Re: [Qemu-devel] [PATCH v5 19/19] tcg-arm: Tidy exit_tb

[Aurelien Jarno]

On Sun, Mar 31, 2013 at 03:35:05PM -0700, Richard Henderson wrote:
> Use tcg_out_movi32 when it's profitable, which is always for v7.
> Simplify the logic around tcg_out_goto, now that we're sure that
> it won't generate a multi-insn branch.
> 
> Signed-off-by: Richard Henderson <address@hidden>
> ---
>  tcg/arm/tcg-target.c | 19 +++++++++----------
>  1 file changed, 9 insertions(+), 10 deletions(-)
> 
> diff --git a/tcg/arm/tcg-target.c b/tcg/arm/tcg-target.c
> index c27e4ee..eaade4a 100644
> --- a/tcg/arm/tcg-target.c
> +++ b/tcg/arm/tcg-target.c
> @@ -1604,17 +1604,16 @@ static inline void tcg_out_op(TCGContext *s, 
> TCGOpcode opc,
>  
>      switch (opc) {
>      case INDEX_op_exit_tb:
> -        {
> -            uint8_t *ld_ptr = s->code_ptr;
> -            if (args[0] >> 8)
> -                tcg_out_ld32_12(s, COND_AL, TCG_REG_R0, TCG_REG_PC, 0);
> -            else
> -                tcg_out_dat_imm(s, COND_AL, ARITH_MOV, TCG_REG_R0, 0, 
> args[0]);
> +        if (use_armv7_instructions || check_fit_imm(args[0])) {
> +            tcg_out_movi32(s, COND_AL, TCG_REG_R0, args[0]);
>              tcg_out_goto(s, COND_AL, (tcg_target_ulong) tb_ret_addr);
> -            if (args[0] >> 8) {
> -                *ld_ptr = (uint8_t) (s->code_ptr - ld_ptr) - 8;
> -                tcg_out32(s, args[0]);
> -            }
> +        } else {
> +            /* Lacking a real constant pool, use a pc-relative load.  Since
> +               tcg_out_goto will always emit 1 insn, we know without further
> +               ado that 0 plus the standard 8 bias is right.  */
> +            tcg_out_ld32_12(s, COND_AL, TCG_REG_R0, TCG_REG_PC, 0);
> +            tcg_out_goto(s, COND_AL, (tcg_target_ulong) tb_ret_addr);
> +            tcg_out32(s, args[0]);
>          }
>          break;
>      case INDEX_op_goto_tb:

Reviewed-by: Aurelien Jarno <address@hidden>


-- 
Aurelien Jarno                          GPG: 1024D/F1BCDB73
address@hidden                 http://www.aurel32.net