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      1 //===- llvm/CodeGen/SelectionDAG.h - InstSelection DAG ----------*- C++ -*-===//
      2 //
      3 //                     The LLVM Compiler Infrastructure
      4 //
      5 // This file is distributed under the University of Illinois Open Source
      6 // License. See LICENSE.TXT for details.
      7 //
      8 //===----------------------------------------------------------------------===//
      9 //
     10 // This file declares the SelectionDAG class, and transitively defines the
     11 // SDNode class and subclasses.
     12 //
     13 //===----------------------------------------------------------------------===//
     14 
     15 #ifndef LLVM_CODEGEN_SELECTIONDAG_H
     16 #define LLVM_CODEGEN_SELECTIONDAG_H
     17 
     18 #include "llvm/ADT/APFloat.h"
     19 #include "llvm/ADT/APInt.h"
     20 #include "llvm/ADT/ArrayRef.h"
     21 #include "llvm/ADT/DenseMap.h"
     22 #include "llvm/ADT/DenseSet.h"
     23 #include "llvm/ADT/FoldingSet.h"
     24 #include "llvm/ADT/SetVector.h"
     25 #include "llvm/ADT/SmallVector.h"
     26 #include "llvm/ADT/StringMap.h"
     27 #include "llvm/ADT/ilist.h"
     28 #include "llvm/ADT/iterator.h"
     29 #include "llvm/ADT/iterator_range.h"
     30 #include "llvm/Analysis/AliasAnalysis.h"
     31 #include "llvm/CodeGen/DAGCombine.h"
     32 #include "llvm/CodeGen/ISDOpcodes.h"
     33 #include "llvm/CodeGen/MachineFunction.h"
     34 #include "llvm/CodeGen/MachineMemOperand.h"
     35 #include "llvm/CodeGen/MachineValueType.h"
     36 #include "llvm/CodeGen/SelectionDAGNodes.h"
     37 #include "llvm/CodeGen/ValueTypes.h"
     38 #include "llvm/IR/DebugLoc.h"
     39 #include "llvm/IR/Instructions.h"
     40 #include "llvm/IR/Metadata.h"
     41 #include "llvm/Support/Allocator.h"
     42 #include "llvm/Support/ArrayRecycler.h"
     43 #include "llvm/Support/AtomicOrdering.h"
     44 #include "llvm/Support/Casting.h"
     45 #include "llvm/Support/CodeGen.h"
     46 #include "llvm/Support/ErrorHandling.h"
     47 #include "llvm/Support/RecyclingAllocator.h"
     48 #include <algorithm>
     49 #include <cassert>
     50 #include <cstdint>
     51 #include <functional>
     52 #include <map>
     53 #include <string>
     54 #include <tuple>
     55 #include <utility>
     56 #include <vector>
     57 
     58 namespace llvm {
     59 
     60 class BlockAddress;
     61 class Constant;
     62 class ConstantFP;
     63 class ConstantInt;
     64 class DataLayout;
     65 struct fltSemantics;
     66 class GlobalValue;
     67 struct KnownBits;
     68 class LLVMContext;
     69 class MachineBasicBlock;
     70 class MachineConstantPoolValue;
     71 class MCSymbol;
     72 class OptimizationRemarkEmitter;
     73 class SDDbgValue;
     74 class SelectionDAG;
     75 class SelectionDAGTargetInfo;
     76 class TargetLowering;
     77 class TargetMachine;
     78 class TargetSubtargetInfo;
     79 class Value;
     80 
     81 class SDVTListNode : public FoldingSetNode {
     82   friend struct FoldingSetTrait<SDVTListNode>;
     83 
     84   /// A reference to an Interned FoldingSetNodeID for this node.
     85   /// The Allocator in SelectionDAG holds the data.
     86   /// SDVTList contains all types which are frequently accessed in SelectionDAG.
     87   /// The size of this list is not expected to be big so it won't introduce
     88   /// a memory penalty.
     89   FoldingSetNodeIDRef FastID;
     90   const EVT *VTs;
     91   unsigned int NumVTs;
     92   /// The hash value for SDVTList is fixed, so cache it to avoid
     93   /// hash calculation.
