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llvm-mirror/lib/CodeGen/RegAlloc/LiveRangeInfo.cpp
Brian Gaeke d25f86d683 Put all LLVM code into the llvm namespace, as per bug 109. 
llvm-svn: 9903
2003-11-11 22:41:34 +00:00

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