Instantiate fewer templates in PassManager::addPass()

[aeubanks]

Summary

We create many instantiations of PassManager::addPass() in
PassBuilder.cpp. vector::emplace_back() and make_unique() are both
templated and would have many instantiations based on the number of
times we instantiate addPass(). Now we directly construct the
unique_ptr with the type as the actual unique_ptr type in the vector we
are adding it to, so we only have one unique_ptr constructor
instantiation across all addPass() instantiations and only the
non-templated push_back().

This makes PassBuilder.cpp slightly faster to build.

[rnk]

lgtm

I think I understand what's going on: these push_back instantiations are all common instantiations. They are pushing back std::unique_ptr<ZZZConceptT> objects. The emplace_back calls were all unique instantiations depending on the exact pass pointer type.

llvm/include/llvm/IR/PassManager.h

public:
 
   template <typename PassT>
   std::enable_if_t<!std::is_same<PassT, PassManager>::value>
   addPass(PassT &&Pass) {
     using PassModelT =
         detail::PassModel<IRUnitT, PassT, PreservedAnalyses, AnalysisManagerT,
                           ExtraArgTs...>;
 
-    Passes.emplace_back(new PassModelT(std::forward<PassT>(Pass)));
+    // Do not use make_unique or emplace_back, they cause too many template
+    // instantiations, causing terrible compile times.
+    Passes.push_back(std::unique_ptr<PassConceptT>(
+        new PassModelT(std::forward<PassT>(Pass))));
   }
 
   /// When adding a pass manager pass that has the same type as this pass
   /// manager, simply move the passes over. This is because we don't have use
   /// cases rely on executing nested pass managers. Doing this could reduce
   /// implementation complexity and avoid potential invalidation issues that may
   /// happen with nested pass managers of the same type.
   template <typename PassT>
   std::enable_if_t<std::is_same<PassT, PassManager>::value>
   addPass(PassT &&Pass) {
     for (auto &P : Pass.Passes)
-      Passes.emplace_back(std::move(P));
+      Passes.push_back(std::move(P));
   }
 
   /// Returns if the pass manager contains any passes.
   bool isEmpty() const { return Passes.empty(); }
 
   static bool isRequired() { return true; }
 
 protected:

llvm/include/llvm/Transforms/Scalar/LoopPassManager.h

public:
   /// passes in the pass manager later.
   template <typename PassT>
   std::enable_if_t<is_detected<HasRunOnLoopT, PassT>::value>
   addPass(PassT &&Pass) {
     using LoopPassModelT =
         detail::PassModel<Loop, PassT, PreservedAnalyses, LoopAnalysisManager,
                           LoopStandardAnalysisResults &, LPMUpdater &>;
     IsLoopNestPass.push_back(false);
-    LoopPasses.emplace_back(new LoopPassModelT(std::forward<PassT>(Pass)));
+    // Do not use make_unique or emplace_back, they cause too many template
+    // instantiations, causing terrible compile times.
+    LoopPasses.push_back(std::unique_ptr<LoopPassConceptT>(
+        new LoopPassModelT(std::forward<PassT>(Pass))));
   }
 
   template <typename PassT>
   std::enable_if_t<!is_detected<HasRunOnLoopT, PassT>::value>
   addPass(PassT &&Pass) {
     using LoopNestPassModelT =
         detail::PassModel<LoopNest, PassT, PreservedAnalyses,
                           LoopAnalysisManager, LoopStandardAnalysisResults &,
                           LPMUpdater &>;
     IsLoopNestPass.push_back(true);
-    LoopNestPasses.emplace_back(
-        new LoopNestPassModelT(std::forward<PassT>(Pass)));
+    LoopNestPasses.push_back(std::unique_ptr<LoopNestPassConceptT>(
+        new LoopNestPassModelT(std::forward<PassT>(Pass))));
   }
 
   // Specializations of `addPass` for `RepeatedPass`. These are necessary since
   // `RepeatedPass` has a templated `run` method that will result in incorrect
   // detection of `HasRunOnLoopT`.
   template <typename PassT>
   std::enable_if_t<is_detected<HasRunOnLoopT, PassT>::value>
   addPass(RepeatedPass<PassT> &&Pass) {
     using RepeatedLoopPassModelT =
         detail::PassModel<Loop, RepeatedPass<PassT>, PreservedAnalyses,
                           LoopAnalysisManager, LoopStandardAnalysisResults &,
                           LPMUpdater &>;
     IsLoopNestPass.push_back(false);
-    LoopPasses.emplace_back(new RepeatedLoopPassModelT(std::move(Pass)));
+    LoopPasses.push_back(std::unique_ptr<LoopPassConceptT>(
+        new RepeatedLoopPassModelT(std::move(Pass))));
   }
 
   template <typename PassT>
   std::enable_if_t<!is_detected<HasRunOnLoopT, PassT>::value>
   addPass(RepeatedPass<PassT> &&Pass) {
     using RepeatedLoopNestPassModelT =
         detail::PassModel<LoopNest, RepeatedPass<PassT>, PreservedAnalyses,
                           LoopAnalysisManager, LoopStandardAnalysisResults &,
                           LPMUpdater &>;
     IsLoopNestPass.push_back(true);
-    LoopNestPasses.emplace_back(
-        new RepeatedLoopNestPassModelT(std::move(Pass)));
+    LoopNestPasses.push_back(std::unique_ptr<LoopNestPassConceptT>(
+        new RepeatedLoopNestPassModelT(std::move(Pass))));
   }
 
   bool isEmpty() const { return LoopPasses.empty() && LoopNestPasses.empty(); }
 
   static bool isRequired() { return true; }
 
   size_t getNumLoopPasses() const { return LoopPasses.size(); }
   size_t getNumLoopNestPasses() const { return LoopNestPasses.size(); }