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Hi all,</div>
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I am working on a project about pointer analysis based on LLVM IR, and I not very familar with LLVM Development.</div>
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Now, I want to compare the original LLVM alias analysis pass with my tool. I use AAResultsWrapperPass to do this thing, just as below:</div>
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<span><span>
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<span><span style="color:#93a1a1;font-weight:bold">virtual</span><span> </span><span style="color:#93a1a1;font-weight:bold">bool</span><span> </span><span style="color:#268bd2">runOnFunction</span><span>(</span><span style="color:#cb4b16">Function</span><span> </span><span style="color:#93a1a1;font-weight:bold">&</span><span>F)</span></span>
<div><span> {</span></div>
<div><span> </span><span style="color:#cb4b16">AliasAnalysis</span><span> </span><span style="color:#859900">*</span><span style="color:#268bd2">AA</span><span> </span><span style="color:#859900">=</span><span> </span><span style="color:#859900">&</span><span style="color:#268bd2">getAnalysis</span><span><</span><span style="color:#cb4b16">AAResultsWrapperPass</span><span>>().</span><span style="color:#268bd2">getAAResults</span><span>();</span></div>
<div><span> </span><span style="color:#859900">for</span><span> (</span><span style="color:#93a1a1;font-weight:bold">auto</span><span> </span><span style="color:#859900">&</span><span style="color:#268bd2">B</span><span> : F)</span></div>
<div><span> {</span></div>
<div><span> </span><span style="color:#859900">for</span><span> (</span><span style="color:#93a1a1;font-weight:bold">auto</span><span> </span><span style="color:#859900">&</span><span style="color:#268bd2">I</span><span> :
</span><span style="color:#268bd2">B</span><span>)</span></div>
<div><span> {</span></div>
<div><span> </span><span style="color:#859900">if</span><span> (</span><span style="color:#93a1a1;font-weight:bold">auto</span><span> </span><span style="color:#859900">*</span><span style="color:#268bd2">call</span><span> </span><span style="color:#859900">=</span><span> </span><span style="color:#268bd2">dyn_cast</span><span><</span><span style="color:#cb4b16">CallInst</span><span>>(</span><span style="color:#859900">&</span><span style="color:#268bd2">I</span><span>))</span></div>
<div><span> {</span></div>
<div><span> </span><span style="color:#859900">if</span><span> (</span><span style="color:#268bd2">call</span><span>-></span><span style="color:#268bd2">getCalledFunction</span><span>()</span><span style="color:#859900">!=</span><span> </span><span style="color:#268bd2">NULL</span><span>)</span></div>
<div><span> {</span></div>
<div><span> </span><span style="color:#859900">if</span><span>(</span><span style="color:#268bd2">call</span><span>-></span><span style="color:#268bd2">getNumArgOperands</span><span>()
</span><span style="color:#859900">!=</span><span style="color:#d33682">2</span><span>)</span></div>
<div><span> </span><span style="color:#859900">continue</span><span>;</span></div>
<div><span> </span><span style="color:#cb4b16">Value</span><span> </span><span style="color:#859900">*</span><span style="color:#268bd2">V1</span><span> </span><span style="color:#859900">=</span><span> </span><span style="color:#268bd2">call</span><span>-></span><span style="color:#268bd2">getArgOperand</span><span>(</span><span style="color:#d33682">0</span><span>);</span></div>
<div><span> </span><span style="color:#cb4b16">Value</span><span> </span><span style="color:#859900">*</span><span style="color:#268bd2">V2</span><span> </span><span style="color:#859900">=</span><span> </span><span style="color:#268bd2">call</span><span>-></span><span style="color:#268bd2">getArgOperand</span><span>(</span><span style="color:#d33682">1</span><span>);</span></div>
<div> //Get LLVM alias analysi result</div>
<span><span> </span><span style="color:#cb4b16">AliasResult</span><span> </span><span style="color:#268bd2">aares</span><span> </span><span style="color:#859900">=</span><span> </span><span style="color:#268bd2">AA</span><span>-></span><span style="color:#268bd2">alias</span><span>(</span><span style="color:#268bd2">V1</span><span>,
</span><span style="color:#268bd2">V2</span><span>);</span></span></div>
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<span><span> .......................</span></span></div>
</span></span></div>
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I have doubt that wether the AliasResults are analysied by<a href="https://llvm.org/docs/AliasAnalysis.html#available-aliasanalysis-implementations" title="https://llvm.org/docs/AliasAnalysis.html#available-aliasanalysis-implementations"> all LLVM alias pass</a>,
