Re: [PATCH v4 3/5] tcg/sparc: Use the constant pool for 64-bit constants

[Peter Maydell]

On Fri, 4 Feb 2022 at 07:53, Richard Henderson
<richard.henderson@linaro.org> wrote:
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  tcg/sparc/tcg-target.c.inc | 15 +++++++++++++++
>  1 file changed, 15 insertions(+)
>
> diff --git a/tcg/sparc/tcg-target.c.inc b/tcg/sparc/tcg-target.c.inc
> index 6349f750cc..47bdf314a0 100644
> --- a/tcg/sparc/tcg-target.c.inc
> +++ b/tcg/sparc/tcg-target.c.inc
> @@ -332,6 +332,13 @@ static bool patch_reloc(tcg_insn_unit *src_rw, int type,
>          insn &= ~INSN_OFF19(-1);
>          insn |= INSN_OFF19(pcrel);
>          break;
> +    case R_SPARC_13:
> +        if (!check_fit_ptr(value, 13)) {
> +            return false;
> +        }

This code seems to contemplate that the offset might not fit
into the 13-bit immediate field (unlike the other two reloc
cases in this function, which just assert() that it fits)...

> +        insn &= ~INSN_IMM13(-1);
> +        insn |= INSN_IMM13(value);
> +        break;
>      default:
>          g_assert_not_reached();
>      }
> @@ -469,6 +476,14 @@ static void tcg_out_movi_int(TCGContext *s, TCGType 
> type, TCGReg ret,
>          return;
>      }
>
> +    /* Use the constant pool, if possible. */
> +    if (!in_prologue && USE_REG_TB) {
> +        new_pool_label(s, arg, R_SPARC_13, s->code_ptr,
> +                       tcg_tbrel_diff(s, NULL));
> +        tcg_out32(s, LDX | INSN_RD(ret) | INSN_RS1(TCG_REG_TB));
> +        return;
> +    }

...but this code doesn't seem to have any mechanism for
falling back to something else if it won't fit.

> +
>      /* A 64-bit constant decomposed into 2 32-bit pieces.  */
>      if (check_fit_i32(lo, 13)) {
>          hi = (arg - lo) >> 32;
> --
> 2.25.1

thanks
-- PMM