diff options
Diffstat (limited to 'contrib/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp')
| -rw-r--r-- | contrib/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp | 806 |
1 files changed, 805 insertions, 1 deletions
diff --git a/contrib/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp b/contrib/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp index 69c54ed..1fb17eb 100644 --- a/contrib/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp +++ b/contrib/llvm/lib/Target/PowerPC/PPCInstrInfo.cpp @@ -18,8 +18,10 @@ #include "PPCInstrBuilder.h" #include "PPCMachineFunctionInfo.h" #include "PPCTargetMachine.h" +#include "llvm/ADT/Statistic.h" #include "llvm/ADT/STLExtras.h" #include "llvm/CodeGen/MachineFrameInfo.h" +#include "llvm/CodeGen/MachineFunctionPass.h" #include "llvm/CodeGen/MachineInstrBuilder.h" #include "llvm/CodeGen/MachineMemOperand.h" #include "llvm/CodeGen/MachineRegisterInfo.h" @@ -30,6 +32,7 @@ #include "llvm/Support/TargetRegistry.h" #include "llvm/Support/raw_ostream.h" +#define GET_INSTRMAP_INFO #define GET_INSTRINFO_CTOR #include "PPCGenInstrInfo.inc" @@ -39,6 +42,9 @@ static cl:: opt<bool> DisableCTRLoopAnal("disable-ppc-ctrloop-analysis", cl::Hidden, cl::desc("Disable analysis for CTR loops")); +static cl::opt<bool> DisableCmpOpt("disable-ppc-cmp-opt", +cl::desc("Disable compare instruction optimization"), cl::Hidden); + PPCInstrInfo::PPCInstrInfo(PPCTargetMachine &tm) : PPCGenInstrInfo(PPC::ADJCALLSTACKDOWN, PPC::ADJCALLSTACKUP), TM(tm), RI(*TM.getSubtargetImpl(), *this) {} @@ -147,7 +153,8 @@ PPCInstrInfo::commuteInstruction(MachineInstr *MI, bool NewMI) const { MachineFunction &MF = *MI->getParent()->getParent(); // Normal instructions can be commuted the obvious way. - if (MI->getOpcode() != PPC::RLWIMI) + if (MI->getOpcode() != PPC::RLWIMI && + MI->getOpcode() != PPC::RLWIMIo) return TargetInstrInfo::commuteInstruction(MI, NewMI); // Cannot commute if it has a non-zero rotate count. @@ -417,6 +424,105 @@ PPCInstrInfo::InsertBranch(MachineBasicBlock &MBB, MachineBasicBlock *TBB, return 2; } +// Select analysis. +bool PPCInstrInfo::canInsertSelect(const MachineBasicBlock &MBB, + const SmallVectorImpl<MachineOperand> &Cond, + unsigned TrueReg, unsigned FalseReg, + int &CondCycles, int &TrueCycles, int &FalseCycles) const { + if (!TM.getSubtargetImpl()->hasISEL()) + return false; + + if (Cond.size() != 2) + return false; + + // If this is really a bdnz-like condition, then it cannot be turned into a + // select. + if (Cond[1].getReg() == PPC::CTR || Cond[1].getReg() == PPC::CTR8) + return false; + + // Check register classes. + const MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo(); + const TargetRegisterClass *RC = + RI.getCommonSubClass(MRI.getRegClass(TrueReg), MRI.getRegClass(FalseReg)); + if (!RC) + return false; + + // isel is for regular integer GPRs only. + if (!PPC::GPRCRegClass.hasSubClassEq(RC) && + !PPC::G8RCRegClass.hasSubClassEq(RC)) + return false; + + // FIXME: These numbers are for the A2, how well they work for other cores is + // an open question. On the A2, the isel instruction has a 2-cycle latency + // but single-cycle throughput. These numbers are used in combination with + // the MispredictPenalty setting from the active SchedMachineModel. + CondCycles = 1; + TrueCycles = 1; + FalseCycles = 1; + + return true; +} + +void PPCInstrInfo::insertSelect(MachineBasicBlock &MBB, + MachineBasicBlock::iterator MI, DebugLoc dl, + unsigned DestReg, + const SmallVectorImpl<MachineOperand> &Cond, + unsigned TrueReg, unsigned FalseReg) const { + assert(Cond.size() == 2 && + "PPC branch conditions have two