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llvm-mirror/lib/CodeGen/RegAlloc/PhyRegAlloc.cpp
Chris Lattner 99ad379582 *** empty log message *** 
llvm-svn: 2985
2002-07-22 02:10:13 +00:00

1154 lines
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//***************************************************************************
// File:
// PhyRegAlloc.cpp
//
// Purpose:
// Register allocation for LLVM.
//
// History:
// 9/10/01 - Ruchira Sasanka - created.
//**************************************************************************/
#include "llvm/CodeGen/RegisterAllocation.h"
#include "llvm/CodeGen/PhyRegAlloc.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineInstrAnnot.h"
#include "llvm/CodeGen/MachineCodeForBasicBlock.h"
#include "llvm/CodeGen/MachineCodeForMethod.h"
#include "llvm/Analysis/LiveVar/FunctionLiveVarInfo.h"
#include "llvm/Analysis/LoopInfo.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/MachineFrameInfo.h"
#include "llvm/Function.h"
#include "llvm/Type.h"
#include "llvm/iOther.h"
#include "llvm/CodeGen/RegAllocCommon.h"
#include "Support/CommandLine.h"
#include "Support/STLExtras.h"
#include <math.h>
using std::cerr;
using std::vector;
RegAllocDebugLevel_t DEBUG_RA;
static cl::opt<RegAllocDebugLevel_t, true>
DRA_opt("dregalloc", cl::Hidden, cl::location(DEBUG_RA),
cl::desc("enable register allocation debugging information"),
cl::values(
clEnumValN(RA_DEBUG_None , "n", "disable debug output"),
clEnumValN(RA_DEBUG_Normal , "y", "enable debug output"),
clEnumValN(RA_DEBUG_Verbose, "v", "enable extra debug output"),
0));
//----------------------------------------------------------------------------
// RegisterAllocation pass front end...
//----------------------------------------------------------------------------
namespace {
class RegisterAllocator : public FunctionPass {
TargetMachine &Target;
public:
inline RegisterAllocator(TargetMachine &T) : Target(T) {}
const char *getPassName() const { return "Register Allocation"; }
bool runOnFunction(Function &F) {
if (DEBUG_RA)
cerr << "\n********* Function "<< F.getName() << " ***********\n";
PhyRegAlloc PRA(&F, Target, &getAnalysis<FunctionLiveVarInfo>(),
&getAnalysis<LoopInfo>());
PRA.allocateRegisters();
if (DEBUG_RA) cerr << "\nRegister allocation complete!\n";
return false;
}
virtual void getAnalysisUsage(AnalysisUsage &AU) const {
AU.addRequired(LoopInfo::ID);
AU.addRequired(FunctionLiveVarInfo::ID);
}
};
}
Pass *getRegisterAllocator(TargetMachine &T) {
return new RegisterAllocator(T);
}
//----------------------------------------------------------------------------
// Constructor: Init local composite objects and create register classes.
//----------------------------------------------------------------------------
PhyRegAlloc::PhyRegAlloc(Function *F, const TargetMachine& tm,
FunctionLiveVarInfo *Lvi, LoopInfo *LDC)
: TM(tm), Meth(F),
mcInfo(MachineCodeForMethod::get(F)),
LVI(Lvi), LRI(F, tm, RegClassList),
MRI(tm.getRegInfo()),
NumOfRegClasses(MRI.getNumOfRegClasses()),
LoopDepthCalc(LDC) {
// create each RegisterClass and put in RegClassList
//
for (unsigned rc=0; rc < NumOfRegClasses; rc++)
RegClassList.push_back(new RegClass(F, MRI.getMachineRegClass(rc),
&ResColList));
}
//----------------------------------------------------------------------------
// Destructor: Deletes register classes
//----------------------------------------------------------------------------
PhyRegAlloc::~PhyRegAlloc() {
for ( unsigned rc=0; rc < NumOfRegClasses; rc++)
delete RegClassList[rc];
AddedInstrMap.clear();
}
//----------------------------------------------------------------------------
// This method initally creates interference graphs (one in each reg class)
// and IGNodeList (one in each IG). The actual nodes will be pushed later.
//----------------------------------------------------------------------------
void PhyRegAlloc::createIGNodeListsAndIGs() {
if (DEBUG_RA) cerr << "Creating LR lists ...\n";
// hash map iterator
LiveRangeMapType::const_iterator HMI = LRI.getLiveRangeMap()->begin();
// hash map end
LiveRangeMapType::const_iterator HMIEnd = LRI.getLiveRangeMap()->end();
for (; HMI != HMIEnd ; ++HMI ) {
if (HMI->first) {
LiveRange *L = HMI->second; // get the LiveRange
if (!L) {
if (DEBUG_RA) {
cerr << "\n*?!?Warning: Null liver range found for: "
<< RAV(HMI->first) << "\n";
}
continue;
}
// if the Value * is not null, and LR
// is not yet written to the IGNodeList
if (!(L->getUserIGNode()) ) {
RegClass *const RC = // RegClass of first value in the LR
RegClassList[ L->getRegClass()->getID() ];
RC->addLRToIG(L); // add this LR to an IG
}
}
}
// init RegClassList
for ( unsigned rc=0; rc < NumOfRegClasses ; rc++)
RegClassList[rc]->createInterferenceGraph();
if (DEBUG_RA)
cerr << "LRLists Created!\n";
}
//----------------------------------------------------------------------------
// This method will add all interferences at for a given instruction.
