1 /* Title: MethodLiveVarInfo.h -*- C++ -*-
2 Author: Ruchira Sasanka
6 This is the interface for live variable info of a method that is required
7 by any other part of the compiler
9 It must be called like:
11 MethodLiveVarInfo MLVI( Mehtod *); // initializes data structures
12 MLVI.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.
68 #ifndef METH_LIVE_VAR_INFO_H
69 #define METH_LIVE_VAR_INFO_H
71 // set DEBUG_LV for printing out debug messages
72 // if DEBUG_LV is 1 normal output messages
73 // if DEBUG_LV is 2 extensive debug info for each instr
75 static const int DEBUG_LV = 0;
77 #include "LiveVarSet.h"
78 #include "llvm/BasicBlock.h"
79 #include "llvm/Instruction.h"
80 #include "llvm/Method.h"
82 #include "LiveVarMap.h"
83 #include "BBLiveVar.h"
86 class MethodLiveVarInfo
90 // Live var anal is done on this method - set by constructor
91 const Method *const Meth;
93 // A map betwn the BasicBlock and BBLiveVar
94 BBToBBLiveVarMapType BB2BBLVMap;
96 // Machine Instr to LiveVarSet Map for providing LVset BEFORE each inst
97 MInstToLiveVarSetMapType MInst2LVSetBI;
99 // Machine Instr to LiveVarSet Map for providing LVset AFTER each inst
100 MInstToLiveVarSetMapType MInst2LVSetAI;
102 // True if the analyze() method has been called. This is checked when
103 // getInSet/OutSet is called to prevent calling those methods before analyze
107 // --------- private methods -----------------------------------------
109 // constructs BBLiveVars and init Def and In sets
112 // do one backward pass over the CFG
113 bool doSingleBackwardPass();
115 // calculates live var sets for instructions in a BB
116 void calcLiveVarSetsForBB(const BasicBlock *const BB);
120 MethodLiveVarInfo(const Method *const Meth); // constructor
122 ~MethodLiveVarInfo(); // destructor
124 // performs a liver var analysis of a single method
127 // gets OutSet of a BB
128 inline const LiveVarSet *getOutSetOfBB( const BasicBlock *const BB) const {
129 assert( HasAnalyzed && "call analyze() before calling this" );
130 return ( (* (BB2BBLVMap.find(BB)) ).second ) ->getOutSet();
133 // gets InSet of a BB
134 inline const LiveVarSet *getInSetOfBB( const BasicBlock *const BB) const {
135 assert( HasAnalyzed && "call analyze() before calling this" );
136 return ( (* (BB2BBLVMap.find(BB)) ).second )->getInSet();
139 // gets the Live var set BEFORE an instruction
140 const LiveVarSet * getLiveVarSetBeforeMInst(const MachineInstr *const Inst,
141 const BasicBlock *const CurBB);
143 // gets the Live var set AFTER an instruction
144 const LiveVarSet * getLiveVarSetAfterMInst(const MachineInstr *const MInst,
145 const BasicBlock *const CurBB);