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292 lines
8.6 KiB
C++
292 lines
8.6 KiB
C++
/* Title: MethodLiveVarInfo.cpp
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Author: Ruchira Sasanka
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Date: Jun 30, 01
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Purpose:
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This is the interface for live variable info of a method that is required
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by any other part of the compiler.
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*/
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#include "llvm/Analysis/LiveVar/MethodLiveVarInfo.h"
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#include "llvm/CodeGen/MachineInstr.h"
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#include "Support/PostOrderIterator.h"
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//************************** Constructor/Destructor ***************************
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MethodLiveVarInfo::MethodLiveVarInfo(const Method *const M) : Meth(M),
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BB2BBLVMap()
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{
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assert(! M->isExternal() ); // cannot be a prototype decleration
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HasAnalyzed = false; // still we haven't called analyze()
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}
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MethodLiveVarInfo:: ~MethodLiveVarInfo()
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{
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// First delete all BBLiveVar objects created in constructBBs(). A new object
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// of type BBLiveVa is created for every BasicBlock in the method
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// hash map iterator for BB2BBLVMap
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//
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BBToBBLiveVarMapType::iterator HMI = BB2BBLVMap.begin();
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for( ; HMI != BB2BBLVMap.end() ; HMI ++ ) {
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if( (*HMI).first ) // delete all BBLiveVar in BB2BBLVMap
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delete (*HMI).second;
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}
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// Then delete all objects of type LiveVarSet created in calcLiveVarSetsForBB
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// and entered into MInst2LVSetBI and MInst2LVSetAI (these are caches
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// to return LiveVarSet's before/after a machine instruction quickly). It
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// is sufficient to free up all LiveVarSet using only one cache since
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// both caches refer to the same sets
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// hash map iterator for MInst2LVSetBI
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//
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MInstToLiveVarSetMapType::iterator MI = MInst2LVSetBI.begin();
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for( ; MI != MInst2LVSetBI.end() ; MI ++ ) {
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if( (*MI).first ) // delete all LiveVarSets in MInst2LVSetBI
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delete (*MI).second;
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}
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}
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// ************************* support functions ********************************
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//-----------------------------------------------------------------------------
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// constructs BBLiveVars and init Def and In sets
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//-----------------------------------------------------------------------------
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void MethodLiveVarInfo::constructBBs()
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{
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unsigned int POId = 0; // Reverse Depth-first Order ID
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po_iterator<const Method*> BBI = po_begin(Meth);
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for( ; BBI != po_end(Meth) ; ++BBI, ++POId)
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{
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const BasicBlock *BB = *BBI; // get the current BB
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if(DEBUG_LV) { cout << " For BB "; printValue(BB); cout << ":" << endl; }
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// create a new BBLiveVar
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BBLiveVar * LVBB = new BBLiveVar( BB, POId );
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BB2BBLVMap[ BB ] = LVBB; // insert the pair to Map
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LVBB->calcDefUseSets(); // calculates the def and in set
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if(DEBUG_LV)
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LVBB->printAllSets();
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}
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// Since the PO iterator does not discover unreachable blocks,
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// go over the random iterator and init those blocks as well.
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// However, LV info is not correct for those blocks (they are not
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// analyzed)
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Method::const_iterator BBRI = Meth->begin(); // random iterator for BBs
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for( ; BBRI != Meth->end(); ++BBRI, ++POId) {
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if( ! BB2BBLVMap[ *BBRI ] )
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BB2BBLVMap[ *BBRI ] = new BBLiveVar( *BBRI, POId );
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}
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}
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//-----------------------------------------------------------------------------
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// do one backward pass over the CFG (for iterative analysis)
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//-----------------------------------------------------------------------------
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bool MethodLiveVarInfo::doSingleBackwardPass()
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{
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bool ResultFlow, NeedAnotherIteration = false;
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if(DEBUG_LV)
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cout << endl << " After Backward Pass ..." << endl;
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po_iterator<const Method*> BBI = po_begin(Meth);
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for( ; BBI != po_end(Meth) ; ++BBI)
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{
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BBLiveVar* LVBB = BB2BBLVMap[*BBI];
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assert( LVBB );
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if(DEBUG_LV) cout << " For BB " << (*BBI)->getName() << ":" << endl;
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// cout << " (POId=" << LVBB->getPOId() << ")" << endl ;
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ResultFlow = false;
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if( LVBB->isOutSetChanged() )
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LVBB->applyTransferFunc(); // apply the Tran Func to calc InSet
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if( LVBB->isInSetChanged() ) // to calc Outsets of preds
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ResultFlow = LVBB->applyFlowFunc(BB2BBLVMap);
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if(DEBUG_LV) LVBB->printInOutSets();
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if( ResultFlow ) NeedAnotherIteration = true;
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}
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// true if we need to reiterate over the CFG
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return NeedAnotherIteration;
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}
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//-----------------------------------------------------------------------------
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// performs live var anal for a method
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//-----------------------------------------------------------------------------
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void MethodLiveVarInfo::analyze()
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{
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// Don't analyze the same method twice!
