1 //===-- FunctionLiveVarInfo.cpp - Live Variable Analysis for a Function ---===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This is the interface to function level live variable information that is
11 // provided by live variable analysis.
13 //===----------------------------------------------------------------------===//
15 #include "FunctionLiveVarInfo.h"
16 #include "llvm/CodeGen/MachineInstr.h"
17 #include "llvm/CodeGen/MachineFunction.h"
18 #include "llvm/Target/TargetMachine.h"
19 #include "llvm/Target/TargetInstrInfo.h"
20 #include "llvm/Support/CFG.h"
21 #include "llvm/ADT/PostOrderIterator.h"
22 #include "llvm/ADT/SetOperations.h"
23 #include "llvm/Support/CommandLine.h"
24 #include "BBLiveVar.h"
29 static RegisterAnalysis<FunctionLiveVarInfo>
30 X("livevar", "Live Variable Analysis");
32 LiveVarDebugLevel_t DEBUG_LV;
34 static cl::opt<LiveVarDebugLevel_t, true>
35 DEBUG_LV_opt("dlivevar", cl::Hidden, cl::location(DEBUG_LV),
36 cl::desc("enable live-variable debugging information"),
38 clEnumValN(LV_DEBUG_None , "n", "disable debug output"),
39 clEnumValN(LV_DEBUG_Normal , "y", "enable debug output"),
40 clEnumValN(LV_DEBUG_Instr, "i", "print live-var sets before/after "
41 "every machine instrn"),
42 clEnumValN(LV_DEBUG_Verbose, "v", "print def, use sets for every instrn also"),
47 //-----------------------------------------------------------------------------
49 //-----------------------------------------------------------------------------
51 // gets OutSet of a BB
52 const ValueSet &FunctionLiveVarInfo::getOutSetOfBB(const BasicBlock *BB) const {
53 return BBLiveVarInfo.find(BB)->second->getOutSet();
55 ValueSet &FunctionLiveVarInfo::getOutSetOfBB(const BasicBlock *BB) {
56 return BBLiveVarInfo[BB]->getOutSet();
60 const ValueSet &FunctionLiveVarInfo::getInSetOfBB(const BasicBlock *BB) const {
61 return BBLiveVarInfo.find(BB)->second->getInSet();
63 ValueSet &FunctionLiveVarInfo::getInSetOfBB(const BasicBlock *BB) {
64 return BBLiveVarInfo[BB]->getInSet();
68 //-----------------------------------------------------------------------------
69 // Performs live var analysis for a function
70 //-----------------------------------------------------------------------------
72 bool FunctionLiveVarInfo::runOnFunction(Function &F) {
74 if (DEBUG_LV) std::cerr << "Analysing live variables ...\n";
76 // create and initialize all the BBLiveVars of the CFG
80 while (doSingleBackwardPass(M, iter++))
81 ; // Iterate until we are done.
83 if (DEBUG_LV) std::cerr << "Live Variable Analysis complete!\n";
88 //-----------------------------------------------------------------------------
89 // constructs BBLiveVars and init Def and In sets
90 //-----------------------------------------------------------------------------
92 void FunctionLiveVarInfo::constructBBs(const Function *F) {
93 unsigned POId = 0; // Reverse Depth-first Order ID
94 std::map<const BasicBlock*, unsigned> PONumbering;
96 for (po_iterator<const Function*> BBI = po_begin(M), BBE = po_end(M);
98 PONumbering[*BBI] = POId++;
100 MachineFunction &MF = MachineFunction::get(F);
101 for (MachineFunction::iterator I = MF.begin(), E = MF.end(); I != E; ++I) {
102 const BasicBlock &BB = *I->getBasicBlock(); // get the current BB
103 if (DEBUG_LV) std::cerr << " For BB " << RAV(BB) << ":\n";
106 std::map<const BasicBlock*, unsigned>::iterator POI = PONumbering.find(&BB);
107 if (POI != PONumbering.end()) {
108 // create a new BBLiveVar
109 LVBB = new BBLiveVar(BB, *I, POId);
111 // The PO iterator does not discover unreachable blocks, but the random
112 // iterator later may access these blocks. We must make sure to
113 // initialize unreachable blocks as well. However, LV info is not correct
114 // for those blocks (they are not analyzed)
116 LVBB = new BBLiveVar(BB, *I, ++POId);
118 BBLiveVarInfo[&BB] = LVBB;
121 LVBB->printAllSets();
126 //-----------------------------------------------------------------------------
127 // do one backward pass over the CFG (for iterative analysis)
128 //-----------------------------------------------------------------------------
130 bool FunctionLiveVarInfo::doSingleBackwardPass(const Function *M,
132 if (DEBUG_LV) std::cerr << "\n After Backward Pass " << iter << "...\n";
134 bool NeedAnotherIteration = false;
135 for (po_iterator<const Function*> BBI = po_begin(M), BBE = po_end(M);
137 BBLiveVar *LVBB = BBLiveVarInfo[*BBI];
138 assert(LVBB && "BasicBlock information not set for block!");
140 if (DEBUG_LV) std::cerr << " For BB " << (*BBI)->getName() << ":\n";
142 // InSets are initialized to "GenSet". Recompute only if OutSet changed.