components!"); + + assert(TM.getSubtargetImpl()->hasISEL() && + "Cannot insert select on target without ISEL support"); + + // Get the register classes. + MachineRegisterInfo &MRI = MBB.getParent()->getRegInfo(); + const TargetRegisterClass *RC = + RI.getCommonSubClass(MRI.getRegClass(TrueReg), MRI.getRegClass(FalseReg)); + assert(RC && "TrueReg and FalseReg must have overlapping register classes"); + assert((PPC::GPRCRegClass.hasSubClassEq(RC) || + PPC::G8RCRegClass.hasSubClassEq(RC)) && + "isel is for regular integer GPRs only"); + + unsigned OpCode = + PPC::GPRCRegClass.hasSubClassEq(RC) ? PPC::ISEL : PPC::ISEL8; + unsigned SelectPred = Cond[0].getImm(); + + unsigned SubIdx; + bool SwapOps; + switch (SelectPred) { + default: llvm_unreachable("invalid predicate for isel"); + case PPC::PRED_EQ: SubIdx = PPC::sub_eq; SwapOps = false; break; + case PPC::PRED_NE: SubIdx = PPC::sub_eq; SwapOps = true; break; + case PPC::PRED_LT: SubIdx = PPC::sub_lt; SwapOps = false; break; + case PPC::PRED_GE: SubIdx = PPC::sub_lt; SwapOps = true; break; + case PPC::PRED_GT: SubIdx = PPC::sub_gt; SwapOps = false; break; + case PPC::PRED_LE: SubIdx = PPC::sub_gt; SwapOps = true; break; + case PPC::PRED_UN: SubIdx = PPC::sub_un; SwapOps = false; break; + case PPC::PRED_NU: SubIdx = PPC::sub_un; SwapOps = true; break; + } + + unsigned FirstReg = SwapOps ? FalseReg : TrueReg, + SecondReg = SwapOps ? TrueReg : FalseReg; + + // The first input register of isel cannot be r0. If it is a member + // of a register class that can be r0, then copy it first (the + // register allocator should eliminate the copy). + if (MRI.getRegClass(FirstReg)->contains(PPC::R0) || + MRI.getRegClass(FirstReg)->contains(PPC::X0)) { + const TargetRegisterClass *FirstRC = + MRI.getRegClass(FirstReg)->contains(PPC::X0) ? + &PPC::G8RC_NOX0RegClass : &PPC::GPRC_NOR0RegClass; + unsigned OldFirstReg = FirstReg; + FirstReg = MRI.createVirtualRegister(FirstRC); + BuildMI(MBB, MI, dl, get(TargetOpcode::COPY), FirstReg) + .addReg(OldFirstReg); + } + + BuildMI(MBB, MI, dl, get(OpCode), DestReg) + .addReg(FirstReg).addReg(SecondReg) + .addReg(Cond[1].getReg(), 0, SubIdx); +} + void PPCInstrInfo::copyPhysReg(MachineBasicBlock &MBB, MachineBasicBlock::iterator I, DebugLoc DL, unsigned DestReg, unsigned SrcReg, @@ -707,6 +813,555 @@ ReverseBranchCondition(SmallVectorImpl<MachineOperand> &Cond) const { return false; } +bool PPCInstrInfo::FoldImmediate(MachineInstr *UseMI, MachineInstr *DefMI, + unsigned Reg, MachineRegisterInfo *MRI) const { + // For some instructions, it is legal to fold ZERO into the RA register field. + // A zero immediate should always be loaded with a single li. + unsigned DefOpc = DefMI->getOpcode(); + if (DefOpc != PPC::LI && DefOpc != PPC::LI8) + return false; + if (!DefMI->getOperand(1).isImm()) + return false; + if (DefMI->getOperand(1).getImm() != 0) + return false; + + // Note that we cannot here invert the arguments of an isel in order to fold + // a ZERO into what is presented as the second argument. All we have here + // is the condition bit, and that might come from a CR-logical bit operation. + + const MCInstrDesc &UseMCID = UseMI->getDesc(); + + // Only fold into real machine instructions. + if (UseMCID.isPseudo()) + return false; + + unsigned UseIdx; + for (UseIdx = 0; UseIdx < UseMI->getNumOperands(); ++UseIdx) + if (UseMI->getOperand(UseIdx).isReg() && + UseMI->getOperand(UseIdx).getReg() == Reg) + break; + + assert(UseIdx < UseMI->getNumOperands() && "Cannot find Reg in UseMI"); + assert(UseIdx < UseMCID.getNumOperands() && "No operand description for Reg"); + + const MCOperandInfo *UseInfo = &UseMCID.OpInfo[UseIdx]; + + // We can fold the zero if this register requires a GPRC_NOR0/G8RC_NOX0 + // register (which might also be specified as a pointer class kind). + if (UseInfo->isLookupPtrRegClass()) { + if (UseInfo->RegClass /* Kind */ != 1) + return false; + } else { + if (UseInfo->RegClass != PPC::GPRC_NOR0RegClassID && + UseInfo->RegClass != PPC::G8RC_NOX0RegClassID) + return false; + } + + // Make sure this is not tied to an output register (or otherwise + // constrained). This is true for ST?UX registers, for example, which + // are tied to their output registers. + if (UseInfo->Constraints != 0) + return false; + + unsigned ZeroReg; + if (UseInfo->isLookupPtrRegClass()) { + bool isPPC64 = TM.getSubtargetImpl()->isPPC64(); + ZeroReg = isPPC64 ? PPC::ZERO8 : PPC::ZERO; + } else { + ZeroReg = UseInfo->RegClass == PPC::G8RC_NOX0RegClassID ? + PPC::ZERO8 : PPC::ZERO; + } + + bool DeleteDef = MRI->hasOneNonDBGUse(Reg); + UseMI->getOperand(UseIdx).setReg(ZeroReg); + + if (DeleteDef) + DefMI->eraseFromParent(); + + return true; +} + +static bool MBBDefinesCTR(MachineBasicBlock &MBB) { + for (MachineBasicBlock::iterator I = MBB.begin(), IE = MBB.end(); + I != IE; ++I) + if (I->definesRegister(PPC::CTR) || I->definesRegister(PPC::CTR8)) + return true; + return false; +} + +// We should make sure that, if we're going to predicate both sides of a +// condition (a diamond), that both sides don't define the counter register. We +// can predicate counter-decrement-based branches, but while that predicates +// the branching, it does not predicate the counter decrement. If we tried to +// merge the triangle into one predicated block, we'd decrement the counter +// twice. +bool PPCInstrInfo::isProfitableToIfCvt(MachineBasicBlock &TMBB, + unsigned NumT, unsigned ExtraT, + MachineBasicBlock &FMBB, + unsigned NumF, unsigned ExtraF, + const BranchProbability &Probability) const { + return !(MBBDefinesCTR(TMBB) && MBBDefinesCTR(FMBB)); +} + + +bool PPCInstrInfo::isPredicated(const MachineInstr *MI) const { + // The predicated branches are identified by their type, not really by the + // explicit presence of a predicate. Furthermore, some of them can be + // predicated more than once. Because if conversion won't try to predicate + // any instruction which already claims to be predicated (by returning true + // here), always return false. In doing so, we let isPredicable() be the + // final word on whether not the instruction can be (further) predicated. + + return false; +} + +bool PPCInstrInfo::isUnpredicatedTerminator(const MachineInstr *MI) const { + if (!MI->isTerminator()) + return false; + + // Conditional branch is a special case. + if (MI->isBranch() && !MI->isBarrier()) + return true; + + return !isPredicated(MI); +} + +bool PPCInstrInfo::PredicateInstruction( + MachineInstr *MI, + const SmallVectorImpl<MachineOperand> &Pred) const { + unsigned OpC = MI->getOpcode(); + if (OpC == PPC::BLR) { + if (Pred[1].getReg() == PPC::CTR8 || Pred[1].getReg() == PPC::CTR) { + bool isPPC64 = TM.getSubtargetImpl()->isPPC64(); + MI->setDesc(get(Pred[0].getImm() ? + (isPPC64 ? PPC::BDNZLR8 : PPC::BDNZLR) : + (isPPC64 ? PPC::BDZLR8 : PPC::BDZLR))); + } else { + MI->setDesc(get(PPC::BCLR)); + MachineInstrBuilder(*MI->getParent()->getParent(), MI) + .addImm(Pred[0].getImm()) + .addReg(Pred[1].getReg()); + } + + return true; + } else if (OpC == PPC::B) { + if (Pred[1].getReg() == PPC::CTR8 || Pred[1].getReg() == PPC::CTR) { + bool isPPC64 = TM.getSubtargetImpl()->isPPC64(); + MI->setDesc(get(Pred[0].getImm() ? + (isPPC64 ? PPC::BDNZ8 : PPC::BDNZ) : + (isPPC64 ? PPC::BDZ8 : PPC::BDZ))); + } else { + MachineBasicBlock *MBB = MI->getOperand(0).getMBB(); + MI->RemoveOperand(0); + + MI->setDesc(get(PPC::BCC)); + MachineInstrBuilder(*MI->getParent()->getParent(), MI) + .addImm(Pred[0].getImm()) + .addReg(Pred[1].getReg()) + .addMBB(MBB); + } + + return true; + } else if (OpC == PPC::BCTR || OpC == PPC::BCTR8 || + OpC == PPC::BCTRL || OpC == PPC::BCTRL8) { + if (Pred[1].getReg() == PPC::CTR8 || Pred[1].getReg() == PPC::CTR) + llvm_unreachable("Cannot predicate bctr[l] on the ctr register"); + + bool setLR = OpC == PPC::BCTRL || OpC == PPC::BCTRL8; + bool isPPC64 = TM.getSubtargetImpl()->isPPC64(); + MI->setDesc(get(isPPC64 ? (setLR ? PPC::BCCTRL8 : PPC::BCCTR8) : + (setLR ? PPC::BCCTRL : PPC::BCCTR))); + MachineInstrBuilder(*MI->getParent()->getParent(), MI) + .addImm(Pred[0].getImm()) + .addReg(Pred[1].getReg()); + return true; + } + + return false; +} + +bool PPCInstrInfo::SubsumesPredicate( + const SmallVectorImpl<MachineOperand> &Pred1, + const SmallVectorImpl<MachineOperand> &Pred2) const { + assert(Pred1.size() == 2 && "Invalid PPC first predicate"); + assert(Pred2.size() == 2 && "Invalid PPC second predicate"); + + if (Pred1[1].getReg() == PPC::CTR8 || Pred1[1].getReg() == PPC::CTR) + return false; + if (Pred2[1].getReg() == PPC::CTR8 || Pred2[1].getReg() == PPC::CTR) + return false; + + PPC::Predicate P1 = (PPC::Predicate) Pred1[0].getImm(); + PPC::Predicate P2 = (PPC::Predicate) Pred2[0].getImm(); + + if (P1 == P2) + return true; + + // Does P1 subsume P2, e.g. GE subsumes GT. + if (P1 == PPC::PRED_LE && + (P2 == PPC::PRED_LT || P2 == PPC::PRED_EQ)) + return true; + if (P1 == PPC::PRED_GE && + (P2 == PPC::PRED_GT || P2 == PPC::PRED_EQ)) + return true; + + return false; +} + +bool PPCInstrInfo::DefinesPredicate(MachineInstr *MI, + std::vector<MachineOperand> &Pred) const { + // Note: At the present time, the contents of Pred from this function is + // unused by IfConversion. This implementation follows ARM by pushing the + // CR-defining operand. Because the 'DZ' and 'DNZ' count as types of + // predicate, instructions defining CTR or CTR8 are also included as + // predicate-defining instructions. + + const TargetRegisterClass *RCs[] = + { &PPC::CRRCRegClass, &PPC::CRBITRCRegClass, + &PPC::CTRRCRegClass, &PPC::CTRRC8RegClass }; + + bool Found = false; + for (unsigned i = 0, e = MI->getNumOperands(); i != e; ++i) { + const MachineOperand &MO = MI->getOperand(i); + for (unsigned c = 0; c < array_lengthof(RCs) && !Found; ++c) { + const TargetRegisterClass *RC = RCs[c]; + if (MO.isReg()) { + if (MO.isDef() && RC->contains(MO.getReg())) { + Pred.push_back(MO); + Found = true; + } + } else if (MO.isRegMask()) { + for (TargetRegisterClass::iterator I = RC->begin(), + IE = RC->end(); I != IE; ++I) + if (MO.clobbersPhysReg(*I)) { + Pred.push_back(MO); + Found = true; + } + } + } + } + + return Found; +} + +bool PPCInstrInfo::isPredicable(MachineInstr *MI) const { + unsigned OpC = MI->getOpcode(); + switch (OpC) { + default: + return false; + case PPC::B: + case PPC::BLR: + case PPC::BCTR: + case PPC::BCTR8: + case PPC::BCTRL: + case PPC::BCTRL8: + return true; + } +} + +bool PPCInstrInfo::analyzeCompare(const MachineInstr *MI, + unsigned &SrcReg, unsigned &SrcReg2, + int &Mask, int &Value) const { + unsigned Opc = MI->getOpcode(); + + switch (Opc) { + default: return false; + case PPC::CMPWI: + case PPC::CMPLWI: + case PPC::CMPDI: + case PPC::CMPLDI: + SrcReg = MI->getOperand(1).getReg(); + SrcReg2 = 0; + Value = MI->getOperand(2).getImm(); + Mask = 0xFFFF; + return true; + case PPC::CMPW: + case PPC::CMPLW: + case PPC::CMPD: + case PPC::CMPLD: + case PPC::FCMPUS: + case PPC::FCMPUD: + SrcReg = MI->getOperand(1).getReg(); + SrcReg2 = MI->getOperand(2).getReg(); + return true; + } +} + +bool PPCInstrInfo::optimizeCompareInstr(MachineInstr *CmpInstr, + unsigned SrcReg, unsigned SrcReg2, + int Mask, int Value, + const MachineRegisterInfo *MRI) const { + if (DisableCmpOpt) + return false; + + int OpC = CmpInstr->getOpcode(); + unsigned CRReg = CmpInstr->getOperand(0).getReg(); + + // FP record forms set CR1 based on the execption status bits, not a + // comparison with zero. + if (OpC == PPC::FCMPUS || OpC == PPC::FCMPUD) + return false; + + // The record forms set the condition register based on a signed comparison + // with zero (so says the ISA manual). This is not as straightforward as it + // seems, however, because this is always a 64-bit comparison on PPC64, even + // for instructions that are 32-bit in nature (like slw for example). + // So, on PPC32, for unsigned comparisons, we can use the record forms only + // for equality checks (as those don't depend on the sign). On PPC64, + // we are restricted to equality for unsigned 64-bit comparisons and for + // signed 32-bit comparisons the applicability is more restricted. + bool isPPC64 = TM.getSubtargetImpl()->isPPC64(); + bool is32BitSignedCompare = OpC == PPC::CMPWI || OpC == PPC::CMPW; + bool is32BitUnsignedCompare = OpC == PPC::CMPLWI || OpC == PPC::CMPLW; + bool is64BitUnsignedCompare = OpC == PPC::CMPLDI || OpC == PPC::CMPLD; + + // Get the unique definition of SrcReg. + MachineInstr *MI = MRI->getUniqueVRegDef(SrcReg); + if (!MI) return false; + int MIOpC = MI->getOpcode(); + + bool equalityOnly = false; + bool noSub = false; + if (isPPC64) { + if (is32BitSignedCompare) { + // We can perform this optimization only if MI is sign-extending. + if (MIOpC == PPC::SRAW || MIOpC == PPC::SRAWo || + MIOpC == PPC::SRAWI || MIOpC == PPC::SRAWIo || + MIOpC == PPC::EXTSB || MIOpC == PPC::EXTSBo || + MIOpC == PPC::EXTSH || MIOpC == PPC::EXTSHo || + MIOpC == PPC::EXTSW || MIOpC == PPC::EXTSWo) { + noSub = true; + } else + return false; + } else if (is32BitUnsignedCompare) { + // We can perform this optimization, equality only, if MI is + // zero-extending. + if (MIOpC == PPC::CNTLZW || MIOpC == PPC::CNTLZWo || + MIOpC == PPC::SLW || MIOpC == PPC::SLWo || + MIOpC == PPC::SRW || MIOpC == PPC::SRWo) { + noSub = true; + equalityOnly = true; + } else + return false; + } else + equalityOnly = is64BitUnsignedCompare; + } else + equalityOnly = is32BitUnsignedCompare; + + if (equalityOnly) { + // We need to check the uses of the condition register in order to reject + // non-equality comparisons. + for (MachineRegisterInfo::use_iterator I = MRI->use_begin(CRReg), + IE = MRI->use_end(); I != IE; ++I) { + MachineInstr *UseMI = &*I; + if (UseMI->getOpcode() == PPC::BCC) { + unsigned Pred = UseMI->getOperand(0).getImm(); + if (Pred == PPC::PRED_EQ || Pred == PPC::PRED_NE) + continue; + + return false; + } else if (UseMI->getOpcode() == PPC::ISEL || + UseMI->getOpcode() == PPC::ISEL8) { + unsigned SubIdx = UseMI->getOperand(3).getSubReg(); + if (SubIdx == PPC::sub_eq) + continue; + + return false; + } else + return false; + } + } + + // Get ready to iterate backward from CmpInstr. + MachineBasicBlock::iterator I = CmpInstr, E = MI, + B = CmpInstr->getParent()->begin(); + + // Scan forward to find the first use of the compare. + for (MachineBasicBlock::iterator EL = CmpInstr->getParent()->end(); + I != EL; ++I) { + bool FoundUse = false; + for (MachineRegisterInfo::use_iterator J = MRI->use_begin(CRReg), + JE = MRI->use_end(); J != JE; ++J) + if (&*J == &*I) { + FoundUse = true; + break; + } + + if (FoundUse) + break; + } + + // Early exit if we're at the beginning of the BB. + if (I == B) return false; + + // There are two possible candidates which can be changed to set CR[01]. + // One is MI, the other is a SUB instruction. + // For CMPrr(r1,r2), we are looking for SUB(r1,r2) or SUB(r2,r1). + MachineInstr *Sub = NULL; + if (SrcReg2 != 0) + // MI is not a candidate for CMPrr. + MI = NULL; + // FIXME: Conservatively refuse to convert an instruction which isn't in the + // same BB as the comparison. This is to allow the check below to avoid calls + // (and other explicit clobbers); instead we should really check for these + // more explicitly (in at least a few predecessors). + else if (MI->getParent() != CmpInstr->getParent() || Value != 0) { + // PPC does not have a record-form SUBri. + return false; + } + + // Search for Sub. + const TargetRegisterInfo *TRI = &getRegisterInfo(); + --I; + for (; I != E && !noSub; --I) { + const MachineInstr &Instr = *I; + unsigned IOpC = Instr.getOpcode(); + + if (&*I != CmpInstr && ( + Instr.modifiesRegister(PPC::CR0, TRI) || + Instr.readsRegister(PPC::CR0, TRI))) + // This instruction modifies or uses the record condition register after + // the one we want to change. While we could do this transformation, it + // would likely not be profitable. This transformation removes one + // instruction, and so even forcing RA to generate one move probably + // makes it unprofitable. + return false; + + // Check whether CmpInstr can be made redundant by the current instruction. + if ((OpC == PPC::CMPW || OpC == PPC::CMPLW || + OpC == PPC::CMPD || OpC == PPC::CMPLD) && + (IOpC == PPC::SUBF || IOpC == PPC::SUBF8) && + ((Instr.getOperand(1).getReg() == SrcReg && + Instr.getOperand(2).getReg() == SrcReg2) || + (Instr.getOperand(1).getReg() == SrcReg2 && + Instr.getOperand(2).getReg() == SrcReg))) { + Sub = &*I; + break; + } + + if (I == B) + // The 'and' is below the comparison instruction. + return false; + } + + // Return false if no candidates exist. + if (!MI && !Sub) + return false; + + // The single candidate is called MI. + if (!MI) MI = Sub; + + int NewOpC = -1; + MIOpC = MI->getOpcode(); + if (MIOpC == PPC::ANDIo || MIOpC == PPC::ANDIo8) + NewOpC = MIOpC; + else { + NewOpC = PPC::getRecordFormOpcode(MIOpC); + if (NewOpC == -1 && PPC::getNonRecordFormOpcode(MIOpC) != -1) + NewOpC = MIOpC; + } + + // FIXME: On the non-embedded POWER architectures, only some of the record + // forms are fast, and we should use only the fast ones. + + // The defining instruction has a record form (or is already a record + // form). It is possible, however, that we'll need to reverse the condition + // code of the users. + if (NewOpC == -1) + return false; + + SmallVector<std::pair<MachineOperand*, PPC::Predicate>, 4> PredsToUpdate; + SmallVector<std::pair<MachineOperand*, unsigned>, 4> SubRegsToUpdate; + + // If we have SUB(r1, r2) and CMP(r2, r1), the condition code based on CMP + // needs to be updated to be based on SUB. Push the condition code + // operands to OperandsToUpdate. If it is safe to remove CmpInstr, the + // condition code of these operands will be modified. + bool ShouldSwap = false; + if (Sub) { + ShouldSwap = SrcReg2 != 0 && Sub->getOperand(1).getReg() == SrcReg2 && + Sub->getOperand(2).getReg() == SrcReg; + + // The operands to subf are the opposite of sub, so only in the fixed-point + // case, invert the order. + ShouldSwap = !ShouldSwap; + } + + if (ShouldSwap) + for (MachineRegisterInfo::use_iterator I = MRI->use_begin(CRReg), + IE = MRI->use_end(); I != IE; ++I) { + MachineInstr *UseMI = &*I; + if (UseMI->getOpcode() == PPC::BCC) { + PPC::Predicate