This is the mail archive of the mailing list for the GCC project.

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

[WWWDOCS] Document IPA/LTO/FDO/i386 changes in GCC-4.9

there was many changes in this area.  The following are ones I can think of.
Please fell free to suggest more changes.
We probably should mention Teresa's splitting work once it is complete
and new micro-architectures targetd by x86 backend.


Index: changes.html
RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-4.9/changes.html,v
retrieving revision 1.36
diff -u -r1.36 changes.html
--- changes.html	15 Nov 2013 15:40:00 -0000	1.36
+++ changes.html	18 Nov 2013 16:15:32 -0000
@@ -37,14 +37,52 @@
     <li>AddressSanitizer, a fast memory error detector, is now available on ARM.
-  </ul>
-  <ul>
     <li>UndefinedBehaviorSanitizer (ubsan), a fast undefined behavior detector,
         has been added and can be enabled via <code>-fsanitize=undefined</code>.
 	Various computations will be instrumented to detect undefined behavior
 	at runtime.  UndefinedBehaviorSanitizer is currently available for the C
 	and C++ languages.
+    <li>Link-time optimization (LTO) improvements:
+    <ul>
+      <li>Type merging was rewritten. New implementation is significantly faster
+	  and use less memory. 
+      <li>Better partitioning algorithm resulting in less streaming during
+	  link-time.</li>
+      <li>Early removal of virtual methods reduce size of object files and
+	  improve link-time memory usage and compile time.</li>
+      <li>Functions are no longer pointlessly renamed.</li>
+      <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>
+    </ul>
+    Memory usage of Firefox build with debug enabled was reduced from 15GB to
+    3.5GB. Link time from 1700 seconds to 350 seconds.
+    </li>
+    <li>Inter-procedural optimization improvements:
+    <ul>
+      <li>New type inheritance analysis module improving devirtualization.
+	  Devirtualization now take into account anonymous name-spaces and the
+	  C++11 <code>final</code> keyword.</li>
+      <li>New speculative devirtualization pass (controlled by
+	  <code>-fdevirtualize-speculatively</code>.</li>
+      <li>Calls that was speculatively made direct are turned back to indirect
+	  when doing so does not bring any noticeable benefits.</li>
+      <li>Local aliases are introduced for symbols that are known to be
+	  semantically equivalent across shared libraries improving dynamic
+	  linking times.</li>
+    </ul>
+    <li>Feedback directed optimization improvements:
+    <ul>
+      <li>Profiling of programs using C++ inline functions is now more reliable.</li>
+      <li>New time profiling determine typical order in which functions are executed.</li>
+      <li>New function reordering pass (controlled by
+	  <code>-freorder-functions</code>) significantly reduces
+	  startup time of large applications.  Until binutils support is
+ 	  completed, it is effective only with link time optimization.</li>
+      <li>Feedback driven indirect call removal and devirtualization now handle
+	  cross-module calls when link-time optimization is enabled.</li>
+    </ul></li>
 <h2 id="languages">New Languages and Language specific improvements</h2>
@@ -325,9 +363,20 @@
       >Function Multiversioning</a>.
-    <li> GCC now supports the new Intel microarchitecture named Silvermont
+    <li>GCC now supports the new Intel microarchitecture named Silvermont
       through <code>-march=slm</code>.
+    <li><code>-march=generic</code> has been retuned for better support of
+      Intel core and AMD Bulldozer architectures.  Performance of AMD K7, K8,
+      Intel Pentium-M, and Pentium4 based CPUs is no longer considered important
+      for generic.
+    </li>
+    <li>Better inlining of <code>memcpy</code> and <code>memset</code> 
+	that is avare of value ranges and produce shorter alignment prologues.
+    </li>
+    <li><code>-mno-accumulate-outgoing-args</code> is now honored when unwind
+      information is output.  Argument accumulation is also now turned off
+      for portions of program optimized for size.</li>
 <h3 id="nds32">NDS32</h3>

Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]