[Bug tree-optimization/42376] [4.5 Regression] Performance regression of generated code

["rguenth at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #4 from rguenth at gcc dot gnu dot org  2009-12-15 13:15 -------
This is because (quoting http://gcc.gnu.org/gcc-4.5/changes.html):

"GCC now supports handling floating-point excess precision arising from use of
the x87 floating-point unit in a way that conforms to ISO C99. This is enabled
with -fexcess-precision=standard and with standards conformance options such as
-std=c99, and may be disabled using -fexcess-precision=fast."

GCC with -std=c99 makes sure to properly handle the i387 FPU excess precision.
With -fexcess-precision=fast the code is as fast (and non-conforming) like
with GCC 4.4.  Using -std=gnu99 is also an option.


-- 

rguenth at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |jsm28 at gcc dot gnu dot org
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |WONTFIX
            Summary|[4.5] Performance regression|[4.5 Regression] Performance
                   |of generated code           |regression of generated code
   Target Milestone|---                         |4.5.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42376