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Re: i386 and x86_64 fenv support
- From: Joseph Myers <joseph at codesourcery dot com>
- To: Joel Sherrill <joel at rtems dot org>
- Cc: Newlib <newlib at sourceware dot org>
- Date: Tue, 27 Aug 2019 17:10:55 +0000
- Subject: Re: i386 and x86_64 fenv support
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- References: <CAF9ehCWrHVR3MAojGHEVwLp=44D7F-mE96Frr4fHyzkyPrU8ag@mail.gmail.com>
On Tue, 27 Aug 2019, Joel Sherrill wrote:
> FWIW this moved up in importance because the x86_64 RTEMS toolchain
> won't build with the gcc/newlib master because libquadmath assumes the
> existence of the FE_TONEAREST since it the autoconf probe now sees
> we have fenv.h support now. This is probably a bug in this code since it
> can't assume a rounding mode is supported.
The rule in glibc is that architectures without support for rounding modes
still define FE_TONEAREST, and return it from fegetround and accept it for
fesetround, reflecting that to-nearest is the default (and only) rounding
mode.
That is, only architectures that don't support to-nearest at all should
fail to define FE_TONEAREST (and libquadmath doesn't support any such
architectures anyway).
--
Joseph S. Myers
joseph@codesourcery.com