COMMON_FLAGS or COMMON_APPS

[User7z]

As any gentoo user who likes the powerful controll over the system , but i was thinking am i that be a probleme , here is the thing i want do something like compiling with -O3 or even -Ofast and lto , but at any cost ? Making the system unstable ? So 1% performance gain ? I heard some packages get slower !as the wiki says the lto double the time of comlilation ! , but here is the thing , i have the controol over system , so i think a litlle bit and why not to :
-march=native -O2 -pipe , and we have the portage/env/anything_config so apply those optimization and pay the cost for the packages who deserve it ! I hope people gets my point and really benifit from this idea so we really take the advantage of this controll and not the reverse !

also thier my be packages wich gets performance boost but the user doesnot use them often , those attitudes well do the reverse thing.

So the thing know is 3 questions as a desktop user who browsing firefox :

1_which the most list of packages that gets boost from -Ofast , that was the first list , the second is wich do for just -O3

2_ wich do benifit (segnificant boost ) from lto , wich benifit from that other optimization_thing ?

3_what are those essential psckages that all other packages use them., one is gcc we use it to.compile stuff , and the other ones (ffmpeg etc.
.)

If already those question have been answerd plz share it here , and if not and you have some experience plz share with us wich do and wich not , so like that we get the most benifit at cheapest cost !

[BurningMemory]

Please do some research on the wiki, there's a lot of great stuff!
You can also search the older forum posts, because don't expect
other people to do all the research for you. It is considered to be
a good practice of "netiquette" to come to the forums if you've
tried some things and need genuine advice and not just someone
to tell you information that already is on the wiki.
Take a look at this and this.
Almost no software known has huge benefits from setting the cpu optimization
to lvl3, etc. These are pretty much useless options unless you have
a very specific use-case or old hardware.
Have a nice day.