Re: [PATCH v2 05/45] target/hppa: Allow prior nullification in do_ibranch

[Helge Deller <deller@kernel.org>]

* Richard Henderson <richard.henderson@linaro.org>:
> Simplify the function by not attempting a conditional move
> on the branch destination -- just use nullify_over normally.
> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

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

> ---
>  target/hppa/translate.c | 73 +++++++++++------------------------------
>  1 file changed, 20 insertions(+), 53 deletions(-)
> 
> diff --git a/target/hppa/translate.c b/target/hppa/translate.c
> index 4c42b518c5..140dfb747a 100644
> --- a/target/hppa/translate.c
> +++ b/target/hppa/translate.c
> @@ -1871,17 +1871,15 @@ static bool do_cbranch(DisasContext *ctx, int64_t disp, bool is_n,
>  static bool do_ibranch(DisasContext *ctx, TCGv_i64 dest,
>                         unsigned link, bool is_n)
>  {
> -    TCGv_i64 a0, a1, next, tmp;
> -    TCGCond c;
> +    TCGv_i64 next;
>  
> -    assert(ctx->null_lab == NULL);
> +    if (ctx->null_cond.c == TCG_COND_NEVER && ctx->null_lab == NULL) {
> +        next = tcg_temp_new_i64();
> +        tcg_gen_mov_i64(next, dest);
>  
> -    if (ctx->null_cond.c == TCG_COND_NEVER) {
>          if (link != 0) {
>              copy_iaoq_entry(ctx, cpu_gr[link], ctx->iaoq_n, ctx->iaoq_n_var);
>          }
> -        next = tcg_temp_new_i64();
> -        tcg_gen_mov_i64(next, dest);
>          if (is_n) {
>              if (use_nullify_skip(ctx)) {
>                  copy_iaoq_entry(ctx, cpu_iaoq_f, -1, next);
> @@ -1895,60 +1893,29 @@ static bool do_ibranch(DisasContext *ctx, TCGv_i64 dest,
>          }
>          ctx->iaoq_n = -1;
>          ctx->iaoq_n_var = next;
> -    } else if (is_n && use_nullify_skip(ctx)) {
> -        /* The (conditional) branch, B, nullifies the next insn, N,
> -           and we're allowed to skip execution N (no single-step or
> -           tracepoint in effect).  Since the goto_ptr that we must use
> -           for the indirect branch consumes no special resources, we
> -           can (conditionally) skip B and continue execution.  */
> -        /* The use_nullify_skip test implies we have a known control path.  */
> -        tcg_debug_assert(ctx->iaoq_b != -1);
> -        tcg_debug_assert(ctx->iaoq_n != -1);
> +        return true;
> +    }
>  
> -        /* We do have to handle the non-local temporary, DEST, before
> -           branching.  Since IOAQ_F is not really live at this point, we
> -           can simply store DEST optimistically.  Similarly with IAOQ_B.  */
> +    nullify_over(ctx);
> +
> +    if (is_n && use_nullify_skip(ctx)) {
>          copy_iaoq_entry(ctx, cpu_iaoq_f, -1, dest);
>          next = tcg_temp_new_i64();
>          tcg_gen_addi_i64(next, dest, 4);
>          copy_iaoq_entry(ctx, cpu_iaoq_b, -1, next);
> -
> -        nullify_over(ctx);
> -        if (link != 0) {
> -            copy_iaoq_entry(ctx, cpu_gr[link], ctx->iaoq_n, ctx->iaoq_n_var);
> -        }
> -        tcg_gen_lookup_and_goto_ptr();
> -        return nullify_end(ctx);
> +        nullify_set(ctx, 0);
>      } else {
> -        c = ctx->null_cond.c;
> -        a0 = ctx->null_cond.a0;
> -        a1 = ctx->null_cond.a1;
> -
> -        tmp = tcg_temp_new_i64();
> -        next = tcg_temp_new_i64();
> -
> -        copy_iaoq_entry(ctx, tmp, ctx->iaoq_n, ctx->iaoq_n_var);
> -        tcg_gen_movcond_i64(c, next, a0, a1, tmp, dest);
> -        ctx->iaoq_n = -1;
> -        ctx->iaoq_n_var = next;
> -
> -        if (link != 0) {
> -            tcg_gen_movcond_i64(c, cpu_gr[link], a0, a1, cpu_gr[link], tmp);
> -        }
> -
> -        if (is_n) {
> -            /* The branch nullifies the next insn, which means the state of N
> -               after the branch is the inverse of the state of N that applied
> -               to the branch.  */
> -            tcg_gen_setcond_i64(tcg_invert_cond(c), cpu_psw_n, a0, a1);
> -            cond_free(&ctx->null_cond);
> -            ctx->null_cond = cond_make_n();
> -            ctx->psw_n_nonzero = true;
> -        } else {
> -            cond_free(&ctx->null_cond);
> -        }
> +        copy_iaoq_entry(ctx, cpu_iaoq_f, ctx->iaoq_b, cpu_iaoq_b);
> +        copy_iaoq_entry(ctx, cpu_iaoq_b, -1, dest);
> +        nullify_set(ctx, is_n);
>      }
> -    return true;
> +    if (link != 0) {
> +        copy_iaoq_entry(ctx, cpu_gr[link], ctx->iaoq_n, ctx->iaoq_n_var);
> +    }
> +
> +    tcg_gen_lookup_and_goto_ptr();
> +    ctx->base.is_jmp = DISAS_NORETURN;
> +    return nullify_end(ctx);
>  }
>  
>  /* Implement
> -- 
> 2.34.1
>