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Re: Minimum floating-point requirements
- From: Rich Felker <dalias at aerifal dot cx>
- To: David Edelsohn <dje dot gcc at gmail dot com>
- Cc: "Joseph S. Myers" <joseph at codesourcery dot com>, Steve Munroe <sjmunroe at us dot ibm dot com>, Adhemerval Zanella <azanella at linux dot vnet dot ibm dot com>, libc-alpha at sourceware dot org
- Date: Sun, 16 Feb 2014 16:46:24 -0500
- Subject: Re: Minimum floating-point requirements
- Authentication-results: sourceware.org; auth=none
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On Sun, Feb 16, 2014 at 02:40:23PM -0500, David Edelsohn wrote:
> On Sat, Feb 15, 2014 at 11:59 PM, Rich Felker <email@example.com> wrote:
> > On Sat, Feb 15, 2014 at 05:21:29PM +0000, Joseph S. Myers wrote:
> >> But I think this is a matter of imposing a decision about the PowerPC
> >> "ecosystem" (see <https://www.gnu.org/philosophy/words-to-avoid.html>) on
> >> glibc as much as imposing anything from glibc on anything else. And the
> >> ultimate question is about the GNU system rather than that "ecosystem".
> > Indeed. I see this issue as PowerPC folks imposing their legacy
> > brokenness on everybody else (libc and application developers who have
> > to work around it).
> Every ABI has peculiarities and historical baggage. One of the
The original powerpc ABI (which gcc still supports, and which we
require gcc to be configured with for use with musl libc, since it
requires IEEE types) simply has long double == double. The
double-double nonsense was added long after it was known how bad it
is, and it should never have been added in the first place, but
presumably IBM fans pushed it through. So this is not just historical
baggage but a relatively new imposition of a historical mistake onto
the glibc powerpc ABI which used to be free of this mess.
> strengths of the GNU Toolchain has been its acceptance of and
> accommodation of many different ISAs, ABIs and OSes. That is one of
There's a difference between accepting and accomodating legitimate
differences between cpu archs that don't affect the ability to satisfy
the contracts applications expect, and accommodating a nonsensical
type pushed by IBM folks that's not even a native type provided by the
hardware but just a lazy, poorly designed, but fast way of getting
more precision by using a hybrid hard/soft-float approach to operate
on a pair of hardware doubles.