From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55787) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eX6DM-0006xO-Ca for qemu-devel@nongnu.org; Thu, 04 Jan 2018 09:09:52 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eX6DG-0005Do-EE for qemu-devel@nongnu.org; Thu, 04 Jan 2018 09:09:48 -0500 Received: from mail-wm0-x243.google.com ([2a00:1450:400c:c09::243]:46433) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1eX6DG-0005Aj-2x for qemu-devel@nongnu.org; Thu, 04 Jan 2018 09:09:42 -0500 Received: by mail-wm0-x243.google.com with SMTP id r78so3725514wme.5 for ; Thu, 04 Jan 2018 06:09:42 -0800 (PST) References: <20171211125705.16120-1-alex.bennee@linaro.org> <20171211125705.16120-6-alex.bennee@linaro.org> <8b36b09f-eb89-46bf-561b-2536cc93c489@amsat.org> <4c8e62d1-50bd-e429-153d-3b6d8733bb88@linaro.org> From: Alex =?utf-8?Q?Benn=C3=A9e?= In-reply-to: <4c8e62d1-50bd-e429-153d-3b6d8733bb88@linaro.org> Date: Thu, 04 Jan 2018 14:09:39 +0000 Message-ID: <87h8s13ecc.fsf@linaro.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH v1 05/19] include/fpu/softfloat: add some float16 contants List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Richard Henderson Cc: Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , peter.maydell@linaro.org, laurent@vivier.eu, bharata@linux.vnet.ibm.com, andrew@andrewdutcher.com, aleksandar.markovic@imgtec.com, qemu-devel@nongnu.org, Aurelien Jarno Richard Henderson writes: > On 12/15/2017 05:37 AM, Philippe Mathieu-Daud=C3=A9 wrote: >> Hi Alex, >> >> On 12/11/2017 09:56 AM, Alex Benn=C3=A9e wrote: >>> This defines the same set of common constants for float 16 as defined >>> for 32 and 64 bit floats. These are often used by target helper >>> functions. >>> >>> Signed-off-by: Alex Benn=C3=A9e >>> --- >>> include/fpu/softfloat.h | 7 +++++++ >>> 1 file changed, 7 insertions(+) >>> >>> diff --git a/include/fpu/softfloat.h b/include/fpu/softfloat.h >>> index 17dfe60dbd..5a9258c57c 100644 >>> --- a/include/fpu/softfloat.h >>> +++ b/include/fpu/softfloat.h >>> @@ -395,6 +395,13 @@ static inline float16 float16_set_sign(float16 a, = int sign) >>> return make_float16((float16_val(a) & 0x7fff) | (sign << 15)); >>> } >>> >>> +#define float16_zero make_float16(0) >> >> ok >> >>> +#define float16_one make_float16(0x3a00) >> >> I'm a bit confused... >> >>>>> [np.fromstring(struct.pack("> [0, 0x3a00, 0x34d1, 0x4448, 0x3800, 0x7a00]] >> [0.0, 0.75, 0.30103, 4.2812, 0.5, 49152.0] >> >> However: >> >>>>> ['0x' + binascii.hexlify(np.array([x], '>f2').tostring()) for x in >> [0, 1, math.log(2), np.pi, 0.5, np.inf]] >> ['0x0000', '0x3c00', '0x398c', '0x4248', '0x3800', '0x7c00'] >> >> It seems the MSB bit of the mantissa got shifted as the LSB of the >> biased exponent... >> >>> +#define float16_ln2 make_float16(0x34d1) >> >> incorrect? 0x398c >> >>> +#define float16_pi make_float16(0x4448) >> >> incorrect? 0x4248 >> >>> +#define float16_half make_float16(0x3800) >> >> ok >> >>> +#define float16_infinity make_float16(0x7a00) >> >> incorrect? 0x7c00 > > All of Phil's numbers are correct -- I double-checked with gcc. > > Other than 0, 1 and +inf, I doubt any of the others will actually be used. > Perhaps we should just leave them out? I was following the other sizes. It seems it's x80 which uses the additional ones in helpers: floatx80_ln2 floatx80_pi Should I delete all the unused constants from the other sizes as well? -- Alex Benn=C3=A9e