// Interence occurs only if the LR of Def (Inst or Arg) is of the same reg
// class as that of live var. The live var passed to this function is the
// LVset AFTER the instruction
//----------------------------------------------------------------------------
void PhyRegAlloc::addInterference(const Value *Def,
const ValueSet *LVSet,
bool isCallInst) {
ValueSet::const_iterator LIt = LVSet->begin();
// get the live range of instruction
//
const LiveRange *const LROfDef = LRI.getLiveRangeForValue( Def );
IGNode *const IGNodeOfDef = LROfDef->getUserIGNode();
assert( IGNodeOfDef );
RegClass *const RCOfDef = LROfDef->getRegClass();
// for each live var in live variable set
//
for ( ; LIt != LVSet->end(); ++LIt) {
if (DEBUG_RA >= RA_DEBUG_Verbose)
cerr << "< Def=" << RAV(Def) << ", Lvar=" << RAV(*LIt) << "> ";
// get the live range corresponding to live var
//
LiveRange *LROfVar = LRI.getLiveRangeForValue(*LIt);
// LROfVar can be null if it is a const since a const
// doesn't have a dominating def - see Assumptions above
//
if (LROfVar) {
if (LROfDef == LROfVar) // do not set interf for same LR
continue;
// if 2 reg classes are the same set interference
//
if (RCOfDef == LROfVar->getRegClass()) {
RCOfDef->setInterference( LROfDef, LROfVar);
} else if (DEBUG_RA >= RA_DEBUG_Verbose) {
// we will not have LRs for values not explicitly allocated in the
// instruction stream (e.g., constants)
cerr << " warning: no live range for " << RAV(*LIt) << "\n";
}
}
}
}
//----------------------------------------------------------------------------
// For a call instruction, this method sets the CallInterference flag in
// the LR of each variable live int the Live Variable Set live after the
// call instruction (except the return value of the call instruction - since
// the return value does not interfere with that call itself).
//----------------------------------------------------------------------------
void PhyRegAlloc::setCallInterferences(const MachineInstr *MInst,
const ValueSet *LVSetAft) {
if (DEBUG_RA)
cerr << "\n For call inst: " << *MInst;
ValueSet::const_iterator LIt = LVSetAft->begin();
// for each live var in live variable set after machine inst
//
for ( ; LIt != LVSetAft->end(); ++LIt) {
// get the live range corresponding to live var
//
LiveRange *const LR = LRI.getLiveRangeForValue(*LIt );
if (LR && DEBUG_RA) {
cerr << "\n\tLR Aft Call: ";
printSet(*LR);
}
// LR can be null if it is a const since a const
// doesn't have a dominating def - see Assumptions above
//
if (LR ) {
LR->setCallInterference();
if (DEBUG_RA) {
cerr << "\n ++Added call interf for LR: " ;
printSet(*LR);
}
}
}
// Now find the LR of the return value of the call
// We do this because, we look at the LV set *after* the instruction
// to determine, which LRs must be saved across calls. The return value
// of the call is live in this set - but it does not interfere with call
// (i.e., we can allocate a volatile register to the return value)
//
CallArgsDescriptor* argDesc = CallArgsDescriptor::get(MInst);
if (const Value *RetVal = argDesc->getReturnValue()) {
LiveRange *RetValLR = LRI.getLiveRangeForValue( RetVal );
assert( RetValLR && "No LR for RetValue of call");
RetValLR->clearCallInterference();
}
// If the CALL is an indirect call, find the LR of the function pointer.
// That has a call interference because it conflicts with outgoing args.
if (const Value *AddrVal = argDesc->getIndirectFuncPtr()) {
LiveRange *AddrValLR = LRI.getLiveRangeForValue( AddrVal );
assert( AddrValLR && "No LR for indirect addr val of call");
AddrValLR->setCallInterference();
}
}
//----------------------------------------------------------------------------
// This method will walk thru code and create interferences in the IG of
// each RegClass. Also, this method calculates the spill cost of each
// Live Range (it is done in this method to save another pass over the code).
