#define DEBUG_TYPE "regalloc"
#include "RegisterCoalescer.h"
#include "LiveDebugVariables.h"
-#include "RegisterClassInfo.h"
#include "VirtRegMap.h"
#include "llvm/Pass.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/MachineRegisterInfo.h"
#include "llvm/CodeGen/Passes.h"
+#include "llvm/CodeGen/RegisterClassInfo.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
STATISTIC(numExtends , "Number of copies extended");
STATISTIC(NumReMats , "Number of instructions re-materialized");
STATISTIC(NumInflated , "Number of register classes inflated");
+STATISTIC(NumLaneConflicts, "Number of dead lane conflicts tested");
+STATISTIC(NumLaneResolves, "Number of dead lane conflicts resolved");
static cl::opt<bool>
EnableJoining("join-liveintervals",
/// can use this information below to update aliases.
bool joinIntervals(CoalescerPair &CP);
+ /// Attempt joining two virtual registers. Return true on success.
+ bool joinVirtRegs(CoalescerPair &CP);
+
/// Attempt joining with a reserved physreg.
bool joinReservedPhysReg(CoalescerPair &CP);
bool RegisterCoalescer::adjustCopiesBackFrom(const CoalescerPair &CP,
MachineInstr *CopyMI) {
assert(!CP.isPartial() && "This doesn't work for partial copies.");
-
- // Bail if there is no dst interval - can happen when merging physical subreg
- // operations.
- if (!LIS->hasInterval(CP.getDstReg()))
- return false;
+ assert(!CP.isPhys() && "This doesn't work for physreg copies.");
LiveInterval &IntA =
LIS->getInterval(CP.isFlipped() ? CP.getDstReg() : CP.getSrcReg());
// IntB, we can merge them.
if (ValLR+1 != BLR) return false;
- // If a live interval is a physical register, conservatively check if any
- // of its aliases is overlapping the live interval of the virtual register.
- // If so, do not coalesce.
- if (TargetRegisterInfo::isPhysicalRegister(IntB.reg)) {
- for (const uint16_t *AS = TRI->getAliasSet(IntB.reg); *AS; ++AS)
- if (LIS->hasInterval(*AS) && IntA.overlaps(LIS->getInterval(*AS))) {
- DEBUG({
- dbgs() << "\t\tInterfere with alias ";
- LIS->getInterval(*AS).print(dbgs(), TRI);
- });
- return false;
- }
- }
-
- DEBUG({
- dbgs() << "Extending: ";
- IntB.print(dbgs(), TRI);
- });
+ DEBUG(dbgs() << "Extending: " << PrintReg(IntB.reg, TRI));
SlotIndex FillerStart = ValLR->end, FillerEnd = BLR->start;
// We are about to delete CopyMI, so need to remove it as the 'instruction
// two value numbers.
IntB.addRange(LiveRange(FillerStart, FillerEnd, BValNo));
- // If the IntB live range is assigned to a physical register, and if that
- // physreg has sub-registers, update their live intervals as well.
- if (TargetRegisterInfo::isPhysicalRegister(IntB.reg)) {
- for (const uint16_t *SR = TRI->getSubRegisters(IntB.reg); *SR; ++SR) {
- if (!LIS->hasInterval(*SR))
- continue;
- LiveInterval &SRLI = LIS->getInterval(*SR);
- SRLI.addRange(LiveRange(FillerStart, FillerEnd,
- SRLI.getNextValue(FillerStart,
- LIS->getVNInfoAllocator())));
- }
- }
-
// Okay, merge "B1" into the same value number as "B0".
- if (BValNo != ValLR->valno) {
- // If B1 is killed by a PHI, then the merged live range must also be killed
- // by the same PHI, as B0 and B1 can not overlap.
- bool HasPHIKill = BValNo->hasPHIKill();
+ if (BValNo != ValLR->valno)
IntB.MergeValueNumberInto(BValNo, ValLR->valno);
- if (HasPHIKill)
- ValLR->valno->setHasPHIKill(true);
- }
- DEBUG({
- dbgs() << " result = ";
- IntB.print(dbgs(), TRI);
- dbgs() << "\n";
- });
+ DEBUG(dbgs() << " result = " << IntB << '\n');
// If the source instruction was killing the source register before the
// merge, unset the isKill marker given the live range has been extended.
LiveInterval &IntB,
VNInfo *AValNo,
VNInfo *BValNo) {
+ // If AValNo has PHI kills, conservatively assume that IntB defs can reach
+ // the PHI values.
+ if (LIS->hasPHIKill(IntA, AValNo))
+ return true;
+
for (LiveInterval::iterator AI = IntA.begin(), AE = IntA.end();
AI != AE; ++AI) {
if (AI->valno != AValNo) continue;
///
bool RegisterCoalescer::removeCopyByCommutingDef(const CoalescerPair &CP,
MachineInstr *CopyMI) {
- // FIXME: For now, only eliminate the copy by commuting its def when the
- // source register is a virtual register. We want to guard against cases
- // where the copy is a back edge copy and commuting the def lengthen the
- // live interval of the source register to the entire loop.
- if (CP.isPhys() && CP.isFlipped())
- return false;
-
- // Bail if there is no dst interval.
- if (!LIS->hasInterval(CP.getDstReg()))
- return false;
+ assert (!CP.isPhys());
SlotIndex CopyIdx = LIS->getInstructionIndex(CopyMI).getRegSlot();
// AValNo is the value number in A that defines the copy, A3 in the example.
VNInfo *AValNo = IntA.getVNInfoAt(CopyIdx.getRegSlot(true));
assert(AValNo && "COPY source not live");
-
- // If other defs can reach uses of this def, then it's not safe to perform
- // the optimization.
- if (AValNo->isPHIDef() || AValNo->isUnused() || AValNo->hasPHIKill())
+ if (AValNo->isPHIDef() || AValNo->isUnused())
return false;
MachineInstr *DefMI = LIS->getInstructionFromIndex(AValNo->def);
if (!DefMI)
MachineOperand &NewDstMO = DefMI->getOperand(NewDstIdx);
unsigned NewReg = NewDstMO.getReg();
- if (NewReg != IntB.reg || !NewDstMO.isKill())
+ if (NewReg != IntB.reg || !LiveRangeQuery(IntB, AValNo->def).isKill())
return false;
// Make sure there are no other definitions of IntB that would reach the
if (hasOtherReachingDefs(IntA, IntB, AValNo, BValNo))
return false;
- // Abort if the aliases of IntB.reg have values that are not simply the
- // clobbers from the superreg.
- if (TargetRegisterInfo::isPhysicalRegister(IntB.reg))
- for (const uint16_t *AS = TRI->getAliasSet(IntB.reg); *AS; ++AS)
- if (LIS->hasInterval(*AS) &&
- hasOtherReachingDefs(IntA, LIS->getInterval(*AS), AValNo, 0))
- return false;
-
// If some of the uses of IntA.reg is already coalesced away, return false.
// It's not possible to determine whether it's safe to perform the coalescing.
for (MachineRegisterInfo::use_nodbg_iterator UI =
LiveInterval::iterator ULR = IntA.FindLiveRangeContaining(UseIdx);
if (ULR == IntA.end() || ULR->valno != AValNo)
continue;
+ // Kill flags are no longer accurate. They are recomputed after RA.
+ UseMO.setIsKill(false);
if (TargetRegisterInfo::isPhysicalRegister(NewReg))
UseMO.substPhysReg(NewReg, *TRI);
else
SlotIndex NewMIIdx = LIS->getInstructionIndex(NewMI);
for (unsigned i = 0, e = NewMIImplDefs.size(); i != e; ++i) {
- unsigned reg = NewMIImplDefs[i];
- LiveInterval &li = LIS->getInterval(reg);
- VNInfo *DeadDefVN = li.getNextValue(NewMIIdx.getRegSlot(),
- LIS->getVNInfoAllocator());
- LiveRange lr(NewMIIdx.getRegSlot(), NewMIIdx.getDeadSlot(), DeadDefVN);
- li.addRange(lr);
+ unsigned Reg = NewMIImplDefs[i];
+ for (MCRegUnitIterator Units(Reg, TRI); Units.isValid(); ++Units)
+ if (LiveInterval *LI = LIS->getCachedRegUnit(*Units))
+ LI->createDeadDef(NewMIIdx.getRegSlot(), LIS->getVNInfoAllocator());
}
CopyMI->eraseFromParent();
unsigned DstReg,
unsigned SubIdx) {
bool DstIsPhys = TargetRegisterInfo::isPhysicalRegister(DstReg);
- LiveInterval &DstInt = LIS->getInterval(DstReg);
+ LiveInterval *DstInt = DstIsPhys ? 0 : &LIS->getInterval(DstReg);
// Update LiveDebugVariables.
