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/Analysis/LiveVar/BBLiveVar.h"
14 #include "llvm/CodeGen/MachineInstr.h"
15 #include "llvm/BasicBlock.h"
16 #include "Support/PostOrderIterator.h"
19 AnalysisID MethodLiveVarInfo::ID(AnalysisID::create<MethodLiveVarInfo>());
21 //-----------------------------------------------------------------------------
23 //-----------------------------------------------------------------------------
25 // gets OutSet of a BB
26 const LiveVarSet *MethodLiveVarInfo::getOutSetOfBB(const BasicBlock *BB) const {
27 return BB2BBLVMap.find(BB)->second->getOutSet();
31 const LiveVarSet *MethodLiveVarInfo::getInSetOfBB(const BasicBlock *BB) const {
32 return BB2BBLVMap.find(BB)->second->getInSet();
36 //-----------------------------------------------------------------------------
37 // Performs live var analysis for a method
38 //-----------------------------------------------------------------------------
40 bool MethodLiveVarInfo::runOnMethod(Method *M) {
41 if (DEBUG_LV) std::cerr << "Analysing live variables ...\n";
43 // create and initialize all the BBLiveVars of the CFG
46 while (doSingleBackwardPass(M))
47 ; // Iterate until we are done.
49 if (DEBUG_LV) std::cerr << "Live Variable Analysis complete!\n";
54 //-----------------------------------------------------------------------------
55 // constructs BBLiveVars and init Def and In sets
56 //-----------------------------------------------------------------------------
58 void MethodLiveVarInfo::constructBBs(const Method *M) {
59 unsigned int POId = 0; // Reverse Depth-first Order ID
61 for(po_iterator<const Method*> BBI = po_begin(M), BBE = po_end(M);
62 BBI != BBE; ++BBI, ++POId) {
63 const BasicBlock *BB = *BBI; // get the current BB
65 if (DEBUG_LV) { std::cerr << " For BB "; printValue(BB); cerr << ":\n"; }
67 // create a new BBLiveVar
68 BBLiveVar *LVBB = new BBLiveVar(BB, POId);
69 BB2BBLVMap[BB] = LVBB; // insert the pair to Map
71 LVBB->calcDefUseSets(); // calculates the def and in set
77 // Since the PO iterator does not discover unreachable blocks,
78 // go over the random iterator and init those blocks as well.
79 // However, LV info is not correct for those blocks (they are not
82 for (Method::const_iterator BBRI = M->begin(), BBRE = M->end();
83 BBRI != BBRE; ++BBRI, ++POId)
84 if (!BB2BBLVMap[*BBRI]) // Not yet processed?
85 BB2BBLVMap[*BBRI] = new BBLiveVar(*BBRI, POId);
89 //-----------------------------------------------------------------------------
90 // do one backward pass over the CFG (for iterative analysis)
91 //-----------------------------------------------------------------------------
93 bool MethodLiveVarInfo::doSingleBackwardPass(const Method *M) {
94 if (DEBUG_LV) std::cerr << "\n After Backward Pass ...\n";
96 bool NeedAnotherIteration = false;
97 for (po_iterator<const Method*> BBI = po_begin(M); BBI != po_end(M) ; ++BBI) {
98 BBLiveVar *LVBB = BB2BBLVMap[*BBI];
99 assert(LVBB && "BasicBlock information not set for block!");
101 if (DEBUG_LV) std::cerr << " For BB " << (*BBI)->getName() << ":\n";
103 if(LVBB->isOutSetChanged())
104 LVBB->applyTransferFunc(); // apply the Tran Func to calc InSet
106 if (LVBB->isInSetChanged()) // to calc Outsets of preds
107 NeedAnotherIteration |= LVBB->applyFlowFunc(BB2BBLVMap);
109 if (DEBUG_LV) LVBB->printInOutSets();
112 // true if we need to reiterate over the CFG
113 return NeedAnotherIteration;
117 void MethodLiveVarInfo::releaseMemory() {
118 // First delete all BBLiveVar objects created in constructBBs(). A new object
119 // of type BBLiveVar is created for every BasicBlock in the method
121 for (std::map<const BasicBlock *, BBLiveVar *>::iterator
122 HMI = BB2BBLVMap.begin(),
123 HME = BB2BBLVMap.end(); HMI != HME; ++HMI)
124 delete HMI->second; // delete all BBLiveVar in BB2BBLVMap
128 // Then delete all objects of type LiveVarSet created in calcLiveVarSetsForBB
129 // and entered into MInst2LVSetBI and MInst2LVSetAI (these are caches
130 // to return LiveVarSet's before/after a machine instruction quickly). It
131 // is sufficient to free up all LiveVarSet using only one cache since
132 // both caches refer to the same sets
134 for (std::map<const MachineInstr*, const LiveVarSet*>::iterator
135 MI = MInst2LVSetBI.begin(),
136 ME = MInst2LVSetBI.end(); MI != ME; ++MI)
137 delete MI->second; // delete all LiveVarSets in MInst2LVSetBI
139 MInst2LVSetBI.clear();
140 MInst2LVSetAI.clear();
146 //-----------------------------------------------------------------------------
147 // Following functions will give the LiveVar info for any machine instr in
148 // a method. It should be called after a call to analyze().
150 // Thsese functions calucluates live var info for all the machine instrs in a
151 // BB when LVInfo for one inst is requested. Hence, this function is useful
152 // when live var info is required for many (or all) instructions in a basic
153 // block. Also, the arguments to this method does not require specific
155 //-----------------------------------------------------------------------------
157 //-----------------------------------------------------------------------------
158 // Gives live variable information before a machine instruction
159 //-----------------------------------------------------------------------------
162 MethodLiveVarInfo::getLiveVarSetBeforeMInst(const MachineInstr *MInst,
163 const BasicBlock *BB) {
164 if (const LiveVarSet *LVSet = MInst2LVSetBI[MInst]) {
165 return LVSet; // if found, just return the set
167 calcLiveVarSetsForBB(BB); // else, calc for all instrs in BB
168 return MInst2LVSetBI[MInst];
173 //-----------------------------------------------------------------------------
174 // Gives live variable information after a machine instruction
175 //-----------------------------------------------------------------------------
177 MethodLiveVarInfo::getLiveVarSetAfterMInst(const MachineInstr *MI,
178 const BasicBlock *BB) {
180 if (const LiveVarSet *LVSet = MInst2LVSetAI[MI]) {
181 return LVSet; // if found, just return the set
183 calcLiveVarSetsForBB(BB); // else, calc for all instrs in BB
184 return MInst2LVSetAI[MI];
190 //-----------------------------------------------------------------------------
191 // This method calculates the live variable information for all the
192 // instructions in a basic block and enter the newly constructed live
193 // variable sets into a the caches (MInst2LVSetAI, MInst2LVSetBI)
194 //-----------------------------------------------------------------------------
196 void MethodLiveVarInfo::calcLiveVarSetsForBB(const BasicBlock *BB) {
197 const MachineCodeForBasicBlock &MIVec = BB->getMachineInstrVec();
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 (MachineCodeForBasicBlock::const_reverse_iterator MII = MIVec.rbegin(),
205 MIE = MIVec.rend(); MII != MIE; ++MII) {
206 // MI is cur machine inst
207 const MachineInstr *MI = *MII;
209 MInst2LVSetAI[MI] = SetAI; // record in After Inst map
211 CurSet->applyTranferFuncForMInst(MI); // 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[MI] = NewSet; // record in Before Inst map
217 // SetAI will be used in the next iteration