Re: [Qemu-devel] [PATCH 09/60] AArch64: Add b and bl handling

[Claudio Fontana]

Hi Alex,

On 09/27/13 02:48, Alexander Graf wrote:
> This adds handling for the b and bl instructions.
> 
> Signed-off-by: Alexander Graf <address@hidden>
> ---
>  target-arm/translate-a64.c | 61 
> ++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 61 insertions(+)
> 
> diff --git a/target-arm/translate-a64.c b/target-arm/translate-a64.c
> index 73ccade..267fd4d 100644
> --- a/target-arm/translate-a64.c
> +++ b/target-arm/translate-a64.c
> @@ -133,6 +133,58 @@ static void real_unallocated_encoding(DisasContext *s)
>      real_unallocated_encoding(s); \
>      } while (0)
>  
> +static int get_bits(uint32_t inst, int start, int len)
> +{
> +    return (inst >> start) & ((1 << len) - 1);
> +}
> +

do you think it makes sense to reuse extract32 from bitops here?

> +static int get_sbits(uint32_t inst, int start, int len)
> +{
> +    int r = get_bits(inst, start, len);
> +    if (r & (1 << (len - 1))) {
> +        /* Extend the MSB 1 to the higher bits */
> +        r |= -1 & ~((1ULL << len) - 1);
> +    }
> +    return r;
> +}
> +

sextract32?

> +static TCGv_i64 cpu_reg(int reg)
> +{
> +    if (reg == 31) {
> +        /* XXX leaks temps */
> +        return tcg_const_i64(0);

...

> +    } else {
> +        return cpu_X[reg];
> +    }
> +}
> +
> +static inline void gen_goto_tb(DisasContext *s, int n, uint64_t dest)
> +{
> +    TranslationBlock *tb;
> +
> +    tb = s->tb;
> +    if ((tb->pc & TARGET_PAGE_MASK) == (dest & TARGET_PAGE_MASK)) {
> +        tcg_gen_goto_tb(n);
> +        gen_a64_set_pc_im(dest);
> +        tcg_gen_exit_tb((tcg_target_long)tb + n);
> +    } else {
> +        gen_a64_set_pc_im(dest);
> +        tcg_gen_exit_tb(0);
> +    }
> +}
> +
> +static void handle_b(DisasContext *s, uint32_t insn)
> +{
> +    uint64_t addr = s->pc - 4 + (get_sbits(insn, 0, 26) << 2);
> +
> +    if (get_bits(insn, 31, 1)) {
> +        /* BL */
> +        tcg_gen_movi_i64(cpu_reg(30), s->pc);
> +    }
> +    gen_goto_tb(s, 0, addr);
> +    s->is_jmp = DISAS_TB_JUMP;
> +}
> +
>  void disas_a64_insn(CPUARMState *env, DisasContext *s)
>  {
>      uint32_t insn;
> @@ -141,12 +193,21 @@ void disas_a64_insn(CPUARMState *env, DisasContext *s)
>      s->insn = insn;
>      s->pc += 4;
>  
> +    /* One-off branch instruction layout */
> +    switch (insn >> 26) {
> +    case 0x25:
> +    case 0x5:
> +        handle_b(s, insn);
> +        goto insn_done;
> +    }
> +
>      switch ((insn >> 24) & 0x1f) {
>      default:
>          unallocated_encoding(s);
>          break;
>      }
>  
> +insn_done:
>      if (unlikely(s->singlestep_enabled) && (s->is_jmp == DISAS_TB_JUMP)) {
>          /* go through the main loop for single step */
>          s->is_jmp = DISAS_JUMP;
> 

Ciao,

Claudio