//===-- TargetLowering.cpp - Implement the TargetLowering class -----------===// // // The LLVM Compiler Infrastructure // // This file was developed by the LLVM research group and is distributed under // the University of Illinois Open Source License. See LICENSE.TXT for details. // //===----------------------------------------------------------------------===// // // This implements the TargetLowering class. // //===----------------------------------------------------------------------===// #include "llvm/Target/TargetLowering.h" #include "llvm/Target/TargetData.h" #include "llvm/Target/TargetMachine.h" #include "llvm/Target/MRegisterInfo.h" #include "llvm/DerivedTypes.h" #include "llvm/CodeGen/SelectionDAG.h" #include "llvm/ADT/StringExtras.h" #include "llvm/Support/MathExtras.h" using namespace llvm; TargetLowering::TargetLowering(TargetMachine &tm) : TM(tm), TD(TM.getTargetData()) { assert(ISD::BUILTIN_OP_END <= 156 && "Fixed size array in TargetLowering is not large enough!"); // All operations default to being supported. memset(OpActions, 0, sizeof(OpActions)); memset(LoadXActions, 0, sizeof(LoadXActions)); memset(&StoreXActions, 0, sizeof(StoreXActions)); IsLittleEndian = TD->isLittleEndian(); UsesGlobalOffsetTable = false; ShiftAmountTy = SetCCResultTy = PointerTy = getValueType(TD->getIntPtrType()); ShiftAmtHandling = Undefined; memset(RegClassForVT, 0,MVT::LAST_VALUETYPE*sizeof(TargetRegisterClass*)); memset(TargetDAGCombineArray, 0, sizeof(TargetDAGCombineArray)/sizeof(TargetDAGCombineArray[0])); maxStoresPerMemset = maxStoresPerMemcpy = maxStoresPerMemmove = 8; allowUnalignedMemoryAccesses = false; UseUnderscoreSetJmpLongJmp = false; IntDivIsCheap = false; Pow2DivIsCheap = false; StackPointerRegisterToSaveRestore = 0; SchedPreferenceInfo = SchedulingForLatency; JumpBufSize = 0; JumpBufAlignment = 0; } TargetLowering::~TargetLowering() {} /// setValueTypeAction - Set the action for a particular value type. This /// assumes an action has not already been set for this value type. static void SetValueTypeAction(MVT::ValueType VT, TargetLowering::LegalizeAction Action, TargetLowering &TLI, MVT::ValueType *TransformToType, TargetLowering::ValueTypeActionImpl &ValueTypeActions) { ValueTypeActions.setTypeAction(VT, Action); if (Action == TargetLowering::Promote) { MVT::ValueType PromoteTo; if (VT == MVT::f32) PromoteTo = MVT::f64; else { unsigned LargerReg = VT+1; while (!TLI.isTypeLegal((MVT::ValueType)LargerReg)) { ++LargerReg; assert(MVT::isInteger((MVT::ValueType)LargerReg) && "Nothing to promote to??"); } PromoteTo = (MVT::ValueType)LargerReg; } assert(MVT::isInteger(VT) == MVT::isInteger(PromoteTo) && MVT::isFloatingPoint(VT) == MVT::isFloatingPoint(PromoteTo) && "Can only promote from int->int or fp->fp!"); assert(VT < PromoteTo && "Must promote to a larger type!"); TransformToType[VT] = PromoteTo; } else if (Action == TargetLowering::Expand) { assert((VT == MVT::Vector || MVT::isInteger(VT)) && VT > MVT::i8 && "Cannot expand this type: target must support SOME integer reg!"); // Expand to the next smaller integer type! TransformToType[VT] = (MVT::ValueType)(VT-1); } } /// computeRegisterProperties - Once all of the register classes are added, /// this allows us to compute derived properties we expose. void TargetLowering::computeRegisterProperties() { assert(MVT::LAST_VALUETYPE <= 32 && "Too many value types for ValueTypeActions to hold!"); // Everything defaults to one. for (unsigned i = 0; i != MVT::LAST_VALUETYPE; ++i) NumElementsForVT[i] = 1; // Find the largest integer register class. unsigned LargestIntReg = MVT::i128; for (; RegClassForVT[LargestIntReg] == 0; --LargestIntReg) assert(LargestIntReg != MVT::i1 && "No integer registers defined!"); // Every integer value type larger than this largest register takes twice as // many registers to represent as the previous ValueType. unsigned ExpandedReg = LargestIntReg; ++LargestIntReg; for (++ExpandedReg; MVT::isInteger((MVT::ValueType)ExpandedReg);++ExpandedReg) NumElementsForVT[ExpandedReg] = 2*NumElementsForVT[ExpandedReg-1]; // Inspect all of the ValueType's possible, deciding how to process them. for (unsigned IntReg = MVT::i1; IntReg <= MVT::i128; ++IntReg) // If we are expanding this type, expand it! if (getNumElements((MVT::ValueType)IntReg) != 1) SetValueTypeAction((MVT::ValueType)IntReg, Expand, *this, TransformToType, ValueTypeActions); else if (!isTypeLegal((MVT::ValueType)IntReg)) // Otherwise, if we don't have native support, we must promote to a // larger type. SetValueTypeAction((MVT::ValueType)IntReg, Promote, *this, TransformToType, ValueTypeActions); else TransformToType[(MVT::ValueType)IntReg] = (MVT::ValueType)IntReg; // If the target does not have native support for F32, promote it to F64. if (!isTypeLegal(MVT::f32)) SetValueTypeAction(MVT::f32, Promote, *this, TransformToType, ValueTypeActions); else TransformToType[MVT::f32] = MVT::f32; // Set MVT::Vector to always be Expanded SetValueTypeAction(MVT::Vector, Expand, *this, TransformToType, ValueTypeActions); // Loop over all of the legal vector value types, specifying an identity type // transformation. for (unsigned i = MVT::FIRST_VECTOR_VALUETYPE; i <= MVT::LAST_VECTOR_VALUETYPE; ++i) { if (isTypeLegal((MVT::ValueType)i)) TransformToType[i] = (MVT::ValueType)i; } assert(isTypeLegal(MVT::f64) && "Target does not support FP?"); TransformToType[MVT::f64] = MVT::f64; } const char *TargetLowering::getTargetNodeName(unsigned Opcode) const { return NULL; } /// getPackedTypeBreakdown - Packed types are broken down into some number of /// legal first class types. For example, <8 x float> maps to 2 MVT::v4f32 /// with Altivec or SSE1, or 8 promoted MVT::f64 values with the X86 FP stack. /// /// This method returns the number and type of the resultant breakdown. /// unsigned TargetLowering::getPackedTypeBreakdown(const PackedType *PTy, MVT::ValueType &PTyElementVT, MVT::ValueType &PTyLegalElementVT) const { // Figure out the right, legal destination reg to copy into. unsigned NumElts = PTy->getNumElements(); MVT::ValueType EltTy = getValueType(PTy->getElementType()); unsigned NumVectorRegs = 1; // Divide the input until we get to a supported size. This will always // end with a scalar if the target doesn't support vectors. while (NumElts > 1 && !isTypeLegal(getVectorType(EltTy, NumElts))) { NumElts >>= 1; NumVectorRegs <<= 1; } MVT::ValueType VT; if (NumElts == 1) { VT = EltTy; } else { VT = getVectorType(EltTy, NumElts); } PTyElementVT = VT; MVT::ValueType DestVT = getTypeToTransformTo(VT); PTyLegalElementVT = DestVT; if (DestVT < VT) { // Value is expanded, e.g. i64 -> i16. return NumVectorRegs*(MVT::getSizeInBits(VT)/MVT::getSizeInBits(DestVT)); } else { // Otherwise, promotion or legal types use the same number of registers as // the vector decimated