diff options
Diffstat (limited to 'contrib/llvm/lib/CodeGen/RegisterCoalescer.cpp')
| -rw-r--r-- | contrib/llvm/lib/CodeGen/RegisterCoalescer.cpp | 1077 |
1 files changed, 768 insertions, 309 deletions
diff --git a/contrib/llvm/lib/CodeGen/RegisterCoalescer.cpp b/contrib/llvm/lib/CodeGen/RegisterCoalescer.cpp index 9906334..2538f10 100644 --- a/contrib/llvm/lib/CodeGen/RegisterCoalescer.cpp +++ b/contrib/llvm/lib/CodeGen/RegisterCoalescer.cpp @@ -55,6 +55,8 @@ STATISTIC(numCommutes , "Number of instruction commuting performed"); 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", @@ -123,6 +125,9 @@ namespace { /// 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); @@ -193,12 +198,6 @@ INITIALIZE_PASS_END(RegisterCoalescer, "simple-register-coalescing", char RegisterCoalescer::ID = 0; -static unsigned compose(const TargetRegisterInfo &tri, unsigned a, unsigned b) { - if (!a) return b; - if (!b) return a; - return tri.composeSubRegIndices(a, b); -} - static bool isMoveInstr(const TargetRegisterInfo &tri, const MachineInstr *MI, unsigned &Src, unsigned &Dst, unsigned &SrcSub, unsigned &DstSub) { @@ -209,8 +208,8 @@ static bool isMoveInstr(const TargetRegisterInfo &tri, const MachineInstr *MI, SrcSub = MI->getOperand(1).getSubReg(); } else if (MI->isSubregToReg()) { Dst = MI->getOperand(0).getReg(); - DstSub = compose(tri, MI->getOperand(0).getSubReg(), - MI->getOperand(3).getImm()); + DstSub = tri.composeSubRegIndices(MI->getOperand(0).getSubReg(), + MI->getOperand(3).getImm()); Src = MI->getOperand(2).getReg(); SrcSub = MI->getOperand(2).getSubReg(); } else @@ -349,7 +348,8 @@ bool CoalescerPair::isCoalescable(const MachineInstr *MI) const { if (DstReg != Dst) return false; // Registers match, do the subregisters line up? - return compose(TRI, SrcIdx, SrcSub) == compose(TRI, DstIdx, DstSub); + return TRI.composeSubRegIndices(SrcIdx, SrcSub) == + TRI.composeSubRegIndices(DstIdx, DstSub); } } @@ -425,7 +425,8 @@ bool RegisterCoalescer::adjustCopiesBackFrom(const CoalescerPair &CP, // If AValNo is defined as a copy from IntB, we can potentially process this. // Get the instruction that defines this value number. MachineInstr *ACopyMI = LIS->getInstructionFromIndex(AValNo->def); - if (!CP.isCoalescable(ACopyMI)) + // Don't allow any partial copies, even if isCoalescable() allows them. + if (!CP.isCoalescable(ACopyMI) || !ACopyMI->isFullCopy()) return false; // Get the LiveRange in IntB that this value number starts with. @@ -583,7 +584,7 @@ bool RegisterCoalescer::removeCopyByCommutingDef(const CoalescerPair &CP, 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 @@ -849,8 +850,17 @@ void RegisterCoalescer::updateRegDefsUses(unsigned SrcReg, // Update LiveDebugVariables. LDV->renameRegister(SrcReg, DstReg, SubIdx); + SmallPtrSet<MachineInstr*, 8> Visited; for (MachineRegisterInfo::reg_iterator I = MRI->reg_begin(SrcReg); MachineInstr *UseMI = I.skipInstruction();) { + // Each instruction can only be rewritten once because sub-register + // composition is not always idempotent. When SrcReg != DstReg, rewriting + // the UseMI operands removes them from the SrcReg use-def chain, but when + // SrcReg is DstReg we could encounter UseMI twice if it has multiple + // operands mentioning the virtual register. + if (SrcReg == DstReg && !Visited.insert(UseMI)) + continue; + SmallVector<unsigned,8> Ops; bool Reads, Writes; tie(Reads, Writes) = UseMI->readsWritesVirtualRegister(SrcReg, &Ops); @@ -890,7 +900,7 @@ bool RegisterCoalescer::canJoinPhys(CoalescerPair &CP) { /// Always join simple intervals that are defined by a single copy from a /// reserved register. This doesn't increase register pressure, so it is /// always beneficial. - if (!RegClassInfo.isReserved(CP.getDstReg())) { + if (!MRI->isReserved(CP.getDstReg())) { DEBUG(dbgs() << "\tCan only merge into reserved registers.