//----------------------------------------------------------------------------
void PhyRegAlloc::buildInterferenceGraphs()
{
if (DEBUG_RA) cerr << "Creating interference graphs ...\n";
unsigned BBLoopDepthCost;
for (Function::const_iterator BBI = Meth->begin(), BBE = Meth->end();
BBI != BBE; ++BBI) {
// find the 10^(loop_depth) of this BB
//
BBLoopDepthCost = (unsigned)pow(10.0, LoopDepthCalc->getLoopDepth(BBI));
// get the iterator for machine instructions
//
const MachineCodeForBasicBlock& MIVec = MachineCodeForBasicBlock::get(BBI);
MachineCodeForBasicBlock::const_iterator MII = MIVec.begin();
// iterate over all the machine instructions in BB
//
for ( ; MII != MIVec.end(); ++MII) {
const MachineInstr *MInst = *MII;
// get the LV set after the instruction
//
const ValueSet &LVSetAI = LVI->getLiveVarSetAfterMInst(MInst, BBI);
const bool isCallInst = TM.getInstrInfo().isCall(MInst->getOpCode());
if (isCallInst ) {
// set the isCallInterference flag of each live range wich extends
// accross this call instruction. This information is used by graph
// coloring algo to avoid allocating volatile colors to live ranges
// that span across calls (since they have to be saved/restored)
//
setCallInterferences(MInst, &LVSetAI);
}
// iterate over all MI operands to find defs
//
for (MachineInstr::const_val_op_iterator OpI = MInst->begin(),
OpE = MInst->end(); OpI != OpE; ++OpI) {
if (OpI.isDef()) // create a new LR iff this operand is a def
addInterference(*OpI, &LVSetAI, isCallInst);
// Calculate the spill cost of each live range
//
LiveRange *LR = LRI.getLiveRangeForValue(*OpI);
if (LR) LR->addSpillCost(BBLoopDepthCost);
}
// if there are multiple defs in this instruction e.g. in SETX
//
if (TM.getInstrInfo().isPseudoInstr(MInst->getOpCode()))
addInterf4PseudoInstr(MInst);
// Also add interference for any implicit definitions in a machine
// instr (currently, only calls have this).
//
unsigned NumOfImpRefs = MInst->getNumImplicitRefs();
if ( NumOfImpRefs > 0 ) {
for (unsigned z=0; z < NumOfImpRefs; z++)
if (MInst->implicitRefIsDefined(z) )
addInterference( MInst->getImplicitRef(z), &LVSetAI, isCallInst );
}
} // for all machine instructions in BB
} // for all BBs in function
// add interferences for function arguments. Since there are no explict
// defs in the function for args, we have to add them manually
//
addInterferencesForArgs();
if (DEBUG_RA)
cerr << "Interference graphs calculted!\n";
}
//--------------------------------------------------------------------------
// Pseudo instructions will be exapnded to multiple instructions by the
// assembler. Consequently, all the opernds must get distinct registers.
// Therefore, we mark all operands of a pseudo instruction as they interfere
// with one another.
//--------------------------------------------------------------------------
void PhyRegAlloc::addInterf4PseudoInstr(const MachineInstr *MInst) {
bool setInterf = false;
// iterate over MI operands to find defs
//
for (MachineInstr::const_val_op_iterator It1 = MInst->begin(),
ItE = MInst->end(); It1 != ItE; ++It1) {
const LiveRange *LROfOp1 = LRI.getLiveRangeForValue(*It1);
assert((LROfOp1 || !It1.isDef()) && "No LR for Def in PSEUDO insruction");
MachineInstr::const_val_op_iterator It2 = It1;
for (++It2; It2 != ItE; ++It2) {
const LiveRange *LROfOp2 = LRI.getLiveRangeForValue(*It2);
if (LROfOp2) {
RegClass *RCOfOp1 = LROfOp1->getRegClass();
RegClass *RCOfOp2 = LROfOp2->getRegClass();
if (RCOfOp1 == RCOfOp2 ){
RCOfOp1->setInterference( LROfOp1, LROfOp2 );
setInterf = true;
}
} // if Op2 has a LR
} // for all other defs in machine instr
} // for all operands in an instruction
if (!setInterf && MInst->getNumOperands() > 2) {
cerr << "\nInterf not set for any operand in pseudo instr:\n";
cerr << *MInst;
assert(0 && "Interf not set for pseudo instr with > 2 operands" );
}
}
//----------------------------------------------------------------------------
// This method will add interferences for incoming arguments to a function.
//----------------------------------------------------------------------------
void PhyRegAlloc::addInterferencesForArgs() {
// get the InSet of root BB
const ValueSet &InSet = LVI->getInSetOfBB(&Meth->front());
for (Function::const_aiterator AI = Meth->abegin(); AI != Meth->aend(); ++AI) {
// add interferences between args and LVars at start
addInterference(AI, &InSet, false);
if (DEBUG_RA >= RA_DEBUG_Verbose)
cerr << " - %% adding interference for argument " << RAV(AI) << "\n";
}
}
//----------------------------------------------------------------------------
// This method is called after register allocation is complete to set the
// allocated reisters in the machine code. This code will add register numbers
// to MachineOperands that contain a Value. Also it calls target specific
// methods to produce caller saving instructions. At the end, it adds all
// additional instructions produced by the register allocator to the
// instruction stream.
