[llvm] r237978 - MergedLoadStoreMotion preserves MemoryDependenceAnalysis, it does not require it.

[Quentin Colombet]

Hi Daniel,


> On May 21, 2015, at 5:13 PM, Daniel Berlin <dberlin at dberlin.org> wrote:
> 
> Author: dannyb
> Date: Thu May 21 19:13:05 2015
> New Revision: 237978
> 
> URL: http://llvm.org/viewvc/llvm-project?rev=237978&view=rev
> Log:
> MergedLoadStoreMotion preserves MemoryDependenceAnalysis, it does not require it.
> (It already was coded assuming it can sometimes be null, so no other changes are necessary)

What happens when the pass has the MemoryDependenceAnalysis?
Does it perform better?

If so, are we sure this commit does not regress anything?

Thanks,
-Quentin

> 
> Modified:
>    llvm/trunk/lib/Transforms/Scalar/MergedLoadStoreMotion.cpp
> 
> Modified: llvm/trunk/lib/Transforms/Scalar/MergedLoadStoreMotion.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Transforms/Scalar/MergedLoadStoreMotion.cpp?rev=237978&r1=237977&r2=237978&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Transforms/Scalar/MergedLoadStoreMotion.cpp (original)
> +++ llvm/trunk/lib/Transforms/Scalar/MergedLoadStoreMotion.cpp Thu May 21 19:13:05 2015
> @@ -117,8 +117,8 @@ private:
>   // This transformation requires dominator postdominator info
>   void getAnalysisUsage(AnalysisUsage &AU) const override {
>     AU.addRequired<TargetLibraryInfoWrapperPass>();
> -    AU.addRequired<MemoryDependenceAnalysis>();
>     AU.addRequired<AliasAnalysis>();
> +    AU.addPreserved<MemoryDependenceAnalysis>();
>     AU.addPreserved<AliasAnalysis>();
>   }
> 
> @@ -580,7 +580,7 @@ bool MergedLoadStoreMotion::mergeStores(
> /// \brief Run the transformation for each function
> ///
> bool MergedLoadStoreMotion::runOnFunction(Function &F) {
> -  MD = &getAnalysis<MemoryDependenceAnalysis>();
> +  MD = getAnalysisIfAvailable<MemoryDependenceAnalysis>();
>   AA = &getAnalysis<AliasAnalysis>();
> 
>   bool Changed = false;
> 
> 
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