--- /dev/null
+//===- 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
--- /dev/null
+//===- SparsePropagation.cpp - 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.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "sparseprop"
+#include "llvm/Analysis/SparsePropagation.h"
+#include "llvm/Constants.h"
+#include "llvm/Function.h"
+#include "llvm/Instructions.h"
+#include "llvm/Module.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/Streams.h"
+using namespace llvm;
+
+//===----------------------------------------------------------------------===//
+// AbstractLatticeFunction Implementation
+//===----------------------------------------------------------------------===//
+
+AbstractLatticeFunction::~AbstractLatticeFunction() {}
+
+/// PrintValue - Render the specified lattice value to the specified stream.
+void AbstractLatticeFunction::PrintValue(LatticeVal V, std::ostream &OS) {
+ if (V == UndefVal)
+ OS << "undefined";
+ else if (V == OverdefinedVal)
+ OS << "overdefined";
+ else if (V == UntrackedVal)
+ OS << "untracked";
+ else
+ OS << "unknown lattice value";
+}
+
+//===----------------------------------------------------------------------===//
+// SparseSolver Implementation
+//===----------------------------------------------------------------------===//
+
+/// 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.
+///
+SparseSolver::LatticeVal SparseSolver::getOrInitValueState(Value *V) {
+ DenseMap<Value*, LatticeVal>::iterator I = ValueState.find(V);
+ if (I != ValueState.end()) return I->second; // Common case, in the map
+
+ LatticeVal LV;
+ if (LatticeFunc->IsUntrackedValue(V))
+ return LatticeFunc->getUntrackedVal();
+ else if (Constant *C = dyn_cast<Constant>(V))
+ LV = LatticeFunc->ComputeConstant(C);
+ else if (!isa<Instruction>(V))
+ // Non-instructions (e.g. formal arguments) are overdefined.
+ LV = LatticeFunc->getOverdefinedVal();
+ else
+ // All instructions are underdefined by default.
+ LV = LatticeFunc->getUndefVal();
+
+ // If this value is untracked, don't add it to the map.
+ if (LV == LatticeFunc->getUntrackedVal())
+ return LV;
+ return ValueState[V] = LV;
+}
+
+/// UpdateState - When the state for some instruction is potentially updated,
+/// this function notices and adds I to the worklist if needed.
+void SparseSolver::UpdateState(Instruction &Inst, LatticeVal V) {
+ DenseMap<Value*, LatticeVal>::iterator I = ValueState.find(&Inst);
+ if (I != ValueState.end() && I->second == V)
+ return; // No change.
+
+ // An update. Visit uses of I.
+ ValueState[&Inst] = V;
+ InstWorkList.push_back(&Inst);
+}
+
+/// 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 SparseSolver::MarkBlockExecutable(BasicBlock *BB) {
+ DOUT << "Marking Block Executable: " << BB->getNameStart() << "\n";
+ BBExecutable.insert(BB); // Basic block is executable!
+ BBWorkList.push_back(BB); // Add the block to the work list!
+}
+
+/// markEdgeExecutable - Mark a basic block as executable, adding it to the BB
+/// work list if it is not already executable...
+void SparseSolver::markEdgeExecutable(BasicBlock *Source, BasicBlock *Dest) {
+ if (!KnownFeasibleEdges.insert(Edge(Source, Dest)).second)
+ return; // This edge is already known to be executable!
+
+ if (BBExecutable.count(Dest)) {
+ DOUT << "Marking Edge Executable: " << Source->getNameStart()
+ << " -> " << Dest->getNameStart() << "\n";
+
+ // The destination is already executable, but we just made an edge
+ // feasible that wasn't before. Revisit the PHI nodes in the block
+ // because they have potentially new operands.
+ for (BasicBlock::iterator I = Dest->begin(); isa<PHINode>(I); ++I)
+ visitPHINode(*cast<PHINode>(I));
+
+ } else {
+ MarkBlockExecutable(Dest);
+ }
+}
+
+
+/// getFeasibleSuccessors - Return a vector of booleans to indicate which
+/// successors are reachable from a given terminator instruction.
