Re: Gnutools: consideration for upgrade to GCC 4.6

[Sergei Gavrikov <sergei dot gavrikov at gmail dot com>]

Hi all,

John Dallaway wrote:

> Hi Ilija and all
> 
> Ilija Kocho wrote:
> 
> > Our GCC 4.3.2 is ageing and perhaps we should consider an upgrade.
> > My motive is it's lacking of support for Cortex-M4 SIMD (aka DSP)
> > and FPU instructions, but I think that other architectures shall
> > gain from newer compiler too. I have made some signal processing
> > tests with GCC 4.6.2 against current eCos compiler and they show
> > performance gain even with Cortex-M3 setting, though moderate.
> > Performance is considerable when Cortex-M4 setting is selected and
> > is tremendous, as expected, when SIMD are used. Recently introduced
> > Cortex-M products with FPU (Kinetis K70, K61, STM32F4) will further
> > emphasise the benefit.
> > 
> > Another reason, maybe not so important, is that GCC 4.3 is not
> > officially supported any more.
> > 
> > Regarding this, I state my wish that we move to the latest stable
> > GCC release, that is at present rel. 4.6.2, accompanied with
> > respective binutils. I have tested binutils 2.21 but in meantime
> > 2.22 has been released. Of course, the list wouldn't be complete
> > without the latest GDB.
> 
> Moving to a more recent GCC makes sense to me.
> 
> There are sure to be some new compiler warnings to deal with in the
> eCos sources. Are you aware of the scale of this issue with eCos CVS
> and GCC 4.6.2?
> 
> There are a few patches that were applied to current toolchain
> sources:
> 
>   ftp://ecos.sourceware.org/pub/ecos/gnutools/src/
> 
> It would be useful to review these and determine which are still
> relevant. Certainly we would need to adjust the multi-libbing for some
> target architectures.

Also we would take a look at the RTEMS (CVS -> 4.11) patches for their
latest toolchain sources as they does use GCC 4.6.1 & binutils 2.21 for
RTEMS (CVS) builds

  http://www.rtems.org/ftp/pub/rtems/SOURCES/4.11/
  
By the way I like their built-in __rtems__ definition for own GCC builds
and I guess in the end we would propagate __ecos__ for own ones on the
occasion of renewal. What do you think?

IMHO, we also would start to use own labels in the prefixes for eCos
toolchains (http://gcc.gnu.org/install/specific.html). What do you think
about 'ecos' label in the prefixes as an OS-label? In ideal world the
prefixes would be *-*-ecos2.0, *-*-ecos3.0, *-*-ecos4.0 for toolchains
for eCos major releases to prevent the PATH collisions, and, perhaps,
*-*-ecos<major>.<year>, for eCos middle time (not full tested) releases,
e.g.  i386-elf-ecos3.12-gcc for 2012. And may be to have *-*-ecos as the
prefixes is quite enough for us. (Excuse, if above looks like
OFF-TOPIC).

> It would also be useful to test eCos with the new toolchain in an
> automated manner. I wonder if one of the maintainers at eCosCentric
> could set up testing in their test farm? In any case, I would advocate
> a cautious approach to roll out, creating an initial "test release"
> for use mostly by those interested in the new features. We could also
> consider building the toolchain for arm-eabi targets only in the first
> instance to reduce overall effort. Does anyone on this list have a
> particular interest in building eCos with recent GCC for another
> target architecture?

IMHO, if we won't see volunteers for non arm-eabi targets also we should
test new toolchain for Linux synthetic target at least (it would help us
in the efforts on warning clean-ups for new toolchain).

Sergei

> It would be important to retain eCos source compatibility with the
> current toolchains based on GCC 4.3.2.
> 
> John Dallaway
> eCos maintainer
> http://www.dallaway.org.uk/john
>