Re: [PATCH v3 06/57] tcg/i386: Generalize multi-part load overlap test

[Philippe Mathieu-Daudé]

On 24/4/23 07:40, Richard Henderson wrote:
> Test for both base and index; use datahi as a temporary, overwritten
> by the final load.  Always perform the loads in ascending order, so
> that any (user-only) fault sees the correct address.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>   tcg/i386/tcg-target.c.inc | 31 +++++++++++++++----------------
>   1 file changed, 15 insertions(+), 16 deletions(-)
>
> diff --git a/tcg/i386/tcg-target.c.inc b/tcg/i386/tcg-target.c.inc
> index b986109d77..794d440a9e 100644
> --- a/tcg/i386/tcg-target.c.inc
> +++ b/tcg/i386/tcg-target.c.inc
> @@ -2223,23 +2223,22 @@ static void tcg_out_qemu_ld_direct(TCGContext *s, 
> TCGReg datalo, TCGReg datahi,
>           if (TCG_TARGET_REG_BITS == 64) {
>               tcg_out_modrm_sib_offset(s, movop + P_REXW + seg, datalo,
>                                        base, index, 0, ofs);
> +            break;
> +        }
> +        if (use_movbe) {
> +            TCGReg t = datalo;
> +            datalo = datahi;
> +            datahi = t;
> +        }
> +        if (base == datalo || index == datalo) {
> +            tcg_out_modrm_sib_offset(s, OPC_LEA, datahi, base, index, 0, ofs);
> +            tcg_out_modrm_offset(s, movop + seg, datalo, datahi, 0);
> +            tcg_out_modrm_offset(s, movop + seg, datahi, datahi, 4);

LGTM but I'd rather have someone fluent with x86 review this one...

>           } else {
> -            if (use_movbe) {
> -                TCGReg t = datalo;
> -                datalo = datahi;
> -                datahi = t;
> -            }
> -            if (base != datalo) {
> -                tcg_out_modrm_sib_offset(s, movop + seg, datalo,
> -                                         base, index, 0, ofs);
> -                tcg_out_modrm_sib_offset(s, movop + seg, datahi,
> -                                         base, index, 0, ofs + 4);
> -            } else {
> -                tcg_out_modrm_sib_offset(s, movop + seg, datahi,
> -                                         base, index, 0, ofs + 4);
> -                tcg_out_modrm_sib_offset(s, movop + seg, datalo,
> -                                         base, index, 0, ofs);
> -            }
> +            tcg_out_modrm_sib_offset(s, movop + seg, datalo,
> +                                     base, index, 0, ofs);
> +            tcg_out_modrm_sib_offset(s, movop + seg, datahi,
> +                                     base, index, 0, ofs + 4);
>           }
>           break;
>       default: