Re: [Qemu-devel] [PATCH 1/2] tcg/arm: Factor out code to emit immediate or reg-reg op

[Richard Henderson <rth@twiddle.net>]

On 09/26/2012 11:48 AM, Peter Maydell wrote:
>      case INDEX_op_setcond_i32:
> -        if (const_args[2]) {
> -            int rot;
> -            rot = encode_imm(args[2]);
> -            tcg_out_dat_imm(s, COND_AL, ARITH_CMP, 0,
> -                            args[1], rotl(args[2], rot) | (rot << 7));
> -        } else {
> -            tcg_out_dat_reg(s, COND_AL, ARITH_CMP, 0,
> -                            args[1], args[2], SHIFT_IMM_LSL(0));
> -        }
> +        tcg_out_dat_rI(s, COND_AL, ARITH_CMP, 0,
> +                       args[1], args[2], const_args[2]);
>          tcg_out_dat_imm(s, tcg_cond_to_arm_cond[args[3]],
>                          ARITH_MOV, args[0], 0, 1);
>          tcg_out_dat_imm(s, tcg_cond_to_arm_cond[tcg_invert_cond(args[3])],

The patch itself is fine.  But as a followup, if movcc is no longer "free",
then perhaps the setcond sequence is better as

	cmp
	mov
	movcc

i.e. the second move is unconditional?  A register renaming OOO core could
then schedule the mov before the cmp.


r~