[Bug ipa/113907] [11/12/13/14 regression] ICU miscompiled on x86 since r14-5109-ga291237b628f41

["hubicka at ucw dot cz" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=113907

--- Comment #70 from Jan Hubicka <hubicka at ucw dot cz> ---
Hello,
over easter I did some analysis of the cases where ICF is now disabled
due to jump function miscompare.  Most common case (seen also on GCC) is
the situation where function is originally static inline and in some
units its callee is known which enables us to propagate return value
range.  It happens on wide int implementaiton but it is not that
importnat.

Other case is when function has address taken of local label and
ICF two functions taking address of local label and passing it to a
calle (maybe we should not but C standard says nothing).

I tought there is also case where jump function has other function local
stuff, but that does not happen since we avoid putting them to
jumptables (to avoid need to stream function blocal BLOCKS).

Last case is that the function takes as parameter an address of static
symbol that can be merged.  We currently don't do that since we miss any
logic tracking whether value address is eventually used to compare.  So

I think for release branchs and trunk Martin's patch is fine. For next
stage1 we will need to work on using icf's compare_op in the ipa-prop
code and also add merging of value ranges.

Honza