1 /* Title: MethodLiveVarInfo.cpp
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.
12 #include "llvm/Analysis/LiveVar/MethodLiveVarInfo.h"
13 #include "llvm/CodeGen/MachineInstr.h"
14 #include "llvm/BasicBlock.h"
15 #include "Support/PostOrderIterator.h"
19 AnalysisID MethodLiveVarInfo::ID(AnalysisID::create<MethodLiveVarInfo>());
22 //-----------------------------------------------------------------------------
23 // Performs live var analysis for a method
24 //-----------------------------------------------------------------------------
26 bool MethodLiveVarInfo::runOnMethod(Method *M) {
27 if (DEBUG_LV) cerr << "Analysing live variables ...\n";
29 // create and initialize all the BBLiveVars of the CFG
32 while (doSingleBackwardPass(M))
33 ; // Iterate until we are done.
35 if (DEBUG_LV) cerr << "Live Variable Analysis complete!\n";
40 //-----------------------------------------------------------------------------
41 // constructs BBLiveVars and init Def and In sets
42 //-----------------------------------------------------------------------------
44 void MethodLiveVarInfo::constructBBs(const Method *M) {
45 unsigned int POId = 0; // Reverse Depth-first Order ID
47 for(po_iterator<const Method*> BBI = po_begin(M), BBE = po_end(M);
48 BBI != BBE; ++BBI, ++POId) {
49 const BasicBlock *BB = *BBI; // get the current BB
51 if (DEBUG_LV) { cerr << " For BB "; printValue(BB); cerr << ":\n"; }
53 // create a new BBLiveVar
54 BBLiveVar *LVBB = new BBLiveVar(BB, POId);
55 BB2BBLVMap[BB] = LVBB; // insert the pair to Map
57 LVBB->calcDefUseSets(); // calculates the def and in set
63 // Since the PO iterator does not discover unreachable blocks,
64 // go over the random iterator and init those blocks as well.
65 // However, LV info is not correct for those blocks (they are not
68 for (Method::const_iterator BBRI = M->begin(), BBRE = M->end();
69 BBRI != BBRE; ++BBRI, ++POId)
70 if (!BB2BBLVMap[*BBRI]) // Not yet processed?
71 BB2BBLVMap[*BBRI] = new BBLiveVar(*BBRI, POId);
75 //-----------------------------------------------------------------------------
76 // do one backward pass over the CFG (for iterative analysis)
77 //-----------------------------------------------------------------------------
78 bool MethodLiveVarInfo::doSingleBackwardPass(const Method *M) {
79 bool ResultFlow, NeedAnotherIteration = false;
82 cerr << "\n After Backward Pass ...\n";
84 po_iterator<const Method*> BBI = po_begin(M);
86 for( ; BBI != po_end(M) ; ++BBI) {
87 BBLiveVar *LVBB = BB2BBLVMap[*BBI];
90 if (DEBUG_LV) cerr << " For BB " << (*BBI)->getName() << ":\n";
92 if(LVBB->isOutSetChanged())
93 LVBB->applyTransferFunc(); // apply the Tran Func to calc InSet
95 if (LVBB->isInSetChanged()) // to calc Outsets of preds
96 NeedAnotherIteration |= LVBB->applyFlowFunc(BB2BBLVMap);
98 if(DEBUG_LV) LVBB->printInOutSets();
101 // true if we need to reiterate over the CFG
102 return NeedAnotherIteration;
106 void MethodLiveVarInfo::releaseMemory() {
107 // First delete all BBLiveVar objects created in constructBBs(). A new object
108 // of type BBLiveVa is created for every BasicBlock in the method
110 // hash map iterator for BB2BBLVMap
112 BBToBBLiveVarMapType::iterator HMI = BB2BBLVMap.begin();
114 for( ; HMI != BB2BBLVMap.end(); ++HMI)
115 delete HMI->second; // delete all BBLiveVar in BB2BBLVMap
119 // Then delete all objects of type LiveVarSet created in calcLiveVarSetsForBB
120 // and entered into MInst2LVSetBI and MInst2LVSetAI (these are caches
121 // to return LiveVarSet's before/after a machine instruction quickly). It
122 // is sufficient to free up all LiveVarSet using only one cache since
123 // both caches refer to the same sets
125 // hash map iterator for MInst2LVSetBI
127 MInstToLiveVarSetMapType::iterator MI = MInst2LVSetBI.begin();
129 for( ; MI != MInst2LVSetBI.end(); ++MI)
130 delete MI->second; // delete all LiveVarSets in MInst2LVSetBI
132 MInst2LVSetBI.clear();
133 MInst2LVSetAI.clear();
139 //-----------------------------------------------------------------------------
140 /* Following functions will give the LiveVar info for any machine instr in
141 a method. It should be called after a call to analyze().
