1 //===-- BBLiveVar.cpp - Live Variable Analysis for a BasicBlock -----------===//
3 // This is a wrapper class for BasicBlock which is used by live var analysis.
5 //===----------------------------------------------------------------------===//
7 #include "llvm/Analysis/LiveVar/BBLiveVar.h"
8 #include "llvm/Analysis/LiveVar/MethodLiveVarInfo.h"
9 #include "llvm/CodeGen/MachineInstr.h"
10 #include "llvm/BasicBlock.h"
12 /// BROKEN: Should not include sparc stuff directly into here
13 #include "../../Target/Sparc/SparcInternals.h" // Only for PHI defn
17 BBLiveVar::BBLiveVar(const BasicBlock *bb, unsigned id)
19 InSetChanged = OutSetChanged = false;
22 //-----------------------------------------------------------------------------
23 // calculates def and use sets for each BB
24 // There are two passes over operands of a machine instruction. This is
25 // because, we can have instructions like V = V + 1, since we no longer
26 // assume single definition.
27 //-----------------------------------------------------------------------------
29 void BBLiveVar::calcDefUseSets() {
30 // get the iterator for machine instructions
31 const MachineCodeForBasicBlock &MIVec = BB->getMachineInstrVec();
33 // iterate over all the machine instructions in BB
34 for (MachineCodeForBasicBlock::const_reverse_iterator MII = MIVec.rbegin(),
35 MIE = MIVec.rend(); MII != MIE; ++MII) {
36 const MachineInstr *MI = *MII;
38 if (DEBUG_LV > 1) { // debug msg
39 cerr << " *Iterating over machine instr ";
44 // iterate over MI operands to find defs
45 for (MachineInstr::val_const_op_iterator OpI(MI); !OpI.done(); ++OpI)
46 if (OpI.isDef()) // add to Defs only if this operand is a def
49 // do for implicit operands as well
50 for (unsigned i = 0; i < MI->getNumImplicitRefs(); ++i)
51 if (MI->implicitRefIsDefined(i))
52 addDef(MI->getImplicitRef(i));
54 bool IsPhi = MI->getOpCode() == PHI;
56 // iterate over MI operands to find uses
57 for (MachineInstr::val_const_op_iterator OpI(MI); !OpI.done(); ++OpI) {
58 const Value *Op = *OpI;
60 if (Op->getType()->isLabelType())
61 continue; // don't process labels
63 if (!OpI.isDef()) { // add to Defs only if this operand is a use
66 if (IsPhi) { // for a phi node
67 // put args into the PhiArgMap (Val -> BB)
68 const Value *ArgVal = Op;
69 const Value *BBVal = *++OpI; // increment to point to BB of value
71 PhiArgMap[ArgVal] = cast<BasicBlock>(BBVal);
74 cerr << " - phi operand ";
76 cerr << " came from BB ";
77 printValue(PhiArgMap[ArgVal]);
84 // do for implicit operands as well
85 for (unsigned i = 0; i < MI->getNumImplicitRefs(); ++i) {
86 assert(!IsPhi && "Phi cannot have implicit opeands");
87 const Value *Op = MI->getImplicitRef(i);
89 if (Op->getType()->isLabelType()) // don't process labels
92 if (!MI->implicitRefIsDefined(i))
95 } // for all machine instructions
100 //-----------------------------------------------------------------------------
101 // To add an operand which is a def
102 //-----------------------------------------------------------------------------
103 void BBLiveVar::addDef(const Value *Op) {
104 DefSet.insert(Op); // operand is a def - so add to def set
105 InSet.erase(Op); // this definition kills any uses
109 cerr << " +Def: "; printValue( Op ); cerr << "\n";
114 //-----------------------------------------------------------------------------
115 // To add an operand which is a use
116 //-----------------------------------------------------------------------------
117 void BBLiveVar::addUse(const Value *Op) {
118 InSet.insert(Op); // An operand is a use - so add to use set
119 OutSet.erase(Op); // remove if there is a def below this use
123 cerr << " Use: "; printValue( Op ); cerr << "\n";
128 //-----------------------------------------------------------------------------
129 // Applies the transfer function to a basic block to produce the InSet using
131 //-----------------------------------------------------------------------------
133 bool BBLiveVar::applyTransferFunc() {
134 // IMPORTANT: caller should check whether the OutSet changed
135 // (else no point in calling)
137 LiveVarSet OutMinusDef; // set to hold (Out[B] - Def[B])
138 OutMinusDef.setDifference(&OutSet, &DefSet);
139 InSetChanged = InSet.setUnion(&OutMinusDef);
141 OutSetChanged = false; // no change to OutSet since transf func applied
146 //-----------------------------------------------------------------------------
147 // calculates Out set using In sets of the predecessors
148 //-----------------------------------------------------------------------------
150 bool BBLiveVar::setPropagate(LiveVarSet *OutSet, const LiveVarSet *InSet,
151 const BasicBlock *PredBB) {
152 bool Changed = false;
154 // for all all elements in InSet
155 for (LiveVarSet::const_iterator InIt = InSet->begin(), InE = InSet->end();
156 InIt != InE; ++InIt) {
157 const BasicBlock *PredBBOfPhiArg = PhiArgMap[*InIt];
159 // if this var is not a phi arg OR
160 // it's a phi arg and the var went down from this BB
161 if (!PredBBOfPhiArg || PredBBOfPhiArg == PredBB)
162 if (OutSet->insert(*InIt).second)
170 //-----------------------------------------------------------------------------
171 // propogates in set to OutSets of PREDECESSORs
172 //-----------------------------------------------------------------------------
174 bool BBLiveVar::applyFlowFunc(std::map<const BasicBlock *, BBLiveVar *> &LVMap){
175 // IMPORTANT: caller should check whether inset changed
176 // (else no point in calling)
178 // If this BB changed any OutSets of preds whose POID is lower, than we need
179 // another iteration...
181 bool needAnotherIt = false;
183 for (BasicBlock::pred_const_iterator PI = BB->pred_begin(),
184 PE = BB->pred_begin(); PI != PE ; ++PI) {
185 BBLiveVar *PredLVBB = LVMap[*PI];
188 if (setPropagate(&PredLVBB->OutSet, &InSet, *PI)) {
189 PredLVBB->OutSetChanged = true;
191 // if the predec POID is lower than mine
192 if (PredLVBB->getPOId() <= POID)
193 needAnotherIt = true;
197 return needAnotherIt;
202 // ----------------- Methods For Debugging (Printing) -----------------
204 void BBLiveVar::printAllSets() const {
205 cerr << " Defs: "; DefSet.printSet(); cerr << "\n";
206 cerr << " In: "; InSet.printSet(); cerr << "\n";
207 cerr << " Out: "; OutSet.printSet(); cerr << "\n";
210 void BBLiveVar::printInOutSets() const {
211 cerr << " In: "; InSet.printSet(); cerr << "\n";
212 cerr << " Out: "; OutSet.printSet(); cerr << "\n";