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bc001b24a1
info (since multiple reg types may share the same reg class).
(2) Remove machine-specific regalloc. methods that are no longer needed.
In particular, arguments and return value from a call do not need
machine-specific code for allocation.
(3) Rename TargetRegInfo::getRegType variants to avoid unintentional
overloading when an include file is omitted.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@7329 91177308-0d34-0410-b5e6-96231b3b80d8
411 lines
15 KiB
C++
411 lines
15 KiB
C++
//===-- LiveRangeInfo.cpp -------------------------------------------------===//
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//
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// Live range construction for coloring-based register allocation for LLVM.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/CodeGen/LiveRangeInfo.h"
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#include "RegAllocCommon.h"
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#include "RegClass.h"
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#include "llvm/CodeGen/IGNode.h"
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#include "llvm/CodeGen/MachineInstr.h"
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#include "llvm/CodeGen/MachineFunction.h"
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#include "llvm/Target/TargetMachine.h"
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#include "llvm/Target/TargetInstrInfo.h"
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#include "llvm/Target/TargetRegInfo.h"
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#include "llvm/Function.h"
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#include "Support/SetOperations.h"
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using std::cerr;
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unsigned LiveRange::getRegClassID() const { return getRegClass()->getID(); }
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LiveRangeInfo::LiveRangeInfo(const Function *F, const TargetMachine &tm,
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std::vector<RegClass *> &RCL)
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: Meth(F), TM(tm), RegClassList(RCL), MRI(tm.getRegInfo()) { }
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LiveRangeInfo::~LiveRangeInfo() {
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for (LiveRangeMapType::iterator MI = LiveRangeMap.begin();
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MI != LiveRangeMap.end(); ++MI) {
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if (MI->first && MI->second) {
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LiveRange *LR = MI->second;
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// we need to be careful in deleting LiveRanges in LiveRangeMap
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// since two/more Values in the live range map can point to the same
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// live range. We have to make the other entries NULL when we delete
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// a live range.
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for (LiveRange::iterator LI = LR->begin(); LI != LR->end(); ++LI)
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LiveRangeMap[*LI] = 0;
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delete LR;
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}
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}
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}
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//---------------------------------------------------------------------------
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// union two live ranges into one. The 2nd LR is deleted. Used for coalescing.
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// Note: the caller must make sure that L1 and L2 are distinct and both
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// LRs don't have suggested colors
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//---------------------------------------------------------------------------
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void LiveRangeInfo::unionAndUpdateLRs(LiveRange *L1, LiveRange *L2) {
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assert(L1 != L2 && (!L1->hasSuggestedColor() || !L2->hasSuggestedColor()));
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assert(! (L1->hasColor() && L2->hasColor()) ||
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L1->getColor() == L2->getColor());
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set_union(*L1, *L2); // add elements of L2 to L1
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for(ValueSet::iterator L2It = L2->begin(); L2It != L2->end(); ++L2It) {
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//assert(( L1->getTypeID() == L2->getTypeID()) && "Merge:Different types");
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L1->insert(*L2It); // add the var in L2 to L1
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LiveRangeMap[*L2It] = L1; // now the elements in L2 should map
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//to L1
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}
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// set call interference for L1 from L2
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if (L2->isCallInterference())
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L1->setCallInterference();
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// add the spill costs
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L1->addSpillCost(L2->getSpillCost());
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// If L2 has a color, give L1 that color. Note that L1 may have had the same
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// color or none, but would not have a different color as asserted above.
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if (L2->hasColor())
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L1->setColor(L2->getColor());
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// Similarly, if LROfUse(L2) has a suggested color, the new range
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// must have the same color.
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if (L2->hasSuggestedColor())
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L1->setSuggestedColor(L2->getSuggestedColor());
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delete L2; // delete L2 as it is no longer needed
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}
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//---------------------------------------------------------------------------
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// Method for creating a single live range for a definition.
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// The definition must be represented by a virtual register (a Value).
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// Note: this function does *not* check that no live range exists for def.
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//---------------------------------------------------------------------------
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LiveRange*
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LiveRangeInfo::createNewLiveRange(const Value* Def, bool isCC /* = false*/)
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{
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LiveRange* DefRange = new LiveRange(); // Create a new live range,
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DefRange->insert(Def); // add Def to it,
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LiveRangeMap[Def] = DefRange; // and update the map.
