On 5 December 2013 22:26, Richard Henderson <rth@xxxxxxxxxxx> wrote:
> On 12/06/2013 10:51 AM, Peter Maydell wrote:
>> + if (cond >= 0x0e) { /* condition "always" */
>> + tcg_src = read_cpu_reg(s, rn, sf);
>> + tcg_gen_mov_i64(tcg_rd, tcg_src);
>
> I wonder if it's worth adding that 0x0[ef] case to the generic condition
> processing rather than keep replicating it everywhere.
>
>> + } else {
>> + /* OPTME: we could use movcond here, at the cost of duplicating
>> + * a lot of the arm_gen_test_cc() logic.
>> + */
>
> Honestly, arm_gen_test_cc should get refactored to a real test (as opposed to
> branch) sooner rather than later.
By "sooner rather than later" do you mean "as part of this patch series" ?
> Longer term it's probably worth recognizing the special case of Rm==31 &&
> Rn==31 && else_inc as setcond as opposed to movcond.
>
>> + arm_gen_test_cc(cond, label_match);
>> + /* nomatch: */
>> + tcg_src = read_cpu_reg(s, rm, sf);
>> + tcg_gen_mov_i64(tcg_rd, tcg_src);
>> + if (else_inv) {
>> + tcg_gen_not_i64(tcg_rd, tcg_rd);
>> + }
>> + if (else_inc) {
>> + tcg_gen_addi_i64(tcg_rd, tcg_rd, 1);
>> + }
>
> I think better as
>
> if (else_inv && else_inc) {
> tcg_gen_neg_i64(tcg_rd, tcg_src);
> } else if (else_inv) {
> tcg_gen_not_i64(tcg_rd, tcg_src);
> } else if (else_inc) {
> tcg_gen_addi_i64(tcg_rd, tcg_src, 1);
> } else {
> tcg_gen_mov_i64(tcg_rd, tcg_src);
> }
>
>> + if (!sf) {
>> + tcg_gen_ext32u_i64(tcg_rd, tcg_rd);
>> + }
>
> I do wonder about the usefulness of passing SF (as opposed to hardcoding 1) to
> read_cpu_reg to begin, since the ext32u that it generates is redundant with the
> one here at the end, and likely cannot be optimized away.
Mmm. I did think that was a little unfortunate but didn't think of the
idea of just passing 1 to read_cpu_reg() for some reason.
-- PMM
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