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From: "matz at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug target/96895] ABI of returning V1DF differs between GCC and clang
Date: Wed, 02 Sep 2020 12:14:26 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D96895

--- Comment #2 from Michael Matz <matz at gcc dot gnu.org> ---
The psABI doesn't say anything about such types, no.  Maybe it could in some
additional info pages, but it's always a problem to codify behaviour
retroactively
in it, when conflicting implementations already exist.  It is about extensi=
on
types, though, so we might be fine.

FWIW, even ignoring the obvious relation of v1Xf to Xf, GCC behaviour for f=
loat
and clang behaviour for double is the most logical one: this extended type =
is
most
similar to a struct containing one float/double, and such are passed in XMM
registers per psABI.  As this is also consistent with how a single
top-level float is passed, this choice is the most consistent one.  This is
also
what the psABI _would_ say, if we had written it into it, so at least both
compilers would need a change to implement it.=