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LLVM 3.4
author Kaito Tokumori <e105711@ie.u-ryukyu.ac.jp>
date Thu, 12 Dec 2013 13:56:28 +0900
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children 54457678186b
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-1:000000000000 0:95c75e76d11b
1 //===- SparsePropagation.h - Sparse Conditional Property Propagation ------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements an abstract sparse conditional propagation algorithm,
11 // modeled after SCCP, but with a customizable lattice function.
12 //
13 //===----------------------------------------------------------------------===//
14
15 #ifndef LLVM_ANALYSIS_SPARSEPROPAGATION_H
16 #define LLVM_ANALYSIS_SPARSEPROPAGATION_H
17
18 #include "llvm/ADT/DenseMap.h"
19 #include "llvm/ADT/SmallPtrSet.h"
20 #include <set>
21 #include <vector>
22
23 namespace llvm {
24 class Value;
25 class Constant;
26 class Argument;
27 class Instruction;
28 class PHINode;
29 class TerminatorInst;
30 class BasicBlock;
31 class Function;
32 class SparseSolver;
33 class raw_ostream;
34
35 template<typename T> class SmallVectorImpl;
36
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.
43 ///
44 class AbstractLatticeFunction {
45 public:
46 typedef void *LatticeVal;
47 private:
48 LatticeVal UndefVal, OverdefinedVal, UntrackedVal;
49 public:
50 AbstractLatticeFunction(LatticeVal undefVal, LatticeVal overdefinedVal,
51 LatticeVal untrackedVal) {
52 UndefVal = undefVal;
53 OverdefinedVal = overdefinedVal;
54 UntrackedVal = untrackedVal;
55 }
56 virtual ~AbstractLatticeFunction();
57
58 LatticeVal getUndefVal() const { return UndefVal; }
59 LatticeVal getOverdefinedVal() const { return OverdefinedVal; }
60 LatticeVal getUntrackedVal() const { return UntrackedVal; }
61
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) {
66 return false;
67 }
68
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
73 }
74
75 /// IsSpecialCasedPHI - Given a PHI node, determine whether this PHI node is
76 /// one that the we want to handle through ComputeInstructionState.
77 virtual bool IsSpecialCasedPHI(PHINode *PN) {
78 return false;
79 }
80
81 /// GetConstant - If the specified lattice value is representable as an LLVM
82 /// constant value, return it. Otherwise return null. The returned value
83 /// must be in the same LLVM type as Val.
84 virtual Constant *GetConstant(LatticeVal LV, Value *Val, SparseSolver &SS) {
85 return 0;
86 }
87
88 /// ComputeArgument - Given a formal argument value, compute and return a
89 /// lattice value corresponding to the specified argument.
90 virtual LatticeVal ComputeArgument(Argument *I) {
91 return getOverdefinedVal(); // always safe
92 }
93
94 /// MergeValues - Compute and return the merge of the two specified lattice
95 /// values. Merging should only move one direction down the lattice to
96 /// guarantee convergence (toward overdefined).
97 virtual LatticeVal MergeValues(LatticeVal X, LatticeVal Y) {
98 return getOverdefinedVal(); // always safe, never useful.
99 }
100
101 /// ComputeInstructionState - Given an instruction and a vector of its operand
102 /// values, compute the result value of the instruction.
103 virtual LatticeVal ComputeInstructionState(Instruction &I, SparseSolver &SS) {
104 return getOverdefinedVal(); // always safe, never useful.
105 }
106
107 /// PrintValue - Render the specified lattice value to the specified stream.
108 virtual void PrintValue(LatticeVal V, raw_ostream &OS);
109 };
110
111
112 /// SparseSolver - This class is a general purpose solver for Sparse Conditional
113 /// Propagation with a programmable lattice function.
114 ///
115 class SparseSolver {
116 typedef AbstractLatticeFunction::LatticeVal LatticeVal;
117
118 /// LatticeFunc - This is the object that knows the lattice and how to do
119 /// compute transfer functions.
