From patchwork Fri Sep 28 01:22:36 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: [145/147] target-s390: Optimize ADDC/SUBB Date: Thu, 27 Sep 2012 15:22:36 -0000 From: Richard Henderson X-Patchwork-Id: 187690 Message-Id: <1348795356-28963-1-git-send-email-rth@twiddle.net> To: qemu-devel@nongnu.org Cc: Alexander Graf Giving the proper mask to disas_jcc allows us to generate an inline comparison generating the carry/borrow with setcond. In the very worst case, when we must use the external helper to compute a value for CC, we generate (cc > 1) instead of (cc >> 1), which is only very slightly slower on common cpus. In the very best case, when the CC comes from a COMPARE insn and the compiler is using ALCG with zero, everything folds out to become just the setcond that the compiler wanted. Signed-off-by: Richard Henderson --- target-s390x/translate.c | 56 ++++++++++++++++++++++++++++++++---------------- 1 file changed, 37 insertions(+), 19 deletions(-) diff --git a/target-s390x/translate.c b/target-s390x/translate.c index de9ae97..e1888a3 100644 --- a/target-s390x/translate.c +++ b/target-s390x/translate.c @@ -1344,18 +1344,28 @@ static ExitStatus op_add(DisasContext *s, DisasOps *o) static ExitStatus op_addc(DisasContext *s, DisasOps *o) { - TCGv_i64 cc; + DisasCompare cmp; + TCGv_i64 carry; tcg_gen_add_i64(o->out, o->in1, o->in2); - /* XXX possible optimization point */ - gen_op_calc_cc(s); - cc = tcg_temp_new_i64(); - tcg_gen_extu_i32_i64(cc, cc_op); - tcg_gen_shri_i64(cc, cc, 1); + /* The carry flag is the msb of CC, therefore the branch mask that would + create that comparison is 3. Feeding the generated comparison to + setcond produces the carry flag that we desire. */ + disas_jcc(s, &cmp, 3); + carry = tcg_temp_new_i64(); + if (cmp.is_64) { + tcg_gen_setcond_i64(cmp.cond, carry, cmp.u.s64.a, cmp.u.s64.b); + } else { + TCGv_i32 t = tcg_temp_new_i32(); + tcg_gen_setcond_i32(cmp.cond, t, cmp.u.s32.a, cmp.u.s32.b); + tcg_gen_extu_i32_i64(carry, t); + tcg_temp_free_i32(t); + } + free_compare(&cmp); - tcg_gen_add_i64(o->out, o->out, cc); - tcg_temp_free_i64(cc); + tcg_gen_add_i64(o->out, o->out, carry); + tcg_temp_free_i64(carry); return NO_EXIT; } @@ -3397,19 +3407,27 @@ static ExitStatus op_sub(DisasContext *s, DisasOps *o) static ExitStatus op_subb(DisasContext *s, DisasOps *o) { - TCGv_i64 cc; + DisasCompare cmp; + TCGv_i64 borrow; - assert(!o->g_in2); - tcg_gen_not_i64(o->in2, o->in2); - tcg_gen_add_i64(o->out, o->in1, o->in2); + tcg_gen_sub_i64(o->out, o->in1, o->in2); - /* XXX possible optimization point */ - gen_op_calc_cc(s); - cc = tcg_temp_new_i64(); - tcg_gen_extu_i32_i64(cc, cc_op); - tcg_gen_shri_i64(cc, cc, 1); - tcg_gen_add_i64(o->out, o->out, cc); - tcg_temp_free_i64(cc); + /* The !borrow flag is the msb of CC. Since we want the inverse of + that, we ask for a comparison of CC=0 | CC=1 -> mask of 8 | 4. */ + disas_jcc(s, &cmp, 8 | 4); + borrow = tcg_temp_new_i64(); + if (cmp.is_64) { + tcg_gen_setcond_i64(cmp.cond, borrow, cmp.u.s64.a, cmp.u.s64.b); + } else { + TCGv_i32 t = tcg_temp_new_i32(); + tcg_gen_setcond_i32(cmp.cond, t, cmp.u.s32.a, cmp.u.s32.b); + tcg_gen_extu_i32_i64(borrow, t); + tcg_temp_free_i32(t); + } + free_compare(&cmp); + + tcg_gen_sub_i64(o->out, o->out, borrow); + tcg_temp_free_i64(borrow); return NO_EXIT; }