[PATCH][Polly] Re: 0001-Fixup-assert-fails-caused-by-incorrect-LoopInfo-update

[Star Tan]

At 2013-09-02 16:34:24,"Tobias Grosser" <tobias at grosser.es> wrote:

>On 09/01/2013 08:01 PM, Star Tan wrote:
>> At 2013-08-25 02:10:02,"Tobias Grosser" <tobias at grosser.es> wrote:
>>> On 08/23/2013 08:25 AM, Star Tan wrote:
>>>>   Hi all,
>>>>
>>>>
>>>>   I have attached a patch file to fix up the CodeGen assert fail, which is also reported in a recent bug  http://llvm.org/bugs/show_bug.cgi?id=16944
>>>
>>> Hi Star Tan,
>>>
>>> thanks for looking into this bug. The patch itself looks good and the
>>> testcase is nicely small.
>>>
>>> However, when running the test with 'opt' I get:
>>>
>>> PHINode should have one entry for each predecessor of its parent basic
>>> block!
>>>     %indvar = phi i64 [ 0, %entry ], [ %0, %for.inc ]
>>>
>>> So the IR in the test case itself is already incorrect.
>>
>> Sorry for the stupid mistake. I have attached a new patch file!
>
>Great. This one looks correct.
>
>>Also, I am a little unhappy with the fact that we need to run
>>
>>> -polly-opt-isl to reproduce this bug. I would very much prefer to find a
>>> test case that only runs 'opt %loadPolly -polly-codegen  < %s'. This ensures
>>> that changes in -polly-opt-isl can not accidentally stop this test case
>>> from testing the code path you fixed in this patch.
>>
>> Yes, you are right. But it seems difficult to construct a testcase that will show this bug using only "opt %loadPolly -polly-codegen".
>> Our testcase fails with the following command:
>> $ opt %loadPolly -basicaa -polly-opt-isl -polly-codegen test.ll
>>
>> but it works well with the following commands:
>> $ opt %loadPolly -basicaa -polly-opt-isl -S -o test_1.ll test.ll
>> $ opt %loadPolly -basicaa -polly-codegen test_1.ll
>>
>> The key of producing the bug is to construct a stmt_guard statment, so it will call codegen((clast_guard *)). Preliminary investigation shows that the  'stmt_guard' occurs only if we run opt-isl before codegen.  Sorry I have not found such a testcase by now.
>
>I just looked into this and I could also not find a trivial test case 
>that yields a guard statement. However, you can use
>
>opt -polly-opt-isl -polly-export-jscop
>
>to get a jscop file and the use opt -polly-import-jscop to read in this
>jscop file instead of running polly-opt-isl. This at least removes the 
>dependency on the isl scheduler.
>
>test/Cloog/CodeGen/simple_vec_stride_one.ll
>
>The above test case should give an example how to use the import/export 
>of jscops.

Thank you so much for your very helpful suggestion.  Yes, Jscop is a very help tool~
I have attached a new patch file that reads Jscop file to avoid dependence to polly-opt-isl.
Best,
Star Tan
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