POC for GCC ARM back end?

POC for GCC ARM back end?

[Randall Smith]

	Hi.

	We're using GCC (2.95.3, I believe) to compile C++ for the ARM processor.  We're finding that the quality of the code optimization for this processor is fairly low, and would like to talk to someone who is familiar with the history of the ARM back end for GCC, primarily with an eye to seeing whether optimizer improvements have been made since our release and/or are likely to be made in the near future.

	Would it be possible for you to give us the name of someone who can answer these kinds of questions for us (and generally put us in the picture on GCC's ARM support)?  I'm not sure how GCC's contributing support network operates, or what the protocol is for these kinds of requests.

	Also, apologies if this request should have been directed elsewhere.

	Thanks in advance for any assistance!

	Randall Smith


------------------------------------------------------------------
Randall Smith				voice: (858) 651-1565
Staff Software Engineer		fax  : (858) 845-1204
QUALCOMM Corporation			email: rsmith@qualcomm.com
5775 Morehouse Drive, Room L-232D
San Diego, CA  92121-1714
------------------------------------------------------------------

Re: POC for GCC ARM back end?

[Nick Clifton]

Hi Randall,

> 	We're using GCC (2.95.3, I believe) to compile C++ for the ARM
> 	processor.  We're finding that the quality of the code
> 	optimization for this processor is fairly low, and would like
> 	to talk to someone who is familiar with the history of the ARM
> 	back end for GCC, primarily with an eye to seeing whether
> 	optimizer improvements have been made since our release and/or
> 	are likely to be made in the near future.

In general work on optimisations for GCC has tended to be in the
generic part of the compiler, where they will benefit lots of ports,
not just the ARM port.  There are some ARM specific optimisations as
well, but these are not a focal point for development work.

It would definitely be worth your while downloading the latest release
of the GCC sources (3.2.1) and comparing the code it produces with the
code you are currently obtaining from your 2.95.3 compiler.  Beware
however, that the 3.x series of GCC compilers use a different, and
incompatible C++ ABI.  So you would have to rebuild and and all C++
programs and libraries if you wanted them to work with the new
compiler.


> 	Would it be possible for you to give us the name of someone
> 	who can answer these kinds of questions for us (and generally
> 	put us in the picture on GCC's ARM support)?  I'm not sure how
> 	GCC's contributing support network operates, or what the
> 	protocol is for these kinds of requests. 

The best people to ask are the maintainers for the GCC ARM port.  You
can find a list of these people in the MAINTAINERS file which ships as
part of the GCC sources.  Currently the maintainers are myself and
Richard Earnshaw (rearnsha@arm.com).

I would recommend visiting the GCC web site:

  http://www.gnu.org/software/gcc/gcc.html

For information on how contributing and supporting GCC works.  It is
also worth noting that there are companies who will sell you support
and/or development contracts for GCC, should you be interested.

Cheers
        Nick

Re: POC for GCC ARM back end?

[Randall Smith]

        Nick:

        I sincerely appreciate you taking the time to provide us with this information.  We'll take your advice and look at the latest GCC release, and get back in touch with you and Richard when (and if!) we have more specific questions.  (We have the complicating factor that we are using a Wind River port of GCC, so presumably we would need to bring their changes forward, as well as recompile the VxWorks distribution libraries, in order to use a newer GCC release >:-O ).

        Once again, thanks for the timely and helpful response to our query.

        Randall.



At 01:21 AM 2/6/2003, Nick Clifton wrote:
>Hi Randall,
>
>>       We're using GCC (2.95.3, I believe) to compile C++ for the ARM
>>       processor.  We're finding that the quality of the code
>>       optimization for this processor is fairly low, and would like
>>       to talk to someone who is familiar with the history of the ARM
>>       back end for GCC, primarily with an eye to seeing whether
>>       optimizer improvements have been made since our release and/or
>>       are likely to be made in the near future.
>
>In general work on optimisations for GCC has tended to be in the
>generic part of the compiler, where they will benefit lots of ports,
>not just the ARM port.  There are some ARM specific optimisations as
>well, but these are not a focal point for development work.
>
>It would definitely be worth your while downloading the latest release
>of the GCC sources (3.2.1) and comparing the code it produces with the
>code you are currently obtaining from your 2.95.3 compiler.  Beware
>however, that the 3.x series of GCC compilers use a different, and
>incompatible C++ ABI.  So you would have to rebuild and and all C++
>programs and libraries if you wanted them to work with the new
>compiler.
>
>
>>       Would it be possible for you to give us the name of someone
>>       who can answer these kinds of questions for us (and generally
>>       put us in the picture on GCC's ARM support)?  I'm not sure how
>>       GCC's contributing support network operates, or what the
>>       protocol is for these kinds of requests. 
>
>The best people to ask are the maintainers for the GCC ARM port.  You
>can find a list of these people in the MAINTAINERS file which ships as
>part of the GCC sources.  Currently the maintainers are myself and
>Richard Earnshaw (rearnsha@arm.com).
>
>I would recommend visiting the GCC web site:
>
>  http://www.gnu.org/software/gcc/gcc.html
>
>For information on how contributing and supporting GCC works.  It is
>also worth noting that there are companies who will sell you support
>and/or development contracts for GCC, should you be interested.
>
>Cheers
>        Nick

