------- Comment #11 from lucier at math dot purdue dot edu 2007-11-12 21:50
-------
I suspected that the slowdown had nothing to do with computed gotos, so I
regenerated the C code using a switch instead of the computed gotos and got the
following:
For that same copy of mainline
gcc version 4.3.0 20071026 (experimental) [trunk revision 129664] (GCC)
:
(time (direct-fft-recursive-4 a table))
470 ms real time
470 ms cpu time (470 user, 0 system)
no collections
64 bytes allocated
no minor faults
no major faults
For 4.2.2:
(time (direct-fft-recursive-4 a table))
384 ms real time
384 ms cpu time (383 user, 1 system)
no collections
64 bytes allocated
no minor faults
no major faults
So that's almost exactly the same slowdown as with computed gotos.
I changed the subject line to use 22% instead of 33% (I don't know how I got
33% before, perhaps I just mistyped it) and removed the phrase "with computed
gotos".
I'll include the new .i and .s files as attachments.
--
lucier at math dot purdue dot edu changed:
What |Removed |Added
----------------------------------------------------------------------------
Summary|[4.3 Regression] 33% |[4.3 Regression] 22%
|performance slowdown from |performance slowdown from
|4.2.2 to 4.3.0 in floating- |4.2.2 to 4.3.0 in floating-
|point code with computed |point code
|gotos |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33928
