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270 lines
10 KiB
C++
270 lines
10 KiB
C++
//===-- FunctionLiveVarInfo.cpp - Live Variable Analysis for a Function ---===//
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//
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// This is the interface to function level live variable information that is
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// provided by live variable analysis.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Analysis/LiveVar/FunctionLiveVarInfo.h"
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#include "BBLiveVar.h"
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#include "llvm/CodeGen/MachineInstr.h"
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#include "llvm/Support/CFG.h"
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#include "Support/PostOrderIterator.h"
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#include "Support/SetOperations.h"
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#include "Support/CommandLine.h"
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#include <iostream>
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AnalysisID FunctionLiveVarInfo::ID(AnalysisID::create<FunctionLiveVarInfo>());
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LiveVarDebugLevel_t DEBUG_LV;
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static cl::Enum<LiveVarDebugLevel_t> DEBUG_LV_opt(DEBUG_LV, "dlivevar", cl::Hidden,
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"enable live-variable debugging information",
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clEnumValN(LV_DEBUG_None , "n", "disable debug output"),
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clEnumValN(LV_DEBUG_Normal , "y", "enable debug output"),
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clEnumValN(LV_DEBUG_Instr, "i", "print live-var sets before/after every machine instrn"),
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clEnumValN(LV_DEBUG_Verbose, "v", "print def, use sets for every instrn also"), 0);
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//-----------------------------------------------------------------------------
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// Accessor Functions
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//-----------------------------------------------------------------------------
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// gets OutSet of a BB
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const ValueSet &FunctionLiveVarInfo::getOutSetOfBB(const BasicBlock *BB) const {
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return BBLiveVar::GetFromBB(*BB)->getOutSet();
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}
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// gets InSet of a BB
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const ValueSet &FunctionLiveVarInfo::getInSetOfBB(const BasicBlock *BB) const {
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return BBLiveVar::GetFromBB(*BB)->getInSet();
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}
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//-----------------------------------------------------------------------------
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// Performs live var analysis for a function
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//-----------------------------------------------------------------------------
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bool FunctionLiveVarInfo::runOnFunction(Function &F) {
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M = &F;
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if (DEBUG_LV) std::cerr << "Analysing live variables ...\n";
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// create and initialize all the BBLiveVars of the CFG
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constructBBs(M);
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unsigned int iter=0;
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while (doSingleBackwardPass(M, iter++))
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; // Iterate until we are done.
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if (DEBUG_LV) std::cerr << "Live Variable Analysis complete!\n";
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return false;
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}
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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 FunctionLiveVarInfo::constructBBs(const Function *M) {
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unsigned int POId = 0; // Reverse Depth-first Order ID
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for(po_iterator<const Function*> BBI = po_begin(M), BBE = po_end(M);
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BBI != BBE; ++BBI, ++POId) {
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const BasicBlock &BB = **BBI; // get the current BB
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if (DEBUG_LV) std::cerr << " For BB " << RAV(BB) << ":\n";
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// create a new BBLiveVar
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BBLiveVar *LVBB = BBLiveVar::CreateOnBB(BB, POId);
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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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//
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for (Function::const_iterator BBRI = M->begin(), BBRE = M->end();
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BBRI != BBRE; ++BBRI, ++POId)
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if (!BBLiveVar::GetFromBB(*BBRI)) // Not yet processed?
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BBLiveVar::CreateOnBB(*BBRI, POId);
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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 FunctionLiveVarInfo::doSingleBackwardPass(const Function *M,
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unsigned iter) {
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if (DEBUG_LV) std::cerr << "\n After Backward Pass " << iter << "...\n";
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bool NeedAnotherIteration = false;
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for (po_iterator<const Function*> BBI = po_begin(M), BBE = po_end(M);
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BBI != BBE; ++BBI) {
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BBLiveVar *LVBB = BBLiveVar::GetFromBB(**BBI);
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assert(LVBB && "BasicBlock information not set for block!");
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if (DEBUG_LV) std::cerr << " For BB " << (*BBI)->getName() << ":\n";
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// InSets are initialized to "GenSet". Recompute only if OutSet changed.
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if(LVBB->isOutSetChanged())
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LVBB->applyTransferFunc(); // apply the Tran Func to calc InSet
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// OutSets are initialized to EMPTY. Recompute on first iter or if InSet
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// changed.
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if (iter == 0 || LVBB->isInSetChanged()) // to calc Outsets of preds
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NeedAnotherIteration |= LVBB->applyFlowFunc();
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if (DEBUG_LV) LVBB->printInOutSets();
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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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void FunctionLiveVarInfo::releaseMemory() {
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// First remove all BBLiveVar annotations created in constructBBs().
