When I added a '-mfpmath=sse', to CFLAGS environment variable in Gentoo & recompiled entire system I noticed that Dolphin works extremly slow(it enters in folders with latency approximately about 2 minutes). Then I tried to remove this option, and recompiled all again, Dolphin worked fine again. Can you suppose what can bring such strange behavior?

This is certainly not expected behaviour.... do Konqueror, Gwenview or Plasma's folder view exhibit the same behaviour?