to the appropriate level. return NumVectorRegs; } return 1; } //===----------------------------------------------------------------------===// // Optimization Methods //===----------------------------------------------------------------------===// /// ShrinkDemandedConstant - Check to see if the specified operand of the /// specified instruction is a constant integer. If so, check to see if there /// are any bits set in the constant that are not demanded. If so, shrink the /// constant and return true. bool TargetLowering::TargetLoweringOpt::ShrinkDemandedConstant(SDOperand Op, uint64_t Demanded) { // FIXME: ISD::SELECT, ISD::SELECT_CC switch(Op.getOpcode()) { default: break; case ISD::AND: case ISD::OR: case ISD::XOR: if (ConstantSDNode *C = dyn_cast(Op.getOperand(1))) if ((~Demanded & C->getValue()) != 0) { MVT::ValueType VT = Op.getValueType(); SDOperand New = DAG.getNode(Op.getOpcode(), VT, Op.getOperand(0), DAG.getConstant(Demanded & C->getValue(), VT)); return CombineTo(Op, New); } break; } return false; } /// SimplifyDemandedBits - Look at Op. At this point, we know that only the /// DemandedMask bits of the result of Op are ever used downstream. If we can /// use this information to simplify Op, create a new simplified DAG node and /// return true, returning the original and new nodes in Old and New. Otherwise, /// analyze the expression and return a mask of KnownOne and KnownZero bits for /// the expression (used to simplify the caller). The KnownZero/One bits may /// only be accurate for those bits in the DemandedMask. bool TargetLowering::SimplifyDemandedBits(SDOperand Op, uint64_t DemandedMask, uint64_t &KnownZero, uint64_t &KnownOne, TargetLoweringOpt &TLO, unsigned Depth) const { KnownZero = KnownOne = 0; // Don't know anything. // Other users may use these bits. if (!Op.Val->hasOneUse()) { if (Depth != 0) { // If not at the root, Just compute the KnownZero/KnownOne bits to // simplify things downstream. ComputeMaskedBits(Op, DemandedMask, KnownZero, KnownOne, Depth); return false; } // If this is the root being simplified, allow it to have multiple uses, // just set the DemandedMask to all bits. DemandedMask = MVT::getIntVTBitMask(Op.getValueType()); } else if (DemandedMask == 0) { // Not demanding any bits from Op. if (Op.getOpcode() != ISD::UNDEF) return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::UNDEF, Op.getValueType())); return false; } else if (Depth == 6) { // Limit search depth. return false; } uint64_t KnownZero2, KnownOne2, KnownZeroOut, KnownOneOut; switch (Op.getOpcode()) { case ISD::Constant: // We know all of the bits for a constant! KnownOne = cast(Op)->getValue() & DemandedMask; KnownZero = ~KnownOne & DemandedMask; return false; // Don't fall through, will infinitely loop. case ISD::AND: // If the RHS is a constant, check to see if the LHS would be zero without // using the bits from the RHS. Below, we use knowledge about the RHS to // simplify the LHS, here we're using information from the LHS to simplify // the RHS. if (ConstantSDNode *RHSC = dyn_cast(Op.getOperand(1))) { uint64_t LHSZero, LHSOne; ComputeMaskedBits(Op.getOperand(0), DemandedMask, LHSZero, LHSOne, Depth+1); // If the LHS already has zeros where RHSC does, this and is dead. if ((LHSZero & DemandedMask) == (~RHSC->getValue() & DemandedMask)) return TLO.CombineTo(Op, Op.getOperand(0)); // If any of the set bits in the RHS are known zero on the LHS, shrink // the constant. if (TLO.ShrinkDemandedConstant(Op, ~LHSZero & DemandedMask)) return true; } if (SimplifyDemandedBits(Op.getOperand(1), DemandedMask, KnownZero, KnownOne, TLO, Depth+1)) return true; assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); if (SimplifyDemandedBits(Op.getOperand(0), DemandedMask & ~KnownZero, KnownZero2, KnownOne2, TLO, Depth+1)) return true; assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); // If all of the demanded bits are known one on one side, return the other. // These bits cannot contribute to the result of the 'and'. if ((DemandedMask & ~KnownZero2 & KnownOne)==(DemandedMask & ~KnownZero2)) return TLO.CombineTo(Op, Op.getOperand(0)); if ((DemandedMask & ~KnownZero & KnownOne2)==(DemandedMask & ~KnownZero)) return TLO.CombineTo(Op, Op.getOperand(1)); // If all of the demanded bits in the inputs are known zeros, return zero. if ((DemandedMask & (KnownZero|KnownZero2)) == DemandedMask) return TLO.CombineTo(Op, TLO.DAG.getConstant(0, Op.getValueType())); // If the RHS is a constant, see if we can simplify it. if (TLO.ShrinkDemandedConstant(Op, DemandedMask & ~KnownZero2)) return true; // Output known-1 bits are only known if set in both the LHS & RHS. KnownOne &= KnownOne2; // Output known-0 are known to be clear if zero in either the LHS | RHS. KnownZero |= KnownZero2; break; case ISD::OR: if (SimplifyDemandedBits(Op.getOperand(1), DemandedMask, KnownZero, KnownOne, TLO, Depth+1)) return true; assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); if (SimplifyDemandedBits(Op.getOperand(0), DemandedMask & ~KnownOne, KnownZero2, KnownOne2, TLO, Depth+1)) return true; assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); // If all of the demanded bits are known zero on one side, return the other. // These bits cannot contribute to the result of the 'or'. if ((DemandedMask & ~KnownOne2 & KnownZero) == (DemandedMask & ~KnownOne2)) return TLO.CombineTo(Op, Op.getOperand(0)); if ((DemandedMask & ~KnownOne & KnownZero2) == (DemandedMask & ~KnownOne)) return TLO.CombineTo(Op, Op.getOperand(1)); // If all of the potentially set bits on one side are known to be set on // the other side, just use the 'other' side. if ((DemandedMask & (~KnownZero) & KnownOne2) == (DemandedMask & (~KnownZero))) return TLO.CombineTo(Op, Op.getOperand(0)); if ((DemandedMask & (~KnownZero2) & KnownOne) == (DemandedMask & (~KnownZero2))) return TLO.CombineTo(Op, Op.getOperand(1)); // If the RHS is a constant, see if we can simplify it. if (TLO.ShrinkDemandedConstant(Op, DemandedMask)) return true; // Output known-0 bits are only known if clear in both the LHS & RHS. KnownZero &= KnownZero2; // Output known-1 are known to be set if set in either the LHS | RHS. KnownOne |= KnownOne2; break; case ISD::XOR: if (SimplifyDemandedBits(Op.getOperand(1), DemandedMask, KnownZero, KnownOne, TLO, Depth+1)) return true; assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); if (SimplifyDemandedBits(Op.getOperand(0), DemandedMask, KnownZero2, KnownOne2, TLO, Depth+1)) return true; assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); // If all of the demanded bits are known zero on one side, return the other. // These bits cannot contribute to the result of the 'xor'. if ((DemandedMask & KnownZero) == DemandedMask) return TLO.CombineTo(Op, Op.getOperand(0)); if ((DemandedMask & KnownZero2) == DemandedMask) return