143 Thsese functions calucluates live var info for all the machine instrs in a
144 BB when LVInfo for one inst is requested. Hence, this function is useful
145 when live var info is required for many (or all) instructions in a basic
146 block. Also, the arguments to this method does not require specific
149 //-----------------------------------------------------------------------------
151 //-----------------------------------------------------------------------------
152 // Gives live variable information before a machine instruction
153 //-----------------------------------------------------------------------------
155 MethodLiveVarInfo::getLiveVarSetBeforeMInst(const MachineInstr *MInst,
156 const BasicBlock *CurBB) {
157 const LiveVarSet *LVSet = MInst2LVSetBI[MInst];
160 return LVSet; // if found, just return the set
162 calcLiveVarSetsForBB(CurBB); // else, calc for all instrs in BB
163 assert(MInst2LVSetBI[MInst]);
164 return MInst2LVSetBI[MInst];
169 //-----------------------------------------------------------------------------
170 // Gives live variable information after a machine instruction
171 //-----------------------------------------------------------------------------
173 MethodLiveVarInfo::getLiveVarSetAfterMInst(const MachineInstr *MInst,
174 const BasicBlock *CurBB) {
175 const LiveVarSet *LVSet = MInst2LVSetAI[MInst];
178 return LVSet; // if found, just return the set
180 calcLiveVarSetsForBB(CurBB); // else, calc for all instrs in BB
181 assert(MInst2LVSetAI[MInst]);
182 return MInst2LVSetAI[MInst];
188 //-----------------------------------------------------------------------------
189 // This method calculates the live variable information for all the
190 // instructions in a basic block and enter the newly constructed live
191 // variable sets into a the caches ( MInst2LVSetAI, MInst2LVSetBI)
192 //-----------------------------------------------------------------------------
193 void MethodLiveVarInfo::calcLiveVarSetsForBB(const BasicBlock *const BB)
195 const MachineCodeForBasicBlock& MIVec = BB->getMachineInstrVec();
196 MachineCodeForBasicBlock::const_reverse_iterator
197 MInstIterator = MIVec.rbegin();
199 LiveVarSet *CurSet = new LiveVarSet();
200 const LiveVarSet *SetAI = getOutSetOfBB(BB); // init SetAI with OutSet
201 CurSet->setUnion(SetAI); // CurSet now contains OutSet
203 // iterate over all the machine instructions in BB
204 for( ; MInstIterator != MIVec.rend(); MInstIterator++) {
206 // MInst is cur machine inst
207 const MachineInstr * MInst = *MInstIterator;
209 MInst2LVSetAI[MInst] = SetAI; // record in After Inst map
211 CurSet->applyTranferFuncForMInst( MInst ); // apply the transfer Func
212 LiveVarSet *NewSet = new LiveVarSet(); // create a new set and
213 NewSet->setUnion( CurSet ); // copy the set after T/F to it
215 MInst2LVSetBI[MInst] = NewSet; // record in Before Inst map
217 // SetAI will be used in the next iteration