1 //===-- FunctionLiveVarInfo.cpp - Live Variable Analysis for a Function ---===//
3 // This is the interface to function level live variable information that is
4 // provided by live variable analysis.
6 //===----------------------------------------------------------------------===//
8 #include "llvm/Analysis/LiveVar/FunctionLiveVarInfo.h"
10 #include "llvm/CodeGen/MachineInstr.h"
11 #include "llvm/CodeGen/MachineFunction.h"
12 #include "llvm/Support/CFG.h"
13 #include "Support/PostOrderIterator.h"
14 #include "Support/SetOperations.h"
15 #include "Support/CommandLine.h"
17 static RegisterAnalysis<FunctionLiveVarInfo>
18 X("livevar", "Live Variable Analysis");
20 LiveVarDebugLevel_t DEBUG_LV;
22 static cl::opt<LiveVarDebugLevel_t, true>
23 DEBUG_LV_opt("dlivevar", cl::Hidden, cl::location(DEBUG_LV),
24 cl::desc("enable live-variable debugging information"),
26 clEnumValN(LV_DEBUG_None , "n", "disable debug output"),
27 clEnumValN(LV_DEBUG_Normal , "y", "enable debug output"),
28 clEnumValN(LV_DEBUG_Instr, "i", "print live-var sets before/after "
29 "every machine instrn"),
30 clEnumValN(LV_DEBUG_Verbose, "v", "print def, use sets for every instrn also"),
35 //-----------------------------------------------------------------------------
37 //-----------------------------------------------------------------------------
39 // gets OutSet of a BB
40 const ValueSet &FunctionLiveVarInfo::getOutSetOfBB(const BasicBlock *BB) const {
41 return BBLiveVar::GetFromBB(*BB)->getOutSet();
45 const ValueSet &FunctionLiveVarInfo::getInSetOfBB(const BasicBlock *BB) const {
46 return BBLiveVar::GetFromBB(*BB)->getInSet();
50 //-----------------------------------------------------------------------------
51 // Performs live var analysis for a function
52 //-----------------------------------------------------------------------------
54 bool FunctionLiveVarInfo::runOnFunction(Function &F) {
56 if (DEBUG_LV) std::cerr << "Analysing live variables ...\n";
58 // create and initialize all the BBLiveVars of the CFG
62 while (doSingleBackwardPass(M, iter++))
63 ; // Iterate until we are done.
65 if (DEBUG_LV) std::cerr << "Live Variable Analysis complete!\n";
70 //-----------------------------------------------------------------------------
71 // constructs BBLiveVars and init Def and In sets
72 //-----------------------------------------------------------------------------
74 void FunctionLiveVarInfo::constructBBs(const Function *F) {
75 unsigned POId = 0; // Reverse Depth-first Order ID
76 std::map<const BasicBlock*, unsigned> PONumbering;
78 for (po_iterator<const Function*> BBI = po_begin(M), BBE = po_end(M);
80 PONumbering[*BBI] = POId++;
82 MachineFunction &MF = MachineFunction::get(F);
83 for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
84 const BasicBlock &BB = *I->getBasicBlock(); // get the current BB
85 if (DEBUG_LV) std::cerr << " For BB " << RAV(BB) << ":\n";
88 std::map<const BasicBlock*, unsigned>::iterator POI = PONumbering.find(&BB);
89 if (POI != PONumbering.end()) {
90 // create a new BBLiveVar
91 LVBB = BBLiveVar::CreateOnBB(BB, *I, POId);
93 // The PO iterator does not discover unreachable blocks, but the random
94 // iterator later may access these blocks. We must make sure to
95 // initialize unreachable blocks as well. However, LV info is not correct
96 // for those blocks (they are not analyzed)
98 LVBB = BBLiveVar::CreateOnBB(BB, *I, ++POId);
102 LVBB->printAllSets();
107 //-----------------------------------------------------------------------------
108 // do one backward pass over the CFG (for iterative analysis)
109 //-----------------------------------------------------------------------------
111 bool FunctionLiveVarInfo::doSingleBackwardPass(const Function *M,
113 if (DEBUG_LV) std::cerr << "\n After Backward Pass " << iter << "...\n";
115 bool NeedAnotherIteration = false;
116 for (po_iterator<const Function*> BBI = po_begin(M), BBE = po_end(M);
118 BBLiveVar *LVBB = BBLiveVar::GetFromBB(**BBI);
119 assert(LVBB && "BasicBlock information not set for block!");
121 if (DEBUG_LV) std::cerr << " For BB " << (*BBI)->getName() << ":\n";
123 // InSets are initialized to "GenSet". Recompute only if OutSet changed.
124 if(LVBB->isOutSetChanged())
125 LVBB->applyTransferFunc(); // apply the Tran Func to calc InSet
127 // OutSets are initialized to EMPTY. Recompute on first iter or if InSet
129 if (iter == 0 || LVBB->isInSetChanged()) // to calc Outsets of preds
130 NeedAnotherIteration |= LVBB->applyFlowFunc();
132 if (DEBUG_LV) LVBB->printInOutSets();
135 // true if we need to reiterate over the CFG
136 return NeedAnotherIteration;
140 void FunctionLiveVarInfo::releaseMemory() {
141 // First remove all BBLiveVar annotations created in constructBBs().
