[PING*3, Ada] Re: Handle data dependence relations with different bases

[Richard Sandiford <rdsandiford@googlemail.com>]

Ping*3

Richard Sandiford <richard.sandiford@linaro.org> writes:
> Ping*2
>
> Richard Sandiford <richard.sandiford@linaro.org> writes:
>> Ping for this Ada patch/question.
>>
>> Richard Sandiford <richard.sandiford@linaro.org> writes:
>>> Richard Biener <richard.guenther@gmail.com> writes:
>>>>>> How does this look?  Changes since v1:
>>>>>>
>>>>>> - Added access_fn_component_p to check for valid access function
>>>>>> components.
>>>>>>
>>>>>> - Added access_fn_components_comparable_p instead of using
>>>>>>   types_compatibloe_p directly.
>>>>>>
>>>>>> - Added more commentary.
>>>>>>
>>>>>> - Added local structures to represent the sequence, so that it's
>>>>>>   more obvious which variables are temporaries and which aren't.
>>>>>>
>>>>>> - Added the test above to vect-alias-check-3.c.
>>>>>>
>>>>>> Tested on aarch64-linux-gnu and x86_64-linux-gnu.
>>>>
>>>> This is ok.
>>>
>>> Thanks.  Just been retesting, and I think I must have forgotten
>>> to include Ada last time.  It turns out that the patch causes a dg-scan
>>> regression in gnat.dg/vect17.adb, because we now think that if the
>>> array RECORD_TYPEs *do* alias in:
>>>
>>>    procedure Add (X, Y : aliased Sarray; R : aliased out Sarray) is
>>>    begin
>>>       for I in Sarray'Range loop
>>>          R(I) := X(I) + Y(I);
>>>       end loop;
>>>    end;
>>>
>>> then the dependence distance must be zero.  Eric, does that hold true
>>> for Ada?  I.e. if X and R (or Y and R) alias, must it be the case that
>>> X(I) can only alias R(I) and not for example R(I-1) or R(I+1)?  Or are
>>> the arrays allowed to overlap by an arbitrary number of indices?
>>>
>>> If the assumption is correct, is the patch below OK?
>>>
>>> Thanks,
>>> Richard
>>>
>>>
>>> 2017-06-07  Richard Sandiford  <richard.sandiford@linaro.org>
>>>
>>> gcc/testsuite/
>>> 	* gnat.dg/vect17.ads (Sarray): Increase range to 1 .. 5.
>>> 	* gnat.dg/vect17.adb (Add): Create a dependence distance of 1
>>> 	when X = R or Y = R.
>>>
>>> Index: gcc/testsuite/gnat.dg/vect17.ads
>>> ===================================================================
>>> --- gcc/testsuite/gnat.dg/vect17.ads	2015-10-14 14:58:56.000000000 +0100
>>> +++ gcc/testsuite/gnat.dg/vect17.ads	2017-06-07 22:10:24.796368118 +0100
>>> @@ -1,6 +1,6 @@
>>>  package Vect17 is
>>>  
>>> -   type Sarray is array (1 .. 4) of Long_Float;
>>> +   type Sarray is array (1 .. 5) of Long_Float;
>>>     for Sarray'Alignment use 16;
>>>  
>>>     procedure Add (X, Y : aliased Sarray; R : aliased out Sarray);
>>> Index: gcc/testsuite/gnat.dg/vect17.adb
>>> ===================================================================
>>> --- gcc/testsuite/gnat.dg/vect17.adb	2015-10-14 14:58:56.000000000 +0100
>>> +++ gcc/testsuite/gnat.dg/vect17.adb	2017-06-07 22:10:24.796368118 +0100
>>> @@ -5,8 +5,9 @@ package body Vect17 is
>>>  
>>>     procedure Add (X, Y : aliased Sarray; R : aliased out Sarray) is
>>>     begin
>>> -      for I in Sarray'Range loop
>>> -         R(I) := X(I) + Y(I);
>>> +      R(1) := X(5) + Y(5);
>>> +      for I in 1 .. 4 loop
>>> +         R(I + 1) := X(I) + Y(I);
>>>        end loop;
>>>     end;
>>>