From: David Hildenbrand <david@redhat.com>
To: Richard Henderson <richard.henderson@linaro.org>, qemu-devel@nongnu.org
Subject: Re: [PATCH 4/4] target/s390x: Improve SUB LOGICAL WITH BORROW
Date: Tue, 20 Oct 2020 16:17:00 +0200 [thread overview]
Message-ID: <e2bd9942-6fe3-1570-cdc1-2cfd1519e4be@redhat.com> (raw)
In-Reply-To: <20201017022901.78425-5-richard.henderson@linaro.org>
On 17.10.20 04:29, Richard Henderson wrote:
> Now that SUB LOGICAL outputs carry, we can use that as input directly.
> It also means we can re-use CC_OP_ZC and produce an output carry
> directly from SUB LOGICAL WITH BORROW.
>
> Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
> ---
> target/s390x/internal.h | 2 --
> target/s390x/cc_helper.c | 32 -----------------
> target/s390x/helper.c | 2 --
> target/s390x/translate.c | 74 ++++++++++++++++++++------------------
> target/s390x/insn-data.def | 8 ++---
> 5 files changed, 44 insertions(+), 74 deletions(-)
>
> diff --git a/target/s390x/internal.h b/target/s390x/internal.h
> index 4077047494..11515bb617 100644
> --- a/target/s390x/internal.h
> +++ b/target/s390x/internal.h
> @@ -172,14 +172,12 @@ enum cc_op {
>
> CC_OP_ADD_64, /* overflow on add (64bit) */
> CC_OP_SUB_64, /* overflow on subtraction (64bit) */
> - CC_OP_SUBB_64, /* overflow on unsigned sub-borrow (64bit) */
> CC_OP_ABS_64, /* sign eval on abs (64bit) */
> CC_OP_NABS_64, /* sign eval on nabs (64bit) */
> CC_OP_MULS_64, /* overflow on signed multiply (64bit) */
>
> CC_OP_ADD_32, /* overflow on add (32bit) */
> CC_OP_SUB_32, /* overflow on subtraction (32bit) */
> - CC_OP_SUBB_32, /* overflow on unsigned sub-borrow (32bit) */
> CC_OP_ABS_32, /* sign eval on abs (64bit) */
> CC_OP_NABS_32, /* sign eval on nabs (64bit) */
> CC_OP_MULS_32, /* overflow on signed multiply (32bit) */
> diff --git a/target/s390x/cc_helper.c b/target/s390x/cc_helper.c
> index c7728d1225..e7039d0d18 100644
> --- a/target/s390x/cc_helper.c
> +++ b/target/s390x/cc_helper.c
> @@ -164,19 +164,6 @@ static uint32_t cc_calc_sub_64(int64_t a1, int64_t a2, int64_t ar)
> }
> }
>
> -static uint32_t cc_calc_subb_64(uint64_t a1, uint64_t a2, uint64_t ar)
> -{
> - int borrow_out;
> -
> - if (ar != a1 - a2) { /* difference means borrow-in */
> - borrow_out = (a2 >= a1);
> - } else {
> - borrow_out = (a2 > a1);
> - }
> -
> - return (ar != 0) + 2 * !borrow_out;
> -}
> -
> static uint32_t cc_calc_abs_64(int64_t dst)
> {
> if ((uint64_t)dst == 0x8000000000000000ULL) {
> @@ -237,19 +224,6 @@ static uint32_t cc_calc_sub_32(int32_t a1, int32_t a2, int32_t ar)
> }
> }
>
> -static uint32_t cc_calc_subb_32(uint32_t a1, uint32_t a2, uint32_t ar)
> -{
> - int borrow_out;
> -
> - if (ar != a1 - a2) { /* difference means borrow-in */
> - borrow_out = (a2 >= a1);
> - } else {
> - borrow_out = (a2 > a1);
> - }
> -
> - return (ar != 0) + 2 * !borrow_out;
> -}
> -
> static uint32_t cc_calc_abs_32(int32_t dst)
> {
> if ((uint32_t)dst == 0x80000000UL) {
> @@ -450,9 +424,6 @@ static uint32_t do_calc_cc(CPUS390XState *env, uint32_t cc_op,
> case CC_OP_SUB_64:
> r = cc_calc_sub_64(src, dst, vr);
> break;
> - case CC_OP_SUBB_64:
> - r = cc_calc_subb_64(src, dst, vr);
> - break;
> case CC_OP_ABS_64:
> r = cc_calc_abs_64(dst);
> break;
> @@ -472,9 +443,6 @@ static uint32_t do_calc_cc(CPUS390XState *env, uint32_t cc_op,
> case CC_OP_SUB_32:
> r = cc_calc_sub_32(src, dst, vr);
> break;