//----------------------------------------------------------------------------
//-----------------------------
// Utility functions used below
//-----------------------------
inline void
PrependInstructions(vector<MachineInstr *> &IBef,
MachineCodeForBasicBlock& MIVec,
MachineCodeForBasicBlock::iterator& MII,
const std::string& msg)
{
if (!IBef.empty())
{
MachineInstr* OrigMI = *MII;
std::vector<MachineInstr *>::iterator AdIt;
for (AdIt = IBef.begin(); AdIt != IBef.end() ; ++AdIt)
{
if (DEBUG_RA) {
if (OrigMI) cerr << "For MInst: " << *OrigMI;
cerr << msg << " PREPENDed instr: " << **AdIt << "\n";
}
MII = MIVec.insert(MII, *AdIt);
++MII;
}
}
}
inline void
AppendInstructions(std::vector<MachineInstr *> &IAft,
MachineCodeForBasicBlock& MIVec,
MachineCodeForBasicBlock::iterator& MII,
const std::string& msg)
{
if (!IAft.empty())
{
MachineInstr* OrigMI = *MII;
std::vector<MachineInstr *>::iterator AdIt;
for ( AdIt = IAft.begin(); AdIt != IAft.end() ; ++AdIt )
{
if (DEBUG_RA) {
if (OrigMI) cerr << "For MInst: " << *OrigMI;
cerr << msg << " APPENDed instr: " << **AdIt << "\n";
}
++MII; // insert before the next instruction
MII = MIVec.insert(MII, *AdIt);
}
}
}
void PhyRegAlloc::updateMachineCode()
{
MachineCodeForBasicBlock& MIVec = MachineCodeForBasicBlock::get(&Meth->getEntryNode());
// Insert any instructions needed at method entry
MachineCodeForBasicBlock::iterator MII = MIVec.begin();
PrependInstructions(AddedInstrAtEntry.InstrnsBefore, MIVec, MII,
"At function entry: \n");
assert(AddedInstrAtEntry.InstrnsAfter.empty() &&
"InstrsAfter should be unnecessary since we are just inserting at "
"the function entry point here.");
for (Function::const_iterator BBI = Meth->begin(), BBE = Meth->end();
BBI != BBE; ++BBI) {
// iterate over all the machine instructions in BB
MachineCodeForBasicBlock &MIVec = MachineCodeForBasicBlock::get(BBI);
for (MachineCodeForBasicBlock::iterator MII = MIVec.begin();
MII != MIVec.end(); ++MII) {
MachineInstr *MInst = *MII;
unsigned Opcode = MInst->getOpCode();
// do not process Phis
if (TM.getInstrInfo().isDummyPhiInstr(Opcode))
continue;
// Reset tmp stack positions so they can be reused for each machine instr.
mcInfo.popAllTempValues(TM);
// Now insert speical instructions (if necessary) for call/return
// instructions.
//
if (TM.getInstrInfo().isCall(Opcode) ||
TM.getInstrInfo().isReturn(Opcode)) {
AddedInstrns &AI = AddedInstrMap[MInst];
if (TM.getInstrInfo().isCall(Opcode))
MRI.colorCallArgs(MInst, LRI, &AI, *this, BBI);
else if (TM.getInstrInfo().isReturn(Opcode))
MRI.colorRetValue(MInst, LRI, &AI);
}
// Set the registers for operands in the machine instruction
// if a register was successfully allocated. If not, insert
// code to spill the register value.
//
for (unsigned OpNum=0; OpNum < MInst->getNumOperands(); ++OpNum)
{
MachineOperand& Op = MInst->getOperand(OpNum);
if (Op.getOperandType() == MachineOperand::MO_VirtualRegister ||
Op.getOperandType() == MachineOperand::MO_CCRegister)
{
const Value *const Val = Op.getVRegValue();
LiveRange *const LR = LRI.getLiveRangeForValue(Val);
if (!LR) // consts or labels will have no live range
{
// if register is not allocated, mark register as invalid
if (Op.getAllocatedRegNum() == -1)
MInst->SetRegForOperand(OpNum, MRI.getInvalidRegNum());
continue;
}
if (LR->hasColor() )
MInst->SetRegForOperand(OpNum,
MRI.getUnifiedRegNum(LR->getRegClass()->getID(),
LR->getColor()));
else
// LR did NOT receive a color (register). Insert spill code.
insertCode4SpilledLR(LR, MInst, BBI, OpNum );
}
} // for each operand
// Now add instructions that the register allocator inserts before/after
// this machine instructions (done only for calls/rets/incoming args)
// We do this here, to ensure that spill for an instruction is inserted
// closest as possible to an instruction (see above insertCode4Spill...)
//
// If there are instructions to be added, *before* this machine
// instruction, add them now.
//
if (AddedInstrMap.count(MInst)) {
PrependInstructions(AddedInstrMap[MInst].InstrnsBefore, MIVec, MII,"");
}
// If there are instructions to be added *after* this machine
// instruction, add them now
//
if (!AddedInstrMap[MInst].InstrnsAfter.empty()) {
// if there are delay slots for this instruction, the instructions
// added after it must really go after the delayed instruction(s)
// So, we move the InstrAfter of the current instruction to the
// corresponding delayed instruction
unsigned delay;
if ((delay=TM.getInstrInfo().getNumDelaySlots(MInst->getOpCode())) >0){
move2DelayedInstr(MInst, *(MII+delay) );
}
else {
// Here we can add the "instructions after" to the current
// instruction since there are no delay slots for this instruction
AppendInstructions(AddedInstrMap[MInst].InstrnsAfter, MIVec, MII,"");
} // if not delay
}
} // for each machine instruction
}
}
//----------------------------------------------------------------------------
// This method inserts spill code for AN operand whose LR was spilled.
