Re: Patch to fix gcc.c-torture/compile/20010102-1.c on IA64 HP-UX

[Jeff Law <law@redhat.com>]

David Edelsohn wrote:
>
>   
>>> find_base_term() either could check for non-zero base before returning
>>> in the lo_sum/plus/minus case statement or could handle lo_sum
>>> explicitly, like find_base_value().
>>>       
>> I think my suggestion will accomplish the same thing -- and it makes logical
>> sense too -- if we can't determine something from the pointer reg, then we
>> look at other info, such as the symbol_ref within a lo_sum.
>>     
>
> Yes, it will accomplish the same thing for this particular case.
>
> Currently find_base_value and find_base_term differ in their handling
> of LO_SUM.  My question is whether this fix should maintain the difference
> in algorithms. 
I suspect the differences are unintentional and  one could easily argue 
that find_base_value's handling of LO_SUM is better since LO_SUM has 
pretty well defined semantics.  One could also argue that both functions 
shouldn't be so eager to return the results of the recursive call when 
the recursive call returns NULL.

>  Also, RTL alias analysis is very fragile and your suggestion
> may produce more accurate information in other situations, which could
> expose other latent bugs or unexpected behavior.
>   
Part of the intent was to get the more accurate info in the presence of 
registers marked with REG_POINTER.  While it could expose latent bugs, I 
think it's the right thing to do -- though we might look for a change 
with a smaller impact for the upcoming release since I think we're in 
stage3.

jeff