> - case CC_OP_SUBB_32:
> - r = cc_calc_subb_32(src, dst, vr);
> - break;
> case CC_OP_ABS_32:
> r = cc_calc_abs_32(dst);
> break;
> diff --git a/target/s390x/helper.c b/target/s390x/helper.c
> index fa3aa500e5..7678994feb 100644
> --- a/target/s390x/helper.c
> +++ b/target/s390x/helper.c
> @@ -405,12 +405,10 @@ const char *cc_name(enum cc_op cc_op)
> [CC_OP_LTGT0_64] = "CC_OP_LTGT0_64",
> [CC_OP_ADD_64] = "CC_OP_ADD_64",
> [CC_OP_SUB_64] = "CC_OP_SUB_64",
> - [CC_OP_SUBB_64] = "CC_OP_SUBB_64",
> [CC_OP_ABS_64] = "CC_OP_ABS_64",
> [CC_OP_NABS_64] = "CC_OP_NABS_64",
> [CC_OP_ADD_32] = "CC_OP_ADD_32",
> [CC_OP_SUB_32] = "CC_OP_SUB_32",
> - [CC_OP_SUBB_32] = "CC_OP_SUBB_32",
> [CC_OP_ABS_32] = "CC_OP_ABS_32",
> [CC_OP_NABS_32] = "CC_OP_NABS_32",
> [CC_OP_COMP_32] = "CC_OP_COMP_32",
> diff --git a/target/s390x/translate.c b/target/s390x/translate.c
> index 48494a86cc..0d8235a5fb 100644
> --- a/target/s390x/translate.c
> +++ b/target/s390x/translate.c
> @@ -601,10 +601,8 @@ static void gen_op_calc_cc(DisasContext *s)
> /* FALLTHRU */
> case CC_OP_ADD_64:
> case CC_OP_SUB_64:
> - case CC_OP_SUBB_64:
> case CC_OP_ADD_32:
> case CC_OP_SUB_32:
> - case CC_OP_SUBB_32:
> local_cc_op = tcg_const_i32(s->cc_op);
> break;
> case CC_OP_CONST0:
> @@ -663,10 +661,8 @@ static void gen_op_calc_cc(DisasContext *s)
> break;
> case CC_OP_ADD_64:
> case CC_OP_SUB_64:
> - case CC_OP_SUBB_64:
> case CC_OP_ADD_32:
> case CC_OP_SUB_32:
> - case CC_OP_SUBB_32:
> /* 3 arguments */
> gen_helper_calc_cc(cc_op, cpu_env, local_cc_op, cc_src, cc_dst, cc_vr);
> break;
> @@ -4744,29 +4740,49 @@ static DisasJumpType op_subu64(DisasContext *s, DisasOps *o)
> return DISAS_NEXT;
> }
>
> -static DisasJumpType op_subb(DisasContext *s, DisasOps *o)
> +/* Compute borrow (0, -1) into cc_src. */
> +static void compute_borrow(DisasContext *s)
> {
> - DisasCompare cmp;
> - TCGv_i64 borrow;
> -
> - tcg_gen_sub_i64(o->out, o->in1, o->in2);
> -
> - /* 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);
> + switch (s->cc_op) {
> + case CC_OP_SUBU:
> + break;
> + default:
> + gen_op_calc_cc(s);
> + /* fall through */
> + case CC_OP_STATIC:
> + /* The carry flag is the msb of CC; compute into cc_src. */
> + tcg_gen_extu_i32_i64(cc_src, cc_op);
> + tcg_gen_shri_i64(cc_src, cc_src, 1);
> + /* fall through */
> + case CC_OP_ADDU:
Can you give me a hint how we're converting the carry into a borrow?
Can we apply something similar to compute_carry()?
> + tcg_gen_subi_i64(cc_src, cc_src, 1);
> + break;
--
Thanks,
David / dhildenb
next prev parent reply other threads:[~2020-10-20 14:17 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-17 2:28 [PATCH 0/4] target/s390x: Improve carry computation Richard Henderson
2020-10-17 2:28 ` [PATCH 1/4] target/s390x: Improve cc computation for ADD LOGICAL Richard Henderson
2020-10-20 14:08 ` David Hildenbrand
2020-10-17 2:28 ` [PATCH 2/4] target/s390x: Improve ADD LOGICAL WITH CARRY Richard Henderson
2020-10-20 14:12 ` David Hildenbrand
2020-10-17 2:29 ` [PATCH 3/4] target/s390x: Improve cc computation for SUBTRACT LOGICAL Richard Henderson
2020-10-20 14:14 ` David Hildenbrand
2020-10-17 2:29 ` [PATCH 4/4] target/s390x: Improve SUB LOGICAL WITH BORROW Richard Henderson
2020-10-20 14:17 ` David Hildenbrand [this message]
2020-10-20 15:11 ` Richard Henderson
2020-10-20 15:12 ` David Hildenbrand
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