Re: float128 in libstdc++

[Martin Husemann <martin%duskware.de@localhost>]

On Sat, Jun 24, 2017 at 04:03:49PM +0200, Kamil Rytarowski wrote:
> arch/sparc64/c++config.h:/* #undef _GLIBCXX_USE_FLOAT128 */

Something is definitively strange here (as Joerg noted). We use 128 bit
long doubles via softfloat on sparc64. We should actually offer the
hardfloat version too and fix all fallout from the emulator (if there
are any left), but last tests showed this to be slower.

> SYSV ABI AMD64 notes float128 optionally and software emulated for at
> least order hardware.

What amd64 cpus support it in hardware (or which of the strange feature
bit acronyms matches it)? Of course we can not make the library features
depend on runtime cpu support detection.

Martin