Add a new SparsePropagation analysis utility, which allows you to do

SCCP like sparse lattice analysis with relative ease.  Just pick your
lattice function and implement the transfer function and you're good.
Just make sure you don't break monotonicity ;-)


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@50961 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 178 insertions, 0 deletions

diff --git a/include/llvm/Analysis/SparsePropagation.h b/include/llvm/Analysis/SparsePropagation.h
new file mode 100644
index 0000000000..cad18d79bf
--- /dev/null
+++ b/include/llvm/Analysis/SparsePropagation.h
@@ -0,0 +1,178 @@
+//===- SparsePropagation.h - Sparse Conditional Property Propagation ------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file implements an abstract sparse conditional propagation algorithm,
+// modeled after SCCP, but with a customizable lattice function.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ANALYSIS_SPARSE_PROPAGATION_H
+#define LLVM_ANALYSIS_SPARSE_PROPAGATION_H
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/SmallVector.h"
+#include <vector>
+#include <set>
+
+namespace llvm {
+  class Value;
+  class Constant;
+  class Instruction;
+  class PHINode;
+  class TerminatorInst;
+  class BasicBlock;
+  class Function;
+  class SparseSolver;
+  
+/// AbstractLatticeFunction - This class is implemented by the dataflow instance
+/// to specify what the lattice values are and what how they handle merges etc.
+/// This gives the client the power to compute lattice values from instructions,
+/// constants, etc.  The requirement is that lattice values must all fit into
+/// a void*.  If a void* is not sufficient, the implementation should use this
+/// pointer to be a pointer into a uniquing set or something.
+///
+class AbstractLatticeFunction {
+public:
+  typedef void *LatticeVal;
+private:
+  LatticeVal UndefVal, OverdefinedVal, UntrackedVal;
+public:
+  AbstractLatticeFunction(LatticeVal undefVal, LatticeVal overdefinedVal,
+                          LatticeVal untrackedVal) {
+    UndefVal = undefVal;
+    OverdefinedVal = overdefinedVal;
+    UntrackedVal = untrackedVal;
+  }
+  virtual ~AbstractLatticeFunction();
+  
+  LatticeVal getUndefVal()       const { return UndefVal; }
+  LatticeVal getOverdefinedVal() const { return OverdefinedVal; }
+  LatticeVal getUntrackedVal()   const { return UntrackedVal; }
+  
+  /// IsUntrackedValue - If the specified Value is something that is obviously
+  /// uninteresting to the analysis (and would always return UntrackedVal),
+  /// this function can return true to avoid pointless work.
+  virtual bool IsUntrackedValue(Value *V) {
+    return false;
+  }
+  
+  /// ComputeConstant - Given a constant value, compute and return a lattice
+  /// value corresponding to the specified constant.
+  virtual LatticeVal ComputeConstant(Constant *C) {
+    return getOverdefinedVal(); // always safe
+  }
+  
+  /// GetConstant - If the specified lattice value is representable as an LLVM
+  /// constant value, return it.  Otherwise return null.  The returned value
+  /// must be in the same LLVM type as Val.
+  virtual Constant *GetConstant(LatticeVal LV, Value *Val, SparseSolver &SS) {
+    return 0;
+  }
+  
+  /// MergeValues - Compute and return the merge of the two specified lattice
+  /// values.  Merging should only move one direction down the lattice to
+  /// guarantee convergence (toward overdefined).
+  virtual LatticeVal MergeValues(LatticeVal X, LatticeVal Y) {
+    return getOverdefinedVal(); // always safe, never useful.
+  }
+  
+  /// ComputeInstructionState - Given an instruction and a vector of its operand
+  /// values, compute the result value of the instruction.