143 for (Function::const_iterator I = M->begin(), E = M->end(); I != E; ++I)
144 BBLiveVar::RemoveFromBB(*I);
147 // Then delete all objects of type ValueSet created in calcLiveVarSetsForBB
148 // and entered into MInst2LVSetBI and MInst2LVSetAI (these are caches
149 // to return ValueSet's before/after a machine instruction quickly). It
150 // is sufficient to free up all ValueSet using only one cache since
151 // both caches refer to the same sets
153 for (std::map<const MachineInstr*, const ValueSet*>::iterator
154 MI = MInst2LVSetBI.begin(),
155 ME = MInst2LVSetBI.end(); MI != ME; ++MI)
156 delete MI->second; // delete all ValueSets in MInst2LVSetBI
158 MInst2LVSetBI.clear();
159 MInst2LVSetAI.clear();
165 //-----------------------------------------------------------------------------
166 // Following functions will give the LiveVar info for any machine instr in
167 // a function. It should be called after a call to analyze().
169 // Thsese functions calucluates live var info for all the machine instrs in a
170 // BB when LVInfo for one inst is requested. Hence, this function is useful
171 // when live var info is required for many (or all) instructions in a basic
172 // block. Also, the arguments to this function does not require specific
174 //-----------------------------------------------------------------------------
176 //-----------------------------------------------------------------------------
177 // Gives live variable information before a machine instruction
178 //-----------------------------------------------------------------------------
181 FunctionLiveVarInfo::getLiveVarSetBeforeMInst(const MachineInstr *MInst,
182 const BasicBlock *BB) {
183 if (const ValueSet *LVSet = MInst2LVSetBI[MInst]) {
184 return *LVSet; // if found, just return the set
186 calcLiveVarSetsForBB(BB); // else, calc for all instrs in BB
187 return *MInst2LVSetBI[MInst];
192 //-----------------------------------------------------------------------------
193 // Gives live variable information after a machine instruction
194 //-----------------------------------------------------------------------------
196 FunctionLiveVarInfo::getLiveVarSetAfterMInst(const MachineInstr *MI,
197 const BasicBlock *BB) {
199 if (const ValueSet *LVSet = MInst2LVSetAI[MI]) {
200 return *LVSet; // if found, just return the set
202 calcLiveVarSetsForBB(BB); // else, calc for all instrs in BB
203 return *MInst2LVSetAI[MI];
207 // This function applies a machine instr to a live var set (accepts OutSet) and
208 // makes necessary changes to it (produces InSet). Note that two for loops are
209 // used to first kill all defs and then to add all uses. This is because there
210 // can be instructions like Val = Val + 1 since we allow multipe defs to a
211 // machine instruction operand.
213 static void applyTranferFuncForMInst(ValueSet &LVS, const MachineInstr *MInst) {
214 for (MachineInstr::const_val_op_iterator OpI = MInst->begin(),
215 OpE = MInst->end(); OpI != OpE; ++OpI) {
216 if (OpI.isDef()) // kill only if this operand is a def
217 LVS.erase(*OpI); // this definition kills any uses
220 // do for implicit operands as well
221 for (unsigned i=0; i < MInst->getNumImplicitRefs(); ++i) {
222 if (MInst->implicitRefIsDefined(i))
223 LVS.erase(MInst->getImplicitRef(i));
226 for (MachineInstr::const_val_op_iterator OpI = MInst->begin(),
227 OpE = MInst->end(); OpI != OpE; ++OpI) {
228 if (!isa<BasicBlock>(*OpI)) // don't process labels
229 // add only if this operand is a use
230 if (!OpI.isDef() || OpI.isDefAndUse() )
231 LVS.insert(*OpI); // An operand is a use - so add to use set
234 // do for implicit operands as well
235 for (unsigned i = 0, e = MInst->getNumImplicitRefs(); i != e; ++i)
236 if (!MInst->implicitRefIsDefined(i) ||
237 MInst->implicitRefIsDefinedAndUsed(i))
238 LVS.insert(MInst->getImplicitRef(i));
241 //-----------------------------------------------------------------------------
242 // This method calculates the live variable information for all the
243 // instructions in a basic block and enter the newly constructed live
244 // variable sets into a the caches (MInst2LVSetAI, MInst2LVSetBI)
245 //-----------------------------------------------------------------------------
247 void FunctionLiveVarInfo::calcLiveVarSetsForBB(const BasicBlock *BB) {
248 BBLiveVar *BBLV = BBLiveVar::GetFromBB(*BB);
249 assert(BBLV && "BBLiveVar annotation doesn't exist?");
250 const MachineBasicBlock &MIVec = BBLV->getMachineBasicBlock();
252 if (DEBUG_LV >= LV_DEBUG_Instr)
253 std::cerr << "\n======For BB " << BB->getName()
254 << ": Live var sets for instructions======\n";
257 const ValueSet *SetAI = &getOutSetOfBB(BB); // init SetAI with OutSet
258 set_union(CurSet, *SetAI); // CurSet now contains OutSet
260 // iterate over all the machine instructions in BB
261 for (MachineBasicBlock::const_reverse_iterator MII = MIVec.rbegin(),
262 MIE = MIVec.rend(); MII != MIE; ++MII) {
263 // MI is cur machine inst
264 const MachineInstr *MI = *MII;
266 MInst2LVSetAI[MI] = SetAI; // record in After Inst map
268 applyTranferFuncForMInst(CurSet, MI); // apply the transfer Func
269 ValueSet *NewSet = new ValueSet(); // create a new set and
270 set_union(*NewSet, CurSet); // copy the set after T/F to it
272 MInst2LVSetBI[MI] = NewSet; // record in Before Inst map
274 if (DEBUG_LV >= LV_DEBUG_Instr) {
275 std::cerr << "\nLive var sets before/after instruction " << *MI;
276 std::cerr << " Before: "; printSet(*NewSet); std::cerr << "\n";
277 std::cerr << " After : "; printSet(*SetAI); std::cerr << "\n";
280 // SetAI will be used in the next iteration