Re: [PATCH v2 09/11] target/cris: Move delayed branch handling to tb_stop

[Edgar E. Iglesias]

On Sun, Jun 20, 2021 at 02:32:47PM -0700, Richard Henderson wrote:
> By moving the code here, we can re-use other end-of-tb code,
> e.g. the evaluation of flags.  Honor single stepping.

Hi Richard,

Unfortunately this patch seems to break one of the CRIS tests.
tests/tcg/cris/bare/check_xarith.s

I have an old image with the test-case built in the rootfs...

Best regards,
Edgar


> 
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
>  target/cris/translate.c | 82 ++++++++++++++++++++++-------------------
>  1 file changed, 45 insertions(+), 37 deletions(-)
> 
> diff --git a/target/cris/translate.c b/target/cris/translate.c
> index 83b20162f1..0e925320b3 100644
> --- a/target/cris/translate.c
> +++ b/target/cris/translate.c
> @@ -55,6 +55,7 @@
>  /* is_jmp field values */
>  #define DISAS_JUMP    DISAS_TARGET_0 /* only pc was modified dynamically */
>  #define DISAS_UPDATE  DISAS_TARGET_1 /* cpu state was modified dynamically */
> +#define DISAS_DBRANCH DISAS_TARGET_2 /* pc update for delayed branch */
>  
>  /* Used by the decoder.  */
>  #define EXTRACT_FIELD(src, start, end) \
> @@ -3219,43 +3220,8 @@ static void cris_tr_translate_insn(DisasContextBase 
> *dcbase, CPUState *cs)
>       * loop doing nothing for on this program location.
>       */
>      if (dc->delayed_branch && --dc->delayed_branch == 0) {
> -        if (dc->base.tb->flags & 7) {
> -            t_gen_movi_env_TN(dslot, 0);
> -        }
> -
> -        if (dc->cpustate_changed
> -            || !dc->flagx_known
> -            || (dc->flags_x != (dc->base.tb->flags & X_FLAG))) {
> -            cris_store_direct_jmp(dc);
> -        }
> -
> -        if (dc->clear_locked_irq) {
> -            dc->clear_locked_irq = 0;
> -            t_gen_movi_env_TN(locked_irq, 0);
> -        }
> -
> -        if (dc->jmp == JMP_DIRECT_CC) {
> -            TCGLabel *l1 = gen_new_label();
> -            cris_evaluate_flags(dc);
> -
> -            /* Conditional jmp.  */
> -            tcg_gen_brcondi_tl(TCG_COND_EQ, env_btaken, 0, l1);
> -            gen_goto_tb(dc, 1, dc->jmp_pc);
> -            gen_set_label(l1);
> -            gen_goto_tb(dc, 0, dc->pc);
> -            dc->base.is_jmp = DISAS_NORETURN;
> -            dc->jmp = JMP_NOJMP;
> -        } else if (dc->jmp == JMP_DIRECT) {
> -            cris_evaluate_flags(dc);
> -            gen_goto_tb(dc, 0, dc->jmp_pc);
> -            dc->base.is_jmp = DISAS_NORETURN;
> -            dc->jmp = JMP_NOJMP;
> -        } else {
> -            TCGv c = tcg_const_tl(dc->pc);
> -            t_gen_cc_jmp(env_btarget, c);
> -            tcg_temp_free(c);
> -            dc->base.is_jmp = DISAS_JUMP;
> -        }
> +        dc->base.is_jmp = DISAS_DBRANCH;
> +        return;
>      }
>  
>      /* Force an update if the per-tb cpu state has changed.  */
> @@ -3303,6 +3269,48 @@ static void cris_tr_tb_stop(DisasContextBase *dcbase, 
> CPUState *cpu)
>  
>      cris_evaluate_flags(dc);
>  
> +    /* Evaluate delayed branch destination and fold to another is_jmp case. 
> */
> +    if (is_jmp == DISAS_DBRANCH) {
> +        if (dc->base.tb->flags & 7) {
> +            t_gen_movi_env_TN(dslot, 0);
> +        }
> +
> +        switch (dc->jmp) {
> +        case JMP_DIRECT:
> +            npc = dc->jmp_pc;
> +            is_jmp = DISAS_TOO_MANY;
> +            break;
> +
> +        case JMP_DIRECT_CC:
> +            /*
> +             * Use a conditional branch if either taken or not-taken path
> +             * can use goto_tb.  If neither can, then treat it as indirect.
> +             */
> +            if (likely(!dc->base.singlestep_enabled)
> +                && (use_goto_tb(dc, dc->jmp_pc) || use_goto_tb(dc, npc))) {
> +                TCGLabel *not_taken = gen_new_label();
> +
> +                tcg_gen_brcondi_tl(TCG_COND_EQ, env_btaken, 0, not_taken);
> +                gen_goto_tb(dc, 1, dc->jmp_pc);
> +                gen_set_label(not_taken);
> +
> +                /* not-taken case handled below. */
> +                is_jmp = DISAS_TOO_MANY;
> +                break;
> +            }
> +            tcg_gen_movi_tl(env_btarget, dc->jmp_pc);
> +            /* fall through */
> +
> +        case JMP_INDIRECT:
> +            t_gen_cc_jmp(env_btarget, tcg_constant_tl(npc));
> +            is_jmp = DISAS_JUMP;
> +            break;
> +
> +        default:
> +            g_assert_not_reached();
> +        }
> +    }
> +
>      if (unlikely(dc->base.singlestep_enabled)) {
>          switch (is_jmp) {
>          case DISAS_TOO_MANY:
> -- 
> 2.25.1
>