GCC 4.6.x miscompiling arm-linux?

[mol@pengutronix.de (Michael Olbrich)]

On Tue, Sep 11, 2012 at 11:31:39AM +0200, David Jander wrote:
> On Tue, 11 Sep 2012 10:48:53 +0200
> Sascha Hauer <s.hauer@pengutronix.de> wrote:
> 
> > On Tue, Sep 11, 2012 at 09:27:53AM +0200, David Jander wrote:
> > > 
> > > Hi Matt,
> > > 
> > > >         @ Function supports interworking.
> > > >         @ args = 0, pretend = 0, frame = 0
> > > >         @ frame_needed = 0, uses_anonymous_args = 0
> > > >         @ link register save eliminated.
> > > >         cmp     r0, #9
> > > >         mov     r3, #0
> > > >         str     r3, [r1, #0]
> > > >         mov     r0, #0
> > > >         strgt   r3, [r1, #4]
> > > >         bx      lr
> > > >         .size   flexcan_chip_start, .-flexcan_chip_start
> > > >         .ident  "GCC: (GNU) 4.3.3"
> > > >         .section        .note.GNU-stack,"",%progbits
> > > > 
> > > > I think this looks correct. Perhaps you could try the angstrom arm5te
> > > > toolchain and see if it's a toolchain issue?
> > > 
> > > Yes, this looks a lot better, and is exactly what I get when I compile this
> > > code with CodeSourcery GCC-4.4.1
> > > 
> > > I have tries building gcc-4.6.3 also with OSELAS/PTXdist, and it gives the
> > > same (wrong) result as with gcc-4.6.2
> > 
> > AFAIK our OSELAS/PTXdist Toolchains use Linaro patches, this would
> > explain why both have the same result.

No, OSELAS Toolchains only uses the Linaro GCC for Cortex-A8/-A9

> It would indeed, if I had just used OSELAS as-is, but I didn't ;-)
> I made a copy of
> arm-v5te-linux-gnueabi_gcc-4.6.2_glibc-2.14.1_binutils-2.21.1a_kernel-2.6.39-sanitized.ptxconfig
> and replaced the version string 4.6.2 with 4.6.3. AFAIK, this way PTXdist will
> download pristine gcc-4.6.3 sources and not apply any patches, since there is
> no directory named patches/gcc-4.6.3, right? Can I assume that I have an
> unpatched version of gcc-4.6.3 then?

Correct. This way you'll get gcc-4.6.3 without any patches.

> Btw, Here's what I get from it:
> 
> flexcan_chip_start:
>         @ args = 0, pretend = 0, frame = 0
>         @ frame_needed = 0, uses_anonymous_args = 0
>         @ link register save eliminated.
>         mov     r3, #0
>         cmp     r0, #9
>         str     r3, [r1, #0]
>         ldrle   r3, [r1, #4]
>         mov     r0, #0
>         str     r3, [r1, #4]
>         bx      lr
>         .size   flexcan_chip_start, .-flexcan_chip_start
>         .ident  "GCC: (OSELAS.Toolchain-2011.11.1) 4.6.3"
>         .section        .note.GNU-stack,"",%progbits

How can I reproduce this output? I'd like to test this with different
toolchain versions.

> Wrong code.
> See the version string? It is clearly not an existing OSELAS version.

Hmmm, so far it seems all tested gcc-4.6.x versions produce wrong code,
correct?

Regards,
Michael

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