[mlir] [dataflow] Refactoring the definition of program points in dat…

…a flow analysis (#105656)

This patch distinguishes between program points and lattice anchors in
data flow analysis, where lattice anchors represent locations where a
lattice can be attached, while program points denote points in program
execution.

Related discussions:
https://discourse.llvm.org/t/rfc-unify-the-semantics-of-program-points/80671/8

mlir/include/mlir/Analysis/DataFlow/DeadCodeAnalysis.h

@@ -35,21 +35,21 @@ namespace dataflow {
 //===----------------------------------------------------------------------===//
 
 /// This is a simple analysis state that represents whether the associated
-/// program point (either a block or a control-flow edge) is live.
+/// lattice anchor (either a block or a control-flow edge) is live.
 class Executable : public AnalysisState {
 public:
   using AnalysisState::AnalysisState;
 
-  /// Set the state of the program point to live.
+  /// Set the state of the lattice anchor to live.
   ChangeResult setToLive();
 
-  /// Get whether the program point is live.
+  /// Get whether the lattice anchor is live.
   bool isLive() const { return live; }
 
   /// Print the liveness.
   void print(raw_ostream &os) const override;
 
-  /// When the state of the program point is changed to live, re-invoke
+  /// When the state of the lattice anchor is changed to live, re-invoke
   /// subscribed analyses on the operations in the block and on the block
   /// itself.
   void onUpdate(DataFlowSolver *solver) const override;
@@ -60,8 +60,8 @@ class Executable : public AnalysisState {
   }
 
 private:
-  /// Whether the program point is live. Optimistically assume that the program
-  /// point is dead.
+  /// Whether the lattice anchor is live. Optimistically assume that the lattice
+  /// anchor is dead.
   bool live = false;
 
   /// A set of analyses that should be updated when this state changes.
@@ -140,10 +140,10 @@ class PredecessorState : public AnalysisState {
 // CFGEdge
 //===----------------------------------------------------------------------===//
 
-/// This program point represents a control-flow edge between a block and one
+/// This lattice anchor represents a control-flow edge between a block and one
 /// of its successors.
 class CFGEdge
-    : public GenericProgramPointBase<CFGEdge, std::pair<Block *, Block *>> {
+    : public GenericLatticeAnchorBase<CFGEdge, std::pair<Block *, Block *>> {
 public:
   using Base::Base;
 

mlir/include/mlir/Analysis/DataFlow/DenseAnalysis.h

@@ -91,15 +91,16 @@ class AbstractDenseForwardDataFlowAnalysis : public DataFlowAnalysis {
                                            const AbstractDenseLattice &before,
                                            AbstractDenseLattice *after) = 0;
 
-  /// Get the dense lattice after the execution of the given program point.
-  virtual AbstractDenseLattice *getLattice(ProgramPoint point) = 0;
+  /// Get the dense lattice after the execution of the given lattice anchor.
+  virtual AbstractDenseLattice *getLattice(LatticeAnchor anchor) = 0;
 
   /// Get the dense lattice after the execution of the given program point and
-  /// add it as a dependency to a program point. That is, every time the lattice
-  /// after point is updated, the dependent program point must be visited, and
-  /// the newly triggered visit might update the lattice after dependent.
+  /// add it as a dependency to a lattice anchor. That is, every time the
+  /// lattice after anchor is updated, the dependent program point must be
+  /// visited, and the newly triggered visit might update the lattice after
+  /// dependent.
   const AbstractDenseLattice *getLatticeFor(ProgramPoint dependent,
-                                            ProgramPoint point);
+                                            LatticeAnchor anchor);
 
   /// Set the dense lattice at control flow entry point and propagate an update
   /// if it changed.
@@ -249,9 +250,9 @@ class DenseForwardDataFlowAnalysis
   }
 
 protected:
-  /// Get the dense lattice after this program point.
-  LatticeT *getLattice(ProgramPoint point) override {
-    return getOrCreate<LatticeT>(point);
+  /// Get the dense lattice on this lattice anchor.
+  LatticeT *getLattice(LatticeAnchor anchor) override {
+    return getOrCreate<LatticeT>(anchor);
   }
 
   /// Set the dense lattice at control flow entry point and propagate an update
@@ -331,16 +332,16 @@ class AbstractDenseBackwardDataFlowAnalysis : public DataFlowAnalysis {
                                            const AbstractDenseLattice &after,
                                            AbstractDenseLattice *before) = 0;
 
-  /// Get the dense lattice before the execution of the program point. That is,
+  /// Get the dense lattice before the execution of the lattice anchor. That is,
   /// before the execution of the given operation or after the execution of the
   /// block.
-  virtual AbstractDenseLattice *getLattice(ProgramPoint point) = 0;
+  virtual AbstractDenseLattice *getLattice(LatticeAnchor anchor) = 0;
 
-  /// Get the dense lattice before the execution of the program point `point`
-  /// and declare that the `dependent` program point must be updated every time
-  /// `point` is.
+  /// Get the dense lattice before the execution of the program point in
+  /// `anchor` and declare that the `dependent` program point must be updated
+  /// every time `point` is.
   const AbstractDenseLattice *getLatticeFor(ProgramPoint dependent,
-                                            ProgramPoint point);
+                                            LatticeAnchor anchor);
 
   /// Set the dense lattice before at the control flow exit point and propagate
   /// the update if it changed.
@@ -500,9 +501,9 @@ class DenseBackwardDataFlowAnalysis
   }
 
 protected:
-  /// Get the dense lattice at the given program point.
-  LatticeT *getLattice(ProgramPoint point) override {
-    return getOrCreate<LatticeT>(point);
+  /// Get the dense lattice at the given lattice anchor.
+  LatticeT *getLattice(LatticeAnchor anchor) override {
+    return getOrCreate<LatticeT>(anchor);
   }
 
   /// Set the dense lattice at control flow exit point (after the terminator)

mlir/include/mlir/Analysis/DataFlow/IntegerRangeAnalysis.h

@@ -50,7 +50,7 @@ class IntegerRangeAnalysis
   /// At an entry point, we cannot reason about interger value ranges.
   void setToEntryState(IntegerValueRangeLattice *lattice) override {
     propagateIfChanged(lattice, lattice->join(IntegerValueRange::getMaxRange(
-                                    lattice->getPoint())));
+                                    lattice->getAnchor())));
   }
 
   /// Visit an operation. Invoke the transfer function on each operation that

mlir/include/mlir/Analysis/DataFlow/SparseAnalysis.h

@@ -36,8 +36,8 @@ class AbstractSparseLattice : public AnalysisState {
   /// Lattices can only be created for values.
   AbstractSparseLattice(Value value) : AnalysisState(value) {}
 
-  /// Return the program point this lattice is located at.
-  Value getPoint() const { return AnalysisState::getPoint().get<Value>(); }
+  /// Return the value this lattice is located at.
+  Value getAnchor() const { return AnalysisState::getAnchor().get<Value>(); }
 
   /// Join the information contained in 'rhs' into this lattice. Returns
   /// if the value of the lattice changed.
@@ -86,8 +86,8 @@ class Lattice : public AbstractSparseLattice {
 public:
   using AbstractSparseLattice::AbstractSparseLattice;
 
-  /// Return the program point this lattice is located at.
-  Value getPoint() const { return point.get<Value>(); }
+  /// Return the value this lattice is located at.
+  Value getAnchor() const { return anchor.get<Value>(); }
 
   /// Return the value held by this lattice. This requires that the value is
   /// initialized.