LDV->renameRegister(SrcReg, DstReg, SubIdx);
// If SrcReg wasn't read, it may still be the case that DstReg is live-in
// because SrcReg is a sub-register.
- if (!Reads && SubIdx)
- Reads = DstInt.liveAt(LIS->getInstructionIndex(UseMI));
+ if (DstInt && !Reads && SubIdx)
+ Reads = DstInt->liveAt(LIS->getInstructionIndex(UseMI));
// Replace SrcReg with DstReg in all UseMI operands.
for (unsigned i = 0, e = Ops.size(); i != e; ++i) {
Again = false;
DEBUG(dbgs() << LIS->getInstructionIndex(CopyMI) << '\t' << *CopyMI);
- CoalescerPair CP(*TII, *TRI);
+ CoalescerPair CP(*TRI);
if (!CP.setRegisters(CopyMI)) {
DEBUG(dbgs() << "\tNot coalescable.\n");
return false;
return true;
}
- // If they are already joined we continue.
- if (CP.getSrcReg() == CP.getDstReg()) {
- DEBUG(dbgs() << "\tCopy already coalesced.\n");
+ // Eliminate undefs.
+ if (!CP.isPhys() && eliminateUndefCopy(CopyMI, CP)) {
+ DEBUG(dbgs() << "\tEliminated copy of <undef> value.\n");
LIS->RemoveMachineInstrFromMaps(CopyMI);
CopyMI->eraseFromParent();
return false; // Not coalescable.
}
- // Eliminate undefs.
- if (!CP.isPhys() && eliminateUndefCopy(CopyMI, CP)) {
- DEBUG(dbgs() << "\tEliminated copy of <undef> value.\n");
+ // Coalesced copies are normally removed immediately, but transformations
+ // like removeCopyByCommutingDef() can inadvertently create identity copies.
+ // When that happens, just join the values and remove the copy.
+ if (CP.getSrcReg() == CP.getDstReg()) {
+ LiveInterval &LI = LIS->getInterval(CP.getSrcReg());
+ DEBUG(dbgs() << "\tCopy already coalesced: " << LI << '\n');
+ LiveRangeQuery LRQ(LI, LIS->getInstructionIndex(CopyMI));
+ if (VNInfo *DefVNI = LRQ.valueDefined()) {
+ VNInfo *ReadVNI = LRQ.valueIn();
+ assert(ReadVNI && "No value before copy and no <undef> flag.");
+ assert(ReadVNI != DefVNI && "Cannot read and define the same value.");
+ LI.MergeValueNumberInto(DefVNI, ReadVNI);
+ DEBUG(dbgs() << "\tMerged values: " << LI << '\n');
+ }
LIS->RemoveMachineInstrFromMaps(CopyMI);
CopyMI->eraseFromParent();
- return false; // Not coalescable.
+ return true;
}
// Enforce policies.
return true;
// If we can eliminate the copy without merging the live ranges, do so now.
- if (!CP.isPartial()) {
+ if (!CP.isPartial() && !CP.isPhys()) {
if (adjustCopiesBackFrom(CP, CopyMI) ||
removeCopyByCommutingDef(CP, CopyMI)) {
LIS->RemoveMachineInstrFromMaps(CopyMI);
if (!CP.isPhys() && RegClassInfo.isProperSubClass(CP.getNewRC()))
InflateRegs.push_back(CP.getDstReg());
- // Remember to delete the copy instruction.
- LIS->RemoveMachineInstrFromMaps(CopyMI);
- CopyMI->eraseFromParent();
+ // CopyMI has been erased by joinIntervals at this point. Remove it from
+ // ErasedInstrs since copyCoalesceWorkList() won't add a successful join back
+ // to the work list. This keeps ErasedInstrs from growing needlessly.
+ ErasedInstrs.erase(CopyMI);
// Rewrite all SrcReg operands to DstReg.
// Also update DstReg operands to include DstIdx if it is set.
TRI->UpdateRegAllocHint(CP.getSrcReg(), CP.getDstReg(), *MF);
DEBUG({
- LiveInterval &DstInt = LIS->getInterval(CP.getDstReg());
- dbgs() << "\tJoined. Result = ";
- DstInt.print(dbgs(), TRI);
- dbgs() << "\n";
+ dbgs() << "\tJoined. Result = " << PrintReg(CP.getDstReg(), TRI);
+ if (!CP.isPhys())
+ dbgs() << LIS->getInterval(CP.getDstReg());
+ dbgs() << '\n';
});
++numJoins;
assert(CP.isPhys() && "Must be a physreg copy");
assert(RegClassInfo.isReserved(CP.getDstReg()) && "Not a reserved register");
LiveInterval &RHS = LIS->getInterval(CP.getSrcReg());
- DEBUG({ dbgs() << "\t\tRHS = "; RHS.print(dbgs(), TRI); dbgs() << "\n"; });
+ DEBUG(dbgs() << "\t\tRHS = " << PrintReg(CP.getSrcReg()) << ' ' << RHS
+ << '\n');
assert(CP.isFlipped() && RHS.containsOneValue() &&
"Invalid join with reserved register");
// Deny any overlapping intervals. This depends on all the reserved
// register live ranges to look like dead defs.
- for (const uint16_t *AS = TRI->getOverlaps(CP.getDstReg()); *AS; ++AS) {
- if (!LIS->hasInterval(*AS)) {
- // Make sure at least DstReg itself exists before attempting a join.
- if (*AS == CP.getDstReg())
- LIS->getOrCreateInterval(CP.getDstReg());
- continue;
- }
- if (RHS.overlaps(LIS->getInterval(*AS))) {
- DEBUG(dbgs() << "\t\tInterference: " << PrintReg(*AS, TRI) << '\n');
+ for (MCRegUnitIterator UI(CP.getDstReg(), TRI); UI.isValid(); ++UI)
+ if (RHS.overlaps(LIS->getRegUnit(*UI))) {
+ DEBUG(dbgs() << "\t\tInterference: " << PrintRegUnit(*UI, TRI) << '\n');
return false;
}
- }
+
// Skip any value computations, we are not adding new values to the
// reserved register. Also skip merging the live ranges, the reserved
// register live range doesn't need to be accurate as long as all the
// defs are there.
- return true;
-}
-
-/// ComputeUltimateVN - Assuming we are going to join two live intervals,
-/// compute what the resultant value numbers for each value in the input two
-/// ranges will be. This is complicated by copies between the two which can
-/// and will commonly cause multiple value numbers to be merged into one.
-///
-/// VN is the value number that we're trying to resolve. InstDefiningValue
-/// keeps track of the new InstDefiningValue assignment for the result
-/// LiveInterval. ThisFromOther/OtherFromThis are sets that keep track of
-/// whether a value in this or other is a copy from the opposite set.
-/// ThisValNoAssignments/OtherValNoAssignments keep track of value #'s that have
-/// already been assigned.
-///
-/// ThisFromOther[x] - If x is defined as a copy from the other interval, this
-/// contains the value number the copy is from.
-///
-static unsigned ComputeUltimateVN(VNInfo *VNI,
- SmallVector<VNInfo*, 16> &NewVNInfo,
- DenseMap<VNInfo*, VNInfo*> &ThisFromOther,
- DenseMap<VNInfo*, VNInfo*> &OtherFromThis,
- SmallVector<int, 16> &ThisValNoAssignments,
- SmallVector<int, 16> &OtherValNoAssignments) {
- unsigned VN = VNI->id;
-
- // If the VN has already been computed, just return it.
