From: Richard Henderson <richard.henderson@linaro.org>
To: LIU Zhiwei <zhiwei_liu@c-sky.com>,
alistair23@gmail.com, chihmin.chao@sifive.com,
palmer@dabbelt.com
Cc: guoren@linux.alibaba.com, wenmeng_zhang@c-sky.com,
qemu-riscv@nongnu.org, qemu-devel@nongnu.org,
wxy194768@alibaba-inc.com
Subject: Re: [PATCH v6 26/61] target/riscv: vector single-width fractional multiply with rounding and saturation
Date: Fri, 27 Mar 2020 18:08:56 -0700 [thread overview]
Message-ID: <9f5fd1a3-f32f-9779-6d5c-abdedc10fd2d@linaro.org> (raw)
In-Reply-To: <20200317150653.9008-27-zhiwei_liu@c-sky.com>
On 3/17/20 8:06 AM, LIU Zhiwei wrote:
> +static int64_t vsmul64(CPURISCVState *env, int vxrm, int64_t a, int64_t b)
> +{
> + uint8_t round;
> + uint64_t hi_64, lo_64, Hi62;
> + uint8_t hi62, hi63, lo63;
> +
> + muls64(&lo_64, &hi_64, a, b);
> + hi62 = extract64(hi_64, 62, 1);
> + lo63 = extract64(lo_64, 63, 1);
> + hi63 = extract64(hi_64, 63, 1);
> + Hi62 = extract64(hi_64, 0, 62);
This seems like way more work than necessary.
> + if (hi62 != hi63) {
> + env->vxsat = 0x1;
> + return INT64_MAX;
> + }
This can only happen for a == b == INT64_MIN.
Perhaps just test exactly that and move it above the multiply?
> + round = get_round(vxrm, lo_64, 63);
> + if (round && (Hi62 == 0x3fffffff) && lo63) {
> + env->vxsat = 0x1;
> + return hi62 ? INT64_MIN : INT64_MAX;
> + } else {
> + if (lo63 && round) {
> + return (hi_64 + 1) << 1;
> + } else {
> + return (hi_64 << 1) | lo63 | round;
> + }
> + }
/* Cannot overflow, as there are always
2 sign bits after multiply. */
ret = (hi_64 << 1) | (lo_64 >> 63);
if (round) {
if (ret == INT64_MAX) {
env->vxsat = 1;
} else {
ret += 1;
}
}
return ret;
r~
next prev parent reply other threads:[~2020-03-28 1:10 UTC|newest]
Thread overview: 120+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-17 15:05 [PATCH v6 00/61] target/riscv: support vector extension v0.7.1 LIU Zhiwei
2020-03-17 15:05 ` [PATCH v6 01/61] target/riscv: add vector extension field in CPURISCVState LIU Zhiwei
2020-03-17 15:05 ` [PATCH v6 02/61] target/riscv: implementation-defined constant parameters LIU Zhiwei
2020-03-17 15:05 ` [PATCH v6 03/61] target/riscv: support vector extension csr LIU Zhiwei
2020-03-17 15:05 ` [PATCH v6 04/61] target/riscv: add vector configure instruction LIU Zhiwei
2020-03-23 6:51 ` Kito Cheng
2020-03-23 7:10 ` LIU Zhiwei
2020-03-17 15:05 ` [PATCH v6 05/61] target/riscv: add an internals.h header LIU Zhiwei
2020-03-18 23:45 ` Alistair Francis
2020-03-27 23:41 ` Richard Henderson
2020-03-17 15:05 ` [PATCH v6 06/61] target/riscv: add vector stride load and store instructions LIU Zhiwei
2020-03-18 23:54 ` Alistair Francis
2020-03-17 15:05 ` [PATCH v6 07/61] target/riscv: add vector index " LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 08/61] target/riscv: add fault-only-first unit stride load LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 09/61] target/riscv: add vector amo operations LIU Zhiwei
2020-03-19 17:01 ` Alistair Francis
2020-03-27 23:44 ` Richard Henderson
2020-03-17 15:06 ` [PATCH v6 10/61] target/riscv: vector single-width integer add and subtract LIU Zhiwei
2020-03-20 18:31 ` Alistair Francis
2020-03-27 23:54 ` Richard Henderson
2020-03-28 14:42 ` LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 11/61] target/riscv: vector widening " LIU Zhiwei
2020-03-19 16:28 ` Alistair Francis
2020-03-17 15:06 ` [PATCH v6 12/61] target/riscv: vector integer add-with-carry / subtract-with-borrow instructions LIU Zhiwei
2020-03-19 17:29 ` Alistair Francis
2020-03-28 0:00 ` Richard Henderson
2020-03-17 15:06 ` [PATCH v6 13/61] target/riscv: vector bitwise logical instructions LIU Zhiwei
2020-03-20 18:34 ` Alistair Francis
2020-03-17 15:06 ` [PATCH v6 14/61] target/riscv: vector single-width bit shift instructions LIU Zhiwei
2020-03-19 20:10 ` Alistair Francis
2020-03-17 15:06 ` [PATCH v6 15/61] target/riscv: vector narrowing integer right " LIU Zhiwei
2020-03-20 18:43 ` Alistair Francis
2020-03-17 15:06 ` [PATCH v6 16/61] target/riscv: vector integer comparison instructions LIU Zhiwei
2020-03-25 17:32 ` Alistair Francis
2020-03-17 15:06 ` [PATCH v6 17/61] target/riscv: vector integer min/max instructions LIU Zhiwei
2020-03-20 18:49 ` Alistair Francis
2020-03-17 15:06 ` [PATCH v6 18/61] target/riscv: vector single-width integer multiply instructions LIU Zhiwei
2020-03-25 17:36 ` Alistair Francis
2020-03-28 0:06 ` Richard Henderson
2020-03-28 15:17 ` LIU Zhiwei
2020-03-28 15:47 ` Richard Henderson
2020-03-28 16:13 ` LIU Zhiwei
2020-03-29 4:00 ` LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 19/61] target/riscv: vector integer divide instructions LIU Zhiwei
2020-03-20 18:51 ` Alistair Francis
2020-03-17 15:06 ` [PATCH v6 20/61] target/riscv: vector widening integer multiply instructions LIU Zhiwei
2020-03-25 17:25 ` Alistair Francis
2020-03-17 15:06 ` [PATCH v6 21/61] target/riscv: vector single-width integer multiply-add instructions LIU Zhiwei
2020-03-25 17:27 ` Alistair Francis
2020-03-17 15:06 ` [PATCH v6 22/61] target/riscv: vector widening " LIU Zhiwei
2020-03-25 17:42 ` Alistair Francis
2020-03-17 15:06 ` [PATCH v6 23/61] target/riscv: vector integer merge and move instructions LIU Zhiwei
2020-03-26 17:57 ` Alistair Francis
2020-03-28 0:18 ` Richard Henderson
