[llvm] r228988 - Prevent division by 0.

[Michael Zolotukhin]

Committed in r228995.

Michael

> On Feb 12, 2015, at 4:24 PM, David Majnemer <david.majnemer at gmail.com> wrote:
> 
> Testcase?
> 
> On Thu, Feb 12, 2015 at 4:17 PM, Michael Zolotukhin <mzolotukhin at apple.com <mailto:mzolotukhin at apple.com>> wrote:
> Author: mzolotukhin
> Date: Thu Feb 12 18:17:03 2015
> New Revision: 228988
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=228988&view=rev <http://llvm.org/viewvc/llvm-project?rev=228988&view=rev>
> Log:
> Prevent division by 0.
> 
> When we try to estimate number of potentially removed instructions in
> loop unroller, we analyze first N iterations and then scale the
> computed number by TripCount/N. We should bail out early if N is 0.
> 
> Modified:
>     llvm/trunk/lib/Transforms/Scalar/LoopUnrollPass.cpp
> 
> Modified: llvm/trunk/lib/Transforms/Scalar/LoopUnrollPass.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopUnrollPass.cpp?rev=228988&r1=228987&r2=228988&view=diff <http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/LoopUnrollPass.cpp?rev=228988&r1=228987&r2=228988&view=diff>
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Scalar/LoopUnrollPass.cpp (original)
> +++ llvm/trunk/lib/Transforms/Scalar/LoopUnrollPass.cpp Thu Feb 12 18:17:03 2015
> @@ -548,7 +548,7 @@ static unsigned
>  approximateNumberOfOptimizedInstructions(const Loop *L, ScalarEvolution &SE,
>                                           unsigned TripCount,
>                                           const TargetTransformInfo &TTI) {
> -  if (!TripCount)
> +  if (!TripCount || !UnrollMaxIterationsCountToAnalyze)
>      return 0;
> 
>    UnrollAnalyzer UA(L, TripCount, SE, TTI);
> 
> 
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