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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.11.0 MIME-Version: 1.0 In-Reply-To: <87o8lnnt3m.fsf@linaro.org> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=david@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=63.128.21.124; envelope-from=david@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/10/01 02:15:30 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.26, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Peter Maydell , Thomas Huth , Cornelia Huck , Richard Henderson , qemu-devel@nongnu.org, qemu-s390x@nongnu.org, Aurelien Jarno Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 30.09.20 18:10, Alex Bennée wrote: > > David Hildenbrand writes: > >> Implementation inspired by minmax_floats(). Unfortuantely, we don't have >> any tests we can simply adjust/unlock. >> >> Cc: Aurelien Jarno >> Cc: Peter Maydell >> Cc: "Alex Bennée" >> Signed-off-by: David Hildenbrand >> --- >> fpu/softfloat.c | 100 ++++++++++++++++++++++++++++++++++++++++ >> include/fpu/softfloat.h | 6 +++ >> 2 files changed, 106 insertions(+) >> >> diff --git a/fpu/softfloat.c b/fpu/softfloat.c >> index 9af75b9146..9463c5ea56 100644 >> --- a/fpu/softfloat.c >> +++ b/fpu/softfloat.c >> @@ -621,6 +621,8 @@ static inline FloatParts float64_unpack_raw(float64 f) >> return unpack_raw(float64_params, f); >> } >> >> +static void float128_unpack(FloatParts128 *p, float128 a, float_status *status); >> + >> /* Pack a float from parts, but do not canonicalize. */ >> static inline uint64_t pack_raw(FloatFmt fmt, FloatParts p) >> { >> @@ -3180,6 +3182,89 @@ static FloatParts minmax_floats(FloatParts a, FloatParts b, bool ismin, >> } >> } > > It would be desirable to share as much logic for this as possible with > the existing minmax_floats code. I appreciate at some point we end up > having to deal with fractions and we haven't found a good way to > efficiently handle dealing with FloatParts and FloatParts128 in the same > unrolled code, however: > >> >> +static float128 float128_minmax(float128 a, float128 b, bool ismin, bool ieee, >> + bool ismag, float_status *s) >> +{ >> + FloatParts128 pa, pb; >> + int a_exp, b_exp; >> + bool a_less; >> + >> + float128_unpack(&pa, a, s); >> + float128_unpack(&pb, b, s); >> + > > From here: >> + if (unlikely(is_nan(pa.cls) || is_nan(pb.cls))) { >> + /* See comment in minmax_floats() */ >> + if (ieee && !is_snan(pa.cls) && !is_snan(pb.cls)) { >> + if (is_nan(pa.cls) && !is_nan(pb.cls)) { >> + return b; >> + } else if (is_nan(pb.cls) && !is_nan(pa.cls)) { >> + return a; >> + } >> + } >> + >> + /* Similar logic to pick_nan(), avoiding re-packing. */ >> + if (is_snan(pa.cls) || is_snan(pb.cls)) { >> + s->float_exception_flags |= float_flag_invalid; >> + } >> + if (s->default_nan_mode) { >> + return float128_default_nan(s); >> + } > > to here is common logic - is there anyway we could share it? I can try to factor it out, similar to pickNaN() - passing weird boolean flags and such. It most certainly won't win in a beauty contest, that's for sure. > >> + if (pickNaN(pa.cls, pb.cls, >> + pa.frac0 > pb.frac0 || >> + (pa.frac0 == pb.frac0 && pa.frac1 > pb.frac1) || >> + (pa.frac0 == pb.frac0 && pa.frac1 == pb.frac1 && >> + pa.sign < pb.sign), s)) { >> + return is_snan(pb.cls) ? float128_silence_nan(b, s) : b; >> + } >> + return is_snan(pa.cls) ? float128_silence_nan(a, s) : a; >> + } >> + >> + switch (pa.cls) { >> + case float_class_normal: >> + a_exp = pa.exp; >> + break; >> + case float_class_inf: >> + a_exp = INT_MAX; >> + break; >> + case float_class_zero: >> + a_exp = INT_MIN; >> + break; >> + default: >> + g_assert_not_reached(); >> + break; >> + } > > Likewise I wonder if there is scope for a float_minmax_exp helper that > could be shared here? I'll try, but I have the feeling that it might make the code harder to read than actually help. Will give it a try. Thanks! -- Thanks, David / dhildenb