Re: [RFC v0 0/4] Give a type to constants too

From: Linus Torvalds <torvalds@linux-foundation.org>
To: Dibyendu Majumdar <mobile@majumdar.org.uk>
Cc: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>,
	Sparse Mailing-list <linux-sparse@vger.kernel.org>,
	Christopher Li <sparse@chrisli.org>,
	Jeff Garzik <jeff@garzik.org>, Pekka Enberg <penberg@kernel.org>
Subject: Re: [RFC v0 0/4] Give a type to constants too
Date: Thu, 16 Mar 2017 13:43:05 -0700	[thread overview]
Message-ID: <CA+55aFzWLUXdTPRRfyN+SCxDvedZ4pnCOcaYMQ17zLA-id3tJQ@mail.gmail.com> (raw)
In-Reply-To: <CACXZuxd6O_c39=So7ruVwus9OV70gVo+dkjdPGHJVwcrRjzuVg@mail.gmail.com>

On Thu, Mar 16, 2017 at 1:19 PM, Dibyendu Majumdar
<mobile@majumdar.org.uk> wrote:
>
> The issue is not with the type of %r6 but %arg3 and %arg4 if these
> happen to be integer constants, and the function is variadic so we
> cannot work out the type from the function prototype.

Yes. Ok, I see the problem.

I think we could add a 'size' to the pseudo, and solve it that way.
CSE and other linearization artifacts may mean that the type is
undefined, but the size should be well-defined.

Alternatively - and this might be the better solution - the OP_CALL
instruction might be better off split up a bit. Instead of having just
that

    struct pseudo_list *arguments;

that lists the arguments, maybe it should have a

    struct instruction_list *arguments;

with a new OP_ARG instruction to generate the argument.

That way all the arguments would have a size, and always a generating
instruction.

              Linus