[Bug ipa/113907] [11/12/13/14 regression] ICU miscompiled since 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 #57 from Jan Hubicka <hubicka at ucw dot cz> ---
> So, we can punt on differences there (that is desirable for backporting and
> maybe GCC 14 too), or we could at that point populate an int vector, which maps
Yep, that is what I do.
I had bug in that so I am re-running (forgot to check that callers and
callee argument count matches and this cuases ICE during LLVM LTO link).
It seems these extra checks makes no difference in practice. 
During bootstrap there are no pairs of functions during bootstrap where
we new checks punt on value range difference or jump function
difference that would be merged otherwise.

Most common case where we could merge but we don't are those triggered
by TBAA.
> the callee
> vector indexes to indexes in the callee vector in the other candidate function.
> If unsuccessful, we just free the vector, if successful, we first walk all the
> callees and union stuff in there using that vector.
This is the plan for metadata merging. A small complication here is that
ICF works by comparing bodies to a leader of equivalence class but this
leader is not necessarilly the surviving function body.  So if we
compared A to L (leader) and B to L and then decided replace A by B, we
need to be able to combine the permutations so we know how to map call
sites in A to ones in B.  The same is true about SSA names and basic
blocks.  I have patch for that for next stage1.