143 if(LVBB->isOutSetChanged())
144 LVBB->applyTransferFunc(); // apply the Tran Func to calc InSet
146 // OutSets are initialized to EMPTY. Recompute on first iter or if InSet
148 if (iter == 0 || LVBB->isInSetChanged()) // to calc Outsets of preds
149 NeedAnotherIteration |= LVBB->applyFlowFunc(BBLiveVarInfo);
151 if (DEBUG_LV) LVBB->printInOutSets();
154 // true if we need to reiterate over the CFG
155 return NeedAnotherIteration;
159 void FunctionLiveVarInfo::releaseMemory() {
160 // First remove all BBLiveVars created in constructBBs().
162 for (Function::const_iterator I = M->begin(), E = M->end(); I != E; ++I)
163 delete BBLiveVarInfo[I];
164 BBLiveVarInfo.clear();
168 // Then delete all objects of type ValueSet created in calcLiveVarSetsForBB
169 // and entered into MInst2LVSetBI and MInst2LVSetAI (these are caches
170 // to return ValueSet's before/after a machine instruction quickly).
171 // We do not need to free up ValueSets in MInst2LVSetAI because it holds
172 // pointers to the same sets as in MInst2LVSetBI (for all instructions
173 // except the last one in a BB) or in BBLiveVar (for the last instruction).
175 for (hash_map<const MachineInstr*, ValueSet*>::iterator
176 MI = MInst2LVSetBI.begin(),
177 ME = MInst2LVSetBI.end(); MI != ME; ++MI)
178 delete MI->second; // delete all ValueSets in MInst2LVSetBI
180 MInst2LVSetBI.clear();
181 MInst2LVSetAI.clear();
187 //-----------------------------------------------------------------------------
188 // Following functions will give the LiveVar info for any machine instr in
189 // a function. It should be called after a call to analyze().
191 // These functions calculate live var info for all the machine instrs in a
192 // BB when LVInfo for one inst is requested. Hence, this function is useful
193 // when live var info is required for many (or all) instructions in a basic
194 // block. Also, the arguments to this function does not require specific
196 //-----------------------------------------------------------------------------
198 //-----------------------------------------------------------------------------
199 // Gives live variable information before a machine instruction
200 //-----------------------------------------------------------------------------
203 FunctionLiveVarInfo::getLiveVarSetBeforeMInst(const MachineInstr *MI,
204 const BasicBlock *BB) {
205 ValueSet* &LVSet = MInst2LVSetBI[MI]; // ref. to map entry
206 if (LVSet == NULL && BB != NULL) { // if not found and BB provided
207 calcLiveVarSetsForBB(BB); // calc LVSet for all instrs in BB
208 assert(LVSet != NULL);
214 //-----------------------------------------------------------------------------
215 // Gives live variable information after a machine instruction
216 //-----------------------------------------------------------------------------
219 FunctionLiveVarInfo::getLiveVarSetAfterMInst(const MachineInstr *MI,
220 const BasicBlock *BB) {
222 ValueSet* &LVSet = MInst2LVSetAI[MI]; // ref. to map entry
223 if (LVSet == NULL && BB != NULL) { // if not found and BB provided
224 calcLiveVarSetsForBB(BB); // calc LVSet for all instrs in BB
225 assert(LVSet != NULL);
230 // This function applies a machine instr to a live var set (accepts OutSet) and
231 // makes necessary changes to it (produces InSet). Note that two for loops are
232 // used to first kill all defs and then to add all uses. This is because there
233 // can be instructions like Val = Val + 1 since we allow multiple defs to a
234 // machine instruction operand.
