[wwwdocs] Mention ipa-ICF and auto-FDO

Jan Hubicka hubicka@ucw.cz
Wed Jan 21 22:32:00 GMT 2015


Hi,
these two rather noticeable features are not mentioned.

Honza

Index: changes.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-5/changes.html,v
retrieving revision 1.69
diff -u -r1.69 changes.html
--- changes.html	20 Jan 2015 16:37:54 -0000	1.69
+++ changes.html	21 Jan 2015 21:57:30 -0000
@@ -35,7 +35,15 @@
   <ul>
     <li>Inter-procedural optimization improvements:
     <ul>
-     <li>The devirtualization pass was significantly improved by adding
+     <li>New identical code folding pass (controled via <code>-fipa-icf</code>).
+	 Compared to the identical code folding performed by Gold linker this
+	 pass does not require function sections.  It also performs merging
+	 pre-inline so inter-procedural optimizations are aware of the
+	 code re-use. On the other hand not all unifications performed
+	 by linker are doable by GCC pass; the GCC pass must honnor
+	 aliasing information. During link-time optimization of Firefox,
+	 the pass unify about 29000 functions that is 10% overall</li>
+     <li>Devirtualization pass was significantly improved by adding
 	 better support for speculative devirtualization and dynamic type
 	 detection. About 50% of virtual calls in Firefox are speculatively
 	 devirtualized during link-time optimization.</li>
@@ -72,6 +80,11 @@
     </ul></li>
     <li>Feedback directed optimization improvements:
     <ul>
+      <li>New auto-FDO mode that use profiles collected by low overhead
+	  profiling tools (perf) instead of more expensive program
+	  instrumentation (via <code>-fprofile-generate</code>). SPEC2006
+	  benchmarks improve by 4.7% with auto-FDO and by 7.3% with
+	  traditional feedback directed optimization.
       <li>Profile precision was improved in presence of C++ inline and extern
 	  inline functions.</li>
       <li>New <code>gcov-tool</code> to manipulate profiles.</li>



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