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Date: Tue, 28 Jan 2020 11:53:00 -0000
From: Jakub Jelinek <jakub@redhat.com>
To: Prathamesh Kulkarni <prathamesh.kulkarni@linaro.org>
Cc: Richard Biener <richard.guenther@gmail.com>,        Joseph Myers <joseph@codesourcery.com>,        gcc Patches <gcc-patches@gcc.gnu.org>
Subject: Re: [RFC] [c-family] PR92867 - Add returns_arg attribute
Message-ID: <20200128113036.GX17695@tucnak>
Reply-To: Jakub Jelinek <jakub@redhat.com>
References: <CAAgBjMk19xq3shJVX5c7eQGfcn1w3YTGFVOP1f9EmctgX6upFg@mail.gmail.com> <alpine.DEB.2.21.2001202253430.5014@digraph.polyomino.org.uk> <CAAgBjM=KfwBuQvpnhGyWoerJhk8rqrbdJtrxQRahH6eUFfW0CA@mail.gmail.com> <alpine.DEB.2.21.2001242251100.25706@digraph.polyomino.org.uk> <CAFiYyc3wxYF_QvpZCssEiqjvK=pJJcdFLkPB7PQJs9-GDMvWBg@mail.gmail.com> <CAAgBjMn9hEtbf=40kF4HRZzbKwB2HR0eNPPjMC1-wgCusxtpDQ@mail.gmail.com>
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On Tue, Jan 28, 2020 at 04:56:59PM +0530, Prathamesh Kulkarni wrote:
> Thanks for the suggestions. In the attached patch I bumped up value of
> ERF_RETURNS_ARG_MASK
> to UINT_MAX >> 2, and use highest two bits for ERF_NOALIAS and ERF_RETURN=
S_ARG.
> And use fn spec "Z<argnum>" to store the argument number in fn-spec forma=
t.
> Does that look OK ?

No.

+#define ERF_RETURN_ARG_MASK    (UINT_MAX >> 2)=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
 /* Nonzero if the return value is equal to the argument number=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20
    flags & ERF_RETURN_ARG_MASK.  */=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
-#define ERF_RETURNS_ARG                (1 << 2)=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20
+#define ERF_RETURNS_ARG                (1 << (BITS_PER_WORD - 2))=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=20=
=20=20=20

How is size of host int related to BITS_PER_WORD?  Not to mention that
if BITS_PER_WORD is 64 and host int is 32-bit, 1 << (64 - 2) is UB.

	Jakub