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 //===----------------------------------------------------------------------===//
15 #include "LiveRangeInfo.h"
16 #include "RegAllocCommon.h"
18 #include "llvm/Function.h"
19 #include "llvm/CodeGen/MachineInstr.h"
20 #include "llvm/CodeGen/MachineFunction.h"
21 #include "llvm/Target/TargetMachine.h"
22 #include "llvm/Target/TargetInstrInfo.h"
23 #include "llvm/Target/TargetRegInfo.h"
24 #include "Support/SetOperations.h"
28 unsigned LiveRange::getRegClassID() const { return getRegClass()->getID(); }
30 LiveRangeInfo::LiveRangeInfo(const Function *F, const TargetMachine &tm,
31 std::vector<RegClass *> &RCL)
32 : Meth(F), TM(tm), RegClassList(RCL), MRI(tm.getRegInfo()) { }
35 LiveRangeInfo::~LiveRangeInfo() {
36 for (LiveRangeMapType::iterator MI = LiveRangeMap.begin();
37 MI != LiveRangeMap.end(); ++MI) {
39 if (MI->first && MI->second) {
40 LiveRange *LR = MI->second;
42 // we need to be careful in deleting LiveRanges in LiveRangeMap
43 // since two/more Values in the live range map can point to the same
44 // live range. We have to make the other entries NULL when we delete
47 for (LiveRange::iterator LI = LR->begin(); LI != LR->end(); ++LI)
48 LiveRangeMap[*LI] = 0;
56 //---------------------------------------------------------------------------
57 // union two live ranges into one. The 2nd LR is deleted. Used for coalescing.
58 // Note: the caller must make sure that L1 and L2 are distinct and both
59 // LRs don't have suggested colors
60 //---------------------------------------------------------------------------
62 void LiveRangeInfo::unionAndUpdateLRs(LiveRange *L1, LiveRange *L2) {
63 assert(L1 != L2 && (!L1->hasSuggestedColor() || !L2->hasSuggestedColor()));
64 assert(! (L1->hasColor() && L2->hasColor()) ||
65 L1->getColor() == L2->getColor());
67 set_union(*L1, *L2); // add elements of L2 to L1
69 for(ValueSet::iterator L2It = L2->begin(); L2It != L2->end(); ++L2It) {
70 //assert(( L1->getTypeID() == L2->getTypeID()) && "Merge:Different types");
72 L1->insert(*L2It); // add the var in L2 to L1
73 LiveRangeMap[*L2It] = L1; // now the elements in L2 should map
77 // set call interference for L1 from L2
78 if (L2->isCallInterference())
79 L1->setCallInterference();
81 // add the spill costs
82 L1->addSpillCost(L2->getSpillCost());
84 // If L2 has a color, give L1 that color. Note that L1 may have had the same
85 // color or none, but would not have a different color as asserted above.
87 L1->setColor(L2->getColor());
89 // Similarly, if LROfUse(L2) has a suggested color, the new range
90 // must have the same color.
91 if (L2->hasSuggestedColor())
92 L1->setSuggestedColor(L2->getSuggestedColor());
94 delete L2; // delete L2 as it is no longer needed
98 //---------------------------------------------------------------------------
99 // Method for creating a single live range for a definition.
100 // The definition must be represented by a virtual register (a Value).
101 // Note: this function does *not* check that no live range exists for def.
102 //---------------------------------------------------------------------------
105 LiveRangeInfo::createNewLiveRange(const Value* Def, bool isCC /* = false*/)
107 LiveRange* DefRange = new LiveRange(); // Create a new live range,
108 DefRange->insert(Def); // add Def to it,
109 LiveRangeMap[Def] = DefRange; // and update the map.
111 // set the register class of the new live range
112 DefRange->setRegClass(RegClassList[MRI.getRegClassIDOfType(Def->getType(),
115 if (DEBUG_RA >= RA_DEBUG_LiveRanges) {
116 std::cerr << " Creating a LR for def ";
117 if (isCC) std::cerr << " (CC Register!)";
118 std::cerr << " : " << RAV(Def) << "\n";
125 LiveRangeInfo::createOrAddToLiveRange(const Value* Def, bool isCC /* = false*/)
127 LiveRange *DefRange = LiveRangeMap[Def];
129 // check if the LR is already there (because of multiple defs)
131 DefRange = createNewLiveRange(Def, isCC);
132 } else { // live range already exists
133 DefRange->insert(Def); // add the operand to the range
134 LiveRangeMap[Def] = DefRange; // make operand point to merged set
135 if (DEBUG_RA >= RA_DEBUG_LiveRanges)
136 std::cerr << " Added to existing LR for def: " << RAV(Def) << "\n";
142 //---------------------------------------------------------------------------
143 // Method for constructing all live ranges in a function. It creates live
144 // ranges for all values defined in the instruction stream. Also, it
145 // creates live ranges for all incoming arguments of the function.