- if (ThisValNoAssignments[VN] >= 0)
- return ThisValNoAssignments[VN];
- assert(ThisValNoAssignments[VN] != -2 && "Cyclic value numbers");
-
- // If this val is not a copy from the other val, then it must be a new value
- // number in the destination.
- DenseMap<VNInfo*, VNInfo*>::iterator I = ThisFromOther.find(VNI);
- if (I == ThisFromOther.end()) {
- NewVNInfo.push_back(VNI);
- return ThisValNoAssignments[VN] = NewVNInfo.size()-1;
- }
- VNInfo *OtherValNo = I->second;
-
- // Otherwise, this *is* a copy from the RHS. If the other side has already
- // been computed, return it.
- if (OtherValNoAssignments[OtherValNo->id] >= 0)
- return ThisValNoAssignments[VN] = OtherValNoAssignments[OtherValNo->id];
-
- // Mark this value number as currently being computed, then ask what the
- // ultimate value # of the other value is.
- ThisValNoAssignments[VN] = -2;
- unsigned UltimateVN =
- ComputeUltimateVN(OtherValNo, NewVNInfo, OtherFromThis, ThisFromOther,
- OtherValNoAssignments, ThisValNoAssignments);
- return ThisValNoAssignments[VN] = UltimateVN;
-}
+ // Delete the identity copy.
+ MachineInstr *CopyMI = MRI->getVRegDef(RHS.reg);
+ LIS->RemoveMachineInstrFromMaps(CopyMI);
+ CopyMI->eraseFromParent();
-// Find out if we have something like
-// A = X
-// B = X
-// if so, we can pretend this is actually
-// A = X
-// B = A
-// which allows us to coalesce A and B.
-// VNI is the definition of B. LR is the life range of A that includes
-// the slot just before B. If we return true, we add "B = X" to DupCopies.
-// This implies that A dominates B.
-static bool RegistersDefinedFromSameValue(LiveIntervals &li,
- const TargetRegisterInfo &tri,
- CoalescerPair &CP,
- VNInfo *VNI,
- LiveRange *LR,
- SmallVector<MachineInstr*, 8> &DupCopies) {
- // FIXME: This is very conservative. For example, we don't handle
- // physical registers.
-
- MachineInstr *MI = li.getInstructionFromIndex(VNI->def);
-
- if (!MI || !MI->isFullCopy() || CP.isPartial() || CP.isPhys())
- return false;
+ // We don't track kills for reserved registers.
+ MRI->clearKillFlags(CP.getSrcReg());
- unsigned Dst = MI->getOperand(0).getReg();
- unsigned Src = MI->getOperand(1).getReg();
+ return true;
+}
- if (!TargetRegisterInfo::isVirtualRegister(Src) ||
- !TargetRegisterInfo::isVirtualRegister(Dst))
- return false;
+//===----------------------------------------------------------------------===//
+// Interference checking and interval joining
+//===----------------------------------------------------------------------===//
+//
+// In the easiest case, the two live ranges being joined are disjoint, and
+// there is no interference to consider. It is quite common, though, to have
+// overlapping live ranges, and we need to check if the interference can be
+// resolved.
+//
+// The live range of a single SSA value forms a sub-tree of the dominator tree.
+// This means that two SSA values overlap if and only if the def of one value
+// is contained in the live range of the other value. As a special case, the
+// overlapping values can be defined at the same index.
+//
+// The interference from an overlapping def can be resolved in these cases:
+//
+// 1. Coalescable copies. The value is defined by a copy that would become an
+// identity copy after joining SrcReg and DstReg. The copy instruction will
+// be removed, and the value will be merged with the source value.
+//
+// There can be several copies back and forth, causing many values to be
+// merged into one. We compute a list of ultimate values in the joined live
+// range as well as a mappings from the old value numbers.
+//
+// 2. IMPLICIT_DEF. This instruction is only inserted to ensure all PHI
+// predecessors have a live out value. It doesn't cause real interference,
+// and can be merged into the value it overlaps. Like a coalescable copy, it
+// can be erased after joining.
+//
+// 3. Copy of external value. The overlapping def may be a copy of a value that
+// is already in the other register. This is like a coalescable copy, but
+// the live range of the source register must be trimmed after erasing the
+// copy instruction:
+//
+// %src = COPY %ext
+// %dst = COPY %ext <-- Remove this COPY, trim the live range of %ext.
+//
+// 4. Clobbering undefined lanes. Vector registers are sometimes built by
+// defining one lane at a time:
+//
+// %dst:ssub0<def,read-undef> = FOO
+// %src = BAR
+// %dst:ssub1<def> = COPY %src
+//
+// The live range of %src overlaps the %dst value defined by FOO, but
+// merging %src into %dst:ssub1 is only going to clobber the ssub1 lane
+// which was undef anyway.
+//
+// The value mapping is more complicated in this case. The final live range
+// will have different value numbers for both FOO and BAR, but there is no
+// simple mapping from old to new values. It may even be necessary to add
+// new PHI values.
+//
+// 5. Clobbering dead lanes. A def may clobber a lane of a vector register that
+// is live, but never read. This can happen because we don't compute
+// individual live ranges per lane.
+//
+// %dst<def> = FOO
+// %src = BAR
+// %dst:ssub1<def> = COPY %src
+//
+// This kind of interference is only resolved locally. If the clobbered
+// lane value escapes the block, the join is aborted.
- unsigned A = CP.getDstReg();
- unsigned B = CP.getSrcReg();
+namespace {
+/// Track information about values in a single virtual register about to be
+/// joined. Objects of this class are always created in pairs - one for each
+/// side of the CoalescerPair.
+class JoinVals {
+ LiveInterval &LI;
+
+ // Location of this register in the final joined register.
+ // Either CP.DstIdx or CP.SrcIdx.
+ unsigned SubIdx;
+
+ // Values that will be present in the final live range.
+ SmallVectorImpl<VNInfo*> &NewVNInfo;
+
+ const CoalescerPair &CP;
+ LiveIntervals *LIS;
+ SlotIndexes *Indexes;
+ const TargetRegisterInfo *TRI;
+
+ // Value number assignments. Maps value numbers in LI to entries in NewVNInfo.
+ // This is suitable for passing to LiveInterval::join().
+ SmallVector<int, 8> Assignments;
+
+ // Conflict resolution for overlapping values.
+ enum ConflictResolution {
+ // No overlap, simply keep this value.
+ CR_Keep,
+
+ // Merge this value into OtherVNI and erase the defining instruction.
+ // Used for IMPLICIT_DEF, coalescable copies, and copies from external
+ // values.
+ CR_Erase,
+
+ // Merge this value into OtherVNI but keep the defining instruction.
+ // This is for the special case where OtherVNI is defined by the same
+ // instruction.
+ CR_Merge,
+
+ // Keep this value, and have it replace OtherVNI where possible. This
+ // complicates value mapping since OtherVNI maps to two different values
+ // before and after this def.
+ // Used when clobbering undefined or dead lanes.
+ CR_Replace,
+
+ // Unresolved conflict. Visit later when all values have been mapped.
+ CR_Unresolved,
+
+ // Unresolvable conflict. Abort the join.
+ CR_Impossible
+ };
- if (B == Dst)
- std::swap(A, B);
- assert(Dst == A);
+ // Per-value info for LI. The lane bit masks are all relative to the final
+ // joined register, so they can be compared directly between SrcReg and
+ // DstReg.
+ struct Val {
+ ConflictResolution Resolution;
- VNInfo *Other = LR->valno;
- const MachineInstr *OtherMI = li.getInstructionFromIndex(Other->def);
+ // Lanes written by this def, 0 for unanalyzed values.
+ unsigned WriteLanes;
- if (!OtherMI || !OtherMI->isFullCopy())
- return false;
+ // Lanes with defined values in this register. Other lanes are undef and
+ // safe to clobber.
+ unsigned ValidLanes;
- unsigned OtherDst = OtherMI->getOperand(0).getReg();
- unsigned OtherSrc = OtherMI->getOperand(1).getReg();
+ // Value in LI being redefined by this def.