\n"); return false; } @@ -1065,7 +1075,7 @@ bool RegisterCoalescer::joinCopy(MachineInstr *CopyMI, bool &Again) { /// Attempt joining with a reserved physreg. bool RegisterCoalescer::joinReservedPhysReg(CoalescerPair &CP) { assert(CP.isPhys() && "Must be a physreg copy"); - assert(RegClassInfo.isReserved(CP.getDstReg()) && "Not a reserved register"); + assert(MRI->isReserved(CP.getDstReg()) && "Not a reserved register"); LiveInterval &RHS = LIS->getInterval(CP.getSrcReg()); DEBUG(dbgs() << "\t\tRHS = " << PrintReg(CP.getSrcReg()) << ' ' << RHS << '\n'); @@ -1102,347 +1112,797 @@ bool RegisterCoalescer::joinReservedPhysReg(CoalescerPair &CP) { 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; -} +//===----------------------------------------------------------------------===// +// 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. +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 + }; -// 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, - VNInfo *OtherVNI, - 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 || CP.isPartial() || CP.isPhys()) - return false; + // 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; - unsigned A = CP.getDstReg(); - if (!TargetRegisterInfo::isVirtualRegister(A)) - return false; + // Lanes written by this def, 0 for unanalyzed values. + unsigned WriteLanes; - unsigned B = CP.getSrcReg(); - if (!TargetRegisterInfo::isVirtualRegister(B)) - return false; + // Lanes with defined values in this register. Other lanes are undef and + // safe to clobber. + unsigned ValidLanes; - MachineInstr *OtherMI = li.getInstructionFromIndex(OtherVNI->def); - if (!OtherMI) - return false; + // Value in LI being redefined by this def. + VNInfo *RedefVNI; - if (MI->isImplicitDef()) { - DupCopies.push_back(MI); - return true; - } else { - if (!MI->isFullCopy()) - return false; - unsigned Src = MI->getOperand(1).getReg(); - if (!TargetRegisterInfo::isVirtualRegister(Src)) - return false; - if (!OtherMI->isFullCopy()) - return false; - unsigned OtherSrc = OtherMI->getOperand(1).getReg(); - if (!TargetRegisterInfo::isVirtualRegister(OtherSrc)) - return false; + // Value in the other live range that overlaps this def, if any. + VNInfo *OtherVNI; - if (Src != OtherSrc) - return false; + // Is this value an IMPLICIT_DEF? + bool IsImplicitDef; - // 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(OtherVNI->def) != - SrcInt.getVNInfoBefore(VNI->def)) - return false; + // 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; - DupCopies.push_back(MI); - return true; - } -} + // True once Pruned above has been computed. + bool PrunedComputed; -/// 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); + Val() : Resolution(CR_Keep), WriteLanes(0), ValidLanes(0), + RedefVNI(0), OtherVNI(0), IsImplicitDef(false), Pruned(false), + PrunedComputed(false) {} - LiveInterval &RHS = LIS->getInterval(CP.getSrcReg()); - DEBUG(dbgs() << "\t\tRHS = " << PrintReg(CP.getSrcReg()) << ' ' << RHS - << '\n'); + bool isAnalyzed() const { return WriteLanes != 0; } + }; - // 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; + // 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.data(); } +}; +} // 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( + TRI->composeSubRegIndices(SubIdx, MO->getSubReg())); + if (MO->readsReg()) + Redef = true; + } + return L; +} - SmallVector<MachineInstr*, 8> DupCopies; - SmallVector<MachineInstr*, 8> DeadCopies; +/// 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; +} - LiveInterval &LHS = LIS->getOrCreateInterval(CP.getDstReg()); - DEBUG(dbgs() << "\t\tLHS = " << PrintReg(CP.getDstReg(), TRI) << ' ' << LHS - << '\n'); +/// 