     94   unsigned HashValue;
     95 
     96 public:
     97   SDVTListNode(const FoldingSetNodeIDRef ID, const EVT *VT, unsigned int Num) :
     98       FastID(ID), VTs(VT), NumVTs(Num) {
     99     HashValue = ID.ComputeHash();
    100   }
    101 
    102   SDVTList getSDVTList() {
    103     SDVTList result = {VTs, NumVTs};
    104     return result;
    105   }
    106 };
    107 
    108 /// Specialize FoldingSetTrait for SDVTListNode
    109 /// to avoid computing temp FoldingSetNodeID and hash value.
    110 template<> struct FoldingSetTrait<SDVTListNode> : DefaultFoldingSetTrait<SDVTListNode> {
    111   static void Profile(const SDVTListNode &X, FoldingSetNodeID& ID) {
    112     ID = X.FastID;
    113   }
    114 
    115   static bool Equals(const SDVTListNode &X, const FoldingSetNodeID &ID,
    116                      unsigned IDHash, FoldingSetNodeID &TempID) {
    117     if (X.HashValue != IDHash)
    118       return false;
    119     return ID == X.FastID;
    120   }
    121 
    122   static unsigned ComputeHash(const SDVTListNode &X, FoldingSetNodeID &TempID) {
    123     return X.HashValue;
    124   }
    125 };
    126 
    127 template <> struct ilist_alloc_traits<SDNode> {
    128   static void deleteNode(SDNode *) {
    129     llvm_unreachable("ilist_traits<SDNode> shouldn't see a deleteNode call!");
    130   }
    131 };
    132 
    133 /// Keeps track of dbg_value information through SDISel.  We do
    134 /// not build SDNodes for these so as not to perturb the generated code;
    135 /// instead the info is kept off to the side in this structure. Each SDNode may
    136 /// have one or more associated dbg_value entries. This information is kept in
    137 /// DbgValMap.
    138 /// Byval parameters are handled separately because they don't use alloca's,
    139 /// which busts the normal mechanism.  There is good reason for handling all
    140 /// parameters separately:  they may not have code generated for them, they
    141 /// should always go at the beginning of the function regardless of other code
    142 /// motion, and debug info for them is potentially useful even if the parameter
    143 /// is unused.  Right now only byval parameters are handled separately.
    144 class SDDbgInfo {
    145   BumpPtrAllocator Alloc;
    146   SmallVector<SDDbgValue*, 32> DbgValues;
    147   SmallVector<SDDbgValue*, 32> ByvalParmDbgValues;
    148   using DbgValMapType = DenseMap<const SDNode *, SmallVector<SDDbgValue *, 2>>;
    149   DbgValMapType DbgValMap;
    150 
    151 public:
    152   SDDbgInfo() = default;
    153   SDDbgInfo(const SDDbgInfo &) = delete;
    154   SDDbgInfo &operator=(const SDDbgInfo &) = delete;
    155 
    156   void add(SDDbgValue *V, const SDNode *Node, bool isParameter) {
    157     if (isParameter) {
    158       ByvalParmDbgValues.push_back(V);
    159     } else     DbgValues.push_back(V);
    160     if (Node)
    161       DbgValMap[Node].push_back(V);
    162   }
    163 
    164   /// \brief Invalidate all DbgValues attached to the node and remove
    165   /// it from the Node-to-DbgValues map.
