[llvm] r302058 - [RuntimeLoopUnroller] Add assert that we dont unroll non-rotated loops

[Davide Italiano via llvm-commits]

On Wed, May 3, 2017 at 12:19 PM, Craig Topper via llvm-commits
<llvm-commits at lists.llvm.org> wrote:
> The variable LatchBR is unused in Release builds and throws a warning.
>
> ~Craig
>

Adding (void)LatchBr; immediately after the use should fix the warning
as the variable is only used inside the assert.
This is how we fix these cases, FWIW.

> On Wed, May 3, 2017 at 10:44 AM, Anna Thomas via llvm-commits
> <llvm-commits at lists.llvm.org> wrote:
>>
>> Author: annat
>> Date: Wed May  3 12:43:59 2017
>> New Revision: 302058
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=302058&view=rev
>> Log:
>> [RuntimeLoopUnroller] Add assert that we dont unroll non-rotated loops
>>
>> Summary:
>> Cloning basic blocks in the loop for runtime loop unroller depends on loop
>> being
>> in rotated form (i.e. loop latch target is the exit block).
>> Assert that this is true, so that callers of runtime loop unroller pass in
>> canonical loops.
>> The single caller of this function has that check recently added:
>> https://reviews.llvm.org/rL301239
>>
>> Reviewers: davide
>>
>> Subscribers: llvm-commits
>>
>> Differential Revision: https://reviews.llvm.org/D32801
>>
>> Modified:
>>     llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp
>>
>> Modified: llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp?rev=302058&r1=302057&r2=302058&view=diff
>>
>> ==============================================================================
>> --- llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp (original)
>> +++ llvm/trunk/lib/Transforms/Utils/LoopUnrollRuntime.cpp Wed May  3
>> 12:43:59 2017
>> @@ -512,6 +512,13 @@ bool llvm::UnrollRuntimeLoopRemainder(Lo
>>
>>    BasicBlock *Latch = L->getLoopLatch();
>>
>> +  // Cloning the loop basic blocks (`CloneLoopBlocks`) requires that one
>> of the
>> +  // targets of the Latch be the single exit block out of the loop. This
>> needs
>> +  // to be guaranteed by the callers of UnrollRuntimeLoopRemainder.
>> +  BranchInst *LatchBR = cast<BranchInst>(Latch->getTerminator());
>> +  assert(LatchBR->getSuccessor(0) == Exit ||
>> +         LatchBR->getSuccessor(1) == Exit && "loop latch successor should
>> be "
>> +                                             "exit block!");
>>    // Loop structure is the following:
>>    //
>>    // PreHeader
>>
>>
>> _______________________________________________
>> llvm-commits mailing list
>> llvm-commits at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>
>
>
> _______________________________________________
> llvm-commits mailing list
> llvm-commits at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-commits
>

-- 
Davide

"There are no solved problems; there are only problems that are more
or less solved" -- Henri Poincare