Re: Stricter implicit conversions between vectors, revised patch

[Mark Shinwell <shinwell at codesourcery dot com>]

Gerald Pfeifer wrote:
> On Sat, 23 Dec 2006, Mark Shinwell wrote:
> > These have now been sorted.  This patch has no regressions on
> > x86_64-unknown-linux-gnu and powerpc64-unknown-linux-gnu.  OK to apply?
>
> If/when this goes in, would you mind adding something to 
> gcc-4.3/changes.html as well describing the stricter behavior
> and the new option?

Is this OK?

Mark

--


2007-01-08  Mark Shinwell  <shinwell@codesourcery.com>

	* changes.html (C family): Describe new restrictions on
	implicit conversions between generic vector types.


Index: changes.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-4.3/changes.html,v
retrieving revision 1.17
diff -U3 -r1.17 changes.html
--- changes.html        7 Jan 2007 05:00:08 -0000       1.17
+++ changes.html        8 Jan 2007 09:53:48 -0000
@@ -79,6 +79,23 @@

 <h3>C family</h3>

+  <ul>
+    <li>
+    Implicit conversions between generic vector types are now
+    only permitted when the two vectors in question have the same number
+    of elements and compatible element types.  (Note that the restriction
+    involves <em>compatible</em> element types, not
+    implicitly-convertible element types: thus, a vector type with element
+    type <code>int</code> may not be implicitly converted to a vector
+    type with element type <code>unsigned int</code>.)
+    This restriction, which is in line with specifications for SIMD
+    architectures such as AltiVec, may be relaxed using the
+    flag <code>-flax-vector-conversions</code>.
+    This flag is intended only as a compatibility measure and should not
+    be used for new code.
+    </li>
+  </ul>
+
 <h3>C++</h3>
   <ul>
     <li>Experimental support for the upcoming ISO C++ standard, C++0x,