------------------------------------------------------------------
Randall Smith				voice: (858) 651-1565
Staff Software Engineer		fax  : (858) 845-1204
QUALCOMM Corporation			email: rsmith@qualcomm.com
5775 Morehouse Drive, Room L-232D
San Diego, CA  92121-1714
------------------------------------------------------------------

Re: POC for GCC ARM back end?

[Joel Sherrill]

Randall Smith wrote:
> 
>         Nick:
> 
>         I sincerely appreciate you taking the time to provide us with this information.  We'll take your advice and look at the latest GCC release, and get back in touch with you and Richard when (and if!) we have more specific questions.  (We have the complicating factor that we are using a Wind River port of GCC, so presumably we would need to bring their changes forward, as well as recompile the VxWorks distribution libraries, in order to use a newer GCC release >:-O ).

You can often take the preprocessed output of an OS specific compiler
and feed it into the generic one like arm-elf and see if it fails.
I have done this to see if i386-rtems bugs can be reproduced on
i386-linux
or i386-elf before.  Since the CPU is the same, much of the code is the
same so bugs are often shared.  

>         Once again, thanks for the timely and helpful response to our query.
> 
>         Randall.
> 
> At 01:21 AM 2/6/2003, Nick Clifton wrote:
> >Hi Randall,
> >
> >>       We're using GCC (2.95.3, I believe) to compile C++ for the ARM
> >>       processor.  We're finding that the quality of the code
> >>       optimization for this processor is fairly low, and would like
> >>       to talk to someone who is familiar with the history of the ARM
> >>       back end for GCC, primarily with an eye to seeing whether
> >>       optimizer improvements have been made since our release and/or
> >>       are likely to be made in the near future.
> >
> >In general work on optimisations for GCC has tended to be in the
> >generic part of the compiler, where they will benefit lots of ports,
> >not just the ARM port.  There are some ARM specific optimisations as
> >well, but these are not a focal point for development work.
> >
> >It would definitely be worth your while downloading the latest release
> >of the GCC sources (3.2.1) and comparing the code it produces with the
> >code you are currently obtaining from your 2.95.3 compiler.  Beware
> >however, that the 3.x series of GCC compilers use a different, and
> >incompatible C++ ABI.  So you would have to rebuild and and all C++
> >programs and libraries if you wanted them to work with the new
> >compiler.
> >
> >
> >>       Would it be possible for you to give us the name of someone
> >>       who can answer these kinds of questions for us (and generally
> >>       put us in the picture on GCC's ARM support)?  I'm not sure how
> >>       GCC's contributing support network operates, or what the
> >>       protocol is for these kinds of requests.
> >
> >The best people to ask are the maintainers for the GCC ARM port.  You
> >can find a list of these people in the MAINTAINERS file which ships as
> >part of the GCC sources.  Currently the maintainers are myself and
> >Richard Earnshaw (rearnsha@arm.com).
> >
> >I would recommend visiting the GCC web site:
> >
> >  http://www.gnu.org/software/gcc/gcc.html
> >
> >For information on how contributing and supporting GCC works.  It is
> >also worth noting that there are companies who will sell you support
> >and/or development contracts for GCC, should you be interested.
> >
> >Cheers
> >        Nick
> 
> ------------------------------------------------------------------
> Randall Smith                           voice: (858) 651-1565
> Staff Software Engineer         fax  : (858) 845-1204
> QUALCOMM Corporation                    email: rsmith@qualcomm.com
> 5775 Morehouse Drive, Room L-232D
> San Diego, CA  92121-1714
> ------------------------------------------------------------------

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