Re: [PATCH] ppc: Fix extr_d() on 32-bit PPC

[Paul Cercueil]

Note that with your recent SQRT patches and this one, the checks all 
pass on PowerPC 32-bit now.

Cheers,
-Paul


Le sam., août 27 2022 at 16:17:30 +0100, Paul Cercueil 
<paul@crapouillou.net> a écrit :
> The FCFID instruction is only available on 64-bit PowerPC. Therefore 
> it
> is necesary to use a software mechanism to convert integers to
> floating-point on 32-bit PowerPC.
>
> Tested and working on PowerPC-32 big-endian and little-endian.
>
> Signed-off-by: Paul Cercueil <paul@crapouillou.net>
> ---
>  lib/jit_ppc-fpu.c | 31 ++++++++++++++++++++++++-------
>  1 file changed, 24 insertions(+), 7 deletions(-)
>
> diff --git a/lib/jit_ppc-fpu.c b/lib/jit_ppc-fpu.c
> index 387cc6f..dd66d03 100644
> --- a/lib/jit_ppc-fpu.c
> +++ b/lib/jit_ppc-fpu.c
> @@ -484,23 +484,40 @@ _movi_d(jit_state_t *_jit, jit_int32_t r0, 
> jit_float64_t *i0)
>         ldi_d(r0, (jit_word_t)i0);
>  }
>
> -/* should only work on newer ppc (fcfid is a ppc64 instruction) */
>  static void
>  _extr_d(jit_state_t *_jit, jit_int32_t r0, jit_int32_t r1)
>  {
>  #  if __WORDSIZE == 32
> -    jit_int32_t                reg;
> +    jit_int32_t                reg, freg, off1, off2;
> +
> +#  if __BYTE_ORDER == __BIG_ENDIAN
> +    off1 = alloca_offset - 8;
> +    off2 = alloca_offset - 4;
> +#  else
> +    off1 = alloca_offset - 4;
> +    off2 = alloca_offset - 8;
> +#  endif
> +
>      reg = jit_get_reg(jit_class_gpr);
> -    rshi(rn(reg), r1, 31);
> -    /* use reserved 8 bytes area */
> -    stxi(alloca_offset - 4, _FP_REGNO, r1);
> -    stxi(alloca_offset - 8, _FP_REGNO, rn(reg));
> +    freg = jit_get_reg(jit_class_fpr);
> +
> +    movi(rn(reg), 0x43300000);
> +    stxi_i(off1, _FP_REGNO, rn(reg));
> +    movi(rn(reg), 0x80000000);
> +    stxi_i(off2, _FP_REGNO, rn(reg));
> +    ldxi_d(rn(freg), _FP_REGNO, alloca_offset - 8);
> +    xorr(rn(reg), r1, rn(reg));
> +    stxi_i(off2, _FP_REGNO, rn(reg));
> +    ldxi_d(r0, _FP_REGNO, alloca_offset - 8);
> +    subr_d(r0, r0, rn(freg));
> +
>      jit_unget_reg(reg);
> +    jit_unget_reg(freg);
>  #  else
>      stxi(alloca_offset - 8, _FP_REGNO, r1);
> -#  endif
>      ldxi_d(r0, _FP_REGNO, alloca_offset - 8);
>      FCFID(r0, r0);
> +#  endif
>  }
>
>  static void
> --
> 2.35.1