+ VNInfo *RedefVNI;
- if (!TargetRegisterInfo::isVirtualRegister(OtherSrc) ||
- !TargetRegisterInfo::isVirtualRegister(OtherDst))
- return false;
+ // Value in the other live range that overlaps this def, if any.
+ VNInfo *OtherVNI;
- assert(OtherDst == B);
+ // True when the live range of this value will be pruned because of an
+ // overlapping CR_Replace value in the other live range.
+ bool Pruned;
- if (Src != OtherSrc)
- return false;
+ // True once Pruned above has been computed.
+ bool PrunedComputed;
- // If the copies use two different value numbers of X, we cannot merge
- // A and B.
- LiveInterval &SrcInt = li.getInterval(Src);
- // getVNInfoBefore returns NULL for undef copies. In this case, the
- // optimization is still safe.
- if (SrcInt.getVNInfoBefore(Other->def) != SrcInt.getVNInfoBefore(VNI->def))
- return false;
+ Val() : Resolution(CR_Keep), WriteLanes(0), ValidLanes(0),
+ RedefVNI(0), OtherVNI(0), Pruned(false), PrunedComputed(false) {}
- DupCopies.push_back(MI);
+ bool isAnalyzed() const { return WriteLanes != 0; }
+ };
- return true;
+ // One entry per value number in LI.
+ SmallVector<Val, 8> Vals;
+
+ unsigned computeWriteLanes(const MachineInstr *DefMI, bool &Redef);
+ VNInfo *stripCopies(VNInfo *VNI);
+ ConflictResolution analyzeValue(unsigned ValNo, JoinVals &Other);
+ void computeAssignment(unsigned ValNo, JoinVals &Other);
+ bool taintExtent(unsigned, unsigned, JoinVals&,
+ SmallVectorImpl<std::pair<SlotIndex, unsigned> >&);
+ bool usesLanes(MachineInstr *MI, unsigned, unsigned, unsigned);
+ bool isPrunedValue(unsigned ValNo, JoinVals &Other);
+
+public:
+ JoinVals(LiveInterval &li, unsigned subIdx,
+ SmallVectorImpl<VNInfo*> &newVNInfo,
+ const CoalescerPair &cp,
+ LiveIntervals *lis,
+ const TargetRegisterInfo *tri)
+ : LI(li), SubIdx(subIdx), NewVNInfo(newVNInfo), CP(cp), LIS(lis),
+ Indexes(LIS->getSlotIndexes()), TRI(tri),
+ Assignments(LI.getNumValNums(), -1), Vals(LI.getNumValNums())
+ {}
+
+ /// Analyze defs in LI and compute a value mapping in NewVNInfo.
+ /// Returns false if any conflicts were impossible to resolve.
+ bool mapValues(JoinVals &Other);
+
+ /// Try to resolve conflicts that require all values to be mapped.
+ /// Returns false if any conflicts were impossible to resolve.
+ bool resolveConflicts(JoinVals &Other);
+
+ /// Prune the live range of values in Other.LI where they would conflict with
+ /// CR_Replace values in LI. Collect end points for restoring the live range
+ /// after joining.
+ void pruneValues(JoinVals &Other, SmallVectorImpl<SlotIndex> &EndPoints);
+
+ /// Erase any machine instructions that have been coalesced away.
+ /// Add erased instructions to ErasedInstrs.
+ /// Add foreign virtual registers to ShrinkRegs if their live range ended at
+ /// the erased instrs.
+ void eraseInstrs(SmallPtrSet<MachineInstr*, 8> &ErasedInstrs,
+ SmallVectorImpl<unsigned> &ShrinkRegs);
+
+ /// Get the value assignments suitable for passing to LiveInterval::join.
+ const int *getAssignments() const { return &Assignments[0]; }
+};
+} // end anonymous namespace
+
+/// Compute the bitmask of lanes actually written by DefMI.
+/// Set Redef if there are any partial register definitions that depend on the
+/// previous value of the register.
+unsigned JoinVals::computeWriteLanes(const MachineInstr *DefMI, bool &Redef) {
+ unsigned L = 0;
+ for (ConstMIOperands MO(DefMI); MO.isValid(); ++MO) {
+ if (!MO->isReg() || MO->getReg() != LI.reg || !MO->isDef())
+ continue;
+ L |= TRI->getSubRegIndexLaneMask(compose(*TRI, SubIdx, MO->getSubReg()));
+ if (MO->readsReg())
+ Redef = true;
+ }
+ return L;
}
-/// joinIntervals - Attempt to join these two intervals. On failure, this
-/// returns false.
-bool RegisterCoalescer::joinIntervals(CoalescerPair &CP) {
- // Handle physreg joins separately.
- if (CP.isPhys())
- return joinReservedPhysReg(CP);
-
- LiveInterval &RHS = LIS->getInterval(CP.getSrcReg());
- DEBUG({ dbgs() << "\t\tRHS = "; RHS.print(dbgs(), TRI); dbgs() << "\n"; });
-
- // Compute the final value assignment, assuming that the live ranges can be
- // coalesced.
- SmallVector<int, 16> LHSValNoAssignments;
- SmallVector<int, 16> RHSValNoAssignments;
- DenseMap<VNInfo*, VNInfo*> LHSValsDefinedFromRHS;
- DenseMap<VNInfo*, VNInfo*> RHSValsDefinedFromLHS;
- SmallVector<VNInfo*, 16> NewVNInfo;
-
- SmallVector<MachineInstr*, 8> DupCopies;
-
- LiveInterval &LHS = LIS->getOrCreateInterval(CP.getDstReg());
- DEBUG({ dbgs() << "\t\tLHS = "; LHS.print(dbgs(), TRI); dbgs() << "\n"; });
+/// Find the ultimate value that VNI was copied from.
+VNInfo *JoinVals::stripCopies(VNInfo *VNI) {
+ while (!VNI->isPHIDef()) {
+ MachineInstr *MI = Indexes->getInstructionFromIndex(VNI->def);
+ assert(MI && "No defining instruction");
+ if (!MI->isFullCopy())
+ break;
+ unsigned Reg = MI->getOperand(1).getReg();
+ if (!TargetRegisterInfo::isVirtualRegister(Reg))
+ break;
+ LiveRangeQuery LRQ(LIS->getInterval(Reg), VNI->def);
+ if (!LRQ.valueIn())
+ break;
+ VNI = LRQ.valueIn();
+ }
+ return VNI;
+}
- // Loop over the value numbers of the LHS, seeing if any are defined from
- // the RHS.
- for (LiveInterval::vni_iterator i = LHS.vni_begin(), e = LHS.vni_end();
- i != e; ++i) {
- VNInfo *VNI = *i;
- if (VNI->isUnused() || VNI->isPHIDef())
- continue;
- MachineInstr *MI = LIS->getInstructionFromIndex(VNI->def);
- assert(MI && "Missing def");
- if (!MI->isCopyLike()) // Src not defined by a copy?
- continue;
+/// Analyze ValNo in this live range, and set all fields of Vals[ValNo].
+/// Return a conflict resolution when possible, but leave the hard cases as
+/// CR_Unresolved.
+/// Recursively calls computeAssignment() on this and Other, guaranteeing that
+/// both OtherVNI and RedefVNI have been analyzed and mapped before returning.
+/// The recursion always goes upwards in the dominator tree, making loops
+/// impossible.
+JoinVals::ConflictResolution
+JoinVals::analyzeValue(unsigned ValNo, JoinVals &Other) {
+ Val &V = Vals[ValNo];
+ assert(!V.isAnalyzed() && "Value has already been analyzed!");
+ VNInfo *VNI = LI.getValNumInfo(ValNo);
+ if (VNI->isUnused()) {
+ V.WriteLanes = ~0u;
+ return CR_Keep;
+ }
- // Figure out the value # from the RHS.
- LiveRange *lr = RHS.getLiveRangeContaining(VNI->def.getPrevSlot());
- // The copy could be to an aliased physreg.
- if (!lr) continue;
+ // Get the instruction defining this value, compute the lanes written.