120 AbstractLatticeFunction *LatticeFunc;
121
122 DenseMap<Value*, LatticeVal> ValueState; // The state each value is in.
123 SmallPtrSet<BasicBlock*, 16> BBExecutable; // The bbs that are executable.
124
125 std::vector<Instruction*> InstWorkList; // Worklist of insts to process.
126
127 std::vector<BasicBlock*> BBWorkList; // The BasicBlock work list
128
129 /// KnownFeasibleEdges - Entries in this set are edges which have already had
130 /// PHI nodes retriggered.
131 typedef std::pair<BasicBlock*,BasicBlock*> Edge;
132 std::set<Edge> KnownFeasibleEdges;
133
134 SparseSolver(const SparseSolver&) LLVM_DELETED_FUNCTION;
135 void operator=(const SparseSolver&) LLVM_DELETED_FUNCTION;
136 public:
137 explicit SparseSolver(AbstractLatticeFunction *Lattice)
138 : LatticeFunc(Lattice) {}
139 ~SparseSolver() {
140 delete LatticeFunc;
141 }
142
143 /// Solve - Solve for constants and executable blocks.
144 ///
145 void Solve(Function &F);
146
147 void Print(Function &F, raw_ostream &OS) const;
148
149 /// getLatticeState - Return the LatticeVal object that corresponds to the
150 /// value. If an value is not in the map, it is returned as untracked,
151 /// unlike the getOrInitValueState method.
152 LatticeVal getLatticeState(Value *V) const {
153 DenseMap<Value*, LatticeVal>::const_iterator I = ValueState.find(V);
154 return I != ValueState.end() ? I->second : LatticeFunc->getUntrackedVal();
155 }
156
157 /// getOrInitValueState - Return the LatticeVal object that corresponds to the
158 /// value, initializing the value's state if it hasn't been entered into the
159 /// map yet. This function is necessary because not all values should start
160 /// out in the underdefined state... Arguments should be overdefined, and
161 /// constants should be marked as constants.
162 ///
163 LatticeVal getOrInitValueState(Value *V);
164
165 /// isEdgeFeasible - Return true if the control flow edge from the 'From'
166 /// basic block to the 'To' basic block is currently feasible. If
167 /// AggressiveUndef is true, then this treats values with unknown lattice
168 /// values as undefined. This is generally only useful when solving the
169 /// lattice, not when querying it.
170 bool isEdgeFeasible(BasicBlock *From, BasicBlock *To,
171 bool AggressiveUndef = false);
172
173 /// isBlockExecutable - Return true if there are any known feasible
174 /// edges into the basic block. This is generally only useful when
175 /// querying the lattice.
176 bool isBlockExecutable(BasicBlock *BB) const {
177 return BBExecutable.count(BB);
178 }
179
180 private:
181 /// UpdateState - When the state for some instruction is potentially updated,
182 /// this function notices and adds I to the worklist if needed.
183 void UpdateState(Instruction &Inst, LatticeVal V);
184
185 /// MarkBlockExecutable - This method can be used by clients to mark all of
186 /// the blocks that are known to be intrinsically live in the processed unit.
187 void MarkBlockExecutable(BasicBlock *BB);
188
189 /// markEdgeExecutable - Mark a basic block as executable, adding it to the BB
190 /// work list if it is not already executable.
191 void markEdgeExecutable(BasicBlock *Source, BasicBlock *Dest);
192
193 /// getFeasibleSuccessors - Return a vector of booleans to indicate which
194 /// successors are reachable from a given terminator instruction.
195 void getFeasibleSuccessors(TerminatorInst &TI, SmallVectorImpl<bool> &Succs,
196 bool AggressiveUndef);
197
198 void visitInst(Instruction &I);
199 void visitPHINode(PHINode &I);
200 void visitTerminatorInst(TerminatorInst &TI);
201
202 };
203
204 } // end namespace llvm
205
206 #endif // LLVM_ANALYSIS_SPARSEPROPAGATION_H