* options for later passes
@ 2011-02-21 20:58 kevin diggs
2011-02-21 23:37 ` Andi Hellmund
0 siblings, 1 reply; 4+ messages in thread
From: kevin diggs @ 2011-02-21 20:58 UTC (permalink / raw)
To: gcc-help
Hi,
Is there an easy way to figure out which options need to be passed to
later compilation passes? If I do a:
gcc -S -dA -fverbose-asm -mcpu=750 -O2 -mmultiple -fpic gcc1test.c
What should be used for assembly:
gcc -c ??? gcc1test.s
and linking:
gcc -ogcc1test gcc1test.s
I am pretty sure the link will need the -fpic. Probably also something
like -pthread? Maybe the assembler would need to allow something like
altivec? So as a general rule should it see the cpu (or arch) option?
Does anyone else need the -O2?
kevin
P.S.: Do the order of the optimization options matter: '-O2 -mcpu=750
-mmultiple' the same as '-mmultiple -mcpu=750 -O2'?
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: options for later passes
2011-02-21 20:58 options for later passes kevin diggs
@ 2011-02-21 23:37 ` Andi Hellmund
2011-02-22 0:34 ` kevin diggs
0 siblings, 1 reply; 4+ messages in thread
From: Andi Hellmund @ 2011-02-21 23:37 UTC (permalink / raw)
To: kevin diggs; +Cc: gcc-help
Hey Kevin,
> Is there an easy way to figure out which options need to be passed to
> later compilation passes?
Well, I think it's quite easy: it depends on what you want to build, how
you want to build it and which library it requires. For example,
gcc/linker can't know that function xyz() belongs to libabc.
> What should be used for assembly:
>
> gcc -c ??? gcc1test.s
I doubt that you really need to assemble a file directly, but it also
depends on your needs. I would say that default options (though no
specific options) could be sufficient.
> I am pretty sure the link will need the -fpic.
-fpic _should_ be used when building a shared library.
> Probably also something like -pthread?
Only, if you are building a multi-threaded application. If not, you
don't need to specify -lpthread.
> So as a general rule should it see the cpu (or arch) option?
Sorry, but this also depends. If you for example build an application to
be used by a Linux distro which might run on a various number of CPUs,
you would possible use the "generic" option, but if you are building a
high-performance application, you would specifically tune your
application for the target processor.
> Does anyone else need the -O2?
No, only the compiler (cc1, cc1plus, ...)
> P.S.: Do the order of the optimization options matter: '-O2 -mcpu=750
> -mmultiple' the same as '-mmultiple -mcpu=750 -O2'?
No, it shouldn't. GCC firstly reads in the parameter and then does a
post-processing on the options where necessary.
Best regards,
Andi
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: options for later passes
2011-02-21 23:37 ` Andi Hellmund
@ 2011-02-22 0:34 ` kevin diggs
2011-02-22 15:47 ` Andi Hellmund
0 siblings, 1 reply; 4+ messages in thread
From: kevin diggs @ 2011-02-22 0:34 UTC (permalink / raw)
To: Andi Hellmund; +Cc: gcc-help
On Mon, Feb 21, 2011 at 5:10 PM, Andi Hellmund <mail@andihellmund.com> wrote:
>
>> Does anyone else need the -O2?
>
> No, only the compiler (cc1, cc1plus, ...)
>
Can I assume this also includes all of -O's -f friends?
Thanks!
kevin
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: options for later passes
2011-02-22 0:34 ` kevin diggs
@ 2011-02-22 15:47 ` Andi Hellmund
0 siblings, 0 replies; 4+ messages in thread
From: Andi Hellmund @ 2011-02-22 15:47 UTC (permalink / raw)
To: kevin diggs; +Cc: gcc-help
Hey Kevin,
> Can I assume this also includes all of -O's -f friends?
>
Yes, I think so.
Andi
^ permalink raw reply [flat|nested] 4+ messages in thread
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2011-02-21 20:58 options for later passes kevin diggs
2011-02-21 23:37 ` Andi Hellmund
2011-02-22 0:34 ` kevin diggs
2011-02-22 15:47 ` Andi Hellmund
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