[Bug ipa/65270] [5 regression] ICF needs to match TYPE attributes on memory accesses

[hubicka at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65270

--- Comment #18 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
Here is summary of my current understanding of remaining issues from my last
weekend's audit.

ICF specific:
 - ipa-icf-gimple.c needs to match dependence analysis
   Richard has propsed a patch for it, so I hope he will commit it tomorrow.
 - restrict flag may need to be matched when considering two references
   to variables being equal.
   Here I am waiting for Richards comment. I would propose matching restricts
in compare_cgraph_references same way as we now compare vtables.

non-ICF specific wrong codes
 - tree-vectorizer is picking up wrong alignment
 - fold-const.c's operands_equal_p probably needs same treatment for
   comparing mem-ref as ipa-icf-gimple has.  I think in all cases one can
   construct testcase where tree-tail-merge would produce same incorrect
   merging as ipa-icf does.

stuff that can wait for next stage1
 - ipa-pure-const is probably wrong to check TYPE_NEEDS_CONSTRUCTION flag
   (something to fix for next stage1)
 - expand_builtin_classify_type can probably be dropped, because
fold_classify_type prevails.