 Thanks for confirmation.

 I know those float point math optimization behave like this, if someone build
llvm with gcc and with '-Ofast' that is '-O3 -ffast-math' there are visual
regressions (missing fog, etc), but piglits also shows that regression.

 Weird thing about this is that piglit does not show any regression :( but well
as we confirm visually grass is not there... Lately '-no-nans-fp-math' is also
enabled, so i am a little bit suspicious that it might show similar issue
somewhere too.