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Re: Fix exp in non-default rounding modes (bug 3976)
- From: David Miller <davem at davemloft dot net>
- To: joseph at codesourcery dot com
- Cc: libc-alpha at sourceware dot org
- Date: Tue, 28 Feb 2012 20:42:53 -0500 (EST)
- Subject: Re: Fix exp in non-default rounding modes (bug 3976)
- References: <Pine.LNX.4.64.1202290108400.30081@digraph.polyomino.org.uk>
From: "Joseph S. Myers" <joseph@codesourcery.com>
Date: Wed, 29 Feb 2012 01:10:01 +0000 (UTC)
> Bug 3976 discusses how some libm functions produce wildly incorrect
> results in rounding modes other than round-to-nearest (they don't need
> to be correctly rounded for each mode, but they should still produce
> some reasonable approximation to the correct value of the function).
I don't think we need to be so accomodating.
Calling libm functions in any rounding mode other than
round-to-nearest is completely undefined.
And if that is the case, I seriously question the value of doing
expensive control word changes in any of these routines.