[Bug ipa/63671] [5 Regression] 21% tramp3d-v4 performance hit due to -fdevirtualize

[hubicka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63671

--- Comment #15 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
The performance regression seems solved on my setup (Trevor, can you double
check?).

-Ofast -fdevirtualize:
Time spent in iteration: 4.11598

-Ofast -fno-devirtualize
Time spent in iteration: 4.17063


-Ofast -fno-devirtualize -fno-icf
Time spent in iteration: 3.34953

GCC 4.7:
Time spent in iteration: 5.53831

GCC 4.8:
Time spent in iteration: 3.4625

GCC 4.9:
Time spent in iteration: 2.79834

$ size 4.7 4.9 devirt nodevirt 
   text    data     bss     dec     hex filename
 785615    1204    2904  789723   c0cdb 4.7
 620822    1268    3320  625410   98b02 4.8
 615847    1180    3160  620187   9769b 4.9
 680881    1228    3064  685173   a7475 devirt
 650161    1228    3064  654453   9fc75 nodevirt
 681709    1228    3064  686001   a77b1 tramp-devirt-noicf


So 4.9 still outperforms mainline; ICF confuse inliner and moreover
devirtualization accounts 5% of code for no visible benefits.