Re: [RFA wwwdocs] Re: [PATCH v2] Target-specific limits on vector alignment

["Ulrich Weigand" <uweigand at de dot ibm dot com>]

Richard Earnshaw wrote:

> How about:
> 
> <p>On ARM, a bug has been fixed in GCC's implementation of the AAPCS
> rules for the layout of vectors that could lead to wrong code being
> generated.  Vectors larger than 8 bytes in size are now by default
> aligned to an 8-byte boundary.  This is an ABI change: code that makes
> explicit use of vector types may be incompatible with binary objects
> built with older versions of GCC.  Auto-vectorized code is not affected
> by this change.</p>

Sounds better to me, thanks :-)

Here's what I have committed to wwwdocs.

Bye,
Ulrich

Index: gcc-4.6/changes.html
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RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-4.6/changes.html,v
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--- gcc-4.6/changes.html	10 Aug 2012 16:23:57 -0000
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*** 68,73 ****
--- 68,82 ----
      default by <code>-Wall</code> flag and <code>-Wunused-but-set-parameter</code>
      by <code>-Wall -Wextra</code> flags.</li>
  
+     <li>On ARM, a bug has been fixed in GCC's implementation of the AAPCS
+     rules for the layout of vectors that could lead to wrong code being
+     generated.  Vectors larger than 8 bytes in size are now by default
+     aligned to an 8-byte boundary.  This is an ABI change: code that makes
+     explicit use of vector types may be incompatible with binary objects
+     built with older versions of GCC.  Auto-vectorized code is not affected
+     by this change.  (This change affects GCC versions 4.6.4 and later,
+     with the exception of versions 4.7.0 and 4.7.1.)</li>
+ 
      <li><p>Support for a number of older systems and recently
      unmaintained or untested target ports of GCC has been declared
      obsolete in GCC 4.6.  Unless there is activity to revive them, the
Index: gcc-4.7/changes.html
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RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-4.7/changes.html,v
retrieving revision 1.123
diff -c -p -r1.123 changes.html
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--- gcc-4.7/changes.html	10 Aug 2012 16:23:58 -0000
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*** 121,126 ****
--- 121,134 ----
      different GCC versions and with C++98/C++03 code compiled with any version.
      </li>
  
+     <li>On ARM, a bug has been fixed in GCC's implementation of the AAPCS
+     rules for the layout of vectors that could lead to wrong code being
+     generated.  Vectors larger than 8 bytes in size are now by default
+     aligned to an 8-byte boundary.  This is an ABI change: code that makes
+     explicit use of vector types may be incompatible with binary objects
+     built with older versions of GCC.  Auto-vectorized code is not affected
+     by this change.  (This change affects GCC versions 4.7.2 and later.)</li>
+ 
      <li>More information on porting to GCC 4.7 from previous versions
      of GCC can be found in
      the <a href="http://gcc.gnu.org/gcc-4.7/porting_to.html";>porting
Index: gcc-4.8/changes.html
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RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-4.8/changes.html,v
retrieving revision 1.9
diff -c -p -r1.9 changes.html
*** gcc-4.8/changes.html	31 Jul 2012 12:13:01 -0000	1.9
--- gcc-4.8/changes.html	10 Aug 2012 16:23:58 -0000
*************** more information about requirements to b
*** 24,29 ****
--- 24,37 ----
  <p>The G++ namespace association extension, <code>__attribute ((strong))</code>,
  has been deprecated. Inline namespaces should be used instead.</p>
  
+ <p>On ARM, a bug has been fixed in GCC's implementation of the AAPCS
+ rules for the layout of vectors that could lead to wrong code being
+ generated.  Vectors larger than 8 bytes in size are now by default
+ aligned to an 8-byte boundary.  This is an ABI change: code that makes
+ explicit use of vector types may be incompatible with binary objects
+ built with older versions of GCC.  Auto-vectorized code is not affected
+ by this change.</p>
+ 
  <h2>General Optimizer Improvements</h2>
  
    <ul>

-- 
  Dr. Ulrich Weigand
  GNU Toolchain for Linux on System z and Cell BE
  Ulrich.Weigand@de.ibm.com