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// set the register class of the new live range
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DefRange->setRegClass(RegClassList[MRI.getRegClassIDOfType(Def->getType(),
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isCC)]);
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if (DEBUG_RA >= RA_DEBUG_LiveRanges) {
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cerr << " Creating a LR for def ";
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if (isCC) cerr << " (CC Register!)";
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cerr << " : " << RAV(Def) << "\n";
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}
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return DefRange;
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}
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LiveRange*
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LiveRangeInfo::createOrAddToLiveRange(const Value* Def, bool isCC /* = false*/)
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{
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LiveRange *DefRange = LiveRangeMap[Def];
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// check if the LR is already there (because of multiple defs)
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if (!DefRange) {
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DefRange = createNewLiveRange(Def, isCC);
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} else { // live range already exists
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DefRange->insert(Def); // add the operand to the range
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LiveRangeMap[Def] = DefRange; // make operand point to merged set
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if (DEBUG_RA >= RA_DEBUG_LiveRanges)
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cerr << " Added to existing LR for def: " << RAV(Def) << "\n";
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}
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return DefRange;
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}
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//---------------------------------------------------------------------------
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// Method for constructing all live ranges in a function. It creates live
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// ranges for all values defined in the instruction stream. Also, it
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// creates live ranges for all incoming arguments of the function.
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//---------------------------------------------------------------------------
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void LiveRangeInfo::constructLiveRanges() {
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if (DEBUG_RA >= RA_DEBUG_LiveRanges)
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cerr << "Constructing Live Ranges ...\n";
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// first find the live ranges for all incoming args of the function since
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// those LRs start from the start of the function
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for (Function::const_aiterator AI = Meth->abegin(); AI != Meth->aend(); ++AI)
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createNewLiveRange(AI, /*isCC*/ false);
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// Now suggest hardware registers for these function args
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MRI.suggestRegs4MethodArgs(Meth, *this);
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// Now create LRs for machine instructions. A new LR will be created
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// only for defs in the machine instr since, we assume that all Values are
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// defined before they are used. However, there can be multiple defs for
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// the same Value in machine instructions.
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//
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// Also, find CALL and RETURN instructions, which need extra work.
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//
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MachineFunction &MF = MachineFunction::get(Meth);
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for (MachineFunction::iterator BBI = MF.begin(); BBI != MF.end(); ++BBI) {
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MachineBasicBlock &MBB = *BBI;
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// iterate over all the machine instructions in BB
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for(MachineBasicBlock::iterator MInstIterator = MBB.begin();
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MInstIterator != MBB.end(); ++MInstIterator) {
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MachineInstr *MInst = *MInstIterator;
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// If the machine instruction is a call/return instruction, add it to
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// CallRetInstrList for processing its args, ret value, and ret addr.
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//
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if(TM.getInstrInfo().isReturn(MInst->getOpCode()) ||
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TM.getInstrInfo().isCall(MInst->getOpCode()))
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CallRetInstrList.push_back(MInst);
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// iterate over explicit MI operands and create a new LR
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// for each operand that is defined by the instruction
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for (MachineInstr::val_op_iterator OpI = MInst->begin(),
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OpE = MInst->end(); OpI != OpE; ++OpI)
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if (OpI.isDefOnly() || OpI.isDefAndUse()) {
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const Value *Def = *OpI;
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bool isCC = (OpI.getMachineOperand().getType()
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== MachineOperand::MO_CCRegister);
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LiveRange* LR = createOrAddToLiveRange(Def, isCC);
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// If the operand has a pre-assigned register,
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// set it directly in the LiveRange
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if (OpI.getMachineOperand().hasAllocatedReg()) {
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unsigned getClassId;
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LR->setColor(MRI.getClassRegNum(
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OpI.getMachineOperand().getAllocatedRegNum(),
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getClassId));
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}
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}
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// iterate over implicit MI operands and create a new LR
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// for each operand that is defined by the instruction
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for (unsigned i = 0; i < MInst->getNumImplicitRefs(); ++i)
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if (MInst->getImplicitOp(i).opIsDefOnly() ||
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MInst->getImplicitOp(i).opIsDefAndUse()) {
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const Value *Def = MInst->getImplicitRef(i);
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LiveRange* LR = createOrAddToLiveRange(Def, /*isCC*/ false);
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// If the implicit operand has a pre-assigned register,
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// set it directly in the LiveRange
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if (MInst->getImplicitOp(i).hasAllocatedReg()) {
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unsigned getClassId;
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LR->setColor(MRI.getClassRegNum(
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MInst->getImplicitOp(i).getAllocatedRegNum(),
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getClassId));
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}
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}
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} // for all machine instructions in the BB
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} // for all BBs in function
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// Now we have to suggest clors for call and return arg live ranges.