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; + } - // 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() && !MI->isImplicitDef()) // Src not defined by a copy? - 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; + } - // Figure out the value # from the RHS. - VNInfo *OtherVNI = RHS.getVNInfoBefore(VNI->def); - // The copy could be to an aliased physreg. - if (!OtherVNI) - continue; + // An IMPLICIT_DEF writes undef values. + if (DefMI->isImplicitDef()) { + V.IsImplicitDef = true; + V.ValidLanes &= ~V.WriteLanes; + } + } - // 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)) - DeadCopies.push_back(MI); - else if (!RegistersDefinedFromSameValue(*LIS, *TRI, CP, VNI, OtherVNI, - DupCopies)) - continue; + // 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; + } - LHSValsDefinedFromRHS[VNI] = OtherVNI; + // 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; } - // 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() && !MI->isImplicitDef()) // Src not defined by a copy? - 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; + + // If the other live range is killed by DefMI and the live ranges are still + // overlapping, it must be because we're looking at an early clobber def: + // + // %dst<def,early-clobber> = ASM %src<kill> + // + // In this case, it is illegal to merge the two live ranges since the early + // clobber def would clobber %src before it was read. + if (OtherLRQ.isKill()) { + // This case where the def doesn't overlap the kill is handled above. + assert(VNI->def.isEarlyClobber() && + "Only early clobber defs can overlap a kill"); + return CR_Impossible; + } - // Figure out the value # from the LHS. - VNInfo *OtherVNI = LHS.getVNInfoBefore(VNI->def); - // The copy could be to an aliased physreg. - if (!OtherVNI) - continue; + // 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)) - DeadCopies.push_back(MI); - else if (!RegistersDefinedFromSameValue(*LIS, *TRI, CP, VNI, OtherVNI, - 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] = OtherVNI; +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()) +/// 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; - 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()) + if (!MO->readsReg()) 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 (Lanes & TRI->getSubRegIndexLaneMask( + TRI->composeSubRegIndices(SubIdx, MO->getSubReg()))) + return true; + } + return false; +} + +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; - ComputeUltimateVN(VNI, NewVNInfo, - RHSValsDefinedFromLHS, LHSValsDefinedFromRHS, - RHSValNoAssignments, LHSValNoAssignments); - } + assert(!TaintExtent.empty() && "There should be at least one conflict."); - // 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(); - - // Collect interval end points that will no longer be kills. - SmallVector<MachineInstr*, 8> LHSOldKills; - SmallVector<MachineInstr*, 8> RHSOldKills; - - // 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; + // 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; } - } - - while (I != IE && J != JE) { - // Determine if these two live ranges overlap. - // If so, check value # info to determine if they are really different. - if (I->end > J->start && J->end > I->start) { - // 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]) + 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; - - // Extended live ranges should no longer be killed. - if (!I->end.isBlock() && I->end < J->end) - if (MachineInstr *MI = LIS->getInstructionFromIndex(I->end)) - LHSOldKills.push_back(MI); - if (!J->end.isBlock() && J->end < I->end) - if (MachineInstr *MI = LIS->getInstructionFromIndex(J->end)) - RHSOldKills.push_back(MI); + } + // 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; - } - - // Clear