AVR gives weird error with LTO

AVR gives weird error with LTO

[Andrew Hutchinson]

When AVR target is built, without explicitly disabling LTO, it will produce 1000's of testsuite failures of -LTO -WHOPR tests with this compilation error:

"ld: -f may not be used without -shared"

Any idea what is wrong or how to make LTO work correctly here?

Andy


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42483

Re: AVR gives weird error with LTO

[Dave Korn]

Andrew Hutchinson wrote:
> When AVR target is built, without explicitly disabling LTO, it will
> produce 1000's of testsuite failures of -LTO -WHOPR tests with this
> compilation error:
> 
> "ld: -f may not be used without -shared"
> 
> Any idea what is wrong or how to make LTO work correctly here?

  The standard way to be proceed would be: add -v to the command-line in the
PR; find out what is actually getting passed to ld; figure out what kind of
specs-processing accident (most likely) is causing ld to receive a -f option.

    cheers,
      DaveK

Re: AVR gives weird error with LTO

[Andrew Hutchinson]

I used "v" and progressed a little

The problem seems to be that linker is called with -fwhopr or -flto as 
command line option.

ld -fwhopr .....

Linker find  '-f' and complains.

I assume this is not a valid option for ld?  Or is my linker wrong 
version or something?

Note this is cross compile toolchain.

Andy



Dave Korn wrote:
> Andrew Hutchinson wrote:
>   
>> When AVR target is built, without explicitly disabling LTO, it will
>> produce 1000's of testsuite failures of -LTO -WHOPR tests with this
>> compilation error:
>>
>> "ld: -f may not be used without -shared"
>>
>> Any idea what is wrong or how to make LTO work correctly here?
>>     
>
>   The standard way to be proceed would be: add -v to the command-line in the
> PR; find out what is actually getting passed to ld; figure out what kind of
> specs-processing accident (most likely) is causing ld to receive a -f option.
>
>     cheers,
>       DaveK
>
>   

Re: AVR gives weird error with LTO

[Dave Korn]

Andrew Hutchinson wrote:
> I used "v" and progressed a little
> 
> The problem seems to be that linker is called with -fwhopr or -flto as
> command line option.
> 
> ld -fwhopr .....
> 
> Linker find  '-f' and complains.
> 
> I assume this is not a valid option for ld?  Or is my linker wrong
> version or something?


  It's not a valid option for ld.  It *is* a valid option for the collect2
driver/wrapper executable that gcc uses to invoke ld, which suggests to me
that the AVR port must be configured not to build collect2, but that it is
going to need to do so if it wants to use LTO/WHOPR.  See use_collect2 in
gcc/config.gcc

    cheers,
      DaveK

Re: AVR gives weird error with LTO

[Rafael Espindola]

>  It's not a valid option for ld.  It *is* a valid option for the collect2
> driver/wrapper executable that gcc uses to invoke ld, which suggests to me
> that the AVR port must be configured not to build collect2, but that it is
> going to need to do so if it wants to use LTO/WHOPR.  See use_collect2 in
> gcc/config.gcc

Or you could port gold to AVR and use the plugin :-)

>    cheers,
>      DaveK
>

Cheers,
-- 
Rafael Ávila de Espíndola

Re: AVR gives weird error with LTO

[Dave Korn]

Rafael Espindola wrote:
>>  It's not a valid option for ld.  It *is* a valid option for the collect2
>> driver/wrapper executable that gcc uses to invoke ld, which suggests to me
>> that the AVR port must be configured not to build collect2, but that it is
>> going to need to do so if it wants to use LTO/WHOPR.  See use_collect2 in
>> gcc/config.gcc
> 
> Or you could port gold to AVR and use the plugin :-)

  I hadn't checked, but yeah, since AVR is an ELF platform, that's a nice
solution too.  There might still be reason to build a collect2, for interop
with older binutils.

    cheers,
      DaveK

Re: AVR gives weird error with LTO

[Andrew Hutchinson]

Dave Korn wrote:
> Rafael Espindola wrote:
>   
>>>  It's not a valid option for ld.  It *is* a valid option for the collect2
>>> driver/wrapper executable that gcc uses to invoke ld, which suggests to me
>>> that the AVR port must be configured not to build collect2, but that it is
>>> going to need to do so if it wants to use LTO/WHOPR.  See use_collect2 in
>>> gcc/config.gcc
>>>       
>> Or you could port gold to AVR and use the plugin :-)
>>     
>
>   I hadn't checked, but yeah, since AVR is an ELF platform, that's a nice
> solution too.  There might still be reason to build a collect2, for interop
> with older binutils.
>
>     cheers,
>       DaveK
>
>
>   
Thank you David and Rafel

I will dig further into collect2.  I had noted that avr.h has the following:


/* This is undefined macro for collect2 disabling */
#define LINKER_NAME "ld"


Also, the MINGW host is the most significant for the AVR target - and 
problems with collect2 may be related to maintaining compatibility to that.