+  virtual LatticeVal ComputeInstructionState(Instruction &I, SparseSolver &SS) {
+    return getOverdefinedVal(); // always safe, never useful.
+  }
+  
+  /// PrintValue - Render the specified lattice value to the specified stream.
+  virtual void PrintValue(LatticeVal V, std::ostream &OS);
+};
+
+  
+/// SparseSolver - This class is a general purpose solver for Sparse Conditional
+/// Propagation with a programmable lattice function.
+///
+class SparseSolver {
+  typedef AbstractLatticeFunction::LatticeVal LatticeVal;
+  
+  /// LatticeFunc - This is the object that knows the lattice and how to do
+  /// compute transfer functions.
+  AbstractLatticeFunction *LatticeFunc;
+  
+  DenseMap<Value*, LatticeVal> ValueState;  // The state each value is in.
+  SmallPtrSet<BasicBlock*, 16> BBExecutable;   // The bbs that are executable.
+  
+  std::vector<Instruction*> InstWorkList;   // Worklist of insts to process.
+  
+  std::vector<BasicBlock*> BBWorkList;  // The BasicBlock work list
+  
+  /// KnownFeasibleEdges - Entries in this set are edges which have already had
+  /// PHI nodes retriggered.
+  typedef std::pair<BasicBlock*,BasicBlock*> Edge;
+  std::set<Edge> KnownFeasibleEdges;
+  
+  SparseSolver(const SparseSolver&);    // DO NOT IMPLEMENT
+  void operator=(const SparseSolver&);  // DO NOT IMPLEMENT
+public:
+  SparseSolver(AbstractLatticeFunction *Lattice) : LatticeFunc(Lattice) {}
+  ~SparseSolver() {
+    delete LatticeFunc;
+  }
+  
+  /// Solve - Solve for constants and executable blocks.
+  ///
+  void Solve(Function &F);
+  
+  void Print(Function &F, std::ostream &OS);
+
+  /// getLatticeState - Return the LatticeVal object that corresponds to the
+  /// value.  If an value is not in the map, it is returned as untracked,
+  /// unlike the getOrInitValueState method.
+  LatticeVal getLatticeState(Value *V) const {
+    DenseMap<Value*, LatticeVal>::iterator I = ValueState.find(V);
+    return I != ValueState.end() ? I->second : LatticeFunc->getUntrackedVal();
+  }
+  
+  /// getOrInitValueState - Return the LatticeVal object that corresponds to the
+  /// value, initializing the value's state if it hasn't been entered into the
+  /// map yet.   This function is necessary because not all values should start
+  /// out in the underdefined state... Arguments should be overdefined, and
+  /// constants should be marked as constants.
+  ///
+  LatticeVal getOrInitValueState(Value *V);
+  
+private:
+  /// UpdateState - When the state for some instruction is potentially updated,
+  /// this function notices and adds I to the worklist if needed.
+  void UpdateState(Instruction &Inst, LatticeVal V);
+  
+  /// MarkBlockExecutable - This method can be used by clients to mark all of
+  /// the blocks that are known to be intrinsically live in the processed unit.
+  void MarkBlockExecutable(BasicBlock *BB);
+  
+  /// markEdgeExecutable - Mark a basic block as executable, adding it to the BB
+  /// work list if it is not already executable.
+  void markEdgeExecutable(BasicBlock *Source, BasicBlock *Dest);
+  
+  /// getFeasibleSuccessors - Return a vector of booleans to indicate which
+  /// successors are reachable from a given terminator instruction.
+  void getFeasibleSuccessors(TerminatorInst &TI, SmallVectorImpl<bool> &Succs);
+  
+  /// isEdgeFeasible - Return true if the control flow edge from the 'From'
+  /// basic block to the 'To' basic block is currently feasible...
+  bool isEdgeFeasible(BasicBlock *From, BasicBlock *To);
+  
+  void visitInst(Instruction &I);
+  void visitPHINode(PHINode &I);
+  void visitTerminatorInst(TerminatorInst &TI);
+
+};
+
+} // end namespace llvm
+
+#endif // LLVM_ANALYSIS_SPARSE_PROPAGATION_H