1 /* Title: FunctionLiveVarInfo.h -*- C++ -*-
2 Author: Ruchira Sasanka
6 This is the interface for live variable info of a function that is required
7 by any other part of the compiler
9 It must be called like:
11 FunctionLiveVarInfo FLVI(Function *); // initializes data structures
12 FLVI.analyze(); // do the actural live variable anal
14 After the analysis, getInSetOfBB or getOutSetofBB can be called to get
15 live var info of a BB.
17 The live var set before an instruction can be obtained in 2 ways:
19 1. Use the method getLiveVarSetAfterInst(Instruction *) to get the LV Info
20 just after an instruction. (also exists getLiveVarSetBeforeInst(..))
22 This function caluclates the LV info for a BB only once and caches that
23 info. If the cache does not contain the LV info of the instruction, it
24 calculates the LV info for the whole BB and caches them.
26 Getting liveVar info this way uses more memory since, LV info should be
27 cached. However, if you need LV info of nearly all the instructions of a
28 BB, this is the best and simplest interfrace.
31 2. Use the OutSet and applyTranferFuncForInst(const Instruction *const Inst)
32 declared in LiveVarSet and traverse the instructions of a basic block in
33 reverse (using const_reverse_iterator in the BB class).
35 This is the most memory efficient method if you need LV info for
36 only several instructions in a BasicBlock. An example is given below:
39 LiveVarSet LVSet; // this will be the set used to traverse through each BB
41 // Initialize LVSet so that it is the same as OutSet of the BB
42 LVSet.setUnion( LVI->getOutSetOfBB( *BBI ) );
44 BasicBlock::InstListType::const_reverse_iterator
45 InstIterator = InstListInBB.rbegin(); // get the rev iter for inst in BB
47 // iterate over all the instructions in BB in reverse
48 for( ; InstIterator != InstListInBB.rend(); InstIterator++) {
50 //...... all code here which uses LVSet ........
52 LVSet.applyTranferFuncForInst(*InstIterator);
54 // Now LVSet contains live vars ABOVE the current instrution
57 See buildInterferenceGraph() for the above example.
61 #ifndef FUNCTION_LIVE_VAR_INFO_H
62 #define FUNCTION_LIVE_VAR_INFO_H
64 #include "llvm/Pass.h"
65 #include "llvm/Analysis/LiveVar/ValueSet.h"
70 class FunctionLiveVarInfo : public FunctionPass {
71 // Machine Instr to LiveVarSet Map for providing LVset BEFORE each inst
72 std::map<const MachineInstr *, const ValueSet *> MInst2LVSetBI;
74 // Machine Instr to LiveVarSet Map for providing LVset AFTER each inst
75 std::map<const MachineInstr *, const ValueSet *> MInst2LVSetAI;
77 // Stored Function that the data is computed with respect to
80 // --------- private methods -----------------------------------------
82 // constructs BBLiveVars and init Def and In sets
83 void constructBBs(const Function *F);
85 // do one backward pass over the CFG
86 bool doSingleBackwardPass(const Function *F, unsigned int iter);
88 // calculates live var sets for instructions in a BB
89 void calcLiveVarSetsForBB(const BasicBlock *BB);
92 static AnalysisID ID; // We are an analysis, we must have an ID
94 // --------- Implement the FunctionPass interface ----------------------
96 // runOnFunction - Perform analysis, update internal data structures.
97 virtual bool runOnFunction(Function &F);
99 // releaseMemory - After LiveVariable analysis has been used, forget!
100 virtual void releaseMemory();
102 // getAnalysisUsage - Provide self!
103 virtual void getAnalysisUsage(AnalysisUsage &AU) const {
104 AU.setPreservesAll();
108 // --------- Functions to access analysis results -------------------
110 // gets OutSet of a BB
111 const ValueSet &getOutSetOfBB(const BasicBlock *BB) const;
113 // gets InSet of a BB
114 const ValueSet &getInSetOfBB(const BasicBlock *BB) const;
116 // gets the Live var set BEFORE an instruction
117 const ValueSet &getLiveVarSetBeforeMInst(const MachineInstr *MI,
118 const BasicBlock *BB);
120 // gets the Live var set AFTER an instruction
121 const ValueSet &getLiveVarSetAfterMInst(const MachineInstr *MI,
122 const BasicBlock *BB);