146 //---------------------------------------------------------------------------
147 void LiveRangeInfo::constructLiveRanges() {
149 if (DEBUG_RA >= RA_DEBUG_LiveRanges)
150 std::cerr << "Constructing Live Ranges ...\n";
152 // first find the live ranges for all incoming args of the function since
153 // those LRs start from the start of the function
154 for (Function::const_aiterator AI = Meth->abegin(); AI != Meth->aend(); ++AI)
155 createNewLiveRange(AI, /*isCC*/ false);
157 // Now suggest hardware registers for these function args
158 MRI.suggestRegs4MethodArgs(Meth, *this);
160 // Now create LRs for machine instructions. A new LR will be created
161 // only for defs in the machine instr since, we assume that all Values are
162 // defined before they are used. However, there can be multiple defs for
163 // the same Value in machine instructions.
165 // Also, find CALL and RETURN instructions, which need extra work.
167 MachineFunction &MF = MachineFunction::get(Meth);
168 for (MachineFunction::iterator BBI = MF.begin(); BBI != MF.end(); ++BBI) {
169 MachineBasicBlock &MBB = *BBI;
171 // iterate over all the machine instructions in BB
172 for(MachineBasicBlock::iterator MInstIterator = MBB.begin();
173 MInstIterator != MBB.end(); ++MInstIterator) {
174 MachineInstr *MInst = *MInstIterator;
176 // If the machine instruction is a call/return instruction, add it to
177 // CallRetInstrList for processing its args, ret value, and ret addr.
179 if(TM.getInstrInfo().isReturn(MInst->getOpCode()) ||
180 TM.getInstrInfo().isCall(MInst->getOpCode()))
181 CallRetInstrList.push_back(MInst);
183 // iterate over explicit MI operands and create a new LR
184 // for each operand that is defined by the instruction
185 for (MachineInstr::val_op_iterator OpI = MInst->begin(),
186 OpE = MInst->end(); OpI != OpE; ++OpI)
188 const Value *Def = *OpI;
189 bool isCC = (OpI.getMachineOperand().getType()
190 == MachineOperand::MO_CCRegister);
191 LiveRange* LR = createOrAddToLiveRange(Def, isCC);
193 // If the operand has a pre-assigned register,
194 // set it directly in the LiveRange
195 if (OpI.getMachineOperand().hasAllocatedReg()) {
197 LR->setColor(MRI.getClassRegNum(
198 OpI.getMachineOperand().getAllocatedRegNum(),
203 // iterate over implicit MI operands and create a new LR
204 // for each operand that is defined by the instruction
205 for (unsigned i = 0; i < MInst->getNumImplicitRefs(); ++i)
206 if (MInst->getImplicitOp(i).isDef()) {
207 const Value *Def = MInst->getImplicitRef(i);
208 LiveRange* LR = createOrAddToLiveRange(Def, /*isCC*/ false);
210 // If the implicit operand has a pre-assigned register,
211 // set it directly in the LiveRange
212 if (MInst->getImplicitOp(i).hasAllocatedReg()) {
214 LR->setColor(MRI.getClassRegNum(
215 MInst->getImplicitOp(i).getAllocatedRegNum(),
220 } // 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) {
282 IGNode* lrNode = LR.getUserIGNode();
283 for (unsigned n=0, NN = lrNode->getNumOfNeighbors(); n < NN; n++) {
284 LiveRange *neighLR = lrNode->getAdjIGNode(n)->getParentLR();
285 if (neighLR->hasColor() && neighLR->getColor() == color)
287 if (neighLR->hasSuggestedColor() && neighLR->getSuggestedColor() == color)
293 // Cannot coalesce if any of the following is true:
294 // (1) Both LRs have suggested colors (should be "different suggested colors"?)
295 // (2) Both LR1 and LR2 have colors and the colors are different
296 // (but if the colors are the same, it is definitely safe to coalesce)
297 // (3) LR1 has color and LR2 interferes with any LR that has the same color
298 // (4) LR2 has color and LR1 interferes with any LR that has the same color
300 inline bool InterfsPreventCoalescing(const LiveRange& LROfDef,
301 const LiveRange& LROfUse) {
302 // (4) if they have different suggested colors, cannot coalesce
303 if (LROfDef.hasSuggestedColor() && LROfUse.hasSuggestedColor())
306 // if neither has a color, nothing more to do.
