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To: "fortran@gcc.gnu.org" <fortran@gcc.gnu.org>,
 gcc mailing list <gcc@gcc.gnu.org>, Michael Meissner <meissner@linux.ibm.com>
From: Thomas Koenig <tkoenig@netcologne.de>
Subject: [power-ieee128] Which options for libquadmath / native ieee128
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Date: Mon, 13 Dec 2021 21:29:16 +0100
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Hi,

looking at what the REAL(KIND=17) numbers should be compiled for, I see
the following options that should be considered:

a) xsaddqp and friends are not supported by the CPU; libquadmath should
    be called for all operations, including simple arithmetic.

b) xsaddqp and friends are supported, but glibc is too old and lacks the
    *ieee128 functions.  libquadmath should be called for these
    functions.

c) xsaddqp and friends are supported, and glibc is new enough.  Call
    the *ieee128 functions.

What is the best way to check in the library config files that the quad
precision instructions are supported (to differentiate between a) on the
one hand and b) and c) on the other?

And which options to the compiler make sure the libquadmath library
is called?

Regards

	Thomas