From: David Laight <David.Laight@ACULAB.COM>
To: 'Vincent Chen' <vincentc@andestech.com>,
"green.hu@gmail.com" <green.hu@gmail.com>,
"arnd@arndb.de" <arnd@arndb.de>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Nickhu <nickhu@andestech.com>
Subject: RE: [PATCH v4 2/5] nds32: Support FP emulation
Date: Fri, 23 Nov 2018 10:53:37 +0000 [thread overview]
Message-ID: <f0d20a4682b740659f28184c1278ae7d@AcuMS.aculab.com> (raw)
In-Reply-To: <1542856478-795-3-git-send-email-vincentc@andestech.com>
From: Vincent Chen
> Sent: 22 November 2018 03:15
>
> The Andes FPU coprocessor does not support denormalized number handling.
> According to the specification, FPU generates a denorm input exception
> that requires the kernel to deal with this instrution operation when it
> encounters denormalized operands. Hence an nds32 FPU ISA emulator in the
> kernel is required to meet requirement.
What does the FPU generate for results near zero?
If it doesn't generate denormalised results (but does detect them)
then I assume it never generates FP values with exponent zero.
(So the gap around zero is even larger than it would be if exponent
zero values had a hidden bit.)
So is it really worth doing anything other than treating
denormalised values as zero?
David
-
Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
Registration No: 1397386 (Wales)
next prev parent reply other threads:[~2018-11-23 10:53 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-22 3:14 [PATCH v4 0/5] nds32 FPU port Vincent Chen
2018-11-22 3:14 ` [PATCH v4 1/5] nds32: " Vincent Chen
2018-11-22 3:14 ` [PATCH v4 2/5] nds32: Support FP emulation Vincent Chen
2018-11-23 10:53 ` David Laight [this message]
2018-11-26 1:23 ` Vincent Chen
2018-11-26 10:18 ` David Laight
2018-11-27 2:46 ` Vincent Chen
2018-11-22 3:14 ` [PATCH v4 3/5] nds32: support denormalized result through FP emulator Vincent Chen
2018-11-22 3:14 ` [PATCH v4 4/5] math-emu/op-2.h: Use statement expressions to prevent negative constant shift Vincent Chen
2018-11-22 3:14 ` [PATCH v4 5/5] math-emu/soft-fp.h: (_FP_ROUND_ZERO) cast 0 to void to fix warning Vincent Chen
2018-11-22 10:21 ` [PATCH v4 0/5] nds32 FPU port Greentime Hu
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