1 //===-- LiveRangeInfo.cpp -------------------------------------------------===//
3 // The LLVM Compiler Infrastructure
5 // This file was developed by the LLVM research group and is distributed under
6 // the University of Illinois Open Source License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // Live range construction for coloring-based register allocation for LLVM.
12 //===----------------------------------------------------------------------===//
14 #include "LiveRangeInfo.h"
15 #include "RegAllocCommon.h"
18 #include "llvm/CodeGen/MachineInstr.h"
19 #include "llvm/CodeGen/MachineFunction.h"
20 #include "llvm/Target/TargetMachine.h"
21 #include "llvm/Target/TargetInstrInfo.h"
22 #include "llvm/Target/TargetRegInfo.h"
23 #include "llvm/Function.h"
24 #include "Support/SetOperations.h"
26 unsigned LiveRange::getRegClassID() const { return getRegClass()->getID(); }
28 LiveRangeInfo::LiveRangeInfo(const Function *F, const TargetMachine &tm,
29 std::vector<RegClass *> &RCL)
30 : Meth(F), TM(tm), RegClassList(RCL), MRI(tm.getRegInfo()) { }
33 LiveRangeInfo::~LiveRangeInfo() {
34 for (LiveRangeMapType::iterator MI = LiveRangeMap.begin();
35 MI != LiveRangeMap.end(); ++MI) {
37 if (MI->first && MI->second) {
38 LiveRange *LR = MI->second;
40 // we need to be careful in deleting LiveRanges in LiveRangeMap
41 // since two/more Values in the live range map can point to the same
42 // live range. We have to make the other entries NULL when we delete
45 for (LiveRange::iterator LI = LR->begin(); LI != LR->end(); ++LI)
46 LiveRangeMap[*LI] = 0;
54 //---------------------------------------------------------------------------
55 // union two live ranges into one. The 2nd LR is deleted. Used for coalescing.
56 // Note: the caller must make sure that L1 and L2 are distinct and both
57 // LRs don't have suggested colors
58 //---------------------------------------------------------------------------
60 void LiveRangeInfo::unionAndUpdateLRs(LiveRange *L1, LiveRange *L2) {
61 assert(L1 != L2 && (!L1->hasSuggestedColor() || !L2->hasSuggestedColor()));
62 assert(! (L1->hasColor() && L2->hasColor()) ||
63 L1->getColor() == L2->getColor());
65 set_union(*L1, *L2); // add elements of L2 to L1
67 for(ValueSet::iterator L2It = L2->begin(); L2It != L2->end(); ++L2It) {
68 //assert(( L1->getTypeID() == L2->getTypeID()) && "Merge:Different types");
70 L1->insert(*L2It); // add the var in L2 to L1
71 LiveRangeMap[*L2It] = L1; // now the elements in L2 should map
75 // set call interference for L1 from L2
76 if (L2->isCallInterference())
77 L1->setCallInterference();
79 // add the spill costs
80 L1->addSpillCost(L2->getSpillCost());
82 // If L2 has a color, give L1 that color. Note that L1 may have had the same
83 // color or none, but would not have a different color as asserted above.
85 L1->setColor(L2->getColor());
87 // Similarly, if LROfUse(L2) has a suggested color, the new range
88 // must have the same color.
89 if (L2->hasSuggestedColor())
90 L1->setSuggestedColor(L2->getSuggestedColor());
92 delete L2; // delete L2 as it is no longer needed
96 //---------------------------------------------------------------------------
97 // Method for creating a single live range for a definition.
98 // The definition must be represented by a virtual register (a Value).
99 // Note: this function does *not* check that no live range exists for def.
