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From: "jakub at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/108941] Error: operand type mismatch for `shr' with binutils
 master
Date: Mon, 27 Feb 2023 11:17:10 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108941

--- Comment #11 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
(In reply to jbeulich from comment #9)
> (In reply to Jakub Jelinek from comment #1)
> > How does that look like a gcc bug?  It is either a binutils bug for not
> > accepting it anymore, or ffmpeg-4 bug for relying on the negative shift=
s.
>=20
> While I'm not sure in how far reduction from original code has discarded =
too
> much context, the impression I'm getting is that they use inline assembly
> because if the same way expressed in a similar way in C, the compiler wou=
ld
> warn. And then, rather than making the expression match C standard
> requirements, assembly code was used instead to silence that diagnostic.

Of course the code could use whatever_32bit >> (count & 31) and GCC wouldn't
warn
and on arches like x86 where the shr instruction does effectively the maski=
ng
would fold the masking into the actual shift instruction.  Plus, it would m=
ask
constants at compile time to the right range.=