1 //===- SparsePropagation.h - Sparse Conditional Property Propagation ------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file implements an abstract sparse conditional propagation algorithm,
11 // modeled after SCCP, but with a customizable lattice function.
13 //===----------------------------------------------------------------------===//
15 #ifndef LLVM_ANALYSIS_SPARSE_PROPAGATION_H
16 #define LLVM_ANALYSIS_SPARSE_PROPAGATION_H
18 #include "llvm/ADT/DenseMap.h"
19 #include "llvm/ADT/SmallPtrSet.h"
35 template<typename T> class SmallVectorImpl;
37 /// AbstractLatticeFunction - This class is implemented by the dataflow instance
38 /// to specify what the lattice values are and how they handle merges etc.
39 /// This gives the client the power to compute lattice values from instructions,
40 /// constants, etc. The requirement is that lattice values must all fit into
41 /// a void*. If a void* is not sufficient, the implementation should use this
42 /// pointer to be a pointer into a uniquing set or something.
44 class AbstractLatticeFunction {
46 typedef void *LatticeVal;
48 LatticeVal UndefVal, OverdefinedVal, UntrackedVal;
50 AbstractLatticeFunction(LatticeVal undefVal, LatticeVal overdefinedVal,
51 LatticeVal untrackedVal) {
53 OverdefinedVal = overdefinedVal;
54 UntrackedVal = untrackedVal;
56 virtual ~AbstractLatticeFunction();
58 LatticeVal getUndefVal() const { return UndefVal; }
59 LatticeVal getOverdefinedVal() const { return OverdefinedVal; }
60 LatticeVal getUntrackedVal() const { return UntrackedVal; }
62 /// IsUntrackedValue - If the specified Value is something that is obviously
63 /// uninteresting to the analysis (and would always return UntrackedVal),
64 /// this function can return true to avoid pointless work.
65 virtual bool IsUntrackedValue(Value *V) {
69 /// ComputeConstant - Given a constant value, compute and return a lattice
70 /// value corresponding to the specified constant.
71 virtual LatticeVal ComputeConstant(Constant *C) {
72 return getOverdefinedVal(); // always safe
75 /// GetConstant - If the specified lattice value is representable as an LLVM
76 /// constant value, return it. Otherwise return null. The returned value
77 /// must be in the same LLVM type as Val.
78 virtual Constant *GetConstant(LatticeVal LV, Value *Val, SparseSolver &SS) {
82 /// ComputeArgument - Given a formal argument value, compute and return a
83 /// lattice value corresponding to the specified argument.
84 virtual LatticeVal ComputeArgument(Argument *I) {
85 return getOverdefinedVal(); // always safe
88 /// MergeValues - Compute and return the merge of the two specified lattice
89 /// values. Merging should only move one direction down the lattice to
90 /// guarantee convergence (toward overdefined).
91 virtual LatticeVal MergeValues(LatticeVal X, LatticeVal Y) {
92 return getOverdefinedVal(); // always safe, never useful.
95 /// ComputeInstructionState - Given an instruction and a vector of its operand
96 /// values, compute the result value of the instruction.
97 virtual LatticeVal ComputeInstructionState(Instruction &I, SparseSolver &SS) {
98 return getOverdefinedVal(); // always safe, never useful.
101 /// PrintValue - Render the specified lattice value to the specified stream.
102 virtual void PrintValue(LatticeVal V, std::ostream &OS);
106 /// SparseSolver - This class is a general purpose solver for Sparse Conditional
107 /// Propagation with a programmable lattice function.
110 typedef AbstractLatticeFunction::LatticeVal LatticeVal;
112 /// LatticeFunc - This is the object that knows the lattice and how to do
113 /// compute transfer functions.
114 AbstractLatticeFunction *LatticeFunc;
116 DenseMap<Value*, LatticeVal> ValueState; // The state each value is in.
117 SmallPtrSet<BasicBlock*, 16> BBExecutable; // The bbs that are executable.
119 std::vector<Instruction*> InstWorkList; // Worklist of insts to process.
121 std::vector<BasicBlock*> BBWorkList; // The BasicBlock work list
123 /// KnownFeasibleEdges - Entries in this set are edges which have already had
124 /// PHI nodes retriggered.
125 typedef std::pair<BasicBlock*,BasicBlock*> Edge;
126 std::set<Edge> KnownFeasibleEdges;
128 SparseSolver(const SparseSolver&); // DO NOT IMPLEMENT
129 void operator=(const SparseSolver&); // DO NOT IMPLEMENT
131 explicit SparseSolver(AbstractLatticeFunction *Lattice)
132 : LatticeFunc(Lattice) {}
137 /// Solve - Solve for constants and executable blocks.
139 void Solve(Function &F);
141 void Print(Function &F, std::ostream &OS) const;
143 /// getLatticeState - Return the LatticeVal object that corresponds to the
144 /// value. If an value is not in the map, it is returned as untracked,
145 /// unlike the getOrInitValueState method.
146 LatticeVal getLatticeState(Value *V) const {
147 DenseMap<Value*, LatticeVal>::iterator I = ValueState.find(V);
148 return I != ValueState.end() ? I->second : LatticeFunc->getUntrackedVal();
151 /// getOrInitValueState - Return the LatticeVal object that corresponds to the
152 /// value, initializing the value's state if it hasn't been entered into the
153 /// map yet. This function is necessary because not all values should start
154 /// out in the underdefined state... Arguments should be overdefined, and
155 /// constants should be marked as constants.
157 LatticeVal getOrInitValueState(Value *V);
159 /// isEdgeFeasible - Return true if the control flow edge from the 'From'
160 /// basic block to the 'To' basic block is currently feasible. If
161 /// AggressiveUndef is true, then this treats values with unknown lattice
162 /// values as undefined. This is generally only useful when solving the
163 /// lattice, not when querying it.
164 bool isEdgeFeasible(BasicBlock *From, BasicBlock *To,
165 bool AggressiveUndef = false);
168 /// UpdateState - When the state for some instruction is potentially updated,
169 /// this function notices and adds I to the worklist if needed.
170 void UpdateState(Instruction &Inst, LatticeVal V);
172 /// MarkBlockExecutable - This method can be used by clients to mark all of
173 /// the blocks that are known to be intrinsically live in the processed unit.
174 void MarkBlockExecutable(BasicBlock *BB);
176 /// markEdgeExecutable - Mark a basic block as executable, adding it to the BB
177 /// work list if it is not already executable.
178 void markEdgeExecutable(BasicBlock *Source, BasicBlock *Dest);
180 /// getFeasibleSuccessors - Return a vector of booleans to indicate which
181 /// successors are reachable from a given terminator instruction.
182 void getFeasibleSuccessors(TerminatorInst &TI, SmallVectorImpl<bool> &Succs,
183 bool AggressiveUndef);
185 void visitInst(Instruction &I);
186 void visitPHINode(PHINode &I);
187 void visitTerminatorInst(TerminatorInst &TI);
191 } // end namespace llvm
193 #endif // LLVM_ANALYSIS_SPARSE_PROPAGATION_H