// This method may be called several times for a single machine instruction
// if it contains many spilled operands. Each time it is called, it finds
// a register which is not live at that instruction and also which is not
// used by other spilled operands of the same instruction. Then it uses
// this register temporarily to accomodate the spilled value.
//----------------------------------------------------------------------------
void PhyRegAlloc::insertCode4SpilledLR(const LiveRange *LR,
MachineInstr *MInst,
const BasicBlock *BB,
const unsigned OpNum) {
assert(! TM.getInstrInfo().isCall(MInst->getOpCode()) &&
(! TM.getInstrInfo().isReturn(MInst->getOpCode())) &&
"Arg of a call/ret must be handled elsewhere");
MachineOperand& Op = MInst->getOperand(OpNum);
bool isDef = MInst->operandIsDefined(OpNum);
bool isDefAndUse = MInst->operandIsDefinedAndUsed(OpNum);
unsigned RegType = MRI.getRegType( LR );
int SpillOff = LR->getSpillOffFromFP();
RegClass *RC = LR->getRegClass();
const ValueSet &LVSetBef = LVI->getLiveVarSetBeforeMInst(MInst, BB);
mcInfo.pushTempValue(TM, MRI.getSpilledRegSize(RegType) );
vector<MachineInstr*> MIBef, MIAft;
vector<MachineInstr*> AdIMid;
// Choose a register to hold the spilled value. This may insert code
// before and after MInst to free up the value. If so, this code should
// be first and last in the spill sequence before/after MInst.
int TmpRegU = getUsableUniRegAtMI(RegType, &LVSetBef, MInst, MIBef, MIAft);
// Set the operand first so that it this register does not get used
// as a scratch register for later calls to getUsableUniRegAtMI below
MInst->SetRegForOperand(OpNum, TmpRegU);
// get the added instructions for this instruction
AddedInstrns &AI = AddedInstrMap[MInst];
// We may need a scratch register to copy the spilled value to/from memory.
// This may itself have to insert code to free up a scratch register.
// Any such code should go before (after) the spill code for a load (store).
int scratchRegType = -1;
int scratchReg = -1;
if (MRI.regTypeNeedsScratchReg(RegType, scratchRegType))
{
scratchReg = this->getUsableUniRegAtMI(scratchRegType, &LVSetBef,
MInst, MIBef, MIAft);
assert(scratchReg != MRI.getInvalidRegNum());
MInst->getRegsUsed().insert(scratchReg);
}
if (!isDef || isDefAndUse) {
// for a USE, we have to load the value of LR from stack to a TmpReg
// and use the TmpReg as one operand of instruction
// actual loading instruction(s)
MRI.cpMem2RegMI(AdIMid, MRI.getFramePointer(), SpillOff, TmpRegU, RegType,
scratchReg);
// the actual load should be after the instructions to free up TmpRegU
MIBef.insert(MIBef.end(), AdIMid.begin(), AdIMid.end());
AdIMid.clear();
}
if (isDef) { // if this is a Def
// for a DEF, we have to store the value produced by this instruction
// on the stack position allocated for this LR
// actual storing instruction(s)
MRI.cpReg2MemMI(AdIMid, TmpRegU, MRI.getFramePointer(), SpillOff, RegType,
scratchReg);
MIAft.insert(MIAft.begin(), AdIMid.begin(), AdIMid.end());
} // if !DEF
// Finally, insert the entire spill code sequences before/after MInst
AI.InstrnsBefore.insert(AI.InstrnsBefore.end(), MIBef.begin(), MIBef.end());
AI.InstrnsAfter.insert(AI.InstrnsAfter.begin(), MIAft.begin(), MIAft.end());
if (DEBUG_RA) {
cerr << "\nFor Inst " << *MInst;
cerr << " - SPILLED LR: "; printSet(*LR);
cerr << "\n - Added Instructions:";
for_each(MIBef.begin(), MIBef.end(), std::mem_fun(&MachineInstr::dump));
for_each(MIAft.begin(), MIAft.end(), std::mem_fun(&MachineInstr::dump));
}
}
//----------------------------------------------------------------------------
// We can use the following method to get a temporary register to be used
// BEFORE any given machine instruction. If there is a register available,
// this method will simply return that register and set MIBef = MIAft = NULL.
// Otherwise, it will return a register and MIAft and MIBef will contain
// two instructions used to free up this returned register.
