[PATCH] D36850: [ThinLTO] Add function attribute propagation

[Charles Saternos via Phabricator via llvm-commits]

ncharlie added inline comments.


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Comment at: lib/LTO/LTO.cpp:1051
 
+  propagateFunctionAttrs(ThinLTO.CombinedIndex);
   StringMap<FunctionImporter::ImportMapTy> ImportLists(
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I tried putting this in ThinLTOCodeGenerator::linkCombinedIndex(), but it seems like that function is only called by the thin-lto utility - it's never run by clang?


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Comment at: lib/Transforms/IPO/FunctionImport.cpp:423
+void llvm::propagateFunctionAttrs(ModuleSummaryIndex &Index) {
+  auto addReadAttrs = [](std::vector<FunctionSummary *> &SCCNodes) {
+    bool ReadsMemory = false;
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I just realized this isn't going to ever change any attrs.
 
I based it on the FunctionAttrs pass which does alias analysis first: http://llvm-cs.pcc.me.uk/lib/Transforms/IPO/FunctionAttrs.cpp#185

That can't be done here, since at this point we can only access summaries.

Maybe I need to include a flag in the function summary that marks if the function definitely writes memory and then propagate memory access information to any nodes that are unknown?


https://reviews.llvm.org/D36850