such as -basic-aa, -globalsmodref-aa, -stens-aa. I find the implement of <span style="background-color:rgb(255, 255, 255);display:inline !important">AAResultsWrapperPass contains some code like below:</span></div>
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<span><span>void AAResultsWrapperPass::getAnalysisUsage(AnalysisUsage </span><span style="color:#859900">&</span><span style="color:#cb4b16">AU</span><span>) const {</span></span>
<div><span> </span><span style="color:#cb4b16">AU</span><span>.setPreservesAll();</span></div>
<div><span> </span><span style="color:#cb4b16">AU</span><span>.addRequiredTransitive</span><span style="color:#859900"><</span><span>BasicAAWrapperPass</span><span style="color:#859900">></span><span>();</span></div>
<div><span> </span><span style="color:#cb4b16">AU</span><span>.addRequiredTransitive</span><span style="color:#859900"><</span><span>TargetLibraryInfoWrapperPass</span><span style="color:#859900">></span><span>();</span></div>
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<div><span> </span><span style="color:#859900">//</span><span> We also need to mark
</span><span style="color:#268bd2">all</span><span> the alias analysis passes we will potentially</span></div>
<div><span> </span><span style="color:#859900">//</span><span> probe </span><span style="color:#859900">in</span><span> runOnFunction
</span><span style="color:#859900">as</span><span> used here to ensure the legacy
</span><span style="color:#859900">pass</span><span> manager</span></div>
<div><span> </span><span style="color:#859900">//</span><span> preserves them. This hard coding of lists of alias analyses
</span><span style="color:#859900">is</span><span> specific to</span></div>
<div><span> </span><span style="color:#859900">//</span><span> the legacy </span>
<span style="color:#859900">pass</span><span> manager.</span></div>
<div><span> </span><span style="color:#cb4b16">AU</span><span>.addUsedIfAvailable</span><span style="color:#859900"><</span><span>ScopedNoAliasAAWrapperPass</span><span style="color:#859900">></span><span>();</span></div>
<div><span> </span><span style="color:#cb4b16">AU</span><span>.addUsedIfAvailable</span><span style="color:#859900"><</span><span>TypeBasedAAWrapperPass</span><span style="color:#859900">></span><span>();</span></div>
<div><span> </span><span style="color:#cb4b16">AU</span><span>.addUsedIfAvailable</span><span style="color:#859900"><</span><span>objcarc::ObjCARCAAWrapperPass</span><span style="color:#859900">></span><span>();</span></div>
<div><span> </span><span style="color:#cb4b16">AU</span><span>.addUsedIfAvailable</span><span style="color:#859900"><</span><span>GlobalsAAWrapperPass</span><span style="color:#859900">></span><span>();</span></div>
<div><span> </span><span style="color:#cb4b16">AU</span><span>.addUsedIfAvailable</span><span style="color:#859900"><</span><span>SCEVAAWrapperPass</span><span style="color:#859900">></span><span>();</span></div>
<div><span> </span><span style="color:#cb4b16">AU</span><span>.addUsedIfAvailable</span><span style="color:#859900"><</span><span>CFLAndersAAWrapperPass</span><span style="color:#859900">></span><span>();</span></div>
<div><span> </span><span style="color:#cb4b16">AU</span><span>.addUsedIfAvailable</span><span style="color:#859900"><</span><span>CFLSteensAAWrapperPass</span><span style="color:#859900">></span><span>();</span></div>
<div><span> </span><span style="color:#cb4b16">AU</span><span>.addUsedIfAvailable</span><span style="color:#859900"><</span><span>ExternalAAWrapperPass</span><span style="color:#859900">></span><span>();</span></div>
<span><span>}</span></span></div>
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Does it mean the <span style="background-color:rgb(255, 255, 255);display:inline !important">AAResultsWrapperPass contains all the alias analysis pass result?</span></span></div>
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<span style="background-color:rgb(255, 255, 255);display:inline !important"><span style="background-color:rgb(255, 255, 255);display:inline !important">By the way, is there a better implement to get the LLVM alias analysis result. Thank you for telling me about
that.</span></span></div>
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<span style="background-color:rgb(255, 255, 255);display:inline !important"><span style="background-color:rgb(255, 255, 255);display:inline !important"><br>
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Thanks for you reading. Wishing you have a good day.</div>
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Regards,</div>
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Kunpeng</div>
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