    166   void erase(const SDNode *Node);
    167 
    168   void clear() {
    169     DbgValMap.clear();
    170     DbgValues.clear();
    171     ByvalParmDbgValues.clear();
    172     Alloc.Reset();
    173   }
    174 
    175   BumpPtrAllocator &getAlloc() { return Alloc; }
    176 
    177   bool empty() const {
    178     return DbgValues.empty() && ByvalParmDbgValues.empty();
    179   }
    180 
    181   ArrayRef<SDDbgValue*> getSDDbgValues(const SDNode *Node) {
    182     DbgValMapType::iterator I = DbgValMap.find(Node);
    183     if (I != DbgValMap.end())
    184       return I->second;
    185     return ArrayRef<SDDbgValue*>();
    186   }
    187 
    188   using DbgIterator = SmallVectorImpl<SDDbgValue*>::iterator;
    189 
    190   DbgIterator DbgBegin() { return DbgValues.begin(); }
    191   DbgIterator DbgEnd()   { return DbgValues.end(); }
    192   DbgIterator ByvalParmDbgBegin() { return ByvalParmDbgValues.begin(); }
    193   DbgIterator ByvalParmDbgEnd()   { return ByvalParmDbgValues.end(); }
    194 };
    195 
    196 void checkForCycles(const SelectionDAG *DAG, bool force = false);
    197 
    198 /// This is used to represent a portion of an LLVM function in a low-level
    199 /// Data Dependence DAG representation suitable for instruction selection.
    200 /// This DAG is constructed as the first step of instruction selection in order
    201 /// to allow implementation of machine specific optimizations
    202 /// and code simplifications.
    203 ///
    204 /// The representation used by the SelectionDAG is a target-independent
    205 /// representation, which has some similarities to the GCC RTL representation,
    206 /// but is significantly more simple, powerful, and is a graph form instead of a
    207 /// linear form.
    208 ///
    209 class SelectionDAG {
    210   const TargetMachine &TM;
    211   const SelectionDAGTargetInfo *TSI = nullptr;
    212   const TargetLowering *TLI = nullptr;
    213   MachineFunction *MF;
    214   Pass *SDAGISelPass = nullptr;
    215   LLVMContext *Context;
    216   CodeGenOpt::Level OptLevel;
    217 
    218   /// The function-level optimization remark emitter.  Used to emit remarks
    219   /// whenever manipulating the DAG.
    220   OptimizationRemarkEmitter *ORE;
    221 
    222   /// The starting token.
    223   SDNode EntryNode;
    224 
    225   /// The root of the entire DAG.
    226   SDValue Root;
    227 
    228   /// A linked list of nodes in the current DAG.
    229   ilist<SDNode> AllNodes;
    230 
    231   /// The AllocatorType for allocating SDNodes. We use
    232   /// pool allocation with recycling.
    233   using NodeAllocatorType = RecyclingAllocator<BumpPtrAllocator, SDNode,
    234                                                sizeof(LargestSDNode),
    235                                                alignof(MostAlignedSDNode)>;
    236 
    237   /// Pool allocation for nodes.
    238   NodeAllocatorType NodeAllocator;
    239 
    240   /// This structure is used to memoize nodes, automatically performing
    241   /// CSE with existing nodes when a duplicate is requested.
    242   FoldingSet<SDNode> CSEMap;
    243 
    244   /// Pool allocation for machine-opcode SDNode operands.
    245   BumpPtrAllocator OperandAllocator;
    246   ArrayRecycler<SDUse> OperandRecycler;
    247 
    248   /// Pool allocation for misc. objects that are created once per SelectionDAG.
    249   BumpPtrAllocator Allocator;
    250 
    251   /// Tracks dbg_value information through SDISel.
    252   SDDbgInfo *DbgInfo;
    253 
    254   uint16_t NextPersistentId = 0;
    255 
    256 public:
    257   /// Clients of various APIs that cause global effects on
    258   /// the DAG can optionally implement this interface.  This allows the clients
    259   /// to handle the various sorts of updates that happen.
    260   ///
    261   /// A DAGUpdateListener automatically registers itself with DAG when it is
    262   /// constructed, and removes itself when destroyed in RAII fashion.
    263   struct DAGUpdateListener {
    264     DAGUpdateListener *const Next;
    265     SelectionDAG &DAG;
    266 
    267     explicit DAGUpdateListener(SelectionDAG &D)
    268       : Next(D.UpdateListeners), DAG(D) {
    269       DAG.UpdateListeners = this;
    270     }
    271 
    272     virtual ~DAGUpdateListener() {
    273       assert(DAG.UpdateListeners == this &&
    274              "DAGUpdateListeners must be destroyed in LIFO order");
    275       DAG.UpdateListeners = Next;
    276     }
    277 
    278     /// The node N that was deleted and, if E is not null, an
    279     /// equivalent node E that replaced it.