2020-03-17 15:06 ` [PATCH v6 24/61] target/riscv: vector single-width saturating add and subtract LIU Zhiwei
2020-03-28 0:20 ` Richard Henderson
2020-03-17 15:06 ` [PATCH v6 25/61] target/riscv: vector single-width averaging " LIU Zhiwei
2020-03-19 3:46 ` LIU Zhiwei
2020-03-28 0:32 ` Richard Henderson
2020-03-28 1:07 ` LIU Zhiwei
2020-03-28 1:22 ` Richard Henderson
2020-03-28 15:37 ` LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 26/61] target/riscv: vector single-width fractional multiply with rounding and saturation LIU Zhiwei
2020-03-28 1:08 ` Richard Henderson [this message]
2020-03-28 15:41 ` LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 27/61] target/riscv: vector widening saturating scaled multiply-add LIU Zhiwei
2020-03-28 1:23 ` Richard Henderson
2020-03-17 15:06 ` [PATCH v6 28/61] target/riscv: vector single-width scaling shift instructions LIU Zhiwei
2020-03-28 1:24 ` Richard Henderson
2020-03-17 15:06 ` [PATCH v6 29/61] target/riscv: vector narrowing fixed-point clip instructions LIU Zhiwei
2020-03-28 1:50 ` Richard Henderson
2020-03-17 15:06 ` [PATCH v6 30/61] target/riscv: vector single-width floating-point add/subtract instructions LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 31/61] target/riscv: vector widening " LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 32/61] target/riscv: vector single-width floating-point multiply/divide instructions LIU Zhiwei
2020-03-25 17:46 ` Alistair Francis
2020-03-17 15:06 ` [PATCH v6 33/61] target/riscv: vector widening floating-point multiply LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 34/61] target/riscv: vector single-width floating-point fused multiply-add instructions LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 35/61] target/riscv: vector widening " LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 36/61] target/riscv: vector floating-point square-root instruction LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 37/61] target/riscv: vector floating-point min/max instructions LIU Zhiwei
2020-03-25 17:47 ` Alistair Francis
2020-03-17 15:06 ` [PATCH v6 38/61] target/riscv: vector floating-point sign-injection instructions LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 39/61] target/riscv: vector floating-point compare instructions LIU Zhiwei
2020-03-28 2:01 ` Richard Henderson
2020-03-28 15:44 ` LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 40/61] target/riscv: vector floating-point classify instructions LIU Zhiwei
2020-03-28 2:06 ` Richard Henderson
2020-03-17 15:06 ` [PATCH v6 41/61] target/riscv: vector floating-point merge instructions LIU Zhiwei
2020-03-28 3:23 ` Richard Henderson
2020-03-28 15:47 ` LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 42/61] target/riscv: vector floating-point/integer type-convert instructions LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 43/61] target/riscv: widening " LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 44/61] target/riscv: narrowing " LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 45/61] target/riscv: vector single-width integer reduction instructions LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 46/61] target/riscv: vector wideing " LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 47/61] target/riscv: vector single-width floating-point " LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 48/61] target/riscv: vector widening " LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 49/61] target/riscv: vector mask-register logical instructions LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 50/61] target/riscv: vector mask population count vmpopc LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 51/61] target/riscv: vmfirst find-first-set mask bit LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 52/61] target/riscv: set-X-first " LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 53/61] target/riscv: vector iota instruction LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 54/61] target/riscv: vector element index instruction LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 55/61] target/riscv: integer extract instruction LIU Zhiwei
2020-03-28 3:36 ` Richard Henderson
2020-03-28 16:23 ` LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 56/61] target/riscv: integer scalar move instruction LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 57/61] target/riscv: floating-point scalar move instructions LIU Zhiwei
2020-03-28 3:44 ` Richard Henderson
2020-03-28 16:31 ` LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 58/61] target/riscv: vector slide instructions LIU Zhiwei
2020-03-28 3:50 ` Richard Henderson
2020-03-28 13:40 ` LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 59/61] target/riscv: vector register gather instruction LIU Zhiwei
2020-03-28 3:57 ` Richard Henderson
2020-03-17 15:06 ` [PATCH v6 60/61] target/riscv: vector compress instruction LIU Zhiwei
2020-03-17 15:06 ` [PATCH v6 61/61] target/riscv: configure and turn on vector extension from command line LIU Zhiwei
2020-03-25 17:49 ` Alistair Francis
2020-03-28 4:00 ` Richard Henderson
2020-03-17 20:47 ` [PATCH v6 00/61] target/riscv: support vector extension v0.7.1 no-reply
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