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"
20 #include "llvm/ADT/SmallVector.h"
35 /// AbstractLatticeFunction - This class is implemented by the dataflow instance
36 /// to specify what the lattice values are and how they handle merges etc.
37 /// This gives the client the power to compute lattice values from instructions,
38 /// constants, etc. The requirement is that lattice values must all fit into
39 /// a void*. If a void* is not sufficient, the implementation should use this
40 /// pointer to be a pointer into a uniquing set or something.
42 class AbstractLatticeFunction {
44 typedef void *LatticeVal;
46 LatticeVal UndefVal, OverdefinedVal, UntrackedVal;
48 AbstractLatticeFunction(LatticeVal undefVal, LatticeVal overdefinedVal,
49 LatticeVal untrackedVal) {
51 OverdefinedVal = overdefinedVal;
52 UntrackedVal = untrackedVal;
54 virtual ~AbstractLatticeFunction();
56 LatticeVal getUndefVal() const { return UndefVal; }
57 LatticeVal getOverdefinedVal() const { return OverdefinedVal; }
58 LatticeVal getUntrackedVal() const { return UntrackedVal; }
60 /// IsUntrackedValue - If the specified Value is something that is obviously
61 /// uninteresting to the analysis (and would always return UntrackedVal),
62 /// this function can return true to avoid pointless work.
63 virtual bool IsUntrackedValue(Value *V) {
67 /// ComputeConstant - Given a constant value, compute and return a lattice
68 /// value corresponding to the specified constant.
69 virtual LatticeVal ComputeConstant(Constant *C) {
70 return getOverdefinedVal(); // always safe
73 /// GetConstant - If the specified lattice value is representable as an LLVM
74 /// constant value, return it. Otherwise return null. The returned value
75 /// must be in the same LLVM type as Val.
76 virtual Constant *GetConstant(LatticeVal LV, Value *Val, SparseSolver &SS) {
80 /// ComputeArgument - Given a formal argument value, compute and return a
81 /// lattice value corresponding to the specified argument.
82 virtual LatticeVal ComputeArgument(Argument *I) {
83 return getOverdefinedVal(); // always safe
86 /// MergeValues - Compute and return the merge of the two specified lattice
87 /// values. Merging should only move one direction down the lattice to
88 /// guarantee convergence (toward overdefined).
89 virtual LatticeVal MergeValues(LatticeVal X, LatticeVal Y) {
90 return getOverdefinedVal(); // always safe, never useful.
93 /// ComputeInstructionState - Given an instruction and a vector of its operand
94 /// values, compute the result value of the instruction.
95 virtual LatticeVal ComputeInstructionState(Instruction &I, SparseSolver &SS) {
96 return getOverdefinedVal(); // always safe, never useful.
99 /// PrintValue - Render the specified lattice value to the specified stream.
100 virtual void PrintValue(LatticeVal V, std::ostream &OS);
104 /// SparseSolver - This class is a general purpose solver for Sparse Conditional
105 /// Propagation with a programmable lattice function.
108 typedef AbstractLatticeFunction::LatticeVal LatticeVal;
110 /// LatticeFunc - This is the object that knows the lattice and how to do
111 /// compute transfer functions.
112 AbstractLatticeFunction *LatticeFunc;
114 DenseMap<Value*, LatticeVal> ValueState; // The state each value is in.
115 SmallPtrSet<BasicBlock*, 16> BBExecutable; // The bbs that are executable.
117 std::vector<Instruction*> InstWorkList; // Worklist of insts to process.
119 std::vector<BasicBlock*> BBWorkList; // The BasicBlock work list
121 /// KnownFeasibleEdges - Entries in this set are edges which have already had
122 /// PHI nodes retriggered.
123 typedef std::pair<BasicBlock*,BasicBlock*> Edge;
124 std::set<Edge> KnownFeasibleEdges;
126 SparseSolver(const SparseSolver&); // DO NOT IMPLEMENT
127 void operator=(const SparseSolver&); // DO NOT IMPLEMENT
129 explicit SparseSolver(AbstractLatticeFunction *Lattice)
130 : LatticeFunc(Lattice) {}
135 /// Solve - Solve for constants and executable blocks.
137 void Solve(Function &F);
139 void Print(Function &F, std::ostream &OS);
141 /// getLatticeState - Return the LatticeVal object that corresponds to the
142 /// value. If an value is not in the map, it is returned as untracked,
143 /// unlike the getOrInitValueState method.
144 LatticeVal getLatticeState(Value *V) const {
145 DenseMap<Value*, LatticeVal>::iterator I = ValueState.find(V);
146 return I != ValueState.end() ? I->second : LatticeFunc->getUntrackedVal();
149 /// getOrInitValueState - Return the LatticeVal object that corresponds to the
150 /// value, initializing the value's state if it hasn't been entered into the
151 /// map yet. This function is necessary because not all values should start
152 /// out in the underdefined state... Arguments should be overdefined, and
153 /// constants should be marked as constants.
155 LatticeVal getOrInitValueState(Value *V);
157 /// isEdgeFeasible - Return true if the control flow edge from the 'From'
158 /// basic block to the 'To' basic block is currently feasible. If
159 /// AggressiveUndef is true, then this treats values with unknown lattice
160 /// values as undefined. This is generally only useful when solving the
161 /// lattice, not when querying it.
162 bool isEdgeFeasible(BasicBlock *From, BasicBlock *To,
163 bool AggressiveUndef = false);
166 /// UpdateState - When the state for some instruction is potentially updated,
167 /// this function notices and adds I to the worklist if needed.
168 void UpdateState(Instruction &Inst, LatticeVal V);
170 /// MarkBlockExecutable - This method can be used by clients to mark all of
171 /// the blocks that are known to be intrinsically live in the processed unit.
172 void MarkBlockExecutable(BasicBlock *BB);
174 /// markEdgeExecutable - Mark a basic block as executable, adding it to the BB
175 /// work list if it is not already executable.
176 void markEdgeExecutable(BasicBlock *Source, BasicBlock *Dest);
178 /// getFeasibleSuccessors - Return a vector of booleans to indicate which
179 /// successors are reachable from a given terminator instruction.
180 void getFeasibleSuccessors(TerminatorInst &TI, SmallVectorImpl<bool> &Succs,
181 bool AggressiveUndef);
183 void visitInst(Instruction &I);
184 void visitPHINode(PHINode &I);
185 void visitTerminatorInst(TerminatorInst &TI);
189 } // end namespace llvm
191 #endif // LLVM_ANALYSIS_SPARSE_PROPAGATION_H