[wwwdocs] gcc-4.9/changes.html: Mention that LTO now generates slim objects

[wwwdocs] gcc-4.9/changes.html: Mention that LTO now generates slim objects

[Tobias Burnus]

This patch mentions that -flto now generates slim objects. That's especially
relevant for static libraries as one can there run into surprises, if one
does not know about gcc-ar.

OK - or do you have a better suggestion?

Tobias


--- changes.html        8 Mar 2014 20:45:54 -0000       1.63
+++ changes.html        21 Mar 2014 09:10:32 -0000
@@ -65,6 +65,13 @@
       <li>Function bodies are now loaded on-demand and released early improving
          overall memory usage at link time.</li>
       <li>C++ hidden keyed methods can now be optimized out.</li>
+      <li>By default, compiling with the <code>-flto</code> option now generates
+         slim objects files (<code>.o</code>) which only contain intermediate
+         language representation for LTO. Use <code>-ffat-lto-objects</code> to
+         create files which contain additionally the object code.  To generate
+         static libraries suitable for LTO processing, use <code>gcc-ar</code>
+         and <code>gcc-ranlib</code> (requires that <code>ar</code> and
+         <code>ranlib</code> have been compiled with plugin support).</li>
     </ul>
     Memory usage building Firefox with debug enabled was reduced from 15GB to
     3.5GB; link time from 1700 seconds to 350 seconds.

Re: [wwwdocs] gcc-4.9/changes.html: Mention that LTO now generates slim objects

[Richard Biener]

On Fri, 21 Mar 2014, Tobias Burnus wrote:

> This patch mentions that -flto now generates slim objects. That's especially
> relevant for static libraries as one can there run into surprises, if one
> does not know about gcc-ar.
> 
> OK - or do you have a better suggestion?

Please adjust slightly to "When using a linker-plugin,
compiling with the <code>-flto</code> option now generates slim 
object files by default ..." as the change doesn't affect _all_
configurations but only those with HAVE_LTO_PLUGIN set (thus
-fno-use-linker-plugin overrides the default as well).

I'd also mention gcc-nm which needs to be used to inspect archives
with thin LTO files.

Richard.

> Tobias
> 
> 
> --- changes.html        8 Mar 2014 20:45:54 -0000       1.63
> +++ changes.html        21 Mar 2014 09:10:32 -0000
> @@ -65,6 +65,13 @@
>        <li>Function bodies are now loaded on-demand and released early improving
>           overall memory usage at link time.</li>
>        <li>C++ hidden keyed methods can now be optimized out.</li> + 
> <li>By default, compiling with the <code>-flto</code> option now 
> generates + slim objects files (<code>.o</code>) which only contain 
> intermediate + language representation for LTO. Use 
> <code>-ffat-lto-objects</code> to + create files which contain 
> additionally the object code.  To generate + static libraries suitable 
> for LTO processing, use <code>gcc-ar</code> + and 
> <code>gcc-ranlib</code> (requires that <code>ar</code> and + 
> <code>ranlib</code> have been compiled with plugin support).</li>
>      </ul>
>      Memory usage building Firefox with debug enabled was reduced from 15GB to
>      3.5GB; link time from 1700 seconds to 350 seconds.

Re: [wwwdocs] gcc-4.9/changes.html: Mention that LTO now generates slim objects

[Tobias Burnus]

On Fri, Mar 21, 2014 at 10:40:26AM +0100, Richard Biener wrote:
> On Fri, 21 Mar 2014, Tobias Burnus wrote:
> > This patch mentions that -flto now generates slim objects. That's especially
> > relevant for static libraries as one can there run into surprises, if one
> > does not know about gcc-ar.
> 
> Please adjust slightly to "When using a linker-plugin,
> compiling with the <code>-flto</code> option now generates slim 
> object files by default ..." as the change doesn't affect _all_
> configurations but only those with HAVE_LTO_PLUGIN set (thus
> -fno-use-linker-plugin overrides the default as well).
> 
> I'd also mention gcc-nm which needs to be used to inspect archives
> with thin LTO files.

Thanks for the suggestions - updated patch below.


Tobias

--- changes.html        8 Mar 2014 20:45:54 -0000       1.63
+++ changes.html        21 Mar 2014 12:43:44 -0000
@@ -65,6 +65,16 @@
       <li>Function bodies are now loaded on-demand and released early improving
          overall memory usage at link time.</li>
       <li>C++ hidden keyed methods can now be optimized out.</li>
+      <li>When using a linker plugin, compiling with the <code>-flto</code>
+          option now generates slim objects files (<code>.o</code>) which only
+          contain intermediate language representation for LTO. Use
+          <code>-ffat-lto-objects</code> to create files which contain
+          additionally the object code.  To generate static libraries suitable
+          for LTO processing, use <code>gcc-ar</code> and
+         <code>gcc-ranlib</code>; to list symbols from a slim object file use
+         <code>gcc-nm</code>. (Requires that <code>ar</code>,
+         <code>ranlib</code> and <code>nm</code> have been compiled with
+         plugin support.)</li>
     </ul>
     Memory usage building Firefox with debug enabled was reduced from 15GB to
     3.5GB; link time from 1700 seconds to 350 seconds.