+ const MachineInstr *DefMI = 0;
+ if (VNI->isPHIDef()) {
+ // Conservatively assume that all lanes in a PHI are valid.
+ V.ValidLanes = V.WriteLanes = TRI->getSubRegIndexLaneMask(SubIdx);
+ } else {
+ DefMI = Indexes->getInstructionFromIndex(VNI->def);
+ bool Redef = false;
+ V.ValidLanes = V.WriteLanes = computeWriteLanes(DefMI, Redef);
+
+ // If this is a read-modify-write instruction, there may be more valid
+ // lanes than the ones written by this instruction.
+ // This only covers partial redef operands. DefMI may have normal use
+ // operands reading the register. They don't contribute valid lanes.
+ //
+ // This adds ssub1 to the set of valid lanes in %src:
+ //
+ // %src:ssub1<def> = FOO
+ //
+ // This leaves only ssub1 valid, making any other lanes undef:
+ //
+ // %src:ssub1<def,read-undef> = FOO %src:ssub2
+ //
+ // The <read-undef> flag on the def operand means that old lane values are
+ // not important.
+ if (Redef) {
+ V.RedefVNI = LiveRangeQuery(LI, VNI->def).valueIn();
+ assert(V.RedefVNI && "Instruction is reading nonexistent value");
+ computeAssignment(V.RedefVNI->id, Other);
+ V.ValidLanes |= Vals[V.RedefVNI->id].ValidLanes;
+ }
- // DstReg is known to be a register in the LHS interval. If the src is
- // from the RHS interval, we can use its value #.
- if (!CP.isCoalescable(MI) &&
- !RegistersDefinedFromSameValue(*LIS, *TRI, CP, VNI, lr, DupCopies))
- continue;
+ // An IMPLICIT_DEF writes undef values.
+ if (DefMI->isImplicitDef())
+ V.ValidLanes &= ~V.WriteLanes;
+ }
- LHSValsDefinedFromRHS[VNI] = lr->valno;
+ // Find the value in Other that overlaps VNI->def, if any.
+ LiveRangeQuery OtherLRQ(Other.LI, VNI->def);
+
+ // It is possible that both values are defined by the same instruction, or
+ // the values are PHIs defined in the same block. When that happens, the two
+ // values should be merged into one, but not into any preceding value.
+ // The first value defined or visited gets CR_Keep, the other gets CR_Merge.
+ if (VNInfo *OtherVNI = OtherLRQ.valueDefined()) {
+ assert(SlotIndex::isSameInstr(VNI->def, OtherVNI->def) && "Broken LRQ");
+
+ // One value stays, the other is merged. Keep the earlier one, or the first
+ // one we see.
+ if (OtherVNI->def < VNI->def)
+ Other.computeAssignment(OtherVNI->id, *this);
+ else if (VNI->def < OtherVNI->def && OtherLRQ.valueIn()) {
+ // This is an early-clobber def overlapping a live-in value in the other
+ // register. Not mergeable.
+ V.OtherVNI = OtherLRQ.valueIn();
+ return CR_Impossible;
+ }
+ V.OtherVNI = OtherVNI;
+ Val &OtherV = Other.Vals[OtherVNI->id];
+ // Keep this value, check for conflicts when analyzing OtherVNI.
+ if (!OtherV.isAnalyzed())
+ return CR_Keep;
+ // Both sides have been analyzed now.
+ // Allow overlapping PHI values. Any real interference would show up in a
+ // predecessor, the PHI itself can't introduce any conflicts.
+ if (VNI->isPHIDef())
+ return CR_Merge;
+ if (V.ValidLanes & OtherV.ValidLanes)
+ // Overlapping lanes can't be resolved.
+ return CR_Impossible;
+ else
+ return CR_Merge;
}
- // Loop over the value numbers of the RHS, seeing if any are defined from
- // the LHS.
- for (LiveInterval::vni_iterator i = RHS.vni_begin(), e = RHS.vni_end();
- i != e; ++i) {
- VNInfo *VNI = *i;
- if (VNI->isUnused() || VNI->isPHIDef())
- continue;
- MachineInstr *MI = LIS->getInstructionFromIndex(VNI->def);
- assert(MI && "Missing def");
- if (!MI->isCopyLike()) // Src not defined by a copy?
- continue;
+ // No simultaneous def. Is Other live at the def?
+ V.OtherVNI = OtherLRQ.valueIn();
+ if (!V.OtherVNI)
+ // No overlap, no conflict.
+ return CR_Keep;
+
+ assert(!SlotIndex::isSameInstr(VNI->def, V.OtherVNI->def) && "Broken LRQ");
+
+ // We have overlapping values, or possibly a kill of Other.
+ // Recursively compute assignments up the dominator tree.
+ Other.computeAssignment(V.OtherVNI->id, *this);
+ const Val &OtherV = Other.Vals[V.OtherVNI->id];
+
+ // Allow overlapping PHI values. Any real interference would show up in a
+ // predecessor, the PHI itself can't introduce any conflicts.
+ if (VNI->isPHIDef())
+ return CR_Replace;
+
+ // Check for simple erasable conflicts.
+ if (DefMI->isImplicitDef())
+ return CR_Erase;
+
+ // Include the non-conflict where DefMI is a coalescable copy that kills
+ // OtherVNI. We still want the copy erased and value numbers merged.
+ if (CP.isCoalescable(DefMI)) {
+ // Some of the lanes copied from OtherVNI may be undef, making them undef
+ // here too.
+ V.ValidLanes &= ~V.WriteLanes | OtherV.ValidLanes;
+ return CR_Erase;
+ }
- // Figure out the value # from the LHS.
- LiveRange *lr = LHS.getLiveRangeContaining(VNI->def.getPrevSlot());
- // The copy could be to an aliased physreg.
- if (!lr) continue;
+ // This may not be a real conflict if DefMI simply kills Other and defines
+ // VNI.
+ if (OtherLRQ.isKill() && OtherLRQ.endPoint() <= VNI->def)
+ return CR_Keep;
+
+ // Handle the case where VNI and OtherVNI can be proven to be identical:
+ //
+ // %other = COPY %ext
+ // %this = COPY %ext <-- Erase this copy
+ //
+ if (DefMI->isFullCopy() && !CP.isPartial() &&
+ stripCopies(VNI) == stripCopies(V.OtherVNI))
+ return CR_Erase;
+
+ // If the lanes written by this instruction were all undef in OtherVNI, it is
+ // still safe to join the live ranges. This can't be done with a simple value
+ // mapping, though - OtherVNI will map to multiple values:
+ //
+ // 1 %dst:ssub0 = FOO <-- OtherVNI
+ // 2 %src = BAR <-- VNI
+ // 3 %dst:ssub1 = COPY %src<kill> <-- Eliminate this copy.
+ // 4 BAZ %dst<kill>
+ // 5 QUUX %src<kill>
+ //
+ // Here OtherVNI will map to itself in [1;2), but to VNI in [2;5). CR_Replace
+ // handles this complex value mapping.
+ if ((V.WriteLanes & OtherV.ValidLanes) == 0)
+ return CR_Replace;
+
+ // VNI is clobbering live lanes in OtherVNI, but there is still the
+ // possibility that no instructions actually read the clobbered lanes.
+ // If we're clobbering all the lanes in OtherVNI, at least one must be read.
+ // Otherwise Other.LI wouldn't be live here.
+ if ((TRI->getSubRegIndexLaneMask(Other.SubIdx) & ~V.WriteLanes) == 0)
+ return CR_Impossible;
+
+ // We need to verify that no instructions are reading the clobbered lanes. To
+ // save compile time, we'll only check that locally. Don't allow the tainted
+ // value to escape the basic block.
+ MachineBasicBlock *MBB = Indexes->getMBBFromIndex(VNI->def);
+ if (OtherLRQ.endPoint() >= Indexes->getMBBEndIdx(MBB))
+ return CR_Impossible;
+
+ // There are still some things that could go wrong besides clobbered lanes
+ // being read, for example OtherVNI may be only partially redefined in MBB,
+ // and some clobbered lanes could escape the block. Save this analysis for
+ // resolveConflicts() when all values have been mapped. We need to know
+ // RedefVNI and WriteLanes for any later defs in MBB, and we can't compute
+ // that now - the recursive analyzeValue() calls must go upwards in the
+ // dominator tree.
