[v5++,1/3] tcg/mips: implement goto_ptr

Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
---
 tcg/mips/tcg-target.h     |  2 +-
 tcg/mips/tcg-target.inc.c | 13 +++++++++++++
 2 files changed, 14 insertions(+), 1 deletion(-)

On 04/30/2017 11:52 AM, Aurelien Jarno wrote:
> Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>

Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>

> ---
>  tcg/mips/tcg-target.h     |  2 +-
>  tcg/mips/tcg-target.inc.c | 13 +++++++++++++
>  2 files changed, 14 insertions(+), 1 deletion(-)
>
> diff --git a/tcg/mips/tcg-target.h b/tcg/mips/tcg-target.h
> index e3240cfba7..d75cb63ed3 100644
> --- a/tcg/mips/tcg-target.h
> +++ b/tcg/mips/tcg-target.h
> @@ -130,7 +130,7 @@ extern bool use_mips32r2_instructions;
>  #define TCG_TARGET_HAS_muluh_i32        1
>  #define TCG_TARGET_HAS_mulsh_i32        1
>  #define TCG_TARGET_HAS_bswap32_i32      1
> -#define TCG_TARGET_HAS_goto_ptr         0
> +#define TCG_TARGET_HAS_goto_ptr         1
>
>  #if TCG_TARGET_REG_BITS == 64
>  #define TCG_TARGET_HAS_add2_i32         0
> diff --git a/tcg/mips/tcg-target.inc.c b/tcg/mips/tcg-target.inc.c
> index 01ac7b2c81..9e5b9f42da 100644
> --- a/tcg/mips/tcg-target.inc.c
> +++ b/tcg/mips/tcg-target.inc.c
> @@ -1747,6 +1747,11 @@ static inline void tcg_out_op(TCGContext *s, TCGOpcode opc,
>          tcg_out_nop(s);
>          s->tb_jmp_reset_offset[a0] = tcg_current_code_size(s);
>          break;
> +    case INDEX_op_goto_ptr:
> +        /* jmp to the given host address (could be epilogue) */
> +        tcg_out_opc_reg(s, OPC_JR, 0, a0, 0);
> +        tcg_out_nop(s);
> +        break;
>      case INDEX_op_br:
>          tcg_out_brcond(s, TCG_COND_EQ, TCG_REG_ZERO, TCG_REG_ZERO,
>                         arg_label(a0));
> @@ -2160,6 +2165,7 @@ static const TCGTargetOpDef mips_op_defs[] = {
>      { INDEX_op_exit_tb, { } },
>      { INDEX_op_goto_tb, { } },
>      { INDEX_op_br, { } },
> +    { INDEX_op_goto_ptr, { "r" } },
>
>      { INDEX_op_ld8u_i32, { "r", "r" } },
>      { INDEX_op_ld8s_i32, { "r", "r" } },
> @@ -2451,6 +2457,13 @@ static void tcg_target_qemu_prologue(TCGContext *s)
>      /* delay slot */
>      tcg_out_mov(s, TCG_TYPE_PTR, TCG_AREG0, tcg_target_call_iarg_regs[0]);
>
> +    /*
> +     * Return path for goto_ptr. Set return value to 0, a-la exit_tb,
> +     * and fall through to the rest of the epilogue.
> +     */
> +    s->code_gen_epilogue = s->code_ptr;
> +    tcg_out_mov(s, TCG_TYPE_REG, TCG_REG_V0, TCG_REG_ZERO);
> +
>      /* TB epilogue */
>      tb_ret_addr = s->code_ptr;
>      for (i = 0; i < ARRAY_SIZE(tcg_target_callee_save_regs); i++) {
>

On 04/30/2017 04:52 PM, Aurelien Jarno wrote:
> +        /* jmp to the given host address (could be epilogue) */
> +        tcg_out_opc_reg(s, OPC_JR, 0, a0, 0);
> +        tcg_out_nop(s);

Any particular reason not to do the zeroing in the delay slot...

> +    s->code_gen_epilogue = s->code_ptr;
> +    tcg_out_mov(s, TCG_TYPE_REG, TCG_REG_V0, TCG_REG_ZERO);

... instead of here?


r~

On 2017-05-02 18:21, Richard Henderson wrote:
> On 04/30/2017 04:52 PM, Aurelien Jarno wrote:
> > +        /* jmp to the given host address (could be epilogue) */
> > +        tcg_out_opc_reg(s, OPC_JR, 0, a0, 0);
> > +        tcg_out_nop(s);
> 
> Any particular reason not to do the zeroing in the delay slot...
> 
> > +    s->code_gen_epilogue = s->code_ptr;
> > +    tcg_out_mov(s, TCG_TYPE_REG, TCG_REG_V0, TCG_REG_ZERO);
> 
> ... instead of here?

There is no particular reason in the current usage of goto_ptr. It's
just that in the future we might want to use code_gen_epilogue for
other reasons or use the tcg_out_opc_reg to do other things. It's
probably better to have a consistent behaviour across all TCG
targets.

That said if you prefer, I am find sending a v2 with the zeroing moved
to the delay slot.