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// Later, we need to add change notification here.
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if (HasAnalyzed)
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return;
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if( DEBUG_LV) cout << "Analysing live variables ..." << endl;
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// create and initialize all the BBLiveVars of the CFG
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constructBBs();
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bool NeedAnotherIteration = false;
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do { // do one pass over CFG
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NeedAnotherIteration = doSingleBackwardPass( );
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} while (NeedAnotherIteration ); // repeat until we need more iterations
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HasAnalyzed = true; // finished analysing
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if( DEBUG_LV) cout << "Live Variable Analysis complete!" << endl;
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}
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//-----------------------------------------------------------------------------
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/* Following functions will give the LiveVar info for any machine instr in
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a method. It should be called after a call to analyze().
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Thsese functions calucluates live var info for all the machine instrs in a
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BB when LVInfo for one inst is requested. Hence, this function is useful
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when live var info is required for many (or all) instructions in a basic
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block. Also, the arguments to this method does not require specific
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iterators.
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*/
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//-----------------------------------------------------------------------------
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//-----------------------------------------------------------------------------
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// Gives live variable information before a machine instruction
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//-----------------------------------------------------------------------------
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const LiveVarSet *
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MethodLiveVarInfo::getLiveVarSetBeforeMInst(const MachineInstr *const MInst,
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const BasicBlock *const CurBB)
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{
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const LiveVarSet *LVSet = MInst2LVSetBI[MInst];
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if( LVSet ) return LVSet; // if found, just return the set
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else {
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calcLiveVarSetsForBB( CurBB ); // else, calc for all instrs in BB
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/*if( ! MInst2LVSetBI[ MInst ] ) {
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cerr << "\nFor BB "; printValue( CurBB);
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cerr << "\nRequested LVSet for inst: " << *MInst;
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}*/
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assert( MInst2LVSetBI[ MInst ] );
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return MInst2LVSetBI[ MInst ];
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}
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}
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//-----------------------------------------------------------------------------
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// Gives live variable information after a machine instruction
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//-----------------------------------------------------------------------------
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const LiveVarSet *
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MethodLiveVarInfo::getLiveVarSetAfterMInst(const MachineInstr *const MInst,
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const BasicBlock *const CurBB)
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{
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const LiveVarSet *LVSet = MInst2LVSetAI[MInst];
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if( LVSet ) return LVSet; // if found, just return the set
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else {
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calcLiveVarSetsForBB( CurBB ); // else, calc for all instrs in BB
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assert( MInst2LVSetAI[ MInst ] );
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return MInst2LVSetAI[ MInst ];
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}
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}
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//-----------------------------------------------------------------------------
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// This method calculates the live variable information for all the
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// instructions in a basic block and enter the newly constructed live
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// variable sets into a the caches ( MInst2LVSetAI, MInst2LVSetBI)
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//-----------------------------------------------------------------------------
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void MethodLiveVarInfo::calcLiveVarSetsForBB(const BasicBlock *const BB)
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{
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const MachineCodeForBasicBlock& MIVec = BB->getMachineInstrVec();
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MachineCodeForBasicBlock::const_reverse_iterator
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MInstIterator = MIVec.rbegin();
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LiveVarSet *CurSet = new LiveVarSet();
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const LiveVarSet *SetAI = getOutSetOfBB(BB); // init SetAI with OutSet
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CurSet->setUnion(SetAI); // CurSet now contains OutSet
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// iterate over all the machine instructions in BB
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for( ; MInstIterator != MIVec.rend(); MInstIterator++) {
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// MInst is cur machine inst
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const MachineInstr * MInst = *MInstIterator;
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MInst2LVSetAI[MInst] = SetAI; // record in After Inst map
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CurSet->applyTranferFuncForMInst( MInst ); // apply the transfer Func
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LiveVarSet *NewSet = new LiveVarSet(); // create a new set and
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NewSet->setUnion( CurSet ); // copy the set after T/F to it
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MInst2LVSetBI[MInst] = NewSet; // record in Before Inst map
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// SetAI will be used in the next iteration
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SetAI = NewSet;
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}
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}
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