kill flags where live ranges are extended. - while (!LHSOldKills.empty()) - LHSOldKills.pop_back_val()->clearRegisterKills(LHS.reg, TRI); - while (!RHSOldKills.empty()) - RHSOldKills.pop_back_val()->clearRegisterKills(RHS.reg, TRI); - - if (LHSValNoAssignments.empty()) - LHSValNoAssignments.push_back(-1); - if (RHSValNoAssignments.empty()) - RHSValNoAssignments.push_back(-1); - - // Now erase all the redundant copies. - for (unsigned i = 0, e = DeadCopies.size(); i != e; ++i) { - MachineInstr *MI = DeadCopies[i]; - if (!ErasedInstrs.insert(MI)) - continue; - DEBUG(dbgs() << "\t\terased:\t" << LIS->getInstructionIndex(MI) - << '\t' << *MI); - LIS->RemoveMachineInstrFromMaps(MI); - MI->eraseFromParent(); + // The tainted lanes are unused. + V.Resolution = CR_Replace; + ++NumLaneResolves; } + return true; +} - SmallVector<unsigned, 8> SourceRegisters; - for (SmallVector<MachineInstr*, 8>::iterator I = DupCopies.begin(), - E = DupCopies.end(); I != E; ++I) { - MachineInstr *MI = *I; - if (!ErasedInstrs.insert(MI)) - continue; +// 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; +} - // If MI is a copy, then 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 - // In the case of the implicit_def, we just have to remove it. - if (!MI->isImplicitDef()) { - unsigned Src = MI->getOperand(1).getReg(); - SourceRegisters.push_back(Src); +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); + // Check if we're replacing an IMPLICIT_DEF value. The IMPLICIT_DEF + // instructions are only inserted to provide a live-out value for PHI + // predecessors, so the instruction should simply go away once its value + // has been replaced. + Val &OtherV = Other.Vals[Vals[i].OtherVNI->id]; + bool EraseImpDef = OtherV.IsImplicitDef && OtherV.Resolution == CR_Keep; + if (!Def.isBlock()) { + // Remove <def,read-undef> flags. This def is now a partial redef. + // Also remove <def,dead> flags since the joined live range will + // continue past this instruction. + for (MIOperands MO(Indexes->getInstructionFromIndex(Def)); + MO.isValid(); ++MO) + if (MO->isReg() && MO->isDef() && MO->getReg() == LI.reg) { + MO->setIsUndef(EraseImpDef); + MO->setIsDead(false); + } + // This value will reach instructions below, but we need to make sure + // the live range also reaches the instruction at Def. + if (!EraseImpDef) + 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"); } - 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)); +void JoinVals::eraseInstrs(SmallPtrSet<MachineInstr*, 8> &ErasedInstrs, + SmallVectorImpl<unsigned> &ShrinkRegs) { + for (unsigned i = 0, e = LI.getNumValNums(); i != e; ++i) { + // Get the def location before markUnused() below invalidates it. + SlotIndex Def = LI.getValNumInfo(i)->def; + switch (Vals[i].Resolution) { + case CR_Keep: + // If an IMPLICIT_DEF value is pruned, it doesn't serve a purpose any + // longer. The IMPLICIT_DEF instructions are only inserted by + // PHIElimination to guarantee that all PHI predecessors have a value. + if (!Vals[i].IsImplicitDef || !Vals[i].Pruned) + break; + // Remove value number i from LI. Note that this VNInfo is still present + // in NewVNInfo, so it will appear as an unused value number in the final + // joined interval. + LI.getValNumInfo(i)->markUnused(); + LI.removeValNo(LI.getValNumInfo(i)); + DEBUG(dbgs() << "\t\tremoved " << i << '@' << Def << ": " << LI << '\n'); + // FALL THROUGH. + + case CR_Erase: { + 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(); + break; + } + default: + break; + } } +} + +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. @@ -1564,8 +2024,7 @@ bool RegisterCoalescer::runOnMachineFunction(MachineFunction &fn) { 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"); |
