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