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// Also, if there are implicit defs (e.g., retun value of a call inst)
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// they must be added to the live range list
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//
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suggestRegs4CallRets();
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if( DEBUG_RA >= RA_DEBUG_LiveRanges)
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cerr << "Initial Live Ranges constructed!\n";
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}
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//---------------------------------------------------------------------------
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// If some live ranges must be colored with specific hardware registers
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// (e.g., for outgoing call args), suggesting of colors for such live
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// ranges is done using target specific function. Those functions are called
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// from this function. The target specific methods must:
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// 1) suggest colors for call and return args.
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// 2) create new LRs for implicit defs in machine instructions
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//---------------------------------------------------------------------------
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void LiveRangeInfo::suggestRegs4CallRets() {
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std::vector<MachineInstr*>::iterator It = CallRetInstrList.begin();
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for( ; It != CallRetInstrList.end(); ++It) {
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MachineInstr *MInst = *It;
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MachineOpCode OpCode = MInst->getOpCode();
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if ((TM.getInstrInfo()).isReturn(OpCode))
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MRI.suggestReg4RetValue(MInst, *this);
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else if ((TM.getInstrInfo()).isCall(OpCode))
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MRI.suggestRegs4CallArgs(MInst, *this);
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else
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assert( 0 && "Non call/ret instr in CallRetInstrList" );
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}
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}
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//--------------------------------------------------------------------------
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// The following method coalesces live ranges when possible. This method
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// must be called after the interference graph has been constructed.
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/* Algorithm:
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for each BB in function
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for each machine instruction (inst)
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for each definition (def) in inst
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for each operand (op) of inst that is a use
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if the def and op are of the same register type
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if the def and op do not interfere //i.e., not simultaneously live
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if (degree(LR of def) + degree(LR of op)) <= # avail regs
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if both LRs do not have suggested colors
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merge2IGNodes(def, op) // i.e., merge 2 LRs
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*/
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//---------------------------------------------------------------------------
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// Checks if live range LR interferes with any node assigned or suggested to
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// be assigned the specified color
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//
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inline bool InterferesWithColor(const LiveRange& LR, unsigned color)
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{
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IGNode* lrNode = LR.getUserIGNode();
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for (unsigned n=0, NN = lrNode->getNumOfNeighbors(); n < NN; n++) {
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LiveRange *neighLR = lrNode->getAdjIGNode(n)->getParentLR();
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if (neighLR->hasColor() && neighLR->getColor() == color)
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return true;
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if (neighLR->hasSuggestedColor() && neighLR->getSuggestedColor() == color)
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return true;
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}
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return false;
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}
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// Cannot coalesce if any of the following is true:
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// (1) Both LRs have suggested colors (should be "different suggested colors"?)
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// (2) Both LR1 and LR2 have colors and the colors are different
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// (but if the colors are the same, it is definitely safe to coalesce)
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// (3) LR1 has color and LR2 interferes with any LR that has the same color
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// (4) LR2 has color and LR1 interferes with any LR that has the same color
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//
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inline bool InterfsPreventCoalescing(const LiveRange& LROfDef,
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const LiveRange& LROfUse)
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{
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// (4) if they have different suggested colors, cannot coalesce
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if (LROfDef.hasSuggestedColor() && LROfUse.hasSuggestedColor())
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return true;
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// if neither has a color, nothing more to do.
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if (! LROfDef.hasColor() && ! LROfUse.hasColor())
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return false;
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// (2, 3) if L1 has color...