+void SparseSolver::getFeasibleSuccessors(TerminatorInst &TI,
+ SmallVectorImpl<bool> &Succs) {
+ Succs.resize(TI.getNumSuccessors());
+ if (TI.getNumSuccessors() == 0) return;
+
+ if (BranchInst *BI = dyn_cast<BranchInst>(&TI)) {
+ if (BI->isUnconditional()) {
+ Succs[0] = true;
+ return;
+ }
+
+ LatticeVal BCValue = getOrInitValueState(BI->getCondition());
+ if (BCValue == LatticeFunc->getOverdefinedVal() ||
+ BCValue == LatticeFunc->getUntrackedVal()) {
+ // Overdefined condition variables can branch either way.
+ Succs[0] = Succs[1] = true;
+ return;
+ }
+
+ // If undefined, neither is feasible yet.
+ if (BCValue == LatticeFunc->getUndefVal())
+ return;
+
+ Constant *C = LatticeFunc->GetConstant(BCValue, BI->getCondition(), *this);
+ if (C == 0 || !isa<ConstantInt>(C)) {
+ // Non-constant values can go either way.
+ Succs[0] = Succs[1] = true;
+ return;
+ }
+
+ // Constant condition variables mean the branch can only go a single way
+ Succs[C == ConstantInt::getFalse()] = true;
+ return;
+ }
+
+ if (isa<InvokeInst>(TI)) {
+ // Invoke instructions successors are always executable.
+ // TODO: Could ask the lattice function if the value can throw.
+ Succs[0] = Succs[1] = true;
+ return;
+ }
+
+ SwitchInst &SI = cast<SwitchInst>(TI);
+ LatticeVal SCValue = getOrInitValueState(SI.getCondition());
+ if (SCValue == LatticeFunc->getOverdefinedVal() ||
+ SCValue == LatticeFunc->getUntrackedVal()) {
+ // All destinations are executable!
+ Succs.assign(TI.getNumSuccessors(), true);
+ return;
+ }
+
+ // If undefined, neither is feasible yet.
+ if (SCValue == LatticeFunc->getUndefVal())
+ return;
+
+ Constant *C = LatticeFunc->GetConstant(SCValue, SI.getCondition(), *this);
+ if (C == 0 || !isa<ConstantInt>(C)) {
+ // All destinations are executable!
+ Succs.assign(TI.getNumSuccessors(), true);
+ return;
+ }
+
+ Succs[SI.findCaseValue(cast<ConstantInt>(C))] = true;
+}
+
+
+/// isEdgeFeasible - Return true if the control flow edge from the 'From'
+/// basic block to the 'To' basic block is currently feasible...
+bool SparseSolver::isEdgeFeasible(BasicBlock *From, BasicBlock *To) {
+ SmallVector<bool, 16> SuccFeasible;
+ TerminatorInst *TI = From->getTerminator();
+ getFeasibleSuccessors(*TI, SuccFeasible);
+
+ for (unsigned i = 0, e = TI->getNumSuccessors(); i != e; ++i)
+ if (TI->getSuccessor(i) == To && SuccFeasible[i])
+ return true;
+
+ return false;
+}
+
+void SparseSolver::visitTerminatorInst(TerminatorInst &TI) {
+ SmallVector<bool, 16> SuccFeasible;
+ getFeasibleSuccessors(TI, SuccFeasible);
+
+ BasicBlock *BB = TI.getParent();
+
+ // Mark all feasible successors executable...
+ for (unsigned i = 0, e = SuccFeasible.size(); i != e; ++i)
+ if (SuccFeasible[i])
+ markEdgeExecutable(BB, TI.getSuccessor(i));
+}
+
+void SparseSolver::visitPHINode(PHINode &PN) {
+ LatticeVal PNIV = getOrInitValueState(&PN);
+ LatticeVal Overdefined = LatticeFunc->getOverdefinedVal();
+
+ // If this value is already overdefined (common) just return.