236 static void applyTranferFuncForMInst(ValueSet &LVS, const MachineInstr *MInst) {
237 for (MachineInstr::const_val_op_iterator OpI = MInst->begin(),
238 OpE = MInst->end(); OpI != OpE; ++OpI) {
239 if (OpI.isDef()) // kill if this operand is a def
240 LVS.erase(*OpI); // this definition kills any uses
243 // do for implicit operands as well
244 for (unsigned i=0; i < MInst->getNumImplicitRefs(); ++i) {
245 if (MInst->getImplicitOp(i).isDef())
246 LVS.erase(MInst->getImplicitRef(i));
249 for (MachineInstr::const_val_op_iterator OpI = MInst->begin(),
250 OpE = MInst->end(); OpI != OpE; ++OpI) {
251 if (!isa<BasicBlock>(*OpI)) // don't process labels
252 // add only if this operand is a use
254 LVS.insert(*OpI); // An operand is a use - so add to use set
257 // do for implicit operands as well
258 for (unsigned i = 0, e = MInst->getNumImplicitRefs(); i != e; ++i)
259 if (MInst->getImplicitOp(i).isUse())
260 LVS.insert(MInst->getImplicitRef(i));
263 //-----------------------------------------------------------------------------
264 // This method calculates the live variable information for all the
265 // instructions in a basic block and enter the newly constructed live
266 // variable sets into a the caches (MInst2LVSetAI, MInst2LVSetBI)
267 //-----------------------------------------------------------------------------
269 void FunctionLiveVarInfo::calcLiveVarSetsForBB(const BasicBlock *BB) {
270 BBLiveVar *BBLV = BBLiveVarInfo[BB];
271 assert(BBLV && "BBLiveVar annotation doesn't exist?");
272 const MachineBasicBlock &MIVec = BBLV->getMachineBasicBlock();
273 const MachineFunction &MF = MachineFunction::get(M);
274 const TargetMachine &TM = MF.getTarget();
276 if (DEBUG_LV >= LV_DEBUG_Instr)
277 std::cerr << "\n======For BB " << BB->getName()
278 << ": Live var sets for instructions======\n";
280 ValueSet *SetAI = &getOutSetOfBB(BB); // init SetAI with OutSet
281 ValueSet CurSet(*SetAI); // CurSet now contains OutSet
283 // iterate over all the machine instructions in BB
284 for (MachineBasicBlock::const_reverse_iterator MII = MIVec.rbegin(),
285 MIE = MIVec.rend(); MII != MIE; ++MII) {
286 // MI is cur machine inst
287 const MachineInstr *MI = &*MII;
289 MInst2LVSetAI[MI] = SetAI; // record in After Inst map
291 applyTranferFuncForMInst(CurSet, MI); // apply the transfer Func
292 ValueSet *NewSet = new ValueSet(CurSet); // create a new set with a copy
293 // of the set after T/F
294 MInst2LVSetBI[MI] = NewSet; // record in Before Inst map
296 // If the current machine instruction has delay slots, mark values
297 // used by this instruction as live before and after each delay slot
298 // instruction (After(MI) is the same as Before(MI+1) except for last MI).
299 if (unsigned DS = TM.getInstrInfo()->getNumDelaySlots(MI->getOpcode())) {
300 MachineBasicBlock::const_iterator fwdMII = MII.base(); // ptr to *next* MI
301 for (unsigned i = 0; i < DS; ++i, ++fwdMII) {
302 assert(fwdMII != MIVec.end() && "Missing instruction in delay slot?");
303 const MachineInstr* DelaySlotMI = fwdMII;
304 if (! TM.getInstrInfo()->isNop(DelaySlotMI->getOpcode())) {
305 set_union(*MInst2LVSetBI[DelaySlotMI], *NewSet);
307 set_union(*MInst2LVSetAI[DelaySlotMI], *NewSet);
312 if (DEBUG_LV >= LV_DEBUG_Instr) {
313 std::cerr << "\nLive var sets before/after instruction " << *MI;
314 std::cerr << " Before: "; printSet(*NewSet); std::cerr << "\n";
315 std::cerr << " After : "; printSet(*SetAI); std::cerr << "\n";
318 // SetAI will be used in the next iteration
323 } // End llvm namespace