[Bug tree-optimization/33928] [4.3/4.4 Regression] 30% performance slowdown in floating-point code caused by r118475

[lucier at math dot purdue dot edu]

------- Comment #42 from lucier at math dot purdue dot edu  2008-12-07 19:39 -------
Just a comment that -fforward-propagate isn't enabled at -O1 (the main
optimization option in the test) while the cse code it replaces was enabled at
-O1.  This is presumably why adding -fno-forward-propagate to the command line
in the test a year ago didn't affect the generated code.

Adding -fno-forward-propagate to the command line of the test case with
revision r118475 of gcc changes the generated code, but doesn't improve the
problem code in the main loop.

Updated the title to report the performance hit on

Intel(R) Xeon(R) CPU           X5460  @ 3.16GHz

as reported by /proc/cpuinfo


-- 

lucier at math dot purdue dot edu changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[4.3/4.4 Regression] 22%    |[4.3/4.4 Regression] 30%
                   |performance slowdown from   |performance slowdown in
                   |4.2.2 to 4.3/4.4.0 in       |floating-point code caused
                   |floating-point code         |by  r118475


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33928