[Attributor] Track AA dependency using dependency graph

This patch added dependency graph to the attributor so that we can dump the dependencies between AAs more easily. We can also apply general graph algorithms to the graph, making it easier for us to create deep wrappers.

Reviewed By: jdoerfert

Differential Revision: https://reviews.llvm.org/D78861

llvm/include/llvm/Transforms/IPO/Attributor.h

@@ -97,8 +97,10 @@
 #ifndef LLVM_TRANSFORMS_IPO_ATTRIBUTOR_H
 #define LLVM_TRANSFORMS_IPO_ATTRIBUTOR_H
 
+#include "llvm/ADT/GraphTraits.h"
 #include "llvm/ADT/MapVector.h"
 #include "llvm/ADT/SCCIterator.h"
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SetVector.h"
 #include "llvm/Analysis/AliasAnalysis.h"
 #include "llvm/Analysis/AssumeBundleQueries.h"
@@ -116,10 +118,15 @@
 #include "llvm/IR/ConstantRange.h"
 #include "llvm/IR/PassManager.h"
 #include "llvm/Support/Allocator.h"
+#include "llvm/Support/Casting.h"
+#include "llvm/Support/DOTGraphTraits.h"
+#include "llvm/Support/GraphWriter.h"
 #include "llvm/Transforms/Utils/CallGraphUpdater.h"
 
 namespace llvm {
 
+struct AADepGraphNode;
+struct AADepGraph;
 struct Attributor;
 struct AbstractAttribute;
 struct InformationCache;
@@ -144,6 +151,70 @@ enum class DepClassTy {
 };
 ///}
 
+/// The data structure for the nodes of a dependency graph
+struct AADepGraphNode {
+public:
+  virtual ~AADepGraphNode(){};
+  using DepTy = PointerIntPair<AADepGraphNode *, 1>;
+
+protected:
+  /// Set of dependency graph nodes which this one depends on.
+  /// The bit encodes if it is optional.
+  TinyPtrVector<DepTy> Deps;
+
+  static AADepGraphNode *DepGetVal(DepTy &DT) { return DT.getPointer(); }
+  static AbstractAttribute *DepGetValAA(DepTy &DT) {
+    return cast<AbstractAttribute>(DT.getPointer());
+  }
+
+  operator AbstractAttribute *() { return cast<AbstractAttribute>(this); }
+
+public:
+  using iterator =
+      mapped_iterator<TinyPtrVector<DepTy>::iterator, decltype(&DepGetVal)>;
+  using aaiterator =
+      mapped_iterator<TinyPtrVector<DepTy>::iterator, decltype(&DepGetValAA)>;
+
+  aaiterator begin() { return aaiterator(Deps.begin(), &DepGetValAA); }
+  aaiterator end() { return aaiterator(Deps.end(), &DepGetValAA); }
+  iterator child_begin() { return iterator(Deps.begin(), &DepGetVal); }
+  iterator child_end() { return iterator(Deps.end(), &DepGetVal); }
+
+  virtual void print(raw_ostream &OS) const { OS << "AADepNode Impl\n"; }
+  TinyPtrVector<DepTy> &getDeps() { return Deps; }
+
+  friend struct Attributor;
+  friend struct AADepGraph;
+};
+
+struct AADepGraph {
+  AADepGraph() {}
+  ~AADepGraph() {}
+
+  using DepTy = AADepGraphNode::DepTy;
+  static AADepGraphNode *DepGetVal(DepTy &DT) { return DT.getPointer(); }
+  using iterator =
+      mapped_iterator<TinyPtrVector<DepTy>::iterator, decltype(&DepGetVal)>;
+
+  /// There is no root node for the dependency graph. But the SCCIterator
+  /// requires a single entry point, so we maintain a fake("synthetic") root
+  /// node that depends on every node.
+  AADepGraphNode SyntheticRoot;
+
+  AADepGraphNode *GetEntryNode() { return &SyntheticRoot; }
+
+  iterator begin() { return SyntheticRoot.child_begin(); }
+  iterator end() { return SyntheticRoot.child_end(); }
+
+  void viewGraph();
+
+  /// Dump graph to file
+  void dumpGraph();
+
+  /// Print dependency graph
+  void print();
+};
+
 /// Helper to describe and deal with positions in the LLVM-IR.
 ///
 /// A position in the IR is described by an anchor value and an "offset" that
@@ -1020,7 +1091,9 @@ struct Attributor {
     assert(!AAPtr && "Attribute already in map!");
     AAPtr = &AA;
 