+ return CR_Unresolved;
+}
- // DstReg is known to be a register in the RHS interval. If the src is
- // from the LHS interval, we can use its value #.
- if (!CP.isCoalescable(MI) &&
- !RegistersDefinedFromSameValue(*LIS, *TRI, CP, VNI, lr, DupCopies))
- continue;
+/// Compute the value assignment for ValNo in LI.
+/// This may be called recursively by analyzeValue(), but never for a ValNo on
+/// the stack.
+void JoinVals::computeAssignment(unsigned ValNo, JoinVals &Other) {
+ Val &V = Vals[ValNo];
+ if (V.isAnalyzed()) {
+ // Recursion should always move up the dominator tree, so ValNo is not
+ // supposed to reappear before it has been assigned.
+ assert(Assignments[ValNo] != -1 && "Bad recursion?");
+ return;
+ }
+ switch ((V.Resolution = analyzeValue(ValNo, Other))) {
+ case CR_Erase:
+ case CR_Merge:
+ // Merge this ValNo into OtherVNI.
+ assert(V.OtherVNI && "OtherVNI not assigned, can't merge.");
+ assert(Other.Vals[V.OtherVNI->id].isAnalyzed() && "Missing recursion");
+ Assignments[ValNo] = Other.Assignments[V.OtherVNI->id];
+ DEBUG(dbgs() << "\t\tmerge " << PrintReg(LI.reg) << ':' << ValNo << '@'
+ << LI.getValNumInfo(ValNo)->def << " into "
+ << PrintReg(Other.LI.reg) << ':' << V.OtherVNI->id << '@'
+ << V.OtherVNI->def << " --> @"
+ << NewVNInfo[Assignments[ValNo]]->def << '\n');
+ break;
+ case CR_Replace:
+ case CR_Unresolved:
+ // The other value is going to be pruned if this join is successful.
+ assert(V.OtherVNI && "OtherVNI not assigned, can't prune");
+ Other.Vals[V.OtherVNI->id].Pruned = true;
+ // Fall through.
+ default:
+ // This value number needs to go in the final joined live range.
+ Assignments[ValNo] = NewVNInfo.size();
+ NewVNInfo.push_back(LI.getValNumInfo(ValNo));
+ break;
+ }
+}
- RHSValsDefinedFromLHS[VNI] = lr->valno;
+bool JoinVals::mapValues(JoinVals &Other) {
+ for (unsigned i = 0, e = LI.getNumValNums(); i != e; ++i) {
+ computeAssignment(i, Other);
+ if (Vals[i].Resolution == CR_Impossible) {
+ DEBUG(dbgs() << "\t\tinterference at " << PrintReg(LI.reg) << ':' << i
+ << '@' << LI.getValNumInfo(i)->def << '\n');
+ return false;
+ }
}
+ return true;
+}
- LHSValNoAssignments.resize(LHS.getNumValNums(), -1);
- RHSValNoAssignments.resize(RHS.getNumValNums(), -1);
- NewVNInfo.reserve(LHS.getNumValNums() + RHS.getNumValNums());
+/// Assuming ValNo is going to clobber some valid lanes in Other.LI, compute
+/// the extent of the tainted lanes in the block.
+///
+/// Multiple values in Other.LI can be affected since partial redefinitions can
+/// preserve previously tainted lanes.
+///
+/// 1 %dst = VLOAD <-- Define all lanes in %dst
+/// 2 %src = FOO <-- ValNo to be joined with %dst:ssub0
+/// 3 %dst:ssub1 = BAR <-- Partial redef doesn't clear taint in ssub0
+/// 4 %dst:ssub0 = COPY %src <-- Conflict resolved, ssub0 wasn't read
+///
+/// For each ValNo in Other that is affected, add an (EndIndex, TaintedLanes)
+/// entry to TaintedVals.
+///
+/// Returns false if the tainted lanes extend beyond the basic block.
+bool JoinVals::
+taintExtent(unsigned ValNo, unsigned TaintedLanes, JoinVals &Other,
+ SmallVectorImpl<std::pair<SlotIndex, unsigned> > &TaintExtent) {
+ VNInfo *VNI = LI.getValNumInfo(ValNo);
+ MachineBasicBlock *MBB = Indexes->getMBBFromIndex(VNI->def);
+ SlotIndex MBBEnd = Indexes->getMBBEndIdx(MBB);
+
+ // Scan Other.LI from VNI.def to MBBEnd.
+ LiveInterval::iterator OtherI = Other.LI.find(VNI->def);
+ assert(OtherI != Other.LI.end() && "No conflict?");
+ do {
+ // OtherI is pointing to a tainted value. Abort the join if the tainted
+ // lanes escape the block.
+ SlotIndex End = OtherI->end;
+ if (End >= MBBEnd) {
+ DEBUG(dbgs() << "\t\ttaints global " << PrintReg(Other.LI.reg) << ':'
+ << OtherI->valno->id << '@' << OtherI->start << '\n');
+ return false;
+ }
+ DEBUG(dbgs() << "\t\ttaints local " << PrintReg(Other.LI.reg) << ':'
+ << OtherI->valno->id << '@' << OtherI->start
+ << " to " << End << '\n');
+ // A dead def is not a problem.
+ if (End.isDead())
+ break;
+ TaintExtent.push_back(std::make_pair(End, TaintedLanes));
+
+ // Check for another def in the MBB.
+ if (++OtherI == Other.LI.end() || OtherI->start >= MBBEnd)
+ break;
+
+ // Lanes written by the new def are no longer tainted.
+ const Val &OV = Other.Vals[OtherI->valno->id];
+ TaintedLanes &= ~OV.WriteLanes;
+ if (!OV.RedefVNI)
+ break;
+ } while (TaintedLanes);
+ return true;
+}
- for (LiveInterval::vni_iterator i = LHS.vni_begin(), e = LHS.vni_end();
- i != e; ++i) {
- VNInfo *VNI = *i;
- unsigned VN = VNI->id;
- if (LHSValNoAssignments[VN] >= 0 || VNI->isUnused())
- continue;
- ComputeUltimateVN(VNI, NewVNInfo,
- LHSValsDefinedFromRHS, RHSValsDefinedFromLHS,
- LHSValNoAssignments, RHSValNoAssignments);
- }
- for (LiveInterval::vni_iterator i = RHS.vni_begin(), e = RHS.vni_end();
- i != e; ++i) {
- VNInfo *VNI = *i;
- unsigned VN = VNI->id;
- if (RHSValNoAssignments[VN] >= 0 || VNI->isUnused())
+/// Return true if MI uses any of the given Lanes from Reg.
+/// This does not include partial redefinitions of Reg.
+bool JoinVals::usesLanes(MachineInstr *MI, unsigned Reg, unsigned SubIdx,
+ unsigned Lanes) {
+ if (MI->isDebugValue())
+ return false;
+ for (ConstMIOperands MO(MI); MO.isValid(); ++MO) {
+ if (!MO->isReg() || MO->isDef() || MO->getReg() != Reg)
continue;
- // If this value number isn't a copy from the LHS, it's a new number.
- if (RHSValsDefinedFromLHS.find(VNI) == RHSValsDefinedFromLHS.end()) {
- NewVNInfo.push_back(VNI);
- RHSValNoAssignments[VN] = NewVNInfo.size()-1;
+ if (!MO->readsReg())
continue;
- }
-
- ComputeUltimateVN(VNI, NewVNInfo,
- RHSValsDefinedFromLHS, LHSValsDefinedFromRHS,
- RHSValNoAssignments, LHSValNoAssignments);
+ if (Lanes &
+ TRI->getSubRegIndexLaneMask(compose(*TRI, SubIdx, MO->getSubReg())))
+ return true;
}
+ return false;
+}
- // Armed with the mappings of LHS/RHS values to ultimate values, walk the
- // interval lists to see if these intervals are coalescable.
