[Bug tree-optimization/42376] [4.5 Regression] Performance regression of generated code
rguenth at gcc dot gnu dot org
gcc-bugzilla@gcc.gnu.org
Tue Dec 15 13:16:00 GMT 2009
------- 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
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