[polly] r277263 - Extend the jscop interface to allow the user to declare new arrays and to reference these arrays from access expressions

[Michael Kruse via llvm-commits]

2016-08-11 17:21 GMT+02:00 Roman Gareev <gareevroman at gmail.com>:
> Hi Michael,
>
> thanks for the comments!
>
> 2016-08-10 20:27 GMT+05:00 Michael Kruse <llvm-commits at meinersbur.de>:
>> 2016-07-30 11:25 GMT+02:00 Roman Gareev via llvm-commits
>> <llvm-commits at lists.llvm.org>:
>>
>>> --- polly/trunk/test/Isl/CodeGen/MemAccess/create_arrays.ll (added)
>>> +; CHECK:    Arrays {
>>> +; CHECK:        double E[*][270336][200000]; // Element size 8
>>
>>> --- polly/trunk/test/Isl/CodeGen/MemAccess/create_arrays___%bb9---%bb26.jscop (added)
>>> +      {
>>> +         "name" : "E",
>>> +         "sizes" : [ "270336", "200000" ],
>>> +         "type" : "double"
>>> +      },
>>
>>> +   "statements" : [
>>> +      {
>>> +         "accesses" : [
>>> +            {
>>> +               "kind" : "read",
>>> +               "relation" : "{ Stmt_bb12[i0, i1, i2] -> E[i2, i0] }"
>>> +            },
>>> +            {
>>
>> Hi just noticed some problem here. The array "E" is generated with
>> three dimensions (with the first one unsized), but the array access is
>> changed to only a two-dimensional one.
>
> Сould we change the array access to three-dimensional one (e.g. "{
> Stmt_bb12[i0, i1, i2] -> E[0, i2, i0] }")?

Yes, but is it what you intended? The jscop contains sizes of just two
dimensions. We do not need the size of the outermost dimension in most
cases, but if you are going to allocate memory for such newly created
arrays, that size is needed as well.


>> The array's isl_id is named "E" (not "MemRef_E"). We will get a name
>> clash when introducing an array named "MemRef_A", clashing with the
>> already existing array A.
>
> Could you explain why we get a name clash in this case? I thought that
> if there is already an array named "A" and we introduce an array named
> "MemRef_A", a new array named "MemRef_A" will be created.

Assume you have an existing scop that has an array called A. Each
access will be named "MemRef_A".

Let's create a new array "A" using the JScop (Will there be a clash if
an array with that name already exists?). To add a reference to it, it
seems that one has to call the reference also "A". Eg.
 "{ Stmt_bb12[i0, i1, i2] -> A[i2, i0] }"

Let's create a new array named "MemRef_A". Then we set an array accesses to
 "{ Stmt_bb12[i0, i1, i2] -> MemRef_A[i2, i0] }"
Does it now
1) refer to the previously existing array "A"
2) refer to the newly created array "MemRef_A"
????


> Do you mean that it's better to add prefix "MemRef_" to names of all
> arrays added in a JSCoP?

Yes.


Michael