100 //---------------------------------------------------------------------------
103 LiveRangeInfo::createNewLiveRange(const Value* Def, bool isCC /* = false*/)
105 LiveRange* DefRange = new LiveRange(); // Create a new live range,
106 DefRange->insert(Def); // add Def to it,
107 LiveRangeMap[Def] = DefRange; // and update the map.
109 // set the register class of the new live range
110 DefRange->setRegClass(RegClassList[MRI.getRegClassIDOfType(Def->getType(),
113 if (DEBUG_RA >= RA_DEBUG_LiveRanges) {
114 std::cerr << " Creating a LR for def ";
115 if (isCC) std::cerr << " (CC Register!)";
116 std::cerr << " : " << RAV(Def) << "\n";
123 LiveRangeInfo::createOrAddToLiveRange(const Value* Def, bool isCC /* = false*/)
125 LiveRange *DefRange = LiveRangeMap[Def];
127 // check if the LR is already there (because of multiple defs)
129 DefRange = createNewLiveRange(Def, isCC);
130 } else { // live range already exists
131 DefRange->insert(Def); // add the operand to the range
132 LiveRangeMap[Def] = DefRange; // make operand point to merged set
133 if (DEBUG_RA >= RA_DEBUG_LiveRanges)
134 std::cerr << " Added to existing LR for def: " << RAV(Def) << "\n";
140 //---------------------------------------------------------------------------
141 // Method for constructing all live ranges in a function. It creates live
142 // ranges for all values defined in the instruction stream. Also, it
143 // creates live ranges for all incoming arguments of the function.
144 //---------------------------------------------------------------------------
145 void LiveRangeInfo::constructLiveRanges() {
147 if (DEBUG_RA >= RA_DEBUG_LiveRanges)
148 std::cerr << "Constructing Live Ranges ...\n";
150 // first find the live ranges for all incoming args of the function since
151 // those LRs start from the start of the function
152 for (Function::const_aiterator AI = Meth->abegin(); AI != Meth->aend(); ++AI)
153 createNewLiveRange(AI, /*isCC*/ false);
155 // Now suggest hardware registers for these function args
156 MRI.suggestRegs4MethodArgs(Meth, *this);
158 // Now create LRs for machine instructions. A new LR will be created
159 // only for defs in the machine instr since, we assume that all Values are
160 // defined before they are used. However, there can be multiple defs for
161 // the same Value in machine instructions.
163 // Also, find CALL and RETURN instructions, which need extra work.
165 MachineFunction &MF = MachineFunction::get(Meth);
166 for (MachineFunction::iterator BBI = MF.begin(); BBI != MF.end(); ++BBI) {
167 MachineBasicBlock &MBB = *BBI;
169 // iterate over all the machine instructions in BB
170 for(MachineBasicBlock::iterator MInstIterator = MBB.begin();
171 MInstIterator != MBB.end(); ++MInstIterator) {
172 MachineInstr *MInst = *MInstIterator;
174 // If the machine instruction is a call/return instruction, add it to
175 // CallRetInstrList for processing its args, ret value, and ret addr.
177 if(TM.getInstrInfo().isReturn(MInst->getOpCode()) ||
178 TM.getInstrInfo().isCall(MInst->getOpCode()))
179 CallRetInstrList.push_back(MInst);
181 // iterate over explicit MI operands and create a new LR
182 // for each operand that is defined by the instruction
183 for (MachineInstr::val_op_iterator OpI = MInst->begin(),
184 OpE = MInst->end(); OpI != OpE; ++OpI)
185 if (OpI.isDefOnly() || OpI.isDefAndUse()) {
186 const Value *Def = *OpI;
187 bool isCC = (OpI.getMachineOperand().getType()
188 == MachineOperand::MO_CCRegister);
189 LiveRange* LR = createOrAddToLiveRange(Def, isCC);
191 // If the operand has a pre-assigned register,
192 // set it directly in the LiveRange
193 if (OpI.getMachineOperand().hasAllocatedReg()) {
195 LR->setColor(MRI.getClassRegNum(
196 OpI.getMachineOperand().getAllocatedRegNum(),
201 // iterate over implicit MI operands and create a new LR
202 // for each operand that is defined by the instruction
203 for (unsigned i = 0; i < MInst->getNumImplicitRefs(); ++i)
204 if (MInst->getImplicitOp(i).opIsDefOnly() ||
205 MInst->getImplicitOp(i).opIsDefAndUse()) {
206 const Value *Def = MInst->getImplicitRef(i);
207 LiveRange* LR = createOrAddToLiveRange(Def, /*isCC*/ false);
209 // If the implicit operand has a pre-assigned register,
210 // set it directly in the LiveRange
211 if (MInst->getImplicitOp(i).hasAllocatedReg()) {
213 LR->setColor(MRI.getClassRegNum(
214 MInst->getImplicitOp(i).getAllocatedRegNum(),
219 } // for all machine instructions in the BB
221 } // for all BBs in function
223 // Now we have to suggest clors for call and return arg live ranges.