    280     virtual void NodeDeleted(SDNode *N, SDNode *E);
    281 
    282     /// The node N that was updated.
    283     virtual void NodeUpdated(SDNode *N);
    284   };
    285 
    286   struct DAGNodeDeletedListener : public DAGUpdateListener {
    287     std::function<void(SDNode *, SDNode *)> Callback;
    288 
    289     DAGNodeDeletedListener(SelectionDAG &DAG,
    290                            std::function<void(SDNode *, SDNode *)> Callback)
    291         : DAGUpdateListener(DAG), Callback(std::move(Callback)) {}
    292 
    293     void NodeDeleted(SDNode *N, SDNode *E) override { Callback(N, E); }
    294   };
    295 
    296   /// When true, additional steps are taken to
    297   /// ensure that getConstant() and similar functions return DAG nodes that
    298   /// have legal types. This is important after type legalization since
    299   /// any illegally typed nodes generated after this point will not experience
    300   /// type legalization.
    301   bool NewNodesMustHaveLegalTypes = false;
    302 
    303 private:
    304   /// DAGUpdateListener is a friend so it can manipulate the listener stack.
    305   friend struct DAGUpdateListener;
    306 
    307   /// Linked list of registered DAGUpdateListener instances.
    308   /// This stack is maintained by DAGUpdateListener RAII.
    309   DAGUpdateListener *UpdateListeners = nullptr;
    310 
    311   /// Implementation of setSubgraphColor.
    312   /// Return whether we had to truncate the search.
    313   bool setSubgraphColorHelper(SDNode *N, const char *Color,
    314                               DenseSet<SDNode *> &visited,
    315                               int level, bool &printed);
    316 
    317   template <typename SDNodeT, typename... ArgTypes>
    318   SDNodeT *newSDNode(ArgTypes &&... Args) {
    319     return new (NodeAllocator.template Allocate<SDNodeT>())
    320         SDNodeT(std::forward<ArgTypes>(Args)...);
    321   }
    322 
    323   /// Build a synthetic SDNodeT with the given args and extract its subclass
    324   /// data as an integer (e.g. for use in a folding set).
    325   ///
    326   /// The args to this function are the same as the args to SDNodeT's
    327   /// constructor, except the second arg (assumed to be a const DebugLoc&) is
    328   /// omitted.
    329   template <typename SDNodeT, typename... ArgTypes>
    330   static uint16_t getSyntheticNodeSubclassData(unsigned IROrder,
    331                                                ArgTypes &&... Args) {
    332     // The compiler can reduce this expression to a constant iff we pass an
    333     // empty DebugLoc.  Thankfully, the debug location doesn't have any bearing
    334     // on the subclass data.
    335     return SDNodeT(IROrder, DebugLoc(), std::forward<ArgTypes>(Args)...)
    336         .getRawSubclassData();
    337   }
    338 
    339   void createOperands(SDNode *Node, ArrayRef<SDValue> Vals) {
    340     assert(!Node->OperandList && "Node already has operands");
    341     SDUse *Ops = OperandRecycler.allocate(
    342         ArrayRecycler<SDUse>::Capacity::get(Vals.size()), OperandAllocator);
    343 
    344     for (unsigned I = 0; I != Vals.size(); ++I) {
    345       Ops[I].setUser(Node);
    346       Ops[I].setInitial(Vals[I]);
    347     }
    348     Node->NumOperands = Vals.size();
    349     Node->OperandList = Ops;
    350     checkForCycles(Node);
    351   }
    352 
    353   void removeOperands(SDNode *Node) {
    354     if (!Node->OperandList)
    355       return;
    356     OperandRecycler.deallocate(
    357         ArrayRecycler<SDUse>::Capacity::get(Node->NumOperands),
    358         Node->OperandList);
    359     Node->NumOperands = 0;
    360     Node->OperandList = nullptr;
    361   }
    362 
    363 public:
    364   explicit SelectionDAG(const TargetMachine &TM, CodeGenOpt::Level);
    365   SelectionDAG(const SelectionDAG &) = delete;
    366   SelectionDAG &operator=(const SelectionDAG &) = delete;
    367   ~SelectionDAG();
    368 
    369   /// Prepare this SelectionDAG to process code in the given MachineFunction.
