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Re: [PATCH] Don't do double divide in powf.

From: Jim Wilson <jimw at sifive dot com>
To: Craig Howland <howland at LGSInnovations dot com>, newlib at sourceware dot org
Date: Tue, 12 Dec 2017 11:00:05 -0800
Subject: Re: [PATCH] Don't do double divide in powf.
Authentication-results: sourceware.org; auth=none
References: <20171212034521.8556-1-jimw@sifive.com> <20171212130454.GD9113@calimero.vinschen.de> <69dde7fa-a08c-37e8-a3a4-b4dd568a23f9@LGSInnovations.com>

On 12/12/2017 08:06 AM, Craig Howland wrote:

No to either of the above. The 0/0 construct is to cause a floatingpoint "invalid" exception, which the functions do not do. (The dividehas to be done at runtime to cause the exception.) The double dividecan be made float by changing it to 0.0F/0.0F.


After double checking the ISO C standard Annex F, I have to agree with you.

However, it looks like there are other places that already make thismistake. wf_log.c for instance calls nan, and the ISO C Annex F saysthis case should generate an invalid exception too. There may also beother places that are broken in the same way. This is no excuse for meto make it worse though, so I will post a new patch.

Jim

References:
- [PATCH] Don't do double divide in powf.
  - From: Jim Wilson
- Re: [PATCH] Don't do double divide in powf.
  - From: Corinna Vinschen
- Re: [PATCH] Don't do double divide in powf.
  - From: Craig Howland

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