Andy

Re: AVR gives weird error with LTO

[Richard Guenther]

On Thu, Dec 31, 2009 at 12:04 AM, Andrew Hutchinson
<andrewhutchinson@cox.net> wrote:
>
> Dave Korn wrote:
>>
>> Rafael Espindola wrote:
>>
>>>>
>>>>  It's not a valid option for ld.  It *is* a valid option for the
>>>> collect2
>>>> driver/wrapper executable that gcc uses to invoke ld, which suggests to
>>>> me
>>>> that the AVR port must be configured not to build collect2, but that it
>>>> is
>>>> going to need to do so if it wants to use LTO/WHOPR.  See use_collect2
>>>> in
>>>> gcc/config.gcc
>>>>
>>>
>>> Or you could port gold to AVR and use the plugin :-)
>>>
>>
>>  I hadn't checked, but yeah, since AVR is an ELF platform, that's a nice
>> solution too.  There might still be reason to build a collect2, for
>> interop
>> with older binutils.
>>
>>    cheers,
>>      DaveK
>>
>>
>>
>
> Thank you David and Rafel
>
> I will dig further into collect2.  I had noted that avr.h has the following:
>
>
> /* This is undefined macro for collect2 disabling */
> #define LINKER_NAME "ld"

That's indeed going to break LTO.

Richard.

> Also, the MINGW host is the most significant for the AVR target - and
> problems with collect2 may be related to maintaining compatibility to that.
>
> Andy
>
>

Re: AVR gives weird error with LTO

[Andrew Hutchinson]

>> Thank you David and Rafel
>>
>> I will dig further into collect2.  I had noted that avr.h has the following:
>>
>>
>> /* This is undefined macro for collect2 disabling */
>> #define LINKER_NAME "ld"
>>     
>
> That's indeed going to break LTO.
>
> Richard.
>
>   
That seems to be the key issue.
Without #define LINKER_NAME, AVR is running LTO/WHOPR tests ok ! (No 
idea if it does anything useful though)

Now to figure out why it was added in 2000 (rth). Hopefully Eric 
Weddington or Denis might have some idea and perhaps know if it still 
has a purpose.

Andy

RE: AVR gives weird error with LTO

[Weddington, Eric]

 

> -----Original Message-----
> From: Andrew Hutchinson [mailto:andrewhutchinson@cox.net] 
> Sent: Wednesday, December 30, 2009 4:34 PM
> To: Richard Guenther
> Cc: Dave Korn; Rafael Espindola; GCC Development; Weddington, 
> Eric; Denis Chertykov
> Subject: Re: AVR gives weird error with LTO
> 
> 
> >> Thank you David and Rafel
> >>
> >> I will dig further into collect2.  I had noted that avr.h 
> has the following:
> >>
> >>
> >> /* This is undefined macro for collect2 disabling */
> >> #define LINKER_NAME "ld"
> >>     
> >
> > That's indeed going to break LTO.
> >
> > Richard.
> >
> >   
> That seems to be the key issue.
> Without #define LINKER_NAME, AVR is running LTO/WHOPR tests ok ! (No 
> idea if it does anything useful though)
> 
> Now to figure out why it was added in 2000 (rth). Hopefully Eric 
> Weddington or Denis might have some idea and perhaps know if it still 
> has a purpose.

That was before my time. I didn't get involved (peripherally) until 2002. So it's either Denis Chertykov or Marek Michalkiewicz (CCed).

Eric Weddington

Re: AVR gives weird error with LTO

[Denis Chertykov]

2009/12/31 Weddington, Eric <Eric.Weddington@atmel.com>:
>
>
>> -----Original Message-----
>> From: Andrew Hutchinson [mailto:andrewhutchinson@cox.net]
>> Sent: Wednesday, December 30, 2009 4:34 PM
>> To: Richard Guenther
>> Cc: Dave Korn; Rafael Espindola; GCC Development; Weddington,
>> Eric; Denis Chertykov
>> Subject: Re: AVR gives weird error with LTO
>>
>>
>> >> Thank you David and Rafel
>> >>
>> >> I will dig further into collect2.  I had noted that avr.h
>> has the following:
>> >>
>> >>
>> >> /* This is undefined macro for collect2 disabling */
>> >> #define LINKER_NAME "ld"
>> >>
>> >
>> > That's indeed going to break LTO.
>> >
>> > Richard.
>> >
>> >
>> That seems to be the key issue.
>> Without #define LINKER_NAME, AVR is running LTO/WHOPR tests ok ! (No
>> idea if it does anything useful though)
>>
>> Now to figure out why it was added in 2000 (rth). Hopefully Eric
>> Weddington or Denis might have some idea and perhaps know if it still
>> has a purpose.
>
> That was before my time. I didn't get involved (peripherally) until 2002. So it's either Denis Chertykov or Marek Michalkiewicz (CCed).

I havn't any ideas about LINKER_NAME definition.

Denis.