307 if (! LROfDef.hasColor() && ! LROfUse.hasColor())
310 // (2, 3) if L1 has color...
311 if (LROfDef.hasColor()) {
312 if (LROfUse.hasColor())
313 return (LROfUse.getColor() != LROfDef.getColor());
314 return InterferesWithColor(LROfUse, LROfDef.getColor());
317 // (4) else only LROfUse has a color: check if that could interfere
318 return InterferesWithColor(LROfDef, LROfUse.getColor());
322 void LiveRangeInfo::coalesceLRs()
324 if(DEBUG_RA >= RA_DEBUG_LiveRanges)
325 std::cerr << "\nCoalescing LRs ...\n";
327 MachineFunction &MF = MachineFunction::get(Meth);
328 for (MachineFunction::iterator BBI = MF.begin(); BBI != MF.end(); ++BBI) {
329 MachineBasicBlock &MBB = *BBI;
331 // iterate over all the machine instructions in BB
332 for(MachineBasicBlock::iterator MII = MBB.begin(); MII != MBB.end(); ++MII){
333 const MachineInstr *MI = *MII;
335 if( DEBUG_RA >= RA_DEBUG_LiveRanges) {
336 std::cerr << " *Iterating over machine instr ";
341 // iterate over MI operands to find defs
342 for(MachineInstr::const_val_op_iterator DefI = MI->begin(),
343 DefE = MI->end(); DefI != DefE; ++DefI) {
344 if (DefI.isDef()) { // this operand is modified
345 LiveRange *LROfDef = getLiveRangeForValue( *DefI );
346 RegClass *RCOfDef = LROfDef->getRegClass();
348 MachineInstr::const_val_op_iterator UseI = MI->begin(),
350 for( ; UseI != UseE; ++UseI) { // for all uses
351 LiveRange *LROfUse = getLiveRangeForValue( *UseI );
352 if (!LROfUse) { // if LR of use is not found
353 //don't warn about labels
354 if (!isa<BasicBlock>(*UseI) && DEBUG_RA >= RA_DEBUG_LiveRanges)
355 std::cerr << " !! Warning: No LR for use " << RAV(*UseI)<< "\n";
356 continue; // ignore and continue
359 if (LROfUse == LROfDef) // nothing to merge if they are same
362 if (MRI.getRegTypeForLR(LROfDef) ==
363 MRI.getRegTypeForLR(LROfUse)) {
364 // If the two RegTypes are the same
365 if (!RCOfDef->getInterference(LROfDef, LROfUse) ) {
367 unsigned CombinedDegree =
368 LROfDef->getUserIGNode()->getNumOfNeighbors() +
369 LROfUse->getUserIGNode()->getNumOfNeighbors();
371 if (CombinedDegree > RCOfDef->getNumOfAvailRegs()) {
372 // get more precise estimate of combined degree
373 CombinedDegree = LROfDef->getUserIGNode()->
374 getCombinedDegree(LROfUse->getUserIGNode());
377 if (CombinedDegree <= RCOfDef->getNumOfAvailRegs()) {
378 // if both LRs do not have different pre-assigned colors
379 // and both LRs do not have suggested colors
380 if (! InterfsPreventCoalescing(*LROfDef, *LROfUse)) {
381 RCOfDef->mergeIGNodesOfLRs(LROfDef, LROfUse);
382 unionAndUpdateLRs(LROfDef, LROfUse);
385 } // if combined degree is less than # of regs
386 } // if def and use do not interfere
387 }// if reg classes are the same
391 } // for all machine instructions
394 if (DEBUG_RA >= RA_DEBUG_LiveRanges)
395 std::cerr << "\nCoalescing Done!\n";
398 /*--------------------------- Debug code for printing ---------------*/
401 void LiveRangeInfo::printLiveRanges() {
402 LiveRangeMapType::iterator HMI = LiveRangeMap.begin(); // hash map iterator
403 std::cerr << "\nPrinting Live Ranges from Hash Map:\n";
404 for( ; HMI != LiveRangeMap.end(); ++HMI) {
405 if (HMI->first && HMI->second) {
406 std::cerr << " Value* " << RAV(HMI->first) << "\t: ";
407 if (IGNode* igNode = HMI->second->getUserIGNode())
408 std::cerr << "LR# " << igNode->getIndex();
410 std::cerr << "LR# " << "<no-IGNode>";
411 std::cerr << "\t:Values = "; printSet(*HMI->second); std::cerr << "\n";
416 } // End llvm namespace