Re: [PATCH v2 04/45] target/hppa: Pass displacement to do_dbranch

[Helge Deller <deller@kernel.org>]

* Richard Henderson <richard.henderson@linaro.org>:
> Pass a displacement instead of an absolute value.
> 
> In trans_be, remove the user-only do_dbranch case.  The branch we are
> attempting to optimize is to the zero page, which is perforce on a
> different page than the code currently executing, which means that
> we will *not* use a goto_tb.  Use a plain indirect branch instead,
> which is what we got out of the attempted direct branch anyway.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

Reviewed-by: Helge Deller <deller@gmx.de>

> ---
>  target/hppa/translate.c | 33 +++++++++------------------------
>  1 file changed, 9 insertions(+), 24 deletions(-)
> 
> diff --git a/target/hppa/translate.c b/target/hppa/translate.c
> index 398803981c..4c42b518c5 100644
> --- a/target/hppa/translate.c
> +++ b/target/hppa/translate.c
> @@ -1766,9 +1766,11 @@ static bool do_fop_dedd(DisasContext *ctx, unsigned rt,
>  
>  /* Emit an unconditional branch to a direct target, which may or may not
>     have already had nullification handled.  */
> -static bool do_dbranch(DisasContext *ctx, uint64_t dest,
> +static bool do_dbranch(DisasContext *ctx, int64_t disp,
>                         unsigned link, bool is_n)
>  {
> +    uint64_t dest = iaoq_dest(ctx, disp);
> +
>      if (ctx->null_cond.c == TCG_COND_NEVER && ctx->null_lab == NULL) {
>          if (link != 0) {
>              copy_iaoq_entry(ctx, cpu_gr[link], ctx->iaoq_n, ctx->iaoq_n_var);
> @@ -1815,10 +1817,7 @@ static bool do_cbranch(DisasContext *ctx, int64_t disp, bool is_n,
>  
>      /* Handle TRUE and NEVER as direct branches.  */
>      if (c == TCG_COND_ALWAYS) {
> -        return do_dbranch(ctx, dest, 0, is_n && disp >= 0);
> -    }
> -    if (c == TCG_COND_NEVER) {
> -        return do_dbranch(ctx, ctx->iaoq_n, 0, is_n && disp < 0);
> +        return do_dbranch(ctx, disp, 0, is_n && disp >= 0);
>      }
>  
>      taken = gen_new_label();
> @@ -3914,22 +3913,6 @@ static bool trans_be(DisasContext *ctx, arg_be *a)
>  {
>      TCGv_i64 tmp;
>  
> -#ifdef CONFIG_USER_ONLY
> -    /* ??? It seems like there should be a good way of using
> -       "be disp(sr2, r0)", the canonical gateway entry mechanism
> -       to our advantage.  But that appears to be inconvenient to
> -       manage along side branch delay slots.  Therefore we handle
> -       entry into the gateway page via absolute address.  */
> -    /* Since we don't implement spaces, just branch.  Do notice the special
> -       case of "be disp(*,r0)" using a direct branch to disp, so that we can
> -       goto_tb to the TB containing the syscall.  */
> -    if (a->b == 0) {
> -        return do_dbranch(ctx, a->disp, a->l, a->n);
> -    }
> -#else
> -    nullify_over(ctx);
> -#endif
> -
>      tmp = tcg_temp_new_i64();
>      tcg_gen_addi_i64(tmp, load_gpr(ctx, a->b), a->disp);
>      tmp = do_ibranch_priv(ctx, tmp);
> @@ -3939,6 +3922,8 @@ static bool trans_be(DisasContext *ctx, arg_be *a)
>  #else
>      TCGv_i64 new_spc = tcg_temp_new_i64();
>  
> +    nullify_over(ctx);
> +
>      load_spr(ctx, new_spc, a->sp);
>      if (a->l) {
>          copy_iaoq_entry(ctx, cpu_gr[31], ctx->iaoq_n, ctx->iaoq_n_var);
> @@ -3968,7 +3953,7 @@ static bool trans_be(DisasContext *ctx, arg_be *a)
>  
>  static bool trans_bl(DisasContext *ctx, arg_bl *a)
>  {
> -    return do_dbranch(ctx, iaoq_dest(ctx, a->disp), a->l, a->n);
> +    return do_dbranch(ctx, a->disp, a->l, a->n);
>  }
>  
>  static bool trans_b_gate(DisasContext *ctx, arg_b_gate *a)
> @@ -4022,7 +4007,7 @@ static bool trans_b_gate(DisasContext *ctx, arg_b_gate *a)
>          save_gpr(ctx, a->l, tmp);
>      }
>  
> -    return do_dbranch(ctx, dest, 0, a->n);
> +    return do_dbranch(ctx, dest - iaoq_dest(ctx, 0), 0, a->n);
>  }
>  
>  static bool trans_blr(DisasContext *ctx, arg_blr *a)
> @@ -4035,7 +4020,7 @@ static bool trans_blr(DisasContext *ctx, arg_blr *a)
>          return do_ibranch(ctx, tmp, a->l, a->n);
>      } else {
>          /* BLR R0,RX is a good way to load PC+8 into RX.  */
> -        return do_dbranch(ctx, ctx->iaoq_f + 8, a->l, a->n);
> +        return do_dbranch(ctx, 0, a->l, a->n);
>      }
>  }
>  
> -- 
> 2.34.1
>