// Returned register number is the UNIFIED register number
//----------------------------------------------------------------------------
int PhyRegAlloc::getUsableUniRegAtMI(const int RegType,
const ValueSet *LVSetBef,
MachineInstr *MInst,
std::vector<MachineInstr*>& MIBef,
std::vector<MachineInstr*>& MIAft) {
RegClass* RC = this->getRegClassByID(MRI.getRegClassIDOfRegType(RegType));
int RegU = getUnusedUniRegAtMI(RC, MInst, LVSetBef);
if (RegU == -1) {
// we couldn't find an unused register. Generate code to free up a reg by
// saving it on stack and restoring after the instruction
int TmpOff = mcInfo.pushTempValue(TM, MRI.getSpilledRegSize(RegType) );
RegU = getUniRegNotUsedByThisInst(RC, MInst);
// Check if we need a scratch register to copy this register to memory.
int scratchRegType = -1;
if (MRI.regTypeNeedsScratchReg(RegType, scratchRegType))
{
int scratchReg = this->getUsableUniRegAtMI(scratchRegType, LVSetBef,
MInst, MIBef, MIAft);
assert(scratchReg != MRI.getInvalidRegNum());
// We may as well hold the value in the scratch register instead
// of copying it to memory and back. But we have to mark the
// register as used by this instruction, so it does not get used
// as a scratch reg. by another operand or anyone else.
MInst->getRegsUsed().insert(scratchReg);
MRI.cpReg2RegMI(MIBef, RegU, scratchReg, RegType);
MRI.cpReg2RegMI(MIAft, scratchReg, RegU, RegType);
}
else
{ // the register can be copied directly to/from memory so do it.
MRI.cpReg2MemMI(MIBef, RegU, MRI.getFramePointer(), TmpOff, RegType);
MRI.cpMem2RegMI(MIAft, MRI.getFramePointer(), TmpOff, RegU, RegType);
}
}
return RegU;
}
//----------------------------------------------------------------------------
// This method is called to get a new unused register that can be used to
// accomodate a spilled value.
// This method may be called several times for a single machine instruction
// if it contains many spilled operands. Each time it is called, it finds
// a register which is not live at that instruction and also which is not
// used by other spilled operands of the same instruction.
// Return register number is relative to the register class. NOT
// unified number
//----------------------------------------------------------------------------
int PhyRegAlloc::getUnusedUniRegAtMI(RegClass *RC,
const MachineInstr *MInst,
const ValueSet *LVSetBef) {
unsigned NumAvailRegs = RC->getNumOfAvailRegs();
std::vector<bool> &IsColorUsedArr = RC->getIsColorUsedArr();
for (unsigned i=0; i < NumAvailRegs; i++) // Reset array
IsColorUsedArr[i] = false;
ValueSet::const_iterator LIt = LVSetBef->begin();
// for each live var in live variable set after machine inst
for ( ; LIt != LVSetBef->end(); ++LIt) {
// get the live range corresponding to live var
LiveRange *const LRofLV = LRI.getLiveRangeForValue(*LIt );
// LR can be null if it is a const since a const
// doesn't have a dominating def - see Assumptions above
if (LRofLV && LRofLV->getRegClass() == RC && LRofLV->hasColor() )
IsColorUsedArr[ LRofLV->getColor() ] = true;
}
// It is possible that one operand of this MInst was already spilled
// and it received some register temporarily. If that's the case,
// it is recorded in machine operand. We must skip such registers.
setRelRegsUsedByThisInst(RC, MInst);
for (unsigned c=0; c < NumAvailRegs; c++) // find first unused color
if (!IsColorUsedArr[c])
return MRI.getUnifiedRegNum(RC->getID(), c);
return -1;
}
//----------------------------------------------------------------------------
// Get any other register in a register class, other than what is used
// by operands of a machine instruction. Returns the unified reg number.
//----------------------------------------------------------------------------
int PhyRegAlloc::getUniRegNotUsedByThisInst(RegClass *RC,
const MachineInstr *MInst) {
vector<bool> &IsColorUsedArr = RC->getIsColorUsedArr();
unsigned NumAvailRegs = RC->getNumOfAvailRegs();
for (unsigned i=0; i < NumAvailRegs ; i++) // Reset array
IsColorUsedArr[i] = false;
setRelRegsUsedByThisInst(RC, MInst);
for (unsigned c=0; c < RC->getNumOfAvailRegs(); c++)// find first unused color
if (!IsColorUsedArr[c])
return MRI.getUnifiedRegNum(RC->getID(), c);
assert(0 && "FATAL: No free register could be found in reg class!!");
return 0;
}
//----------------------------------------------------------------------------
// This method modifies the IsColorUsedArr of the register class passed to it.
// It sets the bits corresponding to the registers used by this machine
// instructions. Both explicit and implicit operands are set.
//----------------------------------------------------------------------------
void PhyRegAlloc::setRelRegsUsedByThisInst(RegClass *RC,
const MachineInstr *MInst ) {
vector<bool> &IsColorUsedArr = RC->getIsColorUsedArr();
// Add the registers already marked as used by the instruction.
