> > + else if (TREE_CODE (op) == SSA_NAME
> > + && POINTER_TYPE_P (TREE_TYPE (op)))
> > + {
> > + if (DECL_P (base) && !ptr_deref_may_alias_decl_p (op, base))
> > + return false;
> > + if (TREE_CODE (base) == SSA_NAME
> > + && !ptr_derefs_may_alias_p (op, base))
> > + return false;
> > + }
>
> this all looks redundant - why is it important to look at the
> base of ref, why not simply ask below (*)
>
> > + modref_access_node *access_node;
> > + FOR_EACH_VEC_SAFE_ELT (ref_node->accesses, k, access_node)
> > + {
> > + if (num_tests >= max_tests)
> > + return true;
> > +
> > + if (access_node->parm_index == -1
> > + || (unsigned)access_node->parm_index
> > + >= gimple_call_num_args (stmt))
> > + return true;
> > +
> > + tree op = gimple_call_arg (stmt, access_node->parm_index);
> > +
> > + alias_stats.modref_baseptr_tests++;
> > +
> > + /* Lookup base, if this is the first time we compare bases.
> > */
> > + if (!base)
>
> Meh, so this function is a bit confusing with base_node, ref_node,
> access_node and now 'base' and 'op'. The loop now got a
> new nest as well.
>
> I'm looking for a high-level description of the modref_tree <>
> but cannot find any which makes reviewing this quite difficult...
There is a description in ipa-modref.c though it may need a bit of expanding.
Basically the modref summary represents a decision tree for
tree-ssa-alias that has three levels
1) base which records base alias set,
2) ref which records ref alias set and
3) access wich presently records info whether the access is a
dreference of pointer passed by parameter. In future I will re-add
info about offset/size and base type. It would be posisble to record
the access path though I am not sure if that it is worth the effort
>
> > + {
> > + base = ref->ref;
> > + while (handled_component_p (base))
> > + base = TREE_OPERAND (base, 0);
>
> ao_ref_base (ref)? OK, that might strip an inner
> MEM_REF, yielding in a decl, but ...
>
> > + if (TREE_CODE (base) == MEM_REF
> > + || TREE_CODE (base) == TARGET_MEM_REF)
> > + base = TREE_OPERAND (base, 0);
>
> that might happen here, too. But in the MEM_REF case base
> is a pointer.
>
> > + }
> > +
> > + if (base_may_alias_with_dereference_p (base, op))
>
> So this is a query purely at the caller side - whether 'ref' may
> alias 'op'.
>
> ---
>
> (*) ptr_deref_may_alias_ref_p_1 (op, ref)
>
> without any of the magic?
Hmm, it may actually just work, I did not know that looks through
memrefs, let me re-test the patch.
>
> Can you please amend ipa-modref-tree.h/c with a toplevel comment
> layint out the data structure and what is recorded?
I will do (but need to think bit of a redundancy between comment in
ipa-modref and ipa-modref-tree)
Honza
>
> Thanks,
> Richard.
>
> > + return true;
> > + num_tests++;
> > + }
> > }
> > }
> > return false;
> > @@ -2510,7 +2584,7 @@ ref_maybe_used_by_call_p_1 (gcall *call, ao_ref *ref,
> > bool tbaa_p)
> > modref_summary *summary = get_modref_function_summary (node);
> > if (summary)
> > {
> > - if (!modref_may_conflict (summary->loads, ref, tbaa_p))
> > + if (!modref_may_conflict (call, summary->loads, ref, tbaa_p))
> > {
> > alias_stats.modref_use_no_alias++;
> > if (dump_file && (dump_flags & TDF_DETAILS))
> > @@ -2934,7 +3008,7 @@ call_may_clobber_ref_p_1 (gcall *call, ao_ref *ref,
> > bool tbaa_p)
> > modref_summary *summary = get_modref_function_summary (node);
> > if (summary)
> > {
> > - if (!modref_may_conflict (summary->stores, ref, tbaa_p))
> > + if (!modref_may_conflict (call, summary->stores, ref, tbaa_p))
> > {
> > alias_stats.modref_clobber_no_alias++;
> > if (dump_file && (dump_flags & TDF_DETAILS))