224 // Also, if there are implicit defs (e.g., retun value of a call inst)
225 // they must be added to the live range list
227 suggestRegs4CallRets();
229 if( DEBUG_RA >= RA_DEBUG_LiveRanges)
230 std::cerr << "Initial Live Ranges constructed!\n";
234 //---------------------------------------------------------------------------
235 // If some live ranges must be colored with specific hardware registers
236 // (e.g., for outgoing call args), suggesting of colors for such live
237 // ranges is done using target specific function. Those functions are called
238 // from this function. The target specific methods must:
239 // 1) suggest colors for call and return args.
240 // 2) create new LRs for implicit defs in machine instructions
241 //---------------------------------------------------------------------------
242 void LiveRangeInfo::suggestRegs4CallRets() {
243 std::vector<MachineInstr*>::iterator It = CallRetInstrList.begin();
244 for( ; It != CallRetInstrList.end(); ++It) {
245 MachineInstr *MInst = *It;
246 MachineOpCode OpCode = MInst->getOpCode();
248 if ((TM.getInstrInfo()).isReturn(OpCode))
249 MRI.suggestReg4RetValue(MInst, *this);
250 else if ((TM.getInstrInfo()).isCall(OpCode))
251 MRI.suggestRegs4CallArgs(MInst, *this);
253 assert( 0 && "Non call/ret instr in CallRetInstrList" );
258 //--------------------------------------------------------------------------
259 // The following method coalesces live ranges when possible. This method
260 // must be called after the interference graph has been constructed.
264 for each BB in function
265 for each machine instruction (inst)
266 for each definition (def) in inst
267 for each operand (op) of inst that is a use
268 if the def and op are of the same register type
269 if the def and op do not interfere //i.e., not simultaneously live
270 if (degree(LR of def) + degree(LR of op)) <= # avail regs
271 if both LRs do not have suggested colors
272 merge2IGNodes(def, op) // i.e., merge 2 LRs
275 //---------------------------------------------------------------------------
278 // Checks if live range LR interferes with any node assigned or suggested to
279 // be assigned the specified color
281 inline bool InterferesWithColor(const LiveRange& LR, unsigned color)
283 IGNode* lrNode = LR.getUserIGNode();
284 for (unsigned n=0, NN = lrNode->getNumOfNeighbors(); n < NN; n++) {
285 LiveRange *neighLR = lrNode->getAdjIGNode(n)->getParentLR();
286 if (neighLR->hasColor() && neighLR->getColor() == color)
288 if (neighLR->hasSuggestedColor() && neighLR->getSuggestedColor() == color)
294 // Cannot coalesce if any of the following is true:
295 // (1) Both LRs have suggested colors (should be "different suggested colors"?)
296 // (2) Both LR1 and LR2 have colors and the colors are different
297 // (but if the colors are the same, it is definitely safe to coalesce)
298 // (3) LR1 has color and LR2 interferes with any LR that has the same color
299 // (4) LR2 has color and LR1 interferes with any LR that has the same color
301 inline bool InterfsPreventCoalescing(const LiveRange& LROfDef,
302 const LiveRange& LROfUse)
304 // (4) if they have different suggested colors, cannot coalesce
305 if (LROfDef.hasSuggestedColor() && LROfUse.hasSuggestedColor())
308 // if neither has a color, nothing more to do.
309 if (! LROfDef.hasColor() && ! LROfUse.hasColor())
312 // (2, 3) if L1 has color...