// This should include any scratch registers that are used to save
// values across the instruction (e.g., for saving state register values).
const hash_set<int>& regsUsed = MInst->getRegsUsed();
for (hash_set<int>::const_iterator SI=regsUsed.begin(), SE=regsUsed.end();
SI != SE; ++SI)
{
unsigned classId = 0;
int classRegNum = MRI.getClassRegNum(*SI, classId);
if (RC->getID() == classId)
{
assert(classRegNum < (int) IsColorUsedArr.size() &&
"Illegal register number for this reg class?");
IsColorUsedArr[classRegNum] = true;
}
}
// Now add registers allocated to the live ranges of values used in
// the instruction. These are not yet recorded in the instruction.
for (unsigned OpNum=0; OpNum < MInst->getNumOperands(); ++OpNum)
{
const MachineOperand& Op = MInst->getOperand(OpNum);
if (Op.getOperandType() == MachineOperand::MO_VirtualRegister ||
Op.getOperandType() == MachineOperand::MO_CCRegister)
if (const Value* Val = Op.getVRegValue())
if (MRI.getRegClassIDOfValue(Val) == RC->getID())
if (Op.getAllocatedRegNum() == -1)
if (LiveRange *LROfVal = LRI.getLiveRangeForValue(Val))
if (LROfVal->hasColor() )
// this operand is in a LR that received a color
IsColorUsedArr[LROfVal->getColor()] = true;
}
// If there are implicit references, mark their allocated regs as well
//
for (unsigned z=0; z < MInst->getNumImplicitRefs(); z++)
if (const LiveRange*
LRofImpRef = LRI.getLiveRangeForValue(MInst->getImplicitRef(z)))
if (LRofImpRef->hasColor())
// this implicit reference is in a LR that received a color
IsColorUsedArr[LRofImpRef->getColor()] = true;
}
//----------------------------------------------------------------------------
// If there are delay slots for an instruction, the instructions
// added after it must really go after the delayed instruction(s).
// So, we move the InstrAfter of that instruction to the
// corresponding delayed instruction using the following method.
//----------------------------------------------------------------------------
void PhyRegAlloc::move2DelayedInstr(const MachineInstr *OrigMI,
const MachineInstr *DelayedMI) {
// "added after" instructions of the original instr
std::vector<MachineInstr *> &OrigAft = AddedInstrMap[OrigMI].InstrnsAfter;
// "added instructions" of the delayed instr
AddedInstrns &DelayAdI = AddedInstrMap[DelayedMI];
// "added after" instructions of the delayed instr
std::vector<MachineInstr *> &DelayedAft = DelayAdI.InstrnsAfter;
// go thru all the "added after instructions" of the original instruction
// and append them to the "addded after instructions" of the delayed
// instructions
DelayedAft.insert(DelayedAft.end(), OrigAft.begin(), OrigAft.end());
// empty the "added after instructions" of the original instruction
OrigAft.clear();
}
//----------------------------------------------------------------------------
// This method prints the code with registers after register allocation is
// complete.
//----------------------------------------------------------------------------
void PhyRegAlloc::printMachineCode()
{
cerr << "\n;************** Function " << Meth->getName()
<< " *****************\n";
for (Function::const_iterator BBI = Meth->begin(), BBE = Meth->end();
BBI != BBE; ++BBI) {
cerr << "\n"; printLabel(BBI); cerr << ": ";
// get the iterator for machine instructions
MachineCodeForBasicBlock& MIVec = MachineCodeForBasicBlock::get(BBI);
MachineCodeForBasicBlock::iterator MII = MIVec.begin();
// iterate over all the machine instructions in BB
for ( ; MII != MIVec.end(); ++MII) {
MachineInstr *const MInst = *MII;
cerr << "\n\t";
cerr << TargetInstrDescriptors[MInst->getOpCode()].opCodeString;
for (unsigned OpNum=0; OpNum < MInst->getNumOperands(); ++OpNum) {
MachineOperand& Op = MInst->getOperand(OpNum);
if (Op.getOperandType() == MachineOperand::MO_VirtualRegister ||
Op.getOperandType() == MachineOperand::MO_CCRegister /*||
Op.getOperandType() == MachineOperand::MO_PCRelativeDisp*/ ) {
const Value *const Val = Op.getVRegValue () ;
// ****this code is temporary till NULL Values are fixed
if (! Val ) {
cerr << "\t<*NULL*>";
continue;
}
// if a label or a constant
if (isa<BasicBlock>(Val)) {
cerr << "\t"; printLabel( Op.getVRegValue () );
} else {
// else it must be a register value
const int RegNum = Op.getAllocatedRegNum();
cerr << "\t" << "%" << MRI.getUnifiedRegName( RegNum );
if (Val->hasName() )
cerr << "(" << Val->getName() << ")";
else
cerr << "(" << Val << ")";
if (Op.opIsDef() )
cerr << "*";
const LiveRange *LROfVal = LRI.getLiveRangeForValue(Val);
if (LROfVal )
if (LROfVal->hasSpillOffset() )
cerr << "$";
}
}
else if (Op.getOperandType() == MachineOperand::MO_MachineRegister) {
cerr << "\t" << "%" << MRI.getUnifiedRegName(Op.getMachineRegNum());
}
else
cerr << "\t" << Op; // use dump field
}
unsigned NumOfImpRefs = MInst->getNumImplicitRefs();
if (NumOfImpRefs > 0) {
cerr << "\tImplicit:";
for (unsigned z=0; z < NumOfImpRefs; z++)
cerr << RAV(MInst->getImplicitRef(z)) << "\t";
}
} // for all machine instructions
cerr << "\n";
} // for all BBs
cerr << "\n";
}
//----------------------------------------------------------------------------
//----------------------------------------------------------------------------
void PhyRegAlloc::colorIncomingArgs()
{
const BasicBlock &FirstBB = Meth->front();
const MachineInstr *FirstMI = MachineCodeForBasicBlock::get(&FirstBB).front();
assert(FirstMI && "No machine instruction in entry BB");
MRI.colorMethodArgs(Meth, LRI, &AddedInstrAtEntry);
}
//----------------------------------------------------------------------------
// Used to generate a label for a basic block
//----------------------------------------------------------------------------
void PhyRegAlloc::printLabel(const Value *const Val) {
if (Val->hasName())
cerr << Val->getName();
else
cerr << "Label" << Val;
}
//----------------------------------------------------------------------------
// This method calls setSugColorUsable method of each live range. This
// will determine whether the suggested color of LR is really usable.
