27% regression of gcc 4.3 performance on cpu2k6/calculix

[Grigory Zagorodnev]

Hi!
There is a huge regression of gcc 4.3 performance detected on 
cpu2006/454.calculix benchmark at -O2 optimization level on 
x86_64-redhat-linux.

Regression is caused by mem-ssa merge 12/12/2006 (revision 119760).
http://gcc.gnu.org/viewcvs?view=rev&revision=119760

PS: I'm trying to get a small reproducer
- Grigory