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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/109495] Stack is used (unexpectedly) for copying
 on-heap objects (no problem in clang)
Date: Fri, 14 Apr 2023 08:12:53 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D109495

--- Comment #7 from Richard Biener <rguenth at gcc dot gnu.org> ---
Created attachment 54857
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=3D54857&action=3Dedit
patch

I have tested the attached successfully.  Can you think of a case where
we'd have a BLKmode target but a same size component ref source that
has not?  We could also check the components mode (but emulating what
get_inner_reference does is tricky - but it might be useful to split
the head of it out).

In any case if the concern is just padding it's odd that we have to massage
the _source_.  And if we have to, for larger sizes we could at least
block-copy the large head and just deal with the tail covering the padding
with a temporary.=