;
> +  bfd_vma jvt_end;
>

How do these two variables actually work?


> +/* Print table jump index.  */
> +
> +static bool
> +print_jvt_index (disassemble_info *info, unsigned int index)
> +{
> +  bfd_vma entry_value;
> +  bfd_vma memaddr;
> +  int status;
> +
> +  bfd_byte packet[8] = { 0 };
> +  struct riscv_private_data *pd = info->private_data;
> +
> +  memaddr = pd->jvt_base + index * (xlen / 8);
> +  status = (*info->read_memory_func) (memaddr, packet, xlen / 8, info);
> +  if (status != 0)
> +    return false;
> +
> +  entry_value = xlen == 32 ? bfd_getl32 (packet)
> +                           : bfd_getl64 (packet);
> +
> +  maybe_print_address (pd, 0, entry_value, 0);
> +  return true;
> +}
>

How/When/Who to set the value of jvt_base?  Maybe they are in a different
patch or code?  If that is so then the code here should be moved to there
:-)

Thanks
Nelson
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