Re: Sparse-LLVM issue compiling NULL pointers

From: Dibyendu Majumdar <mobile@majumdar.org.uk>
To: Luc Van Oostenryck <luc.vanoostenryck@gmail.com>
Cc: Linux-Sparse <linux-sparse@vger.kernel.org>
Subject: Re: Sparse-LLVM issue compiling NULL pointers
Date: Thu, 2 Mar 2017 17:03:06 +0000	[thread overview]
Message-ID: <CACXZuxeayh3PUdypas6Ww_1mT23ZOuJiZZA_NWDkSQbfes9Xzw@mail.gmail.com> (raw)
In-Reply-To: <CACXZuxefWw7VT8VJPXuYZ2kBLK-N=eYGc6BF5Lnbg9vP-RqLWw@mail.gmail.com>

On 2 March 2017 at 16:29, Dibyendu Majumdar <mobile@majumdar.org.uk> wrote:
> Here is the output from linearize. I think the way stores and loads
> are handled is broken. It appears that the last store / load
> instruction is stored in insn->target->priv, and then used later on
> ... I do not understand what the code is trying to do. Is it trying to
> optimize away stores and loads?
>
> grow_allocator:
> .L0000022DAFA94A88:
>         <entry-point>
>         call.64     %r1 <- malloc, $16
>         ptrcast.64  %r2 <- (64) %r1
>         load.64     %r4 <- 32[%arg1]
>         load.64     %r6 <- 40[%arg1]
>         mulu.64     %r7 <- %r4, %r6
>         call.64     %r8 <- malloc, %r7
>         ptrcast.64  %r9 <- (64) %r8
>         store.64    %r9 -> 8[%r2]
>         load.64     %r12 <- 0[%arg1]
>         store.64    %r12 -> 0[%r2]

It appears that the sparse-llvm code is storing the LLVM instruction
for '%r2' in pseudo->priv.

>         store.64    %r2 -> 0[%arg1]

And then it using the value of the store instruction whenever it sees '%r2'?

>         load.64     %r18 <- 8[%r2]

But here it fails because it needs to cast the LLVM store instruction
to be a pointer to access 8[]?

Regards