On 2 September 2015 at 18:57, Richard Henderson <r...@twiddle.net> wrote:
> This can allow much of a ccmp to be elided when particular
> flags are subsequently dead.
>
> Signed-off-by: Richard Henderson <r...@twiddle.net>
> ---
> target-arm/translate-a64.c | 65
> +++++++++++++++++++++++++++++++---------------
> 1 file changed, 44 insertions(+), 21 deletions(-)
>
> diff --git a/target-arm/translate-a64.c b/target-arm/translate-a64.c
> index dcac490..48ecf23 100644
> --- a/target-arm/translate-a64.c
> +++ b/target-arm/translate-a64.c
> @@ -3552,8 +3552,9 @@ static void disas_adc_sbc(DisasContext *s, uint32_t
> insn)
> static void disas_cc(DisasContext *s, uint32_t insn)
> {
> unsigned int sf, op, y, cond, rn, nzcv, is_imm;
> - TCGLabel *label_continue = NULL;
> - TCGv_i64 tcg_tmp, tcg_y, tcg_rn;
> + TCGv_i32 tcg_t0, tcg_t1, tcg_t2;
> + TCGv_i64 tcg_res, tcg_y, tcg_rn;
> + DisasCompare c;
>
> if (!extract32(insn, 29, 1)) {
> unallocated_encoding(s);
> @@ -3571,19 +3572,13 @@ static void disas_cc(DisasContext *s, uint32_t insn)
> rn = extract32(insn, 5, 5);
> nzcv = extract32(insn, 0, 4);
>
> - if (cond < 0x0e) { /* not always */
> - TCGLabel *label_match = gen_new_label();
> - label_continue = gen_new_label();
> - arm_gen_test_cc(cond, label_match);
> - /* nomatch: */
> - tcg_tmp = tcg_temp_new_i64();
> - tcg_gen_movi_i64(tcg_tmp, nzcv << 28);
> - gen_set_nzcv(tcg_tmp);
> - tcg_temp_free_i64(tcg_tmp);
> - tcg_gen_br(label_continue);
> - gen_set_label(label_match);
> - }
> - /* match, or condition is always */
> + /* Set T0 = !COND. */
> + tcg_t0 = tcg_temp_new_i32();
> + arm_test_cc(&c, cond);
> + tcg_gen_setcondi_i32(tcg_invert_cond(c.cond), tcg_t0, c.value, 0);
> + arm_free_cc(&c);
> +
> + /* Load the arguments for the new comparison. */
> if (is_imm) {
> tcg_y = new_tmp_a64(s);
> tcg_gen_movi_i64(tcg_y, y);
> @@ -3592,17 +3587,45 @@ static void disas_cc(DisasContext *s, uint32_t insn)
> }
> tcg_rn = cpu_reg(s, rn);
>
> - tcg_tmp = tcg_temp_new_i64();
> + /* Set the flags for the new comparison. */
> + tcg_res = tcg_temp_new_i64();
> if (op) {
> - gen_sub_CC(sf, tcg_tmp, tcg_rn, tcg_y);
> + gen_sub_CC(sf, tcg_res, tcg_rn, tcg_y);
> } else {
> - gen_add_CC(sf, tcg_tmp, tcg_rn, tcg_y);
> + gen_add_CC(sf, tcg_res, tcg_rn, tcg_y);
> }
> - tcg_temp_free_i64(tcg_tmp);
> + tcg_temp_free_i64(tcg_res);
Seems a bit unnecessary to bother changing the name of
this TCG temporary.
>
> - if (cond < 0x0e) { /* continue */
> - gen_set_label(label_continue);
> + /* If COND was false, force the flags to #nzcv.
> + Note that T1 = (COND ? 0 : -1), T2 = (COND ? -1 : 0). */
> + tcg_t1 = tcg_temp_new_i32();
> + tcg_t2 = tcg_temp_new_i32();
> + tcg_gen_neg_i32(tcg_t1, tcg_t0);
> + tcg_gen_subi_i32(tcg_t2, tcg_t0, 1);
t2 is ~t1, right? Do we get better/worse code if we use
tcg_gen_andc_i32(..., tcg_t1) rather than creating t2 and
using gen_and_i32 ?
> +
> + if (nzcv & 8) { /* N */
> + tcg_gen_or_i32(cpu_NF, cpu_NF, tcg_t1);
> + } else {
> + tcg_gen_and_i32(cpu_NF, cpu_NF, tcg_t2);
> + }
> + if (nzcv & 4) { /* Z */
> + tcg_gen_and_i32(cpu_ZF, cpu_ZF, tcg_t2);
> + } else {
> + tcg_gen_or_i32(cpu_ZF, cpu_ZF, tcg_t0);
> + }
> + if (nzcv & 2) { /* C */
> + tcg_gen_or_i32(cpu_CF, cpu_CF, tcg_t0);
> + } else {
> + tcg_gen_and_i32(cpu_CF, cpu_CF, tcg_t2);
> + }
> + if (nzcv & 1) { /* V */
> + tcg_gen_or_i32(cpu_VF, cpu_VF, tcg_t1);
> + } else {
> + tcg_gen_and_i32(cpu_VF, cpu_VF, tcg_t2);
> }
> + tcg_temp_free_i32(tcg_t0);
> + tcg_temp_free_i32(tcg_t1);
> + tcg_temp_free_i32(tcg_t2);
> }
Otherwise looks OK.
-- PMM
