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//===-- BBLiveVar.cpp - Live Variable Analysis for a BasicBlock -----------===//
//
// The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This is a wrapper class for BasicBlock which is used by live var analysis.
//
//===----------------------------------------------------------------------===//
#include "BBLiveVar.h"
#include "FunctionLiveVarInfo.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/Support/CFG.h"
#include "Support/SetOperations.h"
#include "../SparcV9Internals.h"
#include <iostream>
namespace llvm {
BBLiveVar::BBLiveVar(const BasicBlock &bb,
const MachineBasicBlock &mbb,
unsigned id)
: BB(bb), MBB(mbb), POID(id) {
InSetChanged = OutSetChanged = false;
calcDefUseSets();
}
//-----------------------------------------------------------------------------
// calculates def and use sets for each BB
// There are two passes over operands of a machine instruction. This is
// because, we can have instructions like V = V + 1, since we no longer
// assume single definition.
//-----------------------------------------------------------------------------
void BBLiveVar::calcDefUseSets() {
// iterate over all the machine instructions in BB
for (MachineBasicBlock::const_reverse_iterator MII = MBB.rbegin(),
MIE = MBB.rend(); MII != MIE; ++MII) {
const MachineInstr *MI = &*MII;
if (DEBUG_LV >= LV_DEBUG_Verbose) {
std::cerr << " *Iterating over machine instr ";
MI->dump();
std::cerr << "\n";
}
// iterate over MI operands to find defs
for (MachineInstr::const_val_op_iterator OpI = MI->begin(), OpE = MI->end();
OpI != OpE; ++OpI)
if (OpI.isDef()) // add to Defs if this operand is a def
addDef(*OpI);
// do for implicit operands as well
for (unsigned i = 0; i < MI->getNumImplicitRefs(); ++i)
if (MI->getImplicitOp(i).isDef())
addDef(MI->getImplicitRef(i));
// iterate over MI operands to find uses
for (MachineInstr::const_val_op_iterator OpI = MI->begin(), OpE = MI->end();
OpI != OpE; ++OpI) {
const Value *Op = *OpI;
if (isa<BasicBlock>(Op))
continue; // don't process labels
if (OpI.isUse()) { // add to Uses only if this operand is a use
//
// *** WARNING: The following code for handling dummy PHI machine
// instructions is untested. The previous code was broken and I
// fixed it, but it turned out to be unused as long as Phi
// elimination is performed during instruction selection.
//
// Put Phi operands in UseSet for the incoming edge, not node.
// They must not "hide" later defs, and must be handled specially
// during set propagation over the CFG.
if (MI->getOpcode() == V9::PHI) { // for a phi node
const Value *ArgVal = Op;
const BasicBlock *PredBB = cast<BasicBlock>(*++OpI); // next ptr is BB
PredToEdgeInSetMap[PredBB].insert(ArgVal);
if (DEBUG_LV >= LV_DEBUG_Verbose)
std::cerr << " - phi operand " << RAV(ArgVal) << " came from BB "
<< RAV(PredBB) << "\n";
} // if( IsPhi )
else {
// It is not a Phi use: add to regular use set and remove later defs.
addUse(Op);
}
} // if a use
} // for all operands
// do for implicit operands as well
for (unsigned i = 0; i < MI->getNumImplicitRefs(); ++i) {
assert(MI->getOpcode() != V9::PHI && "Phi cannot have implicit operands");
const Value *Op = MI->getImplicitRef(i);
if (Op->getType() == Type::LabelTy) // don't process labels
continue;
if (MI->getImplicitOp(i).isUse())
addUse(Op);
}
} // for all machine instructions
}
//-----------------------------------------------------------------------------
// To add an operand which is a def
//-----------------------------------------------------------------------------
void BBLiveVar::addDef(const Value *Op) {
DefSet.insert(Op); // operand is a def - so add to def set
InSet.erase(Op); // this definition kills any later uses
InSetChanged = true;
if (DEBUG_LV >= LV_DEBUG_Verbose) std::cerr << " +Def: " << RAV(Op) << "\n";
}
//-----------------------------------------------------------------------------
// To add an operand which is a use
//-----------------------------------------------------------------------------
void BBLiveVar::addUse(const Value *Op) {
InSet.insert(Op); // An operand is a use - so add to use set
DefSet.erase(Op); // remove if there is a def below this use
InSetChanged = true;
if (DEBUG_LV >= LV_DEBUG_Verbose) std::cerr << " Use: " << RAV(Op) << "\n";
}
//-----------------------------------------------------------------------------
// Applies the transfer function to a basic block to produce the InSet using
// the OutSet.
//-----------------------------------------------------------------------------
bool BBLiveVar::applyTransferFunc() {
// IMPORTANT: caller should check whether the OutSet changed
// (else no point in calling)
ValueSet OutMinusDef = set_difference(OutSet, DefSet);
InSetChanged = set_union(InSet, OutMinusDef);
OutSetChanged = false; // no change to OutSet since transf func applied
return InSetChanged;
}
//-----------------------------------------------------------------------------
// calculates Out set using In sets of the successors
//-----------------------------------------------------------------------------
bool BBLiveVar::setPropagate(ValueSet *OutSet, const ValueSet *InSet,
const BasicBlock *PredBB) {
bool Changed = false;
// merge all members of InSet into OutSet of the predecessor
for (ValueSet::const_iterator InIt = InSet->begin(), InE = InSet->end();
InIt != InE; ++InIt)
if ((OutSet->insert(*InIt)).second)
Changed = true;
//
//**** WARNING: The following code for handling dummy PHI machine
// instructions is untested. See explanation above.
//
// then merge all members of the EdgeInSet for the predecessor into the OutSet
const ValueSet& EdgeInSet = PredToEdgeInSetMap[PredBB];
for (ValueSet::const_iterator InIt = EdgeInSet.begin(), InE = EdgeInSet.end();
InIt != InE; ++InIt)
if ((OutSet->insert(*InIt)).second)
Changed = true;
//
//****
return Changed;
}
//-----------------------------------------------------------------------------
// propagates in set to OutSets of PREDECESSORs
//-----------------------------------------------------------------------------
bool BBLiveVar::applyFlowFunc(hash_map<const BasicBlock*,
BBLiveVar*> &BBLiveVarInfo) {
// IMPORTANT: caller should check whether inset changed
// (else no point in calling)
// If this BB changed any OutSets of preds whose POID is lower, than we need
// another iteration...
//
bool needAnotherIt = false;
for (pred_const_iterator PI = pred_begin(&BB), PE = pred_end(&BB);
PI != PE ; ++PI) {
BBLiveVar *PredLVBB = BBLiveVarInfo[*PI];
// do set union
if (setPropagate(&PredLVBB->OutSet, &InSet, *PI)) {
PredLVBB->OutSetChanged = true;
// if the predec POID is lower than mine
if (PredLVBB->getPOId() <= POID)
needAnotherIt = true;
}
} // for
return needAnotherIt;
}
// ----------------- Methods For Debugging (Printing) -----------------
void BBLiveVar::printAllSets() const {
std::cerr << " Defs: "; printSet(DefSet); std::cerr << "\n";
std::cerr << " In: "; printSet(InSet); std::cerr << "\n";
std::cerr << " Out: "; printSet(OutSet); std::cerr << "\n";
}
void BBLiveVar::printInOutSets() const {
std::cerr << " In: "; printSet(InSet); std::cerr << "\n";
std::cerr << " Out: "; printSet(OutSet); std::cerr << "\n";
}
} // End llvm namespace
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