- LiveInterval::const_iterator I = LHS.begin();
- LiveInterval::const_iterator IE = LHS.end();
- LiveInterval::const_iterator J = RHS.begin();
- LiveInterval::const_iterator JE = RHS.end();
-
- // Skip ahead until the first place of potential sharing.
- if (I != IE && J != JE) {
- if (I->start < J->start) {
- I = std::upper_bound(I, IE, J->start);
- if (I != LHS.begin()) --I;
- } else if (J->start < I->start) {
- J = std::upper_bound(J, JE, I->start);
- if (J != RHS.begin()) --J;
- }
- }
+bool JoinVals::resolveConflicts(JoinVals &Other) {
+ for (unsigned i = 0, e = LI.getNumValNums(); i != e; ++i) {
+ Val &V = Vals[i];
+ assert (V.Resolution != CR_Impossible && "Unresolvable conflict");
+ if (V.Resolution != CR_Unresolved)
+ continue;
+ DEBUG(dbgs() << "\t\tconflict at " << PrintReg(LI.reg) << ':' << i
+ << '@' << LI.getValNumInfo(i)->def << '\n');
+ ++NumLaneConflicts;
+ assert(V.OtherVNI && "Inconsistent conflict resolution.");
+ VNInfo *VNI = LI.getValNumInfo(i);
+ const Val &OtherV = Other.Vals[V.OtherVNI->id];
+
+ // VNI is known to clobber some lanes in OtherVNI. If we go ahead with the
+ // join, those lanes will be tainted with a wrong value. Get the extent of
+ // the tainted lanes.
+ unsigned TaintedLanes = V.WriteLanes & OtherV.ValidLanes;
+ SmallVector<std::pair<SlotIndex, unsigned>, 8> TaintExtent;
+ if (!taintExtent(i, TaintedLanes, Other, TaintExtent))
+ // Tainted lanes would extend beyond the basic block.
+ return false;
- while (I != IE && J != JE) {
- // Determine if these two live ranges overlap.
- bool Overlaps;
- if (I->start < J->start) {
- Overlaps = I->end > J->start;
- } else {
- Overlaps = J->end > I->start;
- }
+ assert(!TaintExtent.empty() && "There should be at least one conflict.");
- // If so, check value # info to determine if they are really different.
- if (Overlaps) {
- // If the live range overlap will map to the same value number in the
- // result liverange, we can still coalesce them. If not, we can't.
- if (LHSValNoAssignments[I->valno->id] !=
- RHSValNoAssignments[J->valno->id])
+ // Now look at the instructions from VNI->def to TaintExtent (inclusive).
+ MachineBasicBlock *MBB = Indexes->getMBBFromIndex(VNI->def);
+ MachineBasicBlock::iterator MI = MBB->begin();
+ if (!VNI->isPHIDef()) {
+ MI = Indexes->getInstructionFromIndex(VNI->def);
+ // No need to check the instruction defining VNI for reads.
+ ++MI;
+ }
+ assert(!SlotIndex::isSameInstr(VNI->def, TaintExtent.front().first) &&
+ "Interference ends on VNI->def. Should have been handled earlier");
+ MachineInstr *LastMI =
+ Indexes->getInstructionFromIndex(TaintExtent.front().first);
+ assert(LastMI && "Range must end at a proper instruction");
+ unsigned TaintNum = 0;
+ for(;;) {
+ assert(MI != MBB->end() && "Bad LastMI");
+ if (usesLanes(MI, Other.LI.reg, Other.SubIdx, TaintedLanes)) {
+ DEBUG(dbgs() << "\t\ttainted lanes used by: " << *MI);
return false;
+ }
+ // LastMI is the last instruction to use the current value.
+ if (&*MI == LastMI) {
+ if (++TaintNum == TaintExtent.size())
+ break;
+ LastMI = Indexes->getInstructionFromIndex(TaintExtent[TaintNum].first);
+ assert(LastMI && "Range must end at a proper instruction");
+ TaintedLanes = TaintExtent[TaintNum].second;
+ }
+ ++MI;
}
- if (I->end < J->end)
- ++I;
- else
- ++J;
+ // The tainted lanes are unused.
+ V.Resolution = CR_Replace;
+ ++NumLaneResolves;
}
+ return true;
+}
- // Update kill info. Some live ranges are extended due to copy coalescing.
- for (DenseMap<VNInfo*, VNInfo*>::iterator I = LHSValsDefinedFromRHS.begin(),
- E = LHSValsDefinedFromRHS.end(); I != E; ++I) {
- VNInfo *VNI = I->first;
- unsigned LHSValID = LHSValNoAssignments[VNI->id];
- if (VNI->hasPHIKill())
- NewVNInfo[LHSValID]->setHasPHIKill(true);
- }
+// Determine if ValNo is a copy of a value number in LI or Other.LI that will
+// be pruned:
+//
+// %dst = COPY %src
+// %src = COPY %dst <-- This value to be pruned.
+// %dst = COPY %src <-- This value is a copy of a pruned value.
+//
+bool JoinVals::isPrunedValue(unsigned ValNo, JoinVals &Other) {
+ Val &V = Vals[ValNo];
+ if (V.Pruned || V.PrunedComputed)
+ return V.Pruned;
+
+ if (V.Resolution != CR_Erase && V.Resolution != CR_Merge)
+ return V.Pruned;
+
+ // Follow copies up the dominator tree and check if any intermediate value
+ // has been pruned.
+ V.PrunedComputed = true;
+ V.Pruned = Other.isPrunedValue(V.OtherVNI->id, *this);
+ return V.Pruned;
+}
- // Update kill info. Some live ranges are extended due to copy coalescing.
- for (DenseMap<VNInfo*, VNInfo*>::iterator I = RHSValsDefinedFromLHS.begin(),
- E = RHSValsDefinedFromLHS.end(); I != E; ++I) {
- VNInfo *VNI = I->first;
- unsigned RHSValID = RHSValNoAssignments[VNI->id];
- if (VNI->hasPHIKill())
- NewVNInfo[RHSValID]->setHasPHIKill(true);
+void JoinVals::pruneValues(JoinVals &Other,
+ SmallVectorImpl<SlotIndex> &EndPoints) {
+ for (unsigned i = 0, e = LI.getNumValNums(); i != e; ++i) {
+ SlotIndex Def = LI.getValNumInfo(i)->def;
+ switch (Vals[i].Resolution) {
+ case CR_Keep:
+ break;
+ case CR_Replace:
+ // This value takes precedence over the value in Other.LI.
+ LIS->pruneValue(&Other.LI, Def, &EndPoints);
+ // Remove <def,read-undef> flags. This def is now a partial redef.
+ if (!Def.isBlock()) {
+ for (MIOperands MO(Indexes->getInstructionFromIndex(Def));
+ MO.isValid(); ++MO)
+ if (MO->isReg() && MO->isDef() && MO->getReg() == LI.reg)
+ MO->setIsUndef(false);
+ // This value will reach instructions below, but we need to make sure
+ // the live range also reaches the instruction at Def.
+ EndPoints.push_back(Def);
+ }
+ DEBUG(dbgs() << "\t\tpruned " << PrintReg(Other.LI.reg) << " at " << Def
+ << ": " << Other.LI << '\n');
+ break;
+ case CR_Erase:
+ case CR_Merge:
+ if (isPrunedValue(i, Other)) {
+ // This value is ultimately a copy of a pruned value in LI or Other.LI.
+ // We can no longer trust the value mapping computed by
+ // computeAssignment(), the value that was originally copied could have
+ // been replaced.
