llvm dev - Mar 2012 - [LLVMdev] How to unroll loop with non-constant boundary

Hi Benjamin,
> LLVM misses this optimization because ScalarEvolution's
ComputeExitLimitFromICmp doesn't handle signed<= (SLE) and thus can't
compute the number of times the loop is executed. I wonder if there's a
reason for this, it seems like something simple to add.
instsimplify could also be enhanced to clean it up in this particular case, but
it would be better to make scev smarter.

Ciao, Duncan.

On 27.02.2012, at 20:17, Duncan Sands wrote:
> Hi Benjamin,
> 
>> LLVM misses this optimization because ScalarEvolution's
ComputeExitLimitFromICmp doesn't handle signed<= (SLE) and thus can't
compute the number of times the loop is executed. I wonder if there's a
reason for this, it seems like something simple to add.
> 
> instsimplify could also be enhanced to clean it up in this particular case,
but
> it would be better to make scev smarter.
I filed http://llvm.org/bugs/show_bug.cgi?id=12110 to track this.

- Ben
> Ciao, Duncan.
> _______________________________________________
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> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev

Hi guys, 
I attached the modified patch that handles cases with low==end and stride!=1.
Please find it for review.

-Stepan

28.02.2012, 17:41, "Benjamin Kramer" <benny.kra at
googlemail.com>:
> On 27.02.2012, at 20:17, Duncan Sands wrote:
>
>>  Hi Benjamin,
>>>  LLVM misses this optimization because ScalarEvolution's
ComputeExitLimitFromICmp doesn't handle signed<= (SLE) and thus can't
compute the number of times the loop is executed. I wonder if there's a
reason for this, it seems like something simple to add.
>>  instsimplify could also be enhanced to clean it up in this particular
case, but
>>  it would be better to make scev smarter.
>
> I filed http://llvm.org/bugs/show_bug.cgi?id=12110 to track this.
>
> - Ben
>
>>  Ciao, Duncan.
>>  _______________________________________________
>>  LLVM Developers mailing list
>>  LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
>>  http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
> _______________________________________________
> LLVM Developers mailing list
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> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
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