313 if (LROfDef.hasColor()) {
314 if (LROfUse.hasColor())
315 return (LROfUse.getColor() != LROfDef.getColor());
316 return InterferesWithColor(LROfUse, LROfDef.getColor());
319 // (4) else only LROfUse has a color: check if that could interfere
320 return InterferesWithColor(LROfDef, LROfUse.getColor());
324 void LiveRangeInfo::coalesceLRs()
326 if(DEBUG_RA >= RA_DEBUG_LiveRanges)
327 std::cerr << "\nCoalescing LRs ...\n";
329 MachineFunction &MF = MachineFunction::get(Meth);
330 for (MachineFunction::iterator BBI = MF.begin(); BBI != MF.end(); ++BBI) {
331 MachineBasicBlock &MBB = *BBI;
333 // iterate over all the machine instructions in BB
334 for(MachineBasicBlock::iterator MII = MBB.begin(); MII != MBB.end(); ++MII){
335 const MachineInstr *MI = *MII;
337 if( DEBUG_RA >= RA_DEBUG_LiveRanges) {
338 std::cerr << " *Iterating over machine instr ";
343 // iterate over MI operands to find defs
344 for(MachineInstr::const_val_op_iterator DefI = MI->begin(),
345 DefE = MI->end(); DefI != DefE; ++DefI) {
346 if (DefI.isDefOnly() || DefI.isDefAndUse()) { // this operand is modified
347 LiveRange *LROfDef = getLiveRangeForValue( *DefI );
348 RegClass *RCOfDef = LROfDef->getRegClass();
350 MachineInstr::const_val_op_iterator UseI = MI->begin(),
352 for( ; UseI != UseE; ++UseI) { // for all uses
353 LiveRange *LROfUse = getLiveRangeForValue( *UseI );
354 if (!LROfUse) { // if LR of use is not found
355 //don't warn about labels
356 if (!isa<BasicBlock>(*UseI) && DEBUG_RA >= RA_DEBUG_LiveRanges)
357 std::cerr << " !! Warning: No LR for use " << RAV(*UseI)<< "\n";
358 continue; // ignore and continue
361 if (LROfUse == LROfDef) // nothing to merge if they are same
364 if (MRI.getRegTypeForLR(LROfDef) ==
365 MRI.getRegTypeForLR(LROfUse)) {
366 // If the two RegTypes are the same
367 if (!RCOfDef->getInterference(LROfDef, LROfUse) ) {
369 unsigned CombinedDegree =
370 LROfDef->getUserIGNode()->getNumOfNeighbors() +
371 LROfUse->getUserIGNode()->getNumOfNeighbors();
373 if (CombinedDegree > RCOfDef->getNumOfAvailRegs()) {
374 // get more precise estimate of combined degree
375 CombinedDegree = LROfDef->getUserIGNode()->
376 getCombinedDegree(LROfUse->getUserIGNode());
379 if (CombinedDegree <= RCOfDef->getNumOfAvailRegs()) {
380 // if both LRs do not have different pre-assigned colors
381 // and both LRs do not have suggested colors
382 if (! InterfsPreventCoalescing(*LROfDef, *LROfUse)) {
383 RCOfDef->mergeIGNodesOfLRs(LROfDef, LROfUse);
384 unionAndUpdateLRs(LROfDef, LROfUse);
387 } // if combined degree is less than # of regs
388 } // if def and use do not interfere
389 }// if reg classes are the same
393 } // for all machine instructions
396 if (DEBUG_RA >= RA_DEBUG_LiveRanges)
397 std::cerr << "\nCoalescing Done!\n";
400 /*--------------------------- Debug code for printing ---------------*/
403 void LiveRangeInfo::printLiveRanges() {
404 LiveRangeMapType::iterator HMI = LiveRangeMap.begin(); // hash map iterator
405 std::cerr << "\nPrinting Live Ranges from Hash Map:\n";
406 for( ; HMI != LiveRangeMap.end(); ++HMI) {
407 if (HMI->first && HMI->second) {
408 std::cerr << " Value* " << RAV(HMI->first) << "\t: ";
409 if (IGNode* igNode = HMI->second->getUserIGNode())
410 std::cerr << "LR# " << igNode->getIndex();
412 std::cerr << "LR# " << "<no-IGNode>";
413 std::cerr << "\t:Values = "; printSet(*HMI->second); std::cerr << "\n";