+ if (PNIV == Overdefined || PNIV == LatticeFunc->getUntrackedVal())
+ return; // Quick exit
+
+ // Super-extra-high-degree PHI nodes are unlikely to ever be interesting,
+ // and slow us down a lot. Just mark them overdefined.
+ if (PN.getNumIncomingValues() > 64) {
+ UpdateState(PN, Overdefined);
+ return;
+ }
+
+ // Look at all of the executable operands of the PHI node. If any of them
+ // are overdefined, the PHI becomes overdefined as well. Otherwise, ask the
+ // transfer function to give us the merge of the incoming values.
+ for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i) {
+ // If the edge is not yet known to be feasible, it doesn't impact the PHI.
+ if (!isEdgeFeasible(PN.getIncomingBlock(i), PN.getParent()))
+ continue;
+
+ // Merge in this value.
+ LatticeVal OpVal = getOrInitValueState(PN.getIncomingValue(i));
+ if (OpVal != PNIV)
+ PNIV = LatticeFunc->MergeValues(PNIV, OpVal);
+
+ if (PNIV == Overdefined)
+ break; // Rest of input values don't matter.
+ }
+
+ // Update the PHI with the compute value, which is the merge of the inputs.
+ UpdateState(PN, PNIV);
+}
+
+
+void SparseSolver::visitInst(Instruction &I) {
+ // PHIs are handled by the propagation logic, they are never passed into the
+ // transfer functions.
+ if (PHINode *PN = dyn_cast<PHINode>(&I))
+ return visitPHINode(*PN);
+
+ // Otherwise, ask the transfer function what the result is. If this is
+ // something that we care about, remember it.
+ LatticeVal IV = LatticeFunc->ComputeInstructionState(I, *this);
+ if (IV != LatticeFunc->getUntrackedVal())
+ UpdateState(I, IV);
+
+ if (TerminatorInst *TI = dyn_cast<TerminatorInst>(&I))
+ visitTerminatorInst(*TI);
+}
+
+void SparseSolver::Solve(Function &F) {
+ MarkBlockExecutable(F.begin());
+
+ // Process the work lists until they are empty!
+ while (!BBWorkList.empty() || !InstWorkList.empty()) {
+ // Process the instruction work list.
+ while (!InstWorkList.empty()) {
+ Instruction *I = InstWorkList.back();
+ InstWorkList.pop_back();
+
+ DOUT << "\nPopped off I-WL: " << *I;
+
+ // "I" got into the work list because it made a transition. See if any
+ // users are both live and in need of updating.
+ for (Value::use_iterator UI = I->use_begin(), E = I->use_end();
+ UI != E; ++UI) {
+ Instruction *U = cast<Instruction>(*UI);
+ if (BBExecutable.count(U->getParent())) // Inst is executable?
+ visitInst(*U);
+ }
+ }
+
+ // Process the basic block work list.
+ while (!BBWorkList.empty()) {
+ BasicBlock *BB = BBWorkList.back();
+ BBWorkList.pop_back();
+
+ DOUT << "\nPopped off BBWL: " << *BB;
+
+ // Notify all instructions in this basic block that they are newly
+ // executable.
+ for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
+ visitInst(*I);
+ }
+ }
+}
+
+void SparseSolver::Print(Function &F, std::ostream &OS) {
+ OS << "\nFUNCTION: " << F.getNameStr() << "\n";
+ for (Function::iterator BB = F.begin(), E = F.end(); BB != E; ++BB) {
+ if (!BBExecutable.count(BB))
+ OS << "INFEASIBLE: ";
+ OS << "\t";
+ if (BB->hasName())
+ OS << BB->getNameStr() << ":\n";
+ else
+ OS << "; anon bb\n";
+ for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
+ LatticeFunc->PrintValue(getLatticeState(I), OS);
+ OS << *I;
+ }
+
+ OS << "\n";
+ }
+}
+
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