Re: [PATCH v7 15/27] tcg/tci: Change encoding to uint32_t units

[Philippe Mathieu-Daudé]

On 6/1/21 5:00 PM, Richard Henderson wrote:
> This removes all of the problems with unaligned accesses
> to the bytecode stream.
> 
> With an 8-bit opcode at the bottom, we have 24 bits remaining,
> which are generally split into 6 4-bit slots.  This fits well
> with the maximum length opcodes, e.g. INDEX_op_add2_i32, which
> have 6 register operands.
> 
> We have, in previous patches, rearranged things such that there
> are no operations with a label which have more than one other
> operand.  Which leaves us with a 20-bit field in which to encode
> a label, giving us a maximum TB size of 512k -- easily large.
> 
> Change the INDEX_op_tci_movi_{i32,i64} opcodes to tci_mov[il].
> The former puts the immediate in the upper 20 bits of the insn,
> like we do for the label displacement.  The later uses a label
> to reference an entry in the constant pool.  Thus, in the worst
> case we still have a single memory reference for any constant,
> but now the constants are out-of-line of the bytecode and can
> be shared between different moves saving space.
> 
> Change INDEX_op_call to use a label to reference a pair of
> pointers in the constant pool.  This removes the only slightly
> dodgy link with the layout of struct TCGHelperInfo.
> 
> The re-encode cannot be done in pieces.
> 
> Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  include/tcg/tcg-opc.h    |   4 +-
>  tcg/tci/tcg-target.h     |   3 +-
>  tcg/tci.c                | 541 +++++++++++++++------------------------
>  tcg/tci/tcg-target.c.inc | 379 ++++++++++++---------------
>  tcg/tci/README           |  20 +-
>  5 files changed, 384 insertions(+), 563 deletions(-)

> @@ -1082,87 +961,69 @@ static const char *str_c(TCGCond c)
>  /* Disassemble TCI bytecode. */
>  int print_insn_tci(bfd_vma addr, disassemble_info *info)
>  {

>      case INDEX_op_setcond_i32:
>      case INDEX_op_setcond_i64:
> -        tci_args_rrrc(&tb_ptr, &r0, &r1, &r2, &c);
> +        tci_args_rrrc(insn, &r0, &r1, &r2, &c);
>          info->fprintf_func(info->stream, "%-12s  %s, %s, %s, %s",
>                             op_name, str_r(r0), str_r(r1), str_r(r2), 
> str_c(c));
>          break;
>  
> -    case INDEX_op_tci_movi_i32:
> -        tci_args_ri(&tb_ptr, &r0, &i1);
> -        info->fprintf_func(info->stream, "%-12s  %s, 0x%" TCG_PRIlx,
> +    case INDEX_op_tci_movi:
> +        tci_args_ri(insn, &r0, &i1);
> +        info->fprintf_func(info->stream, "%-12s  %s,0x%" TCG_PRIlx "",

Missing space in format: "%s, 0x%"

>                             op_name, str_r(r0), i1);
>          break;
>  
> -#if TCG_TARGET_REG_BITS == 64
> -    case INDEX_op_tci_movi_i64:
> -        tci_args_rI(&tb_ptr, &r0, &i1);
> -        info->fprintf_func(info->stream, "%-12s  %s, 0x%" TCG_PRIlx,
> -                           op_name, str_r(r0), i1);
> +    case INDEX_op_tci_movl:
> +        tci_args_rl(insn, tb_ptr, &r0, &ptr);
> +        info->fprintf_func(info->stream, "%-12s  %s, %p",
> +                           op_name, str_r(r0), ptr);
>          break;
> -#endif