// A suggested color is not usable when the suggested color is volatile
// AND when there are call interferences
//----------------------------------------------------------------------------
void PhyRegAlloc::markUnusableSugColors()
{
if (DEBUG_RA ) cerr << "\nmarking unusable suggested colors ...\n";
// hash map iterator
LiveRangeMapType::const_iterator HMI = (LRI.getLiveRangeMap())->begin();
LiveRangeMapType::const_iterator HMIEnd = (LRI.getLiveRangeMap())->end();
for (; HMI != HMIEnd ; ++HMI ) {
if (HMI->first) {
LiveRange *L = HMI->second; // get the LiveRange
if (L) {
if (L->hasSuggestedColor()) {
int RCID = L->getRegClass()->getID();
if (MRI.isRegVolatile( RCID, L->getSuggestedColor()) &&
L->isCallInterference() )
L->setSuggestedColorUsable( false );
else
L->setSuggestedColorUsable( true );
}
} // if L->hasSuggestedColor()
}
} // for all LR's in hash map
}
//----------------------------------------------------------------------------
// The following method will set the stack offsets of the live ranges that
// are decided to be spillled. This must be called just after coloring the
// LRs using the graph coloring algo. For each live range that is spilled,
// this method allocate a new spill position on the stack.
//----------------------------------------------------------------------------
void PhyRegAlloc::allocateStackSpace4SpilledLRs() {
if (DEBUG_RA) cerr << "\nsetting LR stack offsets ...\n";
LiveRangeMapType::const_iterator HMI = LRI.getLiveRangeMap()->begin();
LiveRangeMapType::const_iterator HMIEnd = LRI.getLiveRangeMap()->end();
for ( ; HMI != HMIEnd ; ++HMI) {
if (HMI->first && HMI->second) {
LiveRange *L = HMI->second; // get the LiveRange
if (!L->hasColor()) // NOTE: ** allocating the size of long Type **
L->setSpillOffFromFP(mcInfo.allocateSpilledValue(TM, Type::LongTy));
}
} // for all LR's in hash map
}
//----------------------------------------------------------------------------
// The entry pont to Register Allocation
//----------------------------------------------------------------------------
void PhyRegAlloc::allocateRegisters()
{
// make sure that we put all register classes into the RegClassList
// before we call constructLiveRanges (now done in the constructor of
// PhyRegAlloc class).
//
LRI.constructLiveRanges(); // create LR info
if (DEBUG_RA)
LRI.printLiveRanges();
createIGNodeListsAndIGs(); // create IGNode list and IGs
buildInterferenceGraphs(); // build IGs in all reg classes
if (DEBUG_RA) {
// print all LRs in all reg classes
for ( unsigned rc=0; rc < NumOfRegClasses ; rc++)
RegClassList[rc]->printIGNodeList();
// print IGs in all register classes
for ( unsigned rc=0; rc < NumOfRegClasses ; rc++)
RegClassList[rc]->printIG();
}
LRI.coalesceLRs(); // coalesce all live ranges
if (DEBUG_RA) {
// print all LRs in all reg classes
for ( unsigned rc=0; rc < NumOfRegClasses ; rc++)
RegClassList[ rc ]->printIGNodeList();
// print IGs in all register classes
for ( unsigned rc=0; rc < NumOfRegClasses ; rc++)
RegClassList[ rc ]->printIG();
}
// mark un-usable suggested color before graph coloring algorithm.
// When this is done, the graph coloring algo will not reserve
// suggested color unnecessarily - they can be used by another LR
//
markUnusableSugColors();
// color all register classes using the graph coloring algo
for (unsigned rc=0; rc < NumOfRegClasses ; rc++)
RegClassList[ rc ]->colorAllRegs();
// Atter grpah coloring, if some LRs did not receive a color (i.e, spilled)
// a poistion for such spilled LRs
//
allocateStackSpace4SpilledLRs();
mcInfo.popAllTempValues(TM); // TODO **Check
// color incoming args - if the correct color was not received
// insert code to copy to the correct register
//
colorIncomingArgs();
// Now update the machine code with register names and add any
// additional code inserted by the register allocator to the instruction
// stream
//
updateMachineCode();
if (DEBUG_RA) {
MachineCodeForMethod::get(Meth).dump();
printMachineCode(); // only for DEBUGGING
}
}
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