Pred = (PPC::Predicate) UseMI->getOperand(0).getImm(); + assert((!equalityOnly || + Pred == PPC::PRED_EQ || Pred == PPC::PRED_NE) && + "Invalid predicate for equality-only optimization"); + PredsToUpdate.push_back(std::make_pair(&((*I).getOperand(0)), + PPC::getSwappedPredicate(Pred))); + } else if (UseMI->getOpcode() == PPC::ISEL || + UseMI->getOpcode() == PPC::ISEL8) { + unsigned NewSubReg = UseMI->getOperand(3).getSubReg(); + assert((!equalityOnly || NewSubReg == PPC::sub_eq) && + "Invalid CR bit for equality-only optimization"); + + if (NewSubReg == PPC::sub_lt) + NewSubReg = PPC::sub_gt; + else if (NewSubReg == PPC::sub_gt) + NewSubReg = PPC::sub_lt; + + SubRegsToUpdate.push_back(std::make_pair(&((*I).getOperand(3)), + NewSubReg)); + } else // We need to abort on a user we don't understand. + return false; + } + + // Create a new virtual register to hold the value of the CR set by the + // record-form instruction. If the instruction was not previously in + // record form, then set the kill flag on the CR. + CmpInstr->eraseFromParent(); + + MachineBasicBlock::iterator MII = MI; + BuildMI(*MI->getParent(), llvm::next(MII), MI->getDebugLoc(), + get(TargetOpcode::COPY), CRReg) + .addReg(PPC::CR0, MIOpC != NewOpC ? RegState::Kill : 0); + + if (MIOpC != NewOpC) { + // We need to be careful here: we're replacing one instruction with + // another, and we need to make sure that we get all of the right + // implicit uses and defs. On the other hand, the caller may be holding + // an iterator to this instruction, and so we can't delete it (this is + // specifically the case if this is the instruction directly after the + // compare). + + const MCInstrDesc &NewDesc = get(NewOpC); + MI->setDesc(NewDesc); + + if (NewDesc.ImplicitDefs) + for (const uint16_t *ImpDefs = NewDesc.getImplicitDefs(); + *ImpDefs; ++ImpDefs) + if (!MI->definesRegister(*ImpDefs)) + MI->addOperand(*MI->getParent()->getParent(), + MachineOperand::CreateReg(*ImpDefs, true, true)); + if (NewDesc.ImplicitUses) + for (const uint16_t *ImpUses = NewDesc.getImplicitUses(); + *ImpUses; ++ImpUses) + if (!MI->readsRegister(*ImpUses)) + MI->addOperand(*MI->getParent()->getParent(), + MachineOperand::CreateReg(*ImpUses, false, true)); + } + + // Modify the condition code of operands in OperandsToUpdate. + // Since we have SUB(r1, r2) and CMP(r2, r1), the condition code needs to + // be changed from r2 > r1 to r1 < r2, from r2 < r1 to r1 > r2, etc. + for (unsigned i = 0, e = PredsToUpdate.size(); i < e; i++) + PredsToUpdate[i].first->setImm(PredsToUpdate[i].second); + + for (unsigned i = 0, e = SubRegsToUpdate.size(); i < e; i++) + SubRegsToUpdate[i].first->setSubReg(SubRegsToUpdate[i].second); + + return true; +} + /// GetInstSize - Return the number of bytes of code the specified /// instruction may be. This returns the maximum number of bytes. /// @@ -729,3 +1384,152 @@ unsigned PPCInstrInfo::GetInstSizeInBytes(const MachineInstr *MI) const { return 4; // PowerPC instructions are all 4 bytes } } + +#undef DEBUG_TYPE +#define DEBUG_TYPE "ppc-early-ret" +STATISTIC(NumBCLR, "Number of early conditional returns"); +STATISTIC(NumBLR, "Number of early returns"); + +namespace llvm { + void initializePPCEarlyReturnPass(PassRegistry&); +} + +namespace { + // PPCEarlyReturn pass - For simple functions without epilogue code, move + // returns up, and create conditional returns, to avoid unnecessary + // branch-to-blr sequences. + struct PPCEarlyReturn : public MachineFunctionPass { + static char ID; + PPCEarlyReturn() : MachineFunctionPass(ID) { + initializePPCEarlyReturnPass(*PassRegistry::getPassRegistry()); + } + + const