-    AllAbstractAttributes.push_back(&AA);
+    DG.SyntheticRoot.Deps.push_back(
+        AADepGraphNode::DepTy(&AA, unsigned(DepClassTy::REQUIRED)));
+
     return AA;
   }
 
@@ -1382,12 +1455,6 @@ struct Attributor {
   /// See getOrCreateAAFor.
   bool shouldSeedAttribute(AbstractAttribute &AA);
 
-  /// The set of all abstract attributes.
-  ///{
-  using AAVector = SmallVector<AbstractAttribute *, 64>;
-  AAVector AllAbstractAttributes;
-  ///}
-
   /// A nested map to lookup abstract attributes based on the argument position
   /// on the outer level, and the addresses of the static member (AAType::ID) on
   /// the inner level.
@@ -1409,6 +1476,9 @@ struct Attributor {
   /// Helper to update an underlying call graph.
   CallGraphUpdater &CGUpdater;
 
+  /// Abstract Attribute dependency graph
+  AADepGraph DG;
+
   /// Set of functions for which we modified the content such that it might
   /// impact the call graph.
   SmallPtrSet<Function *, 8> CGModifiedFunctions;
@@ -1458,6 +1528,8 @@ struct Attributor {
   SmallPtrSet<BasicBlock *, 8> ToBeDeletedBlocks;
   SmallDenseSet<WeakVH, 8> ToBeDeletedInsts;
   ///}
+
+  friend AADepGraph;
 };
 
 /// An interface to query the internal state of an abstract attribute.
@@ -2030,14 +2102,22 @@ struct IRAttribute : public BaseType {
 ///       both directions will be added in the future.
 /// NOTE: The mechanics of adding a new "concrete" abstract attribute are
 ///       described in the file comment.
-struct AbstractAttribute : public IRPosition {
+struct AbstractAttribute : public IRPosition, public AADepGraphNode {
   using StateType = AbstractState;
 
   AbstractAttribute(const IRPosition &IRP) : IRPosition(IRP) {}
 
   /// Virtual destructor.
   virtual ~AbstractAttribute() {}
 
+  /// This function is used to identify if an \p DGN is of type
+  /// AbstractAttribute so that the dyn_cast and cast can use such information
+  /// to cast an AADepGraphNode to an AbstractAttribute.
+  ///
+  /// We eagerly return true here because all AADepGraphNodes except for the
+  /// Synthethis Node are of type AbstractAttribute
+  static bool classof(const AADepGraphNode *DGN) { return true; }
+
   /// Initialize the state with the information in the Attributor \p A.
   ///
   /// This function is called by the Attributor once all abstract attributes
@@ -2059,6 +2139,7 @@ struct AbstractAttribute : public IRPosition {
   /// Helper functions, for debug purposes only.
   ///{
   virtual void print(raw_ostream &OS) const;
+  virtual void printWithDeps(raw_ostream &OS) const;
   void dump() const { print(dbgs()); }
 
   /// This function should return the "summarized" assumed state as string.
@@ -2106,12 +2187,6 @@ struct AbstractAttribute : public IRPosition {
   ///
   /// \Return CHANGED if the internal state changed, otherwise UNCHANGED.
   virtual ChangeStatus updateImpl(Attributor &A) = 0;
-
-private:
-  /// Set of abstract attributes which were queried by this one. The bit encodes
-  /// if there is an optional of required dependence.
-  using DepTy = PointerIntPair<AbstractAttribute *, 1>;
-  TinyPtrVector<DepTy> Deps;
 };
 
 /// Forward declarations of output streams for debug purposes.