Re: PING: two middle-end builtin cproj patches

["Kaveh R. Ghazi" <ghazi at caip dot rutgers dot edu>]

From: "Richard Guenther" <richard.guenther@gmail.com>

> On Sun, Apr 18, 2010 at 6:45 PM, Kaveh R. GHAZI <ghazi@caip.rutgers.edu> 
> wrote:
> > Two patches for builtin cproj:
> >
> > http://gcc.gnu.org/ml/gcc-patches/2010-04/msg00490.html
> >
> > http://gcc.gnu.org/ml/gcc-patches/2010-04/msg00517.html
>
> I am worried that with old glibc still around we now silently change
> cproj semantics.  Can you at least add one executable testcase
> that would FAIL with the incorrect implementation and PASS with
> a correct implementation?  Please add an entry to gcc-4.6/changes,html
> mentioning this change and the newest glibc version affected.
>
> Ok with that change.

and here is the update to the webpage:

Index: changes.html
===================================================================
RCS file: /cvs/gcc/wwwdocs/htdocs/gcc-4.6/changes.html,v
retrieving revision 1.7
diff -u -p -r1.7 changes.html
--- changes.html        25 Apr 2010 15:05:32 -0000      1.7
+++ changes.html        25 Apr 2010 23:19:15 -0000
@@ -21,6 +21,18 @@
    <code>&lt;<em>machine</em>&gt;-gcc-&lt;<em>version</em>&gt;</code>
    to run a different version of <code>gcc</code>. </li>

+    <li>Versions of the GNU C library up to and including 2.11.1
+    included an <a
+    href="http://sourceware.org/bugzilla/show_bug.cgi?id=10401";>incorrect
+    implementation of the <code>cproj</code> function</a>.  GCC
+    optimizes its builtin <code>cproj</code> according to the behavior
+    specified and allowed by the ISO C99 standard.  If you want to
+    avoid discrepancies between the C library and GCC's builtin
+    transformations when using <code>cproj</code> in your code, use
+    GLIBC 2.12 or later.  If you are using an older GLIBC and actually
+    rely on the incorrect behavior of cproj, then you can disable
+    GCC's transformations using <code>-fno-builtin-cproj</code>. </li>
+
</ul>

<h2>General Optimizer Improvements</h2>