Hi,
I went through some statistics on firefox build (it is a source combining many
coding styles).
I was basically curious where we do devirtualization. The result is:
Before inline (i.e. important devirtualization)
624 ssa-pre devirt 0
this is interaprocedural devirutalization happening during early FRE by
propagating
constant accesses into vtables entries. (i.e. not type based at all)
10 ssa-pre devirt2 0
this is type based intraprocedural analysis during early optimizations
177 ipa-prop devirt
devirtualization in ipa-cp
243 ipa-cp inline devirt
this is devirtualization happening at IPA stage during inlining
After inline (i.e. devirtualization where we missed the chance to do something
useful)
82 gimple-fold devirt 1
this is the gimple-fold function in question (it also run pre-inline
but apparently
always fail. I will try the proposed patch and sed updated stats
tomorrow)
27 ipa-prop intra devirt 1
intraprocedural type based analysis
1569 ssa-pre devirt 1
this is interaprocedural devirutalization happening during late FRE
(not type based)
So overall type based analyssi accounts 430 devirtualizations pre-inline and
109 post inline.
Low level propagation of vtable accesses gets 624 pre-inline and 1569 post
inline.
Obviously the post inline numbers shows that we miss majority of interesting
cases.
I hope we can noticeably improve this.
I am re-building with the proposed change now.
Honza