Re: [wwwdocs] gcc-4.9/changes.html: Mention that LTO now generates slim objects

[Richard Biener]

On Fri, 21 Mar 2014, Tobias Burnus wrote:

> On Fri, Mar 21, 2014 at 10:40:26AM +0100, Richard Biener wrote:
> > On Fri, 21 Mar 2014, Tobias Burnus wrote:
> > > This patch mentions that -flto now generates slim objects. That's especially
> > > relevant for static libraries as one can there run into surprises, if one
> > > does not know about gcc-ar.
> > 
> > Please adjust slightly to "When using a linker-plugin,
> > compiling with the <code>-flto</code> option now generates slim 
> > object files by default ..." as the change doesn't affect _all_
> > configurations but only those with HAVE_LTO_PLUGIN set (thus
> > -fno-use-linker-plugin overrides the default as well).
> > 
> > I'd also mention gcc-nm which needs to be used to inspect archives
> > with thin LTO files.
> 
> Thanks for the suggestions - updated patch below.

Ok.

Thanks,
Richard.

> 
> Tobias
> 
> --- changes.html        8 Mar 2014 20:45:54 -0000       1.63
> +++ changes.html        21 Mar 2014 12:43:44 -0000
> @@ -65,6 +65,16 @@
>        <li>Function bodies are now loaded on-demand and released early improving
>           overall memory usage at link time.</li>
>        <li>C++ hidden keyed methods can now be optimized out.</li>
> +      <li>When using a linker plugin, compiling with the <code>-flto</code>
> +          option now generates slim objects files (<code>.o</code>) which only
> +          contain intermediate language representation for LTO. Use
> +          <code>-ffat-lto-objects</code> to create files which contain
> +          additionally the object code.  To generate static libraries suitable
> +          for LTO processing, use <code>gcc-ar</code> and
> +         <code>gcc-ranlib</code>; to list symbols from a slim object file use
> +         <code>gcc-nm</code>. (Requires that <code>ar</code>,
> +         <code>ranlib</code> and <code>nm</code> have been compiled with
> +         plugin support.)</li>
>      </ul>
>      Memory usage building Firefox with debug enabled was reduced from 15GB to
>      3.5GB; link time from 1700 seconds to 350 seconds.
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE / SUSE Labs
SUSE LINUX Products GmbH - Nuernberg - AG Nuernberg - HRB 16746
GF: Jeff Hawn, Jennifer Guild, Felix Imend"orffer

Re: [wwwdocs] gcc-4.9/changes.html: Mention that LTO now generates slim objects

[Jan Hubicka]

> This patch mentions that -flto now generates slim objects. That's especially
> relevant for static libraries as one can there run into surprises, if one
> does not know about gcc-ar.
> 
> OK - or do you have a better suggestion?
> 
> Tobias
> 
> 
> --- changes.html        8 Mar 2014 20:45:54 -0000       1.63
> +++ changes.html        21 Mar 2014 09:10:32 -0000
> @@ -65,6 +65,13 @@
>        <li>Function bodies are now loaded on-demand and released early improving
>           overall memory usage at link time.</li>
>        <li>C++ hidden keyed methods can now be optimized out.</li>
> +      <li>By default, compiling with the <code>-flto</code> option now generates
> +         slim objects files (<code>.o</code>) which only contain intermediate
> +         language representation for LTO. Use <code>-ffat-lto-objects</code> to
> +         create files which contain additionally the object code.  To generate
> +         static libraries suitable for LTO processing, use <code>gcc-ar</code>
> +         and <code>gcc-ranlib</code> (requires that <code>ar</code> and
> +         <code>ranlib</code> have been compiled with plugin support).</li>

Ah,
seems I forgot some of wwwdocs updates, since I wrote one already. But yours is better.
I would perhaps mention that with slim objects the LTO build times are often better (you
can reffer i.e. to SPEC2k6 compilation time) and also mention gcc-nm.

Honza
>      </ul>
>      Memory usage building Firefox with debug enabled was reduced from 15GB to
>      3.5GB; link time from 1700 seconds to 350 seconds.

Re: [wwwdocs] gcc-4.9/changes.html: Mention that LTO now generates slim objects

[Gerald Pfeifer]

On Fri, 21 Mar 2014, Tobias Burnus wrote:
> Thanks for the suggestions - updated patch below.

Here are two small tweaks I just committed on top of this.

Index: changes.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-4.9/changes.html,v
retrieving revision 1.71
retrieving revision 1.72
diff -u -r1.71 -r1.72
--- changes.html	11 Jun 2014 18:49:26 -0000	1.71
+++ changes.html	28 Jun 2014 12:37:43 -0000	1.72
@@ -80,13 +80,13 @@
 	  overall memory usage at link time.</li>
       <li>C++ hidden keyed methods can now be optimized out.</li>
       <li>When using a linker plugin, compiling with the <code>-flto</code>
-          option now generates slim objects files (<code>.o</code>) which only
+          option now generates slim object files (<code>.o</code>) which only
           contain intermediate language representation for LTO. Use
           <code>-ffat-lto-objects</code> to create files which contain
           additionally the object code.  To generate static libraries suitable
           for LTO processing, use <code>gcc-ar</code> and
          <code>gcc-ranlib</code>; to list symbols from a slim object file use
-         <code>gcc-nm</code>. (Requires that <code>ar</code>,
+         <code>gcc-nm</code>. (This requires that <code>ar</code>,
          <code>ranlib</code> and <code>nm</code> have been compiled with
          plugin support.)</li>
     </ul>