TLO.CombineTo(Op, Op.getOperand(1)); // Output known-0 bits are known if clear or set in both the LHS & RHS. KnownZeroOut = (KnownZero & KnownZero2) | (KnownOne & KnownOne2); // Output known-1 are known to be set if set in only one of the LHS, RHS. KnownOneOut = (KnownZero & KnownOne2) | (KnownOne & KnownZero2); // If all of the unknown bits are known to be zero on one side or the other // (but not both) turn this into an *inclusive* or. // e.g. (A & C1)^(B & C2) -> (A & C1)|(B & C2) iff C1&C2 == 0 if (uint64_t UnknownBits = DemandedMask & ~(KnownZeroOut|KnownOneOut)) if ((UnknownBits & (KnownZero|KnownZero2)) == UnknownBits) return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::OR, Op.getValueType(), Op.getOperand(0), Op.getOperand(1))); // If all of the demanded bits on one side are known, and all of the set // bits on that side are also known to be set on the other side, turn this // into an AND, as we know the bits will be cleared. // e.g. (X | C1) ^ C2 --> (X | C1) & ~C2 iff (C1&C2) == C2 if ((DemandedMask & (KnownZero|KnownOne)) == DemandedMask) { // all known if ((KnownOne & KnownOne2) == KnownOne) { MVT::ValueType VT = Op.getValueType(); SDOperand ANDC = TLO.DAG.getConstant(~KnownOne & DemandedMask, VT); return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::AND, VT, Op.getOperand(0), ANDC)); } } // If the RHS is a constant, see if we can simplify it. // FIXME: for XOR, we prefer to force bits to 1 if they will make a -1. if (TLO.ShrinkDemandedConstant(Op, DemandedMask)) return true; KnownZero = KnownZeroOut; KnownOne = KnownOneOut; break; case ISD::SETCC: // If we know the result of a setcc has the top bits zero, use this info. if (getSetCCResultContents() == TargetLowering::ZeroOrOneSetCCResult) KnownZero |= (MVT::getIntVTBitMask(Op.getValueType()) ^ 1ULL); break; case ISD::SELECT: if (SimplifyDemandedBits(Op.getOperand(2), DemandedMask, KnownZero, KnownOne, TLO, Depth+1)) return true; if (SimplifyDemandedBits(Op.getOperand(1), DemandedMask, KnownZero2, KnownOne2, TLO, Depth+1)) return true; assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); // If the operands are constants, see if we can simplify them. if (TLO.ShrinkDemandedConstant(Op, DemandedMask)) return true; // Only known if known in both the LHS and RHS. KnownOne &= KnownOne2; KnownZero &= KnownZero2; break; case ISD::SELECT_CC: if (SimplifyDemandedBits(Op.getOperand(3), DemandedMask, KnownZero, KnownOne, TLO, Depth+1)) return true; if (SimplifyDemandedBits(Op.getOperand(2), DemandedMask, KnownZero2, KnownOne2, TLO, Depth+1)) return true; assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); // If the operands are constants, see if we can simplify them. if (TLO.ShrinkDemandedConstant(Op, DemandedMask)) return true; // Only known if known in both the LHS and RHS. KnownOne &= KnownOne2; KnownZero &= KnownZero2; break; case ISD::SHL: if (ConstantSDNode *SA = dyn_cast(Op.getOperand(1))) { if (SimplifyDemandedBits(Op.getOperand(0), DemandedMask >> SA->getValue(), KnownZero, KnownOne, TLO, Depth+1)) return true; KnownZero <<= SA->getValue(); KnownOne <<= SA->getValue(); KnownZero |= (1ULL << SA->getValue())-1; // low bits known zero. } break; case ISD::SRL: if (ConstantSDNode *SA = dyn_cast(Op.getOperand(1))) { MVT::ValueType VT = Op.getValueType(); unsigned ShAmt = SA->getValue(); // Compute the new bits that are at the top now. uint64_t TypeMask = MVT::getIntVTBitMask(VT); if (SimplifyDemandedBits(Op.getOperand(0), (DemandedMask << ShAmt) & TypeMask, KnownZero, KnownOne, TLO, Depth+1)) return true; assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); KnownZero &= TypeMask; KnownOne &= TypeMask; KnownZero >>= ShAmt; KnownOne >>= ShAmt; uint64_t HighBits = (1ULL << ShAmt)-1; HighBits <<= MVT::getSizeInBits(VT) - ShAmt; KnownZero |= HighBits; // High bits known zero. } break; case ISD::SRA: if (ConstantSDNode *SA = dyn_cast(Op.getOperand(1))) { MVT::ValueType VT = Op.getValueType(); unsigned ShAmt = SA->getValue(); // Compute the new bits that are at the top now. uint64_t TypeMask = MVT::getIntVTBitMask(VT); uint64_t InDemandedMask = (DemandedMask << ShAmt) & TypeMask; // If any of the demanded bits are produced by the sign extension, we also // demand the input sign bit. uint64_t HighBits = (1ULL << ShAmt)-1; HighBits <<= MVT::getSizeInBits(VT) - ShAmt; if (HighBits & DemandedMask) InDemandedMask |= MVT::getIntVTSignBit(VT); if (SimplifyDemandedBits(Op.getOperand(0), InDemandedMask, KnownZero, KnownOne, TLO, Depth+1)) return true; assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); KnownZero &= TypeMask; KnownOne &= TypeMask; KnownZero >>= ShAmt; KnownOne >>= ShAmt; // Handle the sign bits. uint64_t SignBit = MVT::getIntVTSignBit(VT); SignBit >>= ShAmt; // Adjust to where it is now in the mask. // If the input sign bit is known to be zero, or if none of the top bits // are demanded, turn this into an unsigned shift right. if ((KnownZero & SignBit) || (HighBits & ~DemandedMask) == HighBits) { return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::SRL, VT, Op.getOperand(0), Op.getOperand(1))); } else if (KnownOne & SignBit) { // New bits are known one. KnownOne |= HighBits; } } break; case ISD::SIGN_EXTEND_INREG: { MVT::ValueType EVT = cast(Op.getOperand(1))->getVT(); // Sign extension. Compute the demanded bits in the result that are not // present in the input. uint64_t NewBits = ~MVT::getIntVTBitMask(EVT) & DemandedMask; // If none of the extended bits are demanded, eliminate the sextinreg. if (NewBits == 0) return TLO.CombineTo(Op, Op.getOperand(0)); uint64_t InSignBit = MVT::getIntVTSignBit(EVT); int64_t InputDemandedBits = DemandedMask & MVT::getIntVTBitMask(EVT); // Since the sign extended bits are demanded, we know that the sign // bit is demanded. InputDemandedBits |= InSignBit; if (SimplifyDemandedBits(Op.getOperand(0), InputDemandedBits, KnownZero, KnownOne, TLO, Depth+1)) return true; assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); // If the sign bit of the input is known set or clear, then we know the // top bits of the result. // If the input sign bit is known zero, convert this into a zero extension. if (KnownZero & InSignBit) return TLO.CombineTo(Op, TLO.DAG.getZeroExtendInReg(Op.getOperand(0), EVT)); if (KnownOne & InSignBit) { // Input sign bit known set KnownOne |= NewBits; KnownZero &= ~NewBits; } else { // Input sign bit unknown KnownZero &= ~NewBits; KnownOne &= ~NewBits; } break; } case ISD::CTTZ: case ISD::CTLZ: case ISD::CTPOP: { MVT::ValueType VT = Op.getValueType(); unsigned LowBits = Log2_32(MVT::getSizeInBits(VT))+1; KnownZero = ~((1ULL << LowBits)-1) & MVT::getIntVTBitMask(VT); KnownOne = 0; break; } case ISD::LOAD: { if (ISD::isZEXTLoad(Op.Val)) { LoadSDNode *LD = cast(Op); MVT::ValueType VT = LD->getLoadedVT(); KnownZero |= ~MVT::getIntVTBitMask(VT) & DemandedMask; } break; } case ISD::ZERO_EXTEND: { uint64_t InMask = MVT::getIntVTBitMask(Op.getOperand(0).getValueType()); // If none of the top bits are demanded, convert this into an any_extend. uint64_t NewBits = (~InMask) & DemandedMask; if (NewBits == 0) return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::ANY_EXTEND, Op.getValueType(), Op.getOperand(0))); if (SimplifyDemandedBits(Op.getOperand(0), DemandedMask & InMask, KnownZero, KnownOne, TLO, Depth+1)) return true; assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); KnownZero |= NewBits; break; } case ISD::SIGN_EXTEND: { MVT::ValueType InVT = Op.getOperand(0).getValueType(); uint64_t InMask = MVT::getIntVTBitMask(InVT); uint64_t InSignBit = MVT::getIntVTSignBit(InVT); uint64_t NewBits = (~InMask) & DemandedMask; // If none of the top bits are demanded, convert this into an any_extend. if (NewBits == 0) return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::ANY_EXTEND,Op.getValueType(), Op.getOperand(0))); // Since some of the sign extended bits are demanded, we know that the sign // bit is demanded. uint64_t InDemandedBits = DemandedMask & InMask; InDemandedBits |= InSignBit; if (SimplifyDemandedBits(Op.getOperand(0), InDemandedBits, KnownZero, KnownOne, TLO, Depth+1)) return true; // If the sign bit is known zero, convert this to a zero extend. if (KnownZero & InSignBit) return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::ZERO_EXTEND, Op.getValueType(), Op.getOperand(0))); // If the sign bit is known one, the top bits match. if (KnownOne & InSignBit) { KnownOne |= NewBits; KnownZero &= ~NewBits; } else { // Otherwise, top bits aren't known. KnownOne &= ~NewBits; KnownZero &= ~NewBits; } break; } case ISD::ANY_EXTEND: { uint64_t InMask = MVT::getIntVTBitMask(Op.getOperand(0).getValueType()); if (SimplifyDemandedBits(Op.getOperand(0), DemandedMask & InMask, KnownZero, KnownOne, TLO, Depth+1)) return true; assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); break; } case ISD::TRUNCATE: { // Simplify the input, using demanded bit information, and compute the known // zero/one bits live out. if (SimplifyDemandedBits(Op.getOperand(0), DemandedMask, KnownZero, KnownOne, TLO, Depth+1)) return true; // If the input is only used by this truncate, see if we can shrink it based // on the known demanded bits. if (Op.getOperand(0).Val->hasOneUse()) { SDOperand In = Op.getOperand(0); switch (In.getOpcode()) { default: break; case ISD::SRL: // Shrink SRL by a constant if none of the high bits shifted in are // demanded. if (ConstantSDNode *ShAmt = dyn_cast(In.getOperand(1))){ uint64_t HighBits = MVT::getIntVTBitMask(In.getValueType()); HighBits &= ~MVT::getIntVTBitMask(Op.getValueType()); HighBits >>= ShAmt->getValue(); if (ShAmt->getValue() < MVT::getSizeInBits(Op.getValueType()) && (DemandedMask & HighBits) == 0) { // None of the shifted in bits are needed. Add a truncate of the // shift input, then shift it. SDOperand NewTrunc = TLO.DAG.getNode(ISD::TRUNCATE, Op.getValueType(), In.getOperand(0)); return TLO.CombineTo(Op, TLO.DAG.getNode(ISD::SRL,Op.getValueType(), NewTrunc, In.getOperand(1))); } } break; } } assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); uint64_t OutMask = MVT::getIntVTBitMask(Op.getValueType()); KnownZero &= OutMask; KnownOne &= OutMask; break; } case ISD::AssertZext: { MVT::ValueType VT = cast(Op.getOperand(1))->getVT(); uint64_t InMask = MVT::getIntVTBitMask(VT); if (SimplifyDemandedBits(Op.getOperand(0), DemandedMask & InMask, KnownZero, KnownOne, TLO, Depth+1)) return true; assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); KnownZero |= ~InMask & DemandedMask; break; } case ISD::ADD: case ISD::SUB: case ISD::INTRINSIC_WO_CHAIN: case ISD::INTRINSIC_W_CHAIN: case ISD::INTRINSIC_VOID: // Just use ComputeMaskedBits to compute output bits. ComputeMaskedBits(Op, DemandedMask, KnownZero, KnownOne, Depth); break; } // If we know the value of all of the demanded bits, return this as a // constant. if ((DemandedMask & (KnownZero|KnownOne)) == DemandedMask) return TLO.CombineTo(Op, TLO.DAG.getConstant(KnownOne, Op.getValueType())); return false; } /// MaskedValueIsZero - Return true if 'V & Mask' is known to be zero. We use /// this predicate to simplify operations downstream. Mask is known to be zero /// for bits that V cannot have. bool TargetLowering::MaskedValueIsZero(SDOperand Op, uint64_t Mask, unsigned Depth) const { uint64_t KnownZero, KnownOne; ComputeMaskedBits(Op, Mask, KnownZero, KnownOne, Depth); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); return (KnownZero & Mask) == Mask; } /// ComputeMaskedBits - Determine which of the bits specified in Mask are /// known to be either zero or one and return them in the KnownZero/KnownOne /// bitsets. This code only analyzes bits in Mask, in order to short-circuit /// processing. void TargetLowering::ComputeMaskedBits(SDOperand Op, uint64_t Mask, uint64_t &KnownZero, uint64_t &KnownOne, unsigned Depth) const { KnownZero = KnownOne = 0; // Don't know anything. if (Depth == 6 || Mask == 0) return; // Limit search depth. uint64_t KnownZero2, KnownOne2; switch (Op.getOpcode()) { case ISD::Constant: // We know all of the bits for a constant! KnownOne = cast(Op)->getValue() & Mask; KnownZero = ~KnownOne & Mask; return; case ISD::AND: // If either the LHS or the RHS are Zero, the result is zero. ComputeMaskedBits(Op.getOperand(1), Mask, KnownZero, KnownOne, Depth+1); Mask &= ~KnownZero; ComputeMaskedBits(Op.getOperand(0), Mask, KnownZero2, KnownOne2, Depth+1); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); // Output known-1 bits are only known if set in both the LHS & RHS. KnownOne &= KnownOne2; // Output known-0 are known to be clear if zero in either the LHS | RHS. KnownZero |= KnownZero2; return; case ISD::OR: ComputeMaskedBits(Op.getOperand(1), Mask, KnownZero, KnownOne, Depth+1); Mask &= ~KnownOne; ComputeMaskedBits(Op.getOperand(0), Mask, KnownZero2, KnownOne2, Depth+1); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); // Output known-0 bits are only known if clear in both the LHS & RHS. KnownZero &= KnownZero2; // Output known-1 are known to be set if set in either the LHS | RHS. KnownOne |= KnownOne2; return; case ISD::XOR: { ComputeMaskedBits(Op.getOperand(1), Mask, KnownZero, KnownOne, Depth+1); ComputeMaskedBits(Op.getOperand(0), Mask, KnownZero2, KnownOne2, Depth+1); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); // Output known-0 bits are known if clear or set in both the LHS & RHS. uint64_t KnownZeroOut = (KnownZero & KnownZero2) | (KnownOne & KnownOne2); // Output known-1 are known to be set if set in only one of the LHS, RHS. KnownOne = (KnownZero & KnownOne2) | (KnownOne & KnownZero2); KnownZero = KnownZeroOut; return; } case ISD::SELECT: ComputeMaskedBits(Op.getOperand(2), Mask, KnownZero, KnownOne, Depth+1); ComputeMaskedBits(Op.getOperand(1), Mask, KnownZero2, KnownOne2, Depth+1); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); // Only known if known in both the LHS and RHS. KnownOne &= KnownOne2; KnownZero &= KnownZero2; return; case ISD::SELECT_CC: ComputeMaskedBits(Op.getOperand(3), Mask, KnownZero, KnownOne, Depth+1); ComputeMaskedBits(Op.getOperand(2), Mask, KnownZero2, KnownOne2, Depth+1); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); // Only known if known in both the LHS and RHS. KnownOne &= KnownOne2; KnownZero &= KnownZero2; return; case ISD::SETCC: // If we know the result of a setcc has the top bits zero, use this info. if (getSetCCResultContents() == TargetLowering::ZeroOrOneSetCCResult) KnownZero |= (MVT::getIntVTBitMask(Op.getValueType()) ^ 1ULL); return; case ISD::SHL: // (shl X, C1) & C2 == 0 iff (X & C2 >>u C1) == 0 if (ConstantSDNode *SA = dyn_cast(Op.getOperand(1))) { ComputeMaskedBits(Op.getOperand(0), Mask >> SA->getValue(), KnownZero, KnownOne, Depth+1); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); KnownZero <<= SA->getValue(); KnownOne <<= SA->getValue(); KnownZero |= (1ULL << SA->getValue())-1; // low bits known zero. } return; case ISD::SRL: // (ushr X, C1) & C2 == 0 iff (-1 >> C1) & C2 == 0 if (ConstantSDNode *SA = dyn_cast(Op.getOperand(1))) { MVT::ValueType VT = Op.getValueType(); unsigned ShAmt = SA->getValue(); uint64_t TypeMask = MVT::getIntVTBitMask(VT); ComputeMaskedBits(Op.getOperand(0), (Mask << ShAmt) & TypeMask, KnownZero, KnownOne, Depth+1); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); KnownZero &= TypeMask; KnownOne &= TypeMask; KnownZero >>= ShAmt; KnownOne >>= ShAmt; uint64_t HighBits = (1ULL << ShAmt)-1; HighBits <<= MVT::getSizeInBits(VT)-ShAmt; KnownZero |= HighBits; // High bits known zero. } return; case ISD::SRA: if (ConstantSDNode *SA = dyn_cast(Op.getOperand(1))) { MVT::ValueType VT = Op.getValueType(); unsigned ShAmt = SA->getValue(); // Compute the new bits that are at the top now. uint64_t TypeMask = MVT::getIntVTBitMask(VT); uint64_t InDemandedMask = (Mask << ShAmt) & TypeMask; // If any of the demanded bits are produced by the sign extension, we also // demand the input sign bit. uint64_t HighBits = (1ULL << ShAmt)-1; HighBits <<= MVT::getSizeInBits(VT) - ShAmt; if (HighBits & Mask) InDemandedMask |= MVT::getIntVTSignBit(VT); ComputeMaskedBits(Op.getOperand(0), InDemandedMask, KnownZero, KnownOne, Depth+1); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); KnownZero &= TypeMask; KnownOne &= TypeMask; KnownZero >>= ShAmt; KnownOne >>= ShAmt; // Handle the sign bits. uint64_t SignBit = MVT::getIntVTSignBit(VT); SignBit >>= ShAmt; // Adjust to where it is now in the mask. if (KnownZero & SignBit) { KnownZero |= HighBits; // New bits are known zero. } else if (KnownOne & SignBit) { KnownOne |= HighBits; // New bits are known one. } } return; case ISD::SIGN_EXTEND_INREG: { MVT::ValueType EVT = cast(Op.getOperand(1))->getVT(); // Sign extension. Compute the demanded bits in the result that are not // present in the input. uint64_t NewBits = ~MVT::getIntVTBitMask(EVT) & Mask; uint64_t InSignBit = MVT::getIntVTSignBit(EVT); int64_t InputDemandedBits = Mask & MVT::getIntVTBitMask(EVT); // If the sign extended bits are demanded, we know that the sign // bit is demanded. if (NewBits) InputDemandedBits |= InSignBit; ComputeMaskedBits(Op.getOperand(0), InputDemandedBits, KnownZero, KnownOne, Depth+1); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); // If the sign bit of the input is known set or clear, then we know the // top bits of the result. if (KnownZero & InSignBit) { // Input sign bit known clear KnownZero |= NewBits; KnownOne &= ~NewBits; } else if (KnownOne & InSignBit) { // Input sign bit known set KnownOne |= NewBits; KnownZero &= ~NewBits; } else { // Input sign bit unknown KnownZero &= ~NewBits; KnownOne &= ~NewBits; } return; } case ISD::CTTZ: case ISD::CTLZ: case ISD::CTPOP: { MVT::ValueType VT = Op.getValueType(); unsigned LowBits = Log2_32(MVT::getSizeInBits(VT))+1; KnownZero = ~((1ULL << LowBits)-1) & MVT::getIntVTBitMask(VT); KnownOne = 0; return; } case ISD::LOAD: { if (ISD::isZEXTLoad(Op.Val)) { LoadSDNode *LD = cast(Op); MVT::ValueType VT = LD->getLoadedVT(); KnownZero |= ~MVT::getIntVTBitMask(VT) & Mask; } return; } case ISD::ZERO_EXTEND: { uint64_t InMask = MVT::getIntVTBitMask(Op.getOperand(0).getValueType()); uint64_t NewBits = (~InMask) & Mask; ComputeMaskedBits(Op.getOperand(0), Mask & InMask, KnownZero, KnownOne, Depth+1); KnownZero |= NewBits & Mask; KnownOne &= ~NewBits; return; } case ISD::SIGN_EXTEND: { MVT::ValueType InVT = Op.getOperand(0).getValueType(); unsigned InBits = MVT::getSizeInBits(InVT); uint64_t InMask = MVT::getIntVTBitMask(InVT); uint64_t InSignBit = 1ULL << (InBits-1); uint64_t NewBits = (~InMask) & Mask; uint64_t InDemandedBits = Mask & InMask; // If any of the sign extended bits are demanded, we know that the sign // bit is demanded. if (NewBits & Mask) InDemandedBits |= InSignBit; ComputeMaskedBits(Op.getOperand(0), InDemandedBits, KnownZero, KnownOne, Depth+1); // If the sign bit is known zero or one, the top bits match. if (KnownZero & InSignBit) { KnownZero |= NewBits; KnownOne &= ~NewBits; } else if (KnownOne & InSignBit) { KnownOne |= NewBits; KnownZero &= ~NewBits; } else { // Otherwise, top bits aren't known. KnownOne &= ~NewBits; KnownZero &= ~NewBits; } return; } case ISD::ANY_EXTEND: { MVT::ValueType VT = Op.getOperand(0).getValueType(); ComputeMaskedBits(Op.getOperand(0), Mask & MVT::getIntVTBitMask(VT), KnownZero, KnownOne, Depth+1); return; } case ISD::TRUNCATE: { ComputeMaskedBits(Op.getOperand(0), Mask, KnownZero, KnownOne, Depth+1); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); uint64_t OutMask = MVT::getIntVTBitMask(Op.getValueType()); KnownZero &= OutMask; KnownOne &= OutMask; break; } case ISD::AssertZext: { MVT::ValueType VT = cast(Op.getOperand(1))->getVT(); uint64_t InMask = MVT::getIntVTBitMask(VT); ComputeMaskedBits(Op.getOperand(0), Mask & InMask, KnownZero, KnownOne, Depth+1); KnownZero |= (~InMask) & Mask; return; } case ISD::ADD: { // If either the LHS or the RHS are Zero, the result is zero. ComputeMaskedBits(Op.getOperand(1), Mask, KnownZero, KnownOne, Depth+1); ComputeMaskedBits(Op.getOperand(0), Mask, KnownZero2, KnownOne2, Depth+1); assert((KnownZero & KnownOne) == 0 && "Bits known to be one AND zero?"); assert((KnownZero2 & KnownOne2) == 0 && "Bits known to be one AND zero?"); // Output known-0 bits are known if clear or set in both the low clear bits // common to both LHS & RHS. For example, 8+(X<<3) is known to have the // low 3 bits clear. uint64_t KnownZeroOut = std::min(CountTrailingZeros_64(~KnownZero), CountTrailingZeros_64(~KnownZero2)); KnownZero = (1ULL << KnownZeroOut) - 1; KnownOne = 0; return; } case ISD::SUB: { ConstantSDNode *CLHS = dyn_cast(Op.getOperand(0)); if (!CLHS) return; // We know that the top bits of C-X are clear if X contains less bits // than C (i.e. no wrap-around can happen). For example, 20-X is // positive if we can prove that X is >= 0 and < 16. MVT::ValueType VT = CLHS->getValueType(0); if ((CLHS->getValue() & MVT::getIntVTSignBit(VT)) == 0) { // sign bit clear unsigned NLZ = CountLeadingZeros_64(CLHS->getValue()+1); uint64_t MaskV = (1ULL << (63-NLZ))-1; // NLZ can't be 64 with no sign bit MaskV = ~MaskV & MVT::getIntVTBitMask(VT); ComputeMaskedBits(Op.getOperand(1), MaskV, KnownZero, KnownOne, Depth+1); // If all of the MaskV bits are known to be zero, then we know the output // top bits are zero, because we now know that the output is from [0-C]. if ((KnownZero & MaskV) == MaskV) { unsigned NLZ2 = CountLeadingZeros_64(CLHS->getValue()); KnownZero = ~((1ULL << (64-NLZ2))-1) & Mask; // Top bits known zero. KnownOne = 0; // No one bits known. } else { KnownZero = KnownOne = 0; // Otherwise, nothing known. } } return; } default: // Allow the target to implement this method for its nodes. if (Op.getOpcode() >= ISD::BUILTIN_OP_END) { case ISD::INTRINSIC_WO_CHAIN: case ISD::INTRINSIC_W_CHAIN: case ISD::INTRINSIC_VOID: computeMaskedBitsForTargetNode(Op, Mask, KnownZero, KnownOne); } return; } } /// computeMaskedBitsForTargetNode - Determine which of the bits specified /// in Mask are known to be either zero or one and return them in the /// KnownZero/KnownOne bitsets. void TargetLowering::computeMaskedBitsForTargetNode(const SDOperand Op, uint64_t Mask, uint64_t &KnownZero, uint64_t &KnownOne, unsigned Depth) const { assert((Op.getOpcode() >= ISD::BUILTIN_OP_END || Op.getOpcode() == ISD::INTRINSIC_WO_CHAIN || Op.getOpcode() == ISD::INTRINSIC_W_CHAIN || Op.getOpcode() == ISD::INTRINSIC_VOID) && "Should use MaskedValueIsZero if you don't know whether Op" " is a target node!"); KnownZero = 0; KnownOne = 0; } /// ComputeNumSignBits - Return the number of times the sign bit of the /// register is replicated into the other bits. We know that at least 1 bit /// is always equal to the sign bit (itself), but other cases can give us /// information. For example, immediately after an "SRA X, 2", we know that /// the top 3 bits are all equal to each other, so we return 3. unsigned TargetLowering::ComputeNumSignBits(SDOperand Op, unsigned Depth) const{ MVT::ValueType VT = Op.getValueType(); assert(MVT::isInteger(VT) && "Invalid VT!"); unsigned VTBits = MVT::getSizeInBits(VT); unsigned Tmp, Tmp2; if (Depth == 6) return 1; // Limit search depth. switch (Op.getOpcode()) { default: break; case ISD::AssertSext: Tmp = MVT::getSizeInBits(cast(Op.getOperand(1))->getVT()); return VTBits-Tmp+1; case ISD::AssertZext: Tmp = MVT::getSizeInBits(cast(Op.getOperand(1))->getVT()); return VTBits-Tmp; case ISD::Constant: { uint64_t Val = cast(Op)->getValue(); // If negative, invert the bits, then look at it. if (Val & MVT::getIntVTSignBit(VT)) Val = ~Val; // Shift the bits so they are the leading bits in the int64_t. Val <<= 64-VTBits; // Return # leading zeros. We use 'min' here in case Val was zero before // shifting. We don't want to return '64' as for an i32 "0". return std::min(VTBits, CountLeadingZeros_64(Val)); } case ISD::SIGN_EXTEND: Tmp = VTBits-MVT::getSizeInBits(Op.getOperand(0).getValueType()); return ComputeNumSignBits(Op.getOperand(0), Depth+1) + Tmp; case ISD::SIGN_EXTEND_INREG: // Max of the input and what this extends. Tmp = MVT::getSizeInBits(cast(Op.getOperand(1))->getVT()); Tmp = VTBits-Tmp+1; Tmp2 = ComputeNumSignBits(Op.getOperand(0), Depth+1); return std::max(Tmp, Tmp2); case ISD::SRA: Tmp = ComputeNumSignBits(Op.getOperand(0), Depth+1); // SRA X, C -> adds C sign bits. if (ConstantSDNode *C = dyn_cast(Op.getOperand(1))) { Tmp += C->getValue(); if (Tmp > VTBits) Tmp = VTBits; } return Tmp; case ISD::SHL: if (ConstantSDNode *C = dyn_cast(Op.getOperand(1))) { // shl destroys sign bits. Tmp = ComputeNumSignBits(Op.getOperand(0), Depth+1); if (C->getValue() >= VTBits || // Bad shift. C->getValue() >= Tmp) break; // Shifted all sign bits out. return Tmp - C->getValue(); } break; case ISD::AND: case ISD::OR: case ISD::XOR: // NOT is handled here. // Logical binary ops preserve the number of sign bits. Tmp = ComputeNumSignBits(Op.getOperand(0), Depth+1); if (Tmp == 1) return 1; // Early out. Tmp2 = ComputeNumSignBits(Op.getOperand(1), Depth+1); return std::min(Tmp, Tmp2); case ISD::SELECT: Tmp = ComputeNumSignBits(Op.getOperand(0), Depth+1); if (Tmp == 1) return 1; // Early out. Tmp2 = ComputeNumSignBits(Op.getOperand(1), Depth+1); return std::min(Tmp, Tmp2); case ISD::SETCC: // If setcc returns 0/-1, all bits are sign bits. if (getSetCCResultContents() == ZeroOrNegativeOneSetCCResult) return VTBits; break; case ISD::ROTL: case ISD::ROTR: if (ConstantSDNode *C = dyn_cast(Op.getOperand(1))) { unsigned RotAmt = C->getValue() & (VTBits-1); // Handle rotate right by N like a rotate left by 32-N. if (Op.getOpcode() == ISD::ROTR) RotAmt = (VTBits-RotAmt) & (VTBits-1); // If we aren't rotating out all of the known-in sign bits, return the // number that are left. This handles rotl(sext(x), 1) for example. Tmp = ComputeNumSignBits(Op.getOperand(0), Depth+1); if (Tmp > RotAmt+1) return Tmp-RotAmt; } break; case ISD::ADD: // Add can have at most one carry bit. Thus we know that the output // is, at worst, one more bit than the inputs. Tmp = ComputeNumSignBits(Op.getOperand(0), Depth+1); if (Tmp == 1) return 1; // Early out. // Special case decrementing a value (ADD X, -1): if (ConstantSDNode *CRHS = dyn_cast(Op.getOperand(0))) if (CRHS->isAllOnesValue()) { uint64_t KnownZero, KnownOne; uint64_t Mask = MVT::getIntVTBitMask(VT); ComputeMaskedBits(Op.getOperand(0), Mask, KnownZero, KnownOne, Depth+1); // If the input is known to be 0 or 1, the output is 0/-1, which is all // sign bits set. if ((KnownZero|1) == Mask) return VTBits; // If we are subtracting one from a positive number, there is no carry // out of the result. if (KnownZero & MVT::getIntVTSignBit(VT)) return Tmp; } Tmp2 = ComputeNumSignBits(Op.getOperand(1), Depth+1); if (Tmp2 == 1) return 1; return std::min(Tmp, Tmp2)-1; break; case ISD::SUB: Tmp2 = ComputeNumSignBits(Op.getOperand(1), Depth+1); if (Tmp2 == 1) return 1; // Handle NEG. if (ConstantSDNode *CLHS = dyn_cast(Op.getOperand(0))) if (CLHS->getValue() == 0) { uint64_t KnownZero, KnownOne; uint64_t Mask = MVT::getIntVTBitMask(VT); ComputeMaskedBits(Op.getOperand(1), Mask, KnownZero, KnownOne, Depth+1); // If the input is known to be 0 or 1, the output is 0/-1, which is all // sign bits set. if ((KnownZero|1) == Mask) return VTBits; // If the input is known to be positive (the sign bit is known