-o2 vs -oX optimize (vc2008)

[whgwbn]

my test result: for pcsx2, the -o2 will get better performance than -oX
but for plugins, such as GSDX: the -oX will be get better performance.

generally, -oX will get better performance.maybe pcsx2 is special
it puzzled me.

[Air]

As far as pcsx2 is concerned, it's mostly random. The actual culprit affecting speed is ismply the placement of some global variables, which can vary from compiler option to compiler option. Turning off string pooling, for example, can yield a 3% speed up or slow down sometimes. This is a side effect of modern cpus being hyper-sensitive to something called 'Cache Coloring.'

(Cache coloring is a term used to refer to the cache line resolution of cpus, and how that affects their ability to cache certain variables because of cache line conflicts.)