[PATCH] D119880: [FuncSpec] Support function specialization across multiple arguments.

[Alexandros Lamprineas via Phabricator via llvm-commits]

labrinea added inline comments.


================
Comment at: llvm/lib/Transforms/IPO/FunctionSpecialization.cpp:352
+      auto Iter = Sorted.begin();
+      while ((size_t)std::distance(Iter, Sorted.end()) > Sorted.size()/2) {
+        CallBase *Call = Iter->second;
----------------
SjoerdMeijer wrote:
> ... and then we iterate over half the elements in the map here.
> 
> Does the sorting rely on the keys of the map? Not sure I find that the cleanest way of doing it, think it could be a one liner and doing a llvm::stable_sort?
The std::map quarantees ordering of elements based on key (which is the Gain here). Stable sort requires a container with random access iteration. SpecializationMap is SmallMapVector, which might have random access, but Map is SmallDenseMap (hash table). On top of that we have nested structures (a map containing maps) so we can't sort everything all together with stable sort, right?


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  https://reviews.llvm.org/D119880/new/

https://reviews.llvm.org/D119880