clear), // the output of the NEG has the same number of sign bits as the input. if (KnownZero & MVT::getIntVTSignBit(VT)) return Tmp2; // Otherwise, we treat this like a SUB. } // Sub can have at most one carry bit. Thus we know that the output // is, at worst, one more bit than the inputs. Tmp = ComputeNumSignBits(Op.getOperand(0), Depth+1); if (Tmp == 1) return 1; // Early out. return std::min(Tmp, Tmp2)-1; break; case ISD::TRUNCATE: // FIXME: it's tricky to do anything useful for this, but it is an important // case for targets like X86. break; } // Handle LOADX separately here. EXTLOAD case will fallthrough. if (Op.getOpcode() == ISD::LOAD) { LoadSDNode *LD = cast(Op); unsigned ExtType = LD->getExtensionType(); switch (ExtType) { default: break; case ISD::SEXTLOAD: // '17' bits known Tmp = MVT::getSizeInBits(LD->getLoadedVT()); return VTBits-Tmp+1; case ISD::ZEXTLOAD: // '16' bits known Tmp = MVT::getSizeInBits(LD->getLoadedVT()); return VTBits-Tmp; } } // Allow the target to implement this method for its nodes. if (Op.getOpcode() >= ISD::BUILTIN_OP_END || Op.getOpcode() == ISD::INTRINSIC_WO_CHAIN || Op.getOpcode() == ISD::INTRINSIC_W_CHAIN || Op.getOpcode() == ISD::INTRINSIC_VOID) { unsigned NumBits = ComputeNumSignBitsForTargetNode(Op, Depth); if (NumBits > 1) return NumBits; } // Finally, if we can prove that the top bits of the result are 0's or 1's, // use this information. uint64_t KnownZero, KnownOne; uint64_t Mask = MVT::getIntVTBitMask(VT); ComputeMaskedBits(Op, Mask, KnownZero, KnownOne, Depth); uint64_t SignBit = MVT::getIntVTSignBit(VT); if (KnownZero & SignBit) { // SignBit is 0 Mask = KnownZero; } else if (KnownOne & SignBit) { // SignBit is 1; Mask = KnownOne; } else { // Nothing known. return 1; } // Okay, we know that the sign bit in Mask is set. Use CLZ to determine // the number of identical bits in the top of the input value. Mask ^= ~0ULL; Mask <<= 64-VTBits; // Return # leading zeros. We use 'min' here in case Val was zero before // shifting. We don't want to return '64' as for an i32 "0". return std::min(VTBits, CountLeadingZeros_64(Mask)); } /// ComputeNumSignBitsForTargetNode - This method can be implemented by /// targets that want to expose additional information about sign bits to the /// DAG Combiner. unsigned TargetLowering::ComputeNumSignBitsForTargetNode(SDOperand Op, unsigned Depth) const { assert((Op.getOpcode() >= ISD::BUILTIN_OP_END || Op.getOpcode() == ISD::INTRINSIC_WO_CHAIN || Op.getOpcode() == ISD::INTRINSIC_W_CHAIN || Op.getOpcode() == ISD::INTRINSIC_VOID) && "Should use ComputeNumSignBits if you don't know whether Op" " is a target node!"); return 1; } SDOperand TargetLowering:: PerformDAGCombine(SDNode *N, DAGCombinerInfo &DCI) const { // Default implementation: no optimization. return SDOperand(); } //===----------------------------------------------------------------------===// // Inline Assembler Implementation Methods //===----------------------------------------------------------------------===// TargetLowering::ConstraintType TargetLowering::getConstraintType(char ConstraintLetter) const { // FIXME: lots more standard ones to handle. switch (ConstraintLetter) { default: return C_Unknown; case 'r': return C_RegisterClass; case 'm': // memory case 'o': // offsetable case 'V': // not offsetable return C_Memory; case 'i': // Simple Integer or Relocatable Constant case 'n': // Simple Integer case 's': // Relocatable Constant case 'I': // Target registers. case 'J': case 'K': case 'L': case 'M': case 'N': case 'O': case 'P': return C_Other; } } /// isOperandValidForConstraint - Return the specified operand (possibly /// modified) if the specified SDOperand is valid for the specified target /// constraint letter, otherwise return null. SDOperand TargetLowering::isOperandValidForConstraint(SDOperand Op, char ConstraintLetter, SelectionDAG &DAG) { switch (ConstraintLetter) { default: return SDOperand(0,0); case 'i': // Simple Integer or Relocatable Constant case 'n': // Simple Integer case 's': // Relocatable Constant return Op; // FIXME: not right. } } std::vector TargetLowering:: getRegClassForInlineAsmConstraint(const std::string &Constraint, MVT::ValueType VT) const { return std::vector(); } std::pair TargetLowering:: getRegForInlineAsmConstraint(const std::string &Constraint, MVT::ValueType VT) const { if (Constraint[0] != '{') return std::pair(0, 0); assert(*(Constraint.end()-1) == '}' && "Not a brace enclosed constraint?"); // Remove the braces from around the name. std::string RegName(Constraint.begin()+1, Constraint.end()-1); // Figure out which register class contains this reg. const MRegisterInfo *RI = TM.getRegisterInfo(); for (MRegisterInfo::regclass_iterator RCI = RI->regclass_begin(), E = RI->regclass_end(); RCI != E; ++RCI) { const TargetRegisterClass *RC = *RCI; // If none of the the value types for this register class are valid, we // can't use it. For example, 64-bit reg classes on 32-bit targets. bool isLegal = false; for (TargetRegisterClass::vt_iterator I = RC->vt_begin(), E = RC->vt_end(); I != E; ++I) { if (isTypeLegal(*I)) { isLegal = true; break; } } if (!isLegal) continue; for (TargetRegisterClass::iterator I = RC->begin(), E = RC->end(); I != E; ++I) { if (StringsEqualNoCase(RegName, RI->get(*I).Name)) return std::make_pair(*I, RC); } } return std::pair(0, 0); } //===----------------------------------------------------------------------===// // Loop Strength Reduction hooks //===----------------------------------------------------------------------===// /// isLegalAddressImmediate - Return true if the integer value or /// GlobalValue can be used as the offset of the target addressing mode. bool TargetLowering::isLegalAddressImmediate(int64_t V) const { return false; } bool TargetLowering::isLegalAddressImmediate(GlobalValue *GV) const { return false; } // Magic for divide replacement struct ms { int64_t m; // magic number int64_t s; // shift amount }; struct mu { uint64_t m; // magic number int64_t a; // add indicator int64_t s; // shift amount }; /// magic - calculate the magic numbers required to codegen an integer sdiv as /// a sequence of multiply and shifts. Requires that the divisor not be 0, 1, /// or -1. static ms magic32(int32_t d) { int32_t p; uint32_t ad, anc, delta, q1, r1, q2, r2, t; const uint32_t two31 = 0x80000000U; struct ms mag; ad = abs(d); t = two31 + ((uint32_t)d >> 31); anc = t - 1 - t%ad; // absolute value of nc p = 31; // initialize p q1 = two31/anc; // initialize q1 = 2p/abs(nc) r1 = two31 - q1*anc; // initialize r1 = rem(2p,abs(nc)) q2 = two31/ad; // initialize q2 = 2p/abs(d) r2 = two31 - q2*ad; // initialize r2 = rem(2p,abs(d)) do { p = p + 1; q1 = 2*q1; // update q1 = 2p/abs(nc) r1 = 2*r1; // update r1 = rem(2p/abs(nc)) if (r1 >= anc) { // must be unsigned comparison q1 = q1 + 1; r1 = r1 - anc; } q2 = 2*q2; // update q2 = 2p/abs(d) r2 = 2*r2; // update r2 = rem(2p/abs(d)) if (r2 >= ad) { // must be unsigned comparison q2 = q2 + 1; r2 = r2 - ad; } delta = ad - r2; } while (q1 < delta || (q1 == delta && r1 == 0)); mag.m = (int32_t)(q2 + 1); // make sure to sign extend if (d < 0) mag.m = -mag.m; // resulting magic number mag.s = p - 32; // resulting shift return mag; } /// magicu - calculate the magic numbers required to codegen an integer udiv as /// a sequence of multiply, add and shifts. Requires that the divisor not be 0. static mu magicu32(uint32_t d) { int32_t p; uint32_t nc, delta, q1, r1, q2, r2; struct mu magu; magu.a = 0; // initialize "add" indicator nc = - 1 - (-d)%d; p = 31; // initialize p q1 = 0x80000000/nc; // initialize q1 = 2p/nc r1 = 0x80000000 - q1*nc; // initialize r1 = rem(2p,nc) q2 = 0x7FFFFFFF/d; // initialize q2 = (2p-1)/d r2 = 0x7FFFFFFF - q2*d; // initialize r2 = rem((2p-1),d) do { p = p + 1; if (r1 >= nc - r1 ) { q1 = 2*q1 + 1; // update q1 r1 = 2*r1 - nc; // update r1 } else { q1 = 2*q1; // update q1 r1 = 2*r1; // update r1 } if (r2 + 1 >= d - r2) { if (q2 >= 0x7FFFFFFF) magu.a = 1; q2 = 2*q2 + 1; // update q2 r2 = 2*r2 + 1 - d; // update r2 } else { if (q2 >= 0x80000000) magu.a = 1; q2 = 2*q2; // update q2 r2 = 2*r2 + 1; // update r2 } delta = d - 1 - r2; } while (p < 64 && (q1 < delta || (q1 == delta && r1 == 0))); magu.m = q2 + 1; // resulting magic number magu.s = p - 32; // resulting shift return magu; } /// magic - calculate the magic numbers required to codegen an integer sdiv as /// a sequence of multiply and shifts. Requires that the divisor not be 0, 1, /// or -1. static ms magic64(int64_t d) { int64_t p; uint64_t ad, anc, delta, q1, r1, q2, r2, t; const uint64_t two63 = 9223372036854775808ULL; // 2^63 struct ms mag; ad = d >= 0 ? d : -d; t = two63 + ((uint64_t)d >> 63); anc = t - 1 - t%ad; // absolute value of nc p = 63; // initialize p q1 = two63/anc; // initialize q1 = 2p/abs(nc) r1 = two63 - q1*anc; // initialize r1 = rem(2p,abs(nc)) q2 = two63/ad; // initialize q2 = 2p/abs(d) r2 = two63 - q2*ad; // initialize r2 = rem(2p,abs(d)) do { p = p + 1; q1 = 2*q1; // update q1 = 2p/abs(nc) r1 = 2*r1; // update r1 = rem(2p/abs(nc)) if (r1 >= anc) { // must be unsigned comparison q1 = q1 + 1; r1 = r1 - anc; } q2 = 2*q2; // update q2 = 2p/abs(d) r2 = 2*r2; // update r2 = rem(2p/abs(d)) if (r2 >= ad) { // must be unsigned comparison q2 = q2 + 1; r2 = r2 - ad; } delta = ad - r2; } while (q1 < delta || (q1 == delta && r1 == 0)); mag.m = q2 + 1; if (d < 0) mag.m = -mag.m; // resulting magic number mag.s = p - 64; // resulting shift return mag; } /// magicu - calculate the magic numbers required to codegen an integer udiv as /// a sequence of multiply, add and shifts. Requires that the divisor not be 0. static mu magicu64(uint64_t d) { int64_t p; uint64_t nc, delta, q1, r1, q2, r2; struct mu magu; magu.a = 0; // initialize "add" indicator nc = - 1 - (-d)%d; p = 63; // initialize p q1 = 0x8000000000000000ull/nc; // initialize q1 = 2p/nc r1 = 0x8000000000000000ull - q1*nc; // initialize r1 = rem(2p,nc) q2 = 0x7FFFFFFFFFFFFFFFull/d; // initialize q2 = (2p-1)/d r2 = 0x7FFFFFFFFFFFFFFFull - q2*d; // initialize r2 = rem((2p-1),d) do { p = p + 1; if (r1 >= nc - r1 ) { q1 = 2*q1 + 1; // update q1 r1 = 2*r1 - nc; // update r1 } else { q1 = 2*q1; // update q1 r1 = 2*r1; // update r1 } if (r2 + 1 >= d - r2) { if (q2 >= 0x7FFFFFFFFFFFFFFFull) magu.a = 1; q2 = 2*q2 + 1; // update q2 r2 = 2*r2 + 1 - d; // update r2 } else { if (q2 >= 0x8000000000000000ull) magu.a = 1; q2 = 2*q2; // update q2 r2 = 2*r2 + 1; // update r2 } delta = d - 1 - r2; } while (p < 128 && (q1 < delta || (q1 == delta && r1 == 0))); magu.m = q2 + 1; // resulting magic number magu.s = p - 64; // resulting shift return magu; } /// BuildSDIVSequence - Given an ISD::SDIV node expressing a divide by constant, /// return a DAG expression to select that will generate the same value by /// multiplying by a magic number. See: /// SDOperand TargetLowering::BuildSDIV(SDNode *N, SelectionDAG &DAG, std::vector* Created) const { MVT::ValueType VT = N->getValueType(0); // Check to see if we can do this. if (!isTypeLegal(VT) || (VT != MVT::i32 && VT != MVT::i64)) return SDOperand(); // BuildSDIV only operates on i32 or i64 if (!isOperationLegal(ISD::MULHS, VT)) return SDOperand(); // Make sure the target supports MULHS. int64_t d = cast(N->getOperand(1))->getSignExtended(); ms magics = (VT == MVT::i32) ? magic32(d) : magic64(d); // Multiply the numerator (operand 0) by the magic value SDOperand Q = DAG.getNode(ISD::MULHS, VT, N->getOperand(0), DAG.getConstant(magics.m, VT)); // If d > 0 and m < 0, add the numerator if (d > 0 && magics.m < 0) { Q = DAG.getNode(ISD::ADD, VT, Q, N->getOperand(0)); if (Created) Created->push_back(Q.Val); } // If d < 0 and m > 0, subtract the numerator. if (d < 0 && magics.m > 0) { Q = DAG.getNode(ISD::SUB, VT, Q, N->getOperand(0)); if (Created) Created->push_back(Q.Val); } // Shift right algebraic if shift value is nonzero if (magics.s > 0) { Q = DAG.getNode(ISD::SRA, VT, Q, DAG.getConstant(magics.s, getShiftAmountTy())); if (Created) Created->push_back(Q.Val); } // Extract the sign bit and add it to the quotient SDOperand T = DAG.getNode(ISD::SRL, VT, Q, DAG.getConstant(MVT::getSizeInBits(VT)-1, getShiftAmountTy())); if (Created) Created->push_back(T.Val); return DAG.getNode(ISD::ADD, VT, Q, T); } /// BuildUDIVSequence - Given an ISD::UDIV node expressing a divide by constant, /// return a DAG expression to select that will generate the same value by /// multiplying by a magic number. See: /// SDOperand TargetLowering::BuildUDIV(SDNode *N, SelectionDAG &DAG, std::vector* Created) const { MVT::ValueType VT = N->getValueType(0); // Check to see if we can do this. if (!isTypeLegal(VT) || (VT != MVT::i32 && VT != MVT::i64)) return SDOperand(); // BuildUDIV only operates on i32 or i64 if (!isOperationLegal(ISD::MULHU, VT)) return SDOperand(); // Make sure the target supports MULHU. uint64_t d = cast(N->getOperand(1))->getValue(); mu magics = (VT == MVT::i32) ? magicu32(d) : magicu64(d); // Multiply the numerator (operand 0) by the magic value SDOperand Q = DAG.getNode(ISD::MULHU, VT, N->getOperand(0), DAG.getConstant(magics.m, VT)); if (Created) Created->push_back(Q.Val); if (magics.a == 0) { return DAG.getNode(ISD::SRL, VT, Q, DAG.getConstant(magics.s, getShiftAmountTy())); } else { SDOperand NPQ = DAG.getNode(ISD::SUB, VT, N->getOperand(0), Q); if (Created) Created->push_back(NPQ.Val); NPQ = DAG.getNode(ISD::SRL, VT, NPQ, DAG.getConstant(1, getShiftAmountTy())); if (Created) Created->push_back(NPQ.Val); NPQ = DAG.getNode(ISD::ADD, VT, NPQ, Q); if (Created) Created->push_back(NPQ.Val); return DAG.getNode(ISD::SRL, VT, NPQ, DAG.getConstant(magics.s-1, getShiftAmountTy())); } }