RE: Optimisation options turned on at a certain level

RE: Optimisation options turned on at a certain level

[jgrant]

Hi Andrew,

> No, the online docs comes from the info pages.
> What you are seeing is a newer version of the info pages.
> The latest and greatest version of the info page on a web page is  
> located here: http://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html


Ok, thank you both for your replies.


Jonathan

Re: Optimisation options turned on at a certain level

[Andrew Pinski]

On Jan 18, 2004, at 10:28, jgrant@reflectionsinteractive.com wrote:

> Hi Ian
>
> Thanks for the info.
>
>>> Could this be added the documentation? so its clear exactly what is
>>> being done by which options are being passed.
>>
>> My two comments are:
>>
>> 1) Documentation patches are always welcome.
>
> I noticed the info gcc pages were in some ways more detailed, for  
> instance
> this optimisation page:
> http://www-es.fernuni-hagen.de/cgi-bin/info2html? 
> (gcc)Optimize%20Options
>
> Are the gcc online manual documents maintained by different people  
> from the
> gcc info pages?  Perhaps some aspects could be combined.

No, the online docs comes from the info pages.
What you are seeing is a newer version of the info pages.
The latest and greatest version of the info page on a web page is  
located here:
http://gcc.gnu.org/onlinedocs/gcc/Optimize-Options.html


Thanks,
Andrew Pinski

Re: Optimisation options turned on at a certain level

[Ian Lance Taylor]

jgrant@reflectionsinteractive.com writes:

> > 1) Documentation patches are always welcome.
> 
> I noticed the info gcc pages were in some ways more detailed, for instance
> this optimisation page:
> http://www-es.fernuni-hagen.de/cgi-bin/info2html?(gcc)Optimize%20Options
> 
> Are the gcc online manual documents maintained by different people from the
> gcc info pages?  Perhaps some aspects could be combined.

Actually, the online manual and the info pages are generated from the
same source files.  So if there are discrepancies, you must be looking
at different versions of the manual.  Perhaps the documentation has
gotten better since your info files were generated.  Hopefully it
hasn't gotten worse.

Ian

RE: Optimisation options turned on at a certain level

[jgrant]

Hi Ian

Thanks for the info.

> > Could this be added the documentation? so its clear exactly what is 
> > being done by which options are being passed.
> 
> My two comments are:
> 
> 1) Documentation patches are always welcome.

I noticed the info gcc pages were in some ways more detailed, for instance
this optimisation page:
http://www-es.fernuni-hagen.de/cgi-bin/info2html?(gcc)Optimize%20Options

Are the gcc online manual documents maintained by different people from the
gcc info pages?  Perhaps some aspects could be combined.

> 2) But note that the precise meaning of the optimization levels
>    changes for different architectures.  See the OPTIMIZATION_OPTIONS
>    macro as defined in various gcc/config/*/*.h files.

Ok, am doing. Thank you for the direction.

Jonathan

Re: Optimisation options turned on at a certain level

[Ian Lance Taylor]

jgrant@reflectionsinteractive.com writes:

> Could this be added the documentation? so its clear exactly what is being
> done by which options are being passed.

My two comments are:

1) Documentation patches are always welcome.

2) But note that the precise meaning of the optimization levels
   changes for different architectures.  See the OPTIMIZATION_OPTIONS
   macro as defined in various gcc/config/*/*.h files.

Ian

RE: Optimisation options turned on at a certain level

[jgrant]

Hello Ian,

Thank you for the link.  Very useful.

I was hoping for a list of the options as well as the text describing the
different levels.

Could this be added the documentation? so its clear exactly what is being
done by which options are being passed.  Perhaps something like:

Optimisation level  -O1

	-fomit-frame-pointer			When possible do not
generate stack frames
	-fdefer-pop				Defer popping functions args
from stack until later	
	-fthread-jumps				Perform jump threading
optimisations
	-fdelayed-branch			Attempt to fill delay slots
of branch instructions


Optimisation level  -O3

	-funroll-loops
	etc

(I these may not be accurate, just for illustration)


What do you think?



Kind regards

Jonathan

Re: Optimisation options turned on at a certain level

[Ian Lance Taylor]

jgrant@reflectionsinteractive.com writes:

> I'm trying to find where in the gcc documentation the list of optimisations
> that are implied by specifying -O3 and -Os with my gcc3.2 install.  I could
> not find anything yet other than the following:
> 
>   -O[number]              Set optimisation level to [number]
>   -Os                     Optimise for space rather than speed
> 
> from gcc -v --help
> 
> Could someone direct me to where I should be looking for this list of
> optimisations that are turned on with the different levels please?

See the manual under ``Options That Control Optimization,'' or look
here (this is the 3.2.3 manual):

http://gcc.gnu.org/onlinedocs/gcc-3.2.3/gcc/Optimize-Options.html#Optimize%20Options

Ian

Optimisation options turned on at a certain level

[jgrant]

Hello,

I'm trying to find where in the gcc documentation the list of optimisations
that are implied by specifying -O3 and -Os with my gcc3.2 install.  I could
not find anything yet other than the following:

  -O[number]              Set optimisation level to [number]
  -Os                     Optimise for space rather than speed

from gcc -v --help

Could someone direct me to where I should be looking for this list of
optimisations that are turned on with the different levels please?

Kind regards

Jonathan