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Date: Tue, 14 Jan 2020 22:53:41 +0300 (MSK)
From: Alexander Monakov <amonakov@...ras.ru>
To: musl@...ts.openwall.com
Subject: Re: Q: dealing with missing removal of excess precision
On Tue, 14 Jan 2020, Rich Felker wrote:
> > otoh it would be nice if there was a way to tell the compiler not to
> > remove it (e.g. in case the asm already took care of it) even in c99
> > standard mode.
>
> Perhaps this happens if the output constraint is tied to a float
> rather than a long double?
Precisely. That's what previously posted patches do, and they match
existing hand-tuned assembly.
I misspoke when saying that Glibc might return a value with excess precision.
I was looking at fmod-like functions and missed a slightly subtle point that
fprem does not introduce excess precision. So I don't actually have any
example where Glibc might misbehave in that regard.
Alexander
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