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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/Analysis/LiveVar/BBLiveVar.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/BasicBlock.h"
#include "Support/PostOrderIterator.h"
#include <iostream>
AnalysisID MethodLiveVarInfo::ID(AnalysisID::create<MethodLiveVarInfo>());
//-----------------------------------------------------------------------------
// Accessor Functions
//-----------------------------------------------------------------------------
// gets OutSet of a BB
const LiveVarSet *MethodLiveVarInfo::getOutSetOfBB(const BasicBlock *BB) const {
return BB2BBLVMap.find(BB)->second->getOutSet();
}
// gets InSet of a BB
const LiveVarSet *MethodLiveVarInfo::getInSetOfBB(const BasicBlock *BB) const {
return BB2BBLVMap.find(BB)->second->getInSet();
}
//-----------------------------------------------------------------------------
// Performs live var analysis for a method
//-----------------------------------------------------------------------------
bool MethodLiveVarInfo::runOnMethod(Method *M) {
if (DEBUG_LV) std::cerr << "Analysing live variables ...\n";
// create and initialize all the BBLiveVars of the CFG
constructBBs(M);
while (doSingleBackwardPass(M))
; // Iterate until we are done.
if (DEBUG_LV) std::cerr << "Live Variable Analysis complete!\n";
return false;
}
//-----------------------------------------------------------------------------
// constructs BBLiveVars and init Def and In sets
//-----------------------------------------------------------------------------
void MethodLiveVarInfo::constructBBs(const Method *M) {
unsigned int POId = 0; // Reverse Depth-first Order ID
for(po_iterator<const Method*> BBI = po_begin(M), BBE = po_end(M);
BBI != BBE; ++BBI, ++POId) {
const BasicBlock *BB = *BBI; // get the current BB
if (DEBUG_LV) { std::cerr << " For BB "; printValue(BB); cerr << ":\n"; }
// 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)
//
for (Method::const_iterator BBRI = M->begin(), BBRE = M->end();
BBRI != BBRE; ++BBRI, ++POId)
if (!BB2BBLVMap[*BBRI]) // Not yet processed?
BB2BBLVMap[*BBRI] = new BBLiveVar(*BBRI, POId);
}
//-----------------------------------------------------------------------------
// do one backward pass over the CFG (for iterative analysis)
//-----------------------------------------------------------------------------
bool MethodLiveVarInfo::doSingleBackwardPass(const Method *M) {
if (DEBUG_LV) std::cerr << "\n After Backward Pass ...\n";
bool NeedAnotherIteration = false;
for (po_iterator<const Method*> BBI = po_begin(M); BBI != po_end(M) ; ++BBI) {
BBLiveVar *LVBB = BB2BBLVMap[*BBI];
assert(LVBB && "BasicBlock information not set for block!");
if (DEBUG_LV) std::cerr << " For BB " << (*BBI)->getName() << ":\n";
if(LVBB->isOutSetChanged())
LVBB->applyTransferFunc(); // apply the Tran Func to calc InSet
if (LVBB->isInSetChanged()) // to calc Outsets of preds
NeedAnotherIteration |= LVBB->applyFlowFunc(BB2BBLVMap);
if (DEBUG_LV) LVBB->printInOutSets();
}
// true if we need to reiterate over the CFG
return NeedAnotherIteration;
}
void MethodLiveVarInfo::releaseMemory() {
// First delete all BBLiveVar objects created in constructBBs(). A new object
// of type BBLiveVar is created for every BasicBlock in the method
//
for (std::map<const BasicBlock *, BBLiveVar *>::iterator
HMI = BB2BBLVMap.begin(),
HME = BB2BBLVMap.end(); HMI != HME; ++HMI)
delete HMI->second; // delete all BBLiveVar in BB2BBLVMap
BB2BBLVMap.clear();
// Then delete all objects of type LiveVarSet created in calcLiveVarSetsForBB
// and entered into MInst2LVSetBI and MInst2LVSetAI (these are caches
// to return LiveVarSet's before/after a machine instruction quickly). It
// is sufficient to free up all LiveVarSet using only one cache since
// both caches refer to the same sets
//
for (std::map<const MachineInstr*, const LiveVarSet*>::iterator
MI = MInst2LVSetBI.begin(),
ME = MInst2LVSetBI.end(); MI != ME; ++MI)
delete MI->second; // delete all LiveVarSets in MInst2LVSetBI
MInst2LVSetBI.clear();
MInst2LVSetAI.clear();
}
//-----------------------------------------------------------------------------
// Following functions will give the LiveVar info for any machine instr 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.
//-----------------------------------------------------------------------------
//-----------------------------------------------------------------------------
// Gives live variable information before a machine instruction
//-----------------------------------------------------------------------------
const LiveVarSet *
MethodLiveVarInfo::getLiveVarSetBeforeMInst(const MachineInstr *MInst,
const BasicBlock *BB) {
if (const LiveVarSet *LVSet = MInst2LVSetBI[MInst]) {
return LVSet; // if found, just return the set
} else {
calcLiveVarSetsForBB(BB); // else, calc for all instrs in BB
return MInst2LVSetBI[MInst];
}
}
//-----------------------------------------------------------------------------
// Gives live variable information after a machine instruction
//-----------------------------------------------------------------------------
const LiveVarSet *
MethodLiveVarInfo::getLiveVarSetAfterMInst(const MachineInstr *MI,
const BasicBlock *BB) {
if (const LiveVarSet *LVSet = MInst2LVSetAI[MI]) {
return LVSet; // if found, just return the set
} else {
calcLiveVarSetsForBB(BB); // else, calc for all instrs in BB
return MInst2LVSetAI[MI];
}
}
//-----------------------------------------------------------------------------
// This method calculates the live variable information for all the
// instructions in a basic block and enter the newly constructed live
// variable sets into a the caches (MInst2LVSetAI, MInst2LVSetBI)
//-----------------------------------------------------------------------------
void MethodLiveVarInfo::calcLiveVarSetsForBB(const BasicBlock *BB) {
const MachineCodeForBasicBlock &MIVec = BB->getMachineInstrVec();
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 (MachineCodeForBasicBlock::const_reverse_iterator MII = MIVec.rbegin(),
MIE = MIVec.rend(); MII != MIE; ++MII) {
// MI is cur machine inst
const MachineInstr *MI = *MII;
MInst2LVSetAI[MI] = SetAI; // record in After Inst map
CurSet->applyTranferFuncForMInst(MI); // 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[MI] = NewSet; // record in Before Inst map
// SetAI will be used in the next iteration
SetAI = NewSet;
}
}
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