+ LIS->pruneValue(&LI, Def, &EndPoints);
+ DEBUG(dbgs() << "\t\tpruned all of " << PrintReg(LI.reg) << " at "
+ << Def << ": " << LI << '\n');
+ }
+ break;
+ case CR_Unresolved:
+ case CR_Impossible:
+ llvm_unreachable("Unresolved conflicts");
+ }
}
+}
- if (LHSValNoAssignments.empty())
- LHSValNoAssignments.push_back(-1);
- if (RHSValNoAssignments.empty())
- RHSValNoAssignments.push_back(-1);
-
- SmallVector<unsigned, 8> SourceRegisters;
- for (SmallVector<MachineInstr*, 8>::iterator I = DupCopies.begin(),
- E = DupCopies.end(); I != E; ++I) {
- MachineInstr *MI = *I;
-
- // We have pretended that the assignment to B in
- // A = X
- // B = X
- // was actually a copy from A. Now that we decided to coalesce A and B,
- // transform the code into
- // A = X
- unsigned Src = MI->getOperand(1).getReg();
- SourceRegisters.push_back(Src);
+void JoinVals::eraseInstrs(SmallPtrSet<MachineInstr*, 8> &ErasedInstrs,
+ SmallVectorImpl<unsigned> &ShrinkRegs) {
+ for (unsigned i = 0, e = LI.getNumValNums(); i != e; ++i) {
+ if (Vals[i].Resolution != CR_Erase)
+ continue;
+ SlotIndex Def = LI.getValNumInfo(i)->def;
+ MachineInstr *MI = Indexes->getInstructionFromIndex(Def);
+ assert(MI && "No instruction to erase");
+ if (MI->isCopy()) {
+ unsigned Reg = MI->getOperand(1).getReg();
+ if (TargetRegisterInfo::isVirtualRegister(Reg) &&
+ Reg != CP.getSrcReg() && Reg != CP.getDstReg())
+ ShrinkRegs.push_back(Reg);
+ }
ErasedInstrs.insert(MI);
+ DEBUG(dbgs() << "\t\terased:\t" << Def << '\t' << *MI);
LIS->RemoveMachineInstrFromMaps(MI);
MI->eraseFromParent();
}
+}
- // If B = X was the last use of X in a liverange, we have to shrink it now
- // that B = X is gone.
- for (SmallVector<unsigned, 8>::iterator I = SourceRegisters.begin(),
- E = SourceRegisters.end(); I != E; ++I) {
- LIS->shrinkToUses(&LIS->getInterval(*I));
- }
+bool RegisterCoalescer::joinVirtRegs(CoalescerPair &CP) {
+ SmallVector<VNInfo*, 16> NewVNInfo;
+ LiveInterval &RHS = LIS->getInterval(CP.getSrcReg());
+ LiveInterval &LHS = LIS->getInterval(CP.getDstReg());
+ JoinVals RHSVals(RHS, CP.getSrcIdx(), NewVNInfo, CP, LIS, TRI);
+ JoinVals LHSVals(LHS, CP.getDstIdx(), NewVNInfo, CP, LIS, TRI);
+
+ DEBUG(dbgs() << "\t\tRHS = " << PrintReg(CP.getSrcReg()) << ' ' << RHS
+ << "\n\t\tLHS = " << PrintReg(CP.getDstReg()) << ' ' << LHS
+ << '\n');
+
+ // First compute NewVNInfo and the simple value mappings.
+ // Detect impossible conflicts early.
+ if (!LHSVals.mapValues(RHSVals) || !RHSVals.mapValues(LHSVals))
+ return false;
+
+ // Some conflicts can only be resolved after all values have been mapped.
+ if (!LHSVals.resolveConflicts(RHSVals) || !RHSVals.resolveConflicts(LHSVals))
+ return false;
- // If we get here, we know that we can coalesce the live ranges. Ask the
- // intervals to coalesce themselves now.
- LHS.join(RHS, &LHSValNoAssignments[0], &RHSValNoAssignments[0], NewVNInfo,
+ // All clear, the live ranges can be merged.
+
+ // The merging algorithm in LiveInterval::join() can't handle conflicting
+ // value mappings, so we need to remove any live ranges that overlap a
+ // CR_Replace resolution. Collect a set of end points that can be used to
+ // restore the live range after joining.
+ SmallVector<SlotIndex, 8> EndPoints;
+ LHSVals.pruneValues(RHSVals, EndPoints);
+ RHSVals.pruneValues(LHSVals, EndPoints);
+
+ // Erase COPY and IMPLICIT_DEF instructions. This may cause some external
+ // registers to require trimming.
+ SmallVector<unsigned, 8> ShrinkRegs;
+ LHSVals.eraseInstrs(ErasedInstrs, ShrinkRegs);
+ RHSVals.eraseInstrs(ErasedInstrs, ShrinkRegs);
+ while (!ShrinkRegs.empty())
+ LIS->shrinkToUses(&LIS->getInterval(ShrinkRegs.pop_back_val()));
+
+ // Join RHS into LHS.
+ LHS.join(RHS, LHSVals.getAssignments(), RHSVals.getAssignments(), NewVNInfo,
MRI);
+
+ // Kill flags are going to be wrong if the live ranges were overlapping.
+ // Eventually, we should simply clear all kill flags when computing live
+ // ranges. They are reinserted after register allocation.
+ MRI->clearKillFlags(LHS.reg);
+ MRI->clearKillFlags(RHS.reg);
+
+ if (EndPoints.empty())
+ return true;
+
+ // Recompute the parts of the live range we had to remove because of
+ // CR_Replace conflicts.
+ DEBUG(dbgs() << "\t\trestoring liveness to " << EndPoints.size()
+ << " points: " << LHS << '\n');
+ LIS->extendToIndices(&LHS, EndPoints);
return true;
}
+/// joinIntervals - Attempt to join these two intervals. On failure, this
+/// returns false.
+bool RegisterCoalescer::joinIntervals(CoalescerPair &CP) {
+ return CP.isPhys() ? joinReservedPhysReg(CP) : joinVirtRegs(CP);
+}
+
namespace {
// DepthMBBCompare - Comparison predicate that sort first based on the loop
// depth of the basic block (the unsigned), and then on the MBB number.
Loops = &getAnalysis<MachineLoopInfo>();
DEBUG(dbgs() << "********** SIMPLE REGISTER COALESCING **********\n"
- << "********** Function: "
- << ((Value*)MF->getFunction())->getName() << '\n');
+ << "********** Function: " << MF->getName() << '\n');
if (VerifyCoalescing)
MF->verify(this, "Before register coalescing");
RegClassInfo.runOnMachineFunction(fn);
// Join (coalesce) intervals if requested.
- if (EnableJoining) {
+ if (EnableJoining)
joinAllIntervals();
- DEBUG({
- dbgs() << "********** INTERVALS POST JOINING **********\n";
- for (LiveIntervals::iterator I = LIS->begin(), E = LIS->end();
- I != E; ++I){
- I->second->print(dbgs(), TRI);
- dbgs() << "\n";
- }
- });
- }
-
- // Perform a final pass over the instructions and compute spill weights
- // and remove identity moves.
- SmallVector<unsigned, 4> DeadDefs;
- for (MachineFunction::iterator mbbi = MF->begin(), mbbe = MF->end();
- mbbi != mbbe; ++mbbi) {
- MachineBasicBlock* mbb = mbbi;
- for (MachineBasicBlock::iterator mii = mbb->begin(), mie = mbb->end();
- mii != mie; ) {
- MachineInstr *MI = mii;
-
- ++mii;
-
- // Check for now unnecessary kill flags.
- if (LIS->isNotInMIMap(MI)) continue;
- SlotIndex DefIdx = LIS->getInstructionIndex(MI).getRegSlot();
- for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) {
- MachineOperand &MO = MI->getOperand(i);
- if (!MO.isReg() || !MO.isKill()) continue;
- unsigned reg = MO.getReg();
- if (!reg || !LIS->hasInterval(reg)) continue;
- if (!LIS->getInterval(reg).killedAt(DefIdx)) {
- MO.setIsKill(false);
- continue;
- }
- // When leaving a kill flag on a physreg, check if any subregs should
- // remain alive.
- if (!TargetRegisterInfo::isPhysicalRegister(reg))
- continue;
- for (const uint16_t *SR = TRI->getSubRegisters(reg);
- unsigned S = *SR; ++SR)
- if (LIS->hasInterval(S) && LIS->getInterval(S).liveAt(DefIdx))
- MI->addRegisterDefined(S, TRI);
- }
- }
- }
// After deleting a lot of copies, register classes may be less constrained.
// Removing sub-register operands may allow GR32_ABCD -> GR32 and DPR_VFP2 ->
projects / oota-llvm.git / blobdiff