Re: Make nonoverlapping_component_refs work with duplicated main variants

[Bernhard Reutner-Fischer <rep.dot.nop@gmail.com>]

On 9 July 2019 15:37:30 CEST, Richard Biener <rguenther@suse.de> wrote:
>On Tue, 9 Jul 2019, Jan Hubicka wrote:
>
>> Hi,
>> this is updated variant I am testing.
>> It documents better how function works and streamlines the checks.
>> 
>> OK assuming it passes the tests?
>> 
>> Honza
>> 
>> Index: tree-ssa-alias.c
>> ===================================================================
>> --- tree-ssa-alias.c	(revision 273193)
>> +++ tree-ssa-alias.c	(working copy)
>> @@ -1128,6 +1128,91 @@ aliasing_component_refs_p (tree ref1,
>>    return false;
>>  }
>>  
>> +/* FIELD1 and FIELD2 are two fields of component refs.  We assume
>> +   that bases of both component refs are
>> +     (*) are either equivalent or they point to different objects.
>
>are either equivalent(*) or not overlapping
>
>> +   We do not assume that FIELD1 and FIELD2 are of same type.
>
>that the containers of FIELD1 and FIELD2 are of the same type?
>
>> +
>> +   Return 0 if FIELD1 and FIELD2 satisfy (*).
>> +   This is the case when their offsets are the same.
>
>Hmm, so when the offsets are the same then the bases are equivalent?
>I think you want to say
>
>     Return 0 if in case the component refs satisfy (*) we
>     know FIELD1 and FIELD2 are overlapping exactly.
>
>> +   Return 1 if FIELD1 and FIELD2 are non-overlapping.
>> +
>> +   Return -1 otherwise.
>> +
>> +   Main difference between 0 and -1 is to let
>> +   nonoverlapping_component_refs_since_match_p discover the
>semnatically
>
>semantically
>
>otherwise looks good now.
>
>Thanks,
>Richard.
>
>> +   equivalent part of the access path.
>> +
>> +   Note that this function is used even with -fno-strict-aliasing
>> +   and makes use of no TBAA assumptions.  */
>> +
>> +static int
>> +nonoverlapping_component_refs_p_1 (const_tree field1, const_tree
>field2)
>> +{
>> +  /* If both fields are of the same type, we could save hard work of
>> +     comparing offsets.  */
>> +  tree type1 = DECL_CONTEXT (field1);
>> +  tree type2 = DECL_CONTEXT (field2);
>> +
>> +  if (DECL_BIT_FIELD_REPRESENTATIVE (field1))
>> +    field1 = DECL_BIT_FIELD_REPRESENTATIVE (field1);
>> +  if (DECL_BIT_FIELD_REPRESENTATIVE (field2))
>> +    field2 = DECL_BIT_FIELD_REPRESENTATIVE (field1);

Typo: s/field1/field2/

>> +
>> +  /* ??? Bitfields can overlap at RTL level so punt on them.
>> +     FIXME: RTL expansion should be fixed by adjusting the access
>path
>> +     when producing MEM_ATTRs for MEMs which are wider than 
>> +     the bitfields similarly as done in set_mem_attrs_minus_bitpos. 
>*/
>> +  if (DECL_BIT_FIELD (field1) && DECL_BIT_FIELD (field2))
>> +    return -1;

That's a pity.
thanks,