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if (LROfDef.hasColor()) {
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if (LROfUse.hasColor())
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return (LROfUse.getColor() != LROfDef.getColor());
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return InterferesWithColor(LROfUse, LROfDef.getColor());
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}
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// (4) else only LROfUse has a color: check if that could interfere
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return InterferesWithColor(LROfDef, LROfUse.getColor());
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}
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void LiveRangeInfo::coalesceLRs()
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{
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if(DEBUG_RA >= RA_DEBUG_LiveRanges)
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cerr << "\nCoalescing LRs ...\n";
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MachineFunction &MF = MachineFunction::get(Meth);
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for (MachineFunction::iterator BBI = MF.begin(); BBI != MF.end(); ++BBI) {
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MachineBasicBlock &MBB = *BBI;
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// iterate over all the machine instructions in BB
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for(MachineBasicBlock::iterator MII = MBB.begin(); MII != MBB.end(); ++MII){
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const MachineInstr *MI = *MII;
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if( DEBUG_RA >= RA_DEBUG_LiveRanges) {
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cerr << " *Iterating over machine instr ";
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MI->dump();
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cerr << "\n";
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}
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// iterate over MI operands to find defs
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for(MachineInstr::const_val_op_iterator DefI = MI->begin(),
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DefE = MI->end(); DefI != DefE; ++DefI) {
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if (DefI.isDefOnly() || DefI.isDefAndUse()) { // this operand is modified
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LiveRange *LROfDef = getLiveRangeForValue( *DefI );
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RegClass *RCOfDef = LROfDef->getRegClass();
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MachineInstr::const_val_op_iterator UseI = MI->begin(),
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UseE = MI->end();
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for( ; UseI != UseE; ++UseI) { // for all uses
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LiveRange *LROfUse = getLiveRangeForValue( *UseI );
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if (!LROfUse) { // if LR of use is not found
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//don't warn about labels
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if (!isa<BasicBlock>(*UseI) && DEBUG_RA >= RA_DEBUG_LiveRanges)
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cerr << " !! Warning: No LR for use " << RAV(*UseI) << "\n";
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continue; // ignore and continue
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}
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if (LROfUse == LROfDef) // nothing to merge if they are same
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continue;
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if (MRI.getRegTypeForLR(LROfDef) ==
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MRI.getRegTypeForLR(LROfUse)) {
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// If the two RegTypes are the same
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if (!RCOfDef->getInterference(LROfDef, LROfUse) ) {
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unsigned CombinedDegree =
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LROfDef->getUserIGNode()->getNumOfNeighbors() +
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LROfUse->getUserIGNode()->getNumOfNeighbors();
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if (CombinedDegree > RCOfDef->getNumOfAvailRegs()) {
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// get more precise estimate of combined degree
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CombinedDegree = LROfDef->getUserIGNode()->
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getCombinedDegree(LROfUse->getUserIGNode());
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}
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if (CombinedDegree <= RCOfDef->getNumOfAvailRegs()) {
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// if both LRs do not have different pre-assigned colors
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// and both LRs do not have suggested colors
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if (! InterfsPreventCoalescing(*LROfDef, *LROfUse)) {
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RCOfDef->mergeIGNodesOfLRs(LROfDef, LROfUse);
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unionAndUpdateLRs(LROfDef, LROfUse);
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}
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} // if combined degree is less than # of regs
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} // if def and use do not interfere
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}// if reg classes are the same
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} // for all uses
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} // if def
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} // for all defs
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} // for all machine instructions
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} // for all BBs
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if (DEBUG_RA >= RA_DEBUG_LiveRanges)
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cerr << "\nCoalescing Done!\n";
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}
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/*--------------------------- Debug code for printing ---------------*/
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void LiveRangeInfo::printLiveRanges() {
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LiveRangeMapType::iterator HMI = LiveRangeMap.begin(); // hash map iterator
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cerr << "\nPrinting Live Ranges from Hash Map:\n";
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for( ; HMI != LiveRangeMap.end(); ++HMI) {
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if (HMI->first && HMI->second) {
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cerr << " Value* " << RAV(HMI->first) << "\t: ";
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if (IGNode* igNode = HMI->second->getUserIGNode())
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cerr << "LR# " << igNode->getIndex();
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else
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cerr << "LR# " << "<no-IGNode>";
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cerr << "\t:Values = "; printSet(*HMI->second); cerr << "\n";
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}
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}
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}
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