PPCTargetMachine *TM; + const PPCInstrInfo *TII; + +protected: + bool processBlock(MachineBasicBlock &ReturnMBB) { + bool Changed = false; + + MachineBasicBlock::iterator I = ReturnMBB.begin(); + I = ReturnMBB.SkipPHIsAndLabels(I); + + // The block must be essentially empty except for the blr. + if (I == ReturnMBB.end() || I->getOpcode() != PPC::BLR || + I != ReturnMBB.getLastNonDebugInstr()) + return Changed; + + SmallVector<MachineBasicBlock*, 8> PredToRemove; + for (MachineBasicBlock::pred_iterator PI = ReturnMBB.pred_begin(), + PIE = ReturnMBB.pred_end(); PI != PIE; ++PI) { + bool OtherReference = false, BlockChanged = false; + for (MachineBasicBlock::iterator J = (*PI)->getLastNonDebugInstr();;) { + if (J->getOpcode() == PPC::B) { + if (J->getOperand(0).getMBB() == &ReturnMBB) { + // This is an unconditional branch to the return. Replace the + // branch with a blr. + BuildMI(**PI, J, J->getDebugLoc(), TII->get(PPC::BLR)); + MachineBasicBlock::iterator K = J--; + K->eraseFromParent(); + BlockChanged = true; + ++NumBLR; + continue; + } + } else if (J->getOpcode() == PPC::BCC) { + if (J->getOperand(2).getMBB() == &ReturnMBB) { + // This is a conditional branch to the return. Replace the branch + // with a bclr. + BuildMI(**PI, J, J->getDebugLoc(), TII->get(PPC::BCLR)) + .addImm(J->getOperand(0).getImm()) + .addReg(J->getOperand(1).getReg()); + MachineBasicBlock::iterator K = J--; + K->eraseFromParent(); + BlockChanged = true; + ++NumBCLR; + continue; + } + } else if (J->isBranch()) { + if (J->isIndirectBranch()) { + if (ReturnMBB.hasAddressTaken()) + OtherReference = true; + } else + for (unsigned i = 0; i < J->getNumOperands(); ++i) + if (J->getOperand(i).isMBB() && + J->getOperand(i).getMBB() == &ReturnMBB) + OtherReference = true; + } else if (!J->isTerminator() && !J->isDebugValue()) + break; + + if (J == (*PI)->begin()) + break; + + --J; + } + + if ((*PI)->canFallThrough() && (*PI)->isLayoutSuccessor(&ReturnMBB)) + OtherReference = true; + + // Predecessors are stored in a vector and can't be removed here. + if (!OtherReference && BlockChanged) { + PredToRemove.push_back(*PI); + } + + if (BlockChanged) + Changed = true; + } + + for (unsigned i = 0, ie = PredToRemove.size(); i != ie; ++i) + PredToRemove[i]->removeSuccessor(&ReturnMBB); + + if (Changed && !ReturnMBB.hasAddressTaken()) { + // We now might be able to merge this blr-only block into its + // by-layout predecessor. + if (ReturnMBB.pred_size() == 1 && + (*ReturnMBB.pred_begin())->isLayoutSuccessor(&ReturnMBB)) { + // Move the blr into the preceding block. + MachineBasicBlock &PrevMBB = **ReturnMBB.pred_begin(); + PrevMBB.splice(PrevMBB.end(), &ReturnMBB, I); + PrevMBB.removeSuccessor(&ReturnMBB); + } + + if (ReturnMBB.pred_empty()) + ReturnMBB.eraseFromParent(); + } + + return Changed; + } + +public: + virtual bool runOnMachineFunction(MachineFunction &MF) { + TM = static_cast<const PPCTargetMachine *>(&MF.getTarget()); + TII = TM->getInstrInfo(); + + bool Changed = false; + + // If the function does not have at least two blocks, then there is + // nothing to do. + if (MF.size() < 2) + return Changed; + + for (MachineFunction::iterator I = MF.begin(); I != MF.end();) { + MachineBasicBlock &B = *I++; + if (processBlock(B)) + Changed = true; + } + + return Changed; + } + + virtual void getAnalysisUsage(AnalysisUsage &AU) const { + MachineFunctionPass::getAnalysisUsage(AU); + } + }; +} + +INITIALIZE_PASS(PPCEarlyReturn, DEBUG_TYPE, + "PowerPC Early-Return Creation", false, false) + +char PPCEarlyReturn::ID = 0; +FunctionPass* +llvm::createPPCEarlyReturnPass() { return new PPCEarlyReturn(); } + |
