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.