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if (M)
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for (Function::const_iterator I = M->begin(), E = M->end(); I != E; ++I)
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BBLiveVar::RemoveFromBB(*I);
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M = 0;
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// Then delete all objects of type ValueSet created in calcLiveVarSetsForBB
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// and entered into MInst2LVSetBI and MInst2LVSetAI (these are caches
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// to return ValueSet's before/after a machine instruction quickly). It
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// is sufficient to free up all ValueSet using only one cache since
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// both caches refer to the same sets
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//
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for (std::map<const MachineInstr*, const ValueSet*>::iterator
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MI = MInst2LVSetBI.begin(),
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ME = MInst2LVSetBI.end(); MI != ME; ++MI)
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delete MI->second; // delete all ValueSets in MInst2LVSetBI
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MInst2LVSetBI.clear();
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MInst2LVSetAI.clear();
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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 function. It should be called after a call to analyze().
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//
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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 function does not require specific
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// iterators.
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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 ValueSet &
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FunctionLiveVarInfo::getLiveVarSetBeforeMInst(const MachineInstr *MInst,
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const BasicBlock *BB) {
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if (const ValueSet *LVSet = MInst2LVSetBI[MInst]) {
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return *LVSet; // if found, just return the set
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} else {
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calcLiveVarSetsForBB(BB); // else, calc for all instrs in BB
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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 ValueSet &
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FunctionLiveVarInfo::getLiveVarSetAfterMInst(const MachineInstr *MI,
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const BasicBlock *BB) {
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if (const ValueSet *LVSet = MInst2LVSetAI[MI]) {
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return *LVSet; // if found, just return the set
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} else {
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calcLiveVarSetsForBB(BB); // else, calc for all instrs in BB
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return *MInst2LVSetAI[MI];
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}
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}
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// This function applies a machine instr to a live var set (accepts OutSet) and
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// makes necessary changes to it (produces InSet). Note that two for loops are
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// used to first kill all defs and then to add all uses. This is because there
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// can be instructions like Val = Val + 1 since we allow multipe defs to a
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// machine instruction operand.
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//
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static void applyTranferFuncForMInst(ValueSet &LVS, const MachineInstr *MInst) {
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for (MachineInstr::const_val_op_iterator OpI = MInst->begin(),
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OpE = MInst->end(); OpI != OpE; ++OpI) {
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if (OpI.isDef()) // kill only if this operand is a def
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LVS.erase(*OpI); // this definition kills any uses
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}
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// do for implicit operands as well
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for (unsigned i=0; i < MInst->getNumImplicitRefs(); ++i) {
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if (MInst->implicitRefIsDefined(i))
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LVS.erase(MInst->getImplicitRef(i));
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}
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for (MachineInstr::const_val_op_iterator OpI = MInst->begin(),
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OpE = MInst->end(); OpI != OpE; ++OpI) {
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if (!isa<BasicBlock>(*OpI)) // don't process labels
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if (!OpI.isDef()) // add only if this operand is a use
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LVS.insert(*OpI); // An operand is a use - so add to use set
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}
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// do for implicit operands as well
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for (unsigned i = 0, e = MInst->getNumImplicitRefs(); i != e; ++i)
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if (!MInst->implicitRefIsDefined(i))
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LVS.insert(MInst->getImplicitRef(i));
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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 FunctionLiveVarInfo::calcLiveVarSetsForBB(const BasicBlock *BB) {
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const MachineCodeForBasicBlock &MIVec = BB->getMachineInstrVec();
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if (DEBUG_LV >= LV_DEBUG_Instr)
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std::cerr << "\n======For BB " << BB->getName()
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<< ": Live var sets for instructions======\n";
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ValueSet CurSet;
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const ValueSet *SetAI = &getOutSetOfBB(BB); // init SetAI with OutSet
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set_union(CurSet, *SetAI); // CurSet now contains OutSet
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// iterate over all the machine instructions in BB
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for (MachineCodeForBasicBlock::const_reverse_iterator MII = MIVec.rbegin(),
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MIE = MIVec.rend(); MII != MIE; ++MII) {
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// MI is cur machine inst
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const MachineInstr *MI = *MII;
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MInst2LVSetAI[MI] = SetAI; // record in After Inst map
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applyTranferFuncForMInst(CurSet, MI); // apply the transfer Func
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ValueSet *NewSet = new ValueSet(); // create a new set and
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set_union(*NewSet, CurSet); // copy the set after T/F to it
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MInst2LVSetBI[MI] = NewSet; // record in Before Inst map
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if (DEBUG_LV >= LV_DEBUG_Instr) {
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std::cerr << "\nLive var sets before/after instruction " << *MI;
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std::cerr << " Before: "; printSet(*NewSet); std::cerr << "\n";
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std::cerr << " After : "; printSet(*SetAI); std::cerr << "\n";
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}
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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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