    370   void init(MachineFunction &NewMF, OptimizationRemarkEmitter &NewORE,
    371             Pass *PassPtr);
    372 
    373   /// Clear state and free memory necessary to make this
    374   /// SelectionDAG ready to process a new block.
    375   void clear();
    376 
    377   MachineFunction &getMachineFunction() const { return *MF; }
    378   const Pass *getPass() const { return SDAGISelPass; }
    379 
    380   const DataLayout &getDataLayout() const { return MF->getDataLayout(); }
    381   const TargetMachine &getTarget() const { return TM; }
    382   const TargetSubtargetInfo &getSubtarget() const { return MF->getSubtarget(); }
    383   const TargetLowering &getTargetLoweringInfo() const { return *TLI; }
    384   const SelectionDAGTargetInfo &getSelectionDAGInfo() const { return *TSI; }
    385   LLVMContext *getContext() const {return Context; }
    386   OptimizationRemarkEmitter &getORE() const { return *ORE; }
    387 
    388   /// Pop up a GraphViz/gv window with the DAG rendered using 'dot'.
    389   void viewGraph(const std::string &Title);
    390   void viewGraph();
    391 
    392 #ifndef NDEBUG
    393   std::map<const SDNode *, std::string> NodeGraphAttrs;
    394 #endif
    395 
    396   /// Clear all previously defined node graph attributes.
    397   /// Intended to be used from a debugging tool (eg. gdb).
    398   void clearGraphAttrs();
    399 
    400   /// Set graph attributes for a node. (eg. "color=red".)
    401   void setGraphAttrs(const SDNode *N, const char *Attrs);
    402 
    403   /// Get graph attributes for a node. (eg. "color=red".)
    404   /// Used from getNodeAttributes.
    405   const std::string getGraphAttrs(const SDNode *N) const;
    406 
    407   /// Convenience for setting node color attribute.
    408   void setGraphColor(const SDNode *N, const char *Color);
    409 
    410   /// Convenience for setting subgraph color attribute.
    411   void setSubgraphColor(SDNode *N, const char *Color);
    412 
    413   using allnodes_const_iterator = ilist<SDNode>::const_iterator;
    414 
    415   allnodes_const_iterator allnodes_begin() const { return AllNodes.begin(); }
    416   allnodes_const_iterator allnodes_end() const { return AllNodes.end(); }
    417 
    418   using allnodes_iterator = ilist<SDNode>::iterator;
    419 
    420   allnodes_iterator allnodes_begin() { return AllNodes.begin(); }
    421   allnodes_iterator allnodes_end() { return AllNodes.end(); }
    422 
    423   ilist<SDNode>::size_type allnodes_size() const {
    424     return AllNodes.size();
    425   }
    426 
    427   iterator_range<allnodes_iterator> allnodes() {
    428     return make_range(allnodes_begin(), allnodes_end());
    429   }
    430   iterator_range<allnodes_const_iterator> allnodes() const {
    431     return make_range(allnodes_begin(), allnodes_end());
    432   }
    433 
    434   /// Return the root tag of the SelectionDAG.
    435   const SDValue &getRoot() const { return Root; }
    436 
    437   /// Return the token chain corresponding to the entry of the function.
    438   SDValue getEntryNode() const {
    439     return SDValue(const_cast<SDNode *>(&EntryNode), 0);
    440   }
    441 
    442   /// Set the current root tag of the SelectionDAG.
    443   ///
    444   const SDValue &setRoot(SDValue N) {
    445     assert((!N.getNode() || N.getValueType() == MVT::Other) &&
    446            "DAG root value is not a chain!");
    447     if (N.getNode())
    448       checkForCycles(N.getNode(), this);
    449     Root = N;
    450     if (N.getNode())
    451       checkForCycles(this);
    452     return Root;
    453   }
    454 
    455   /// This iterates over the nodes in the SelectionDAG, folding
    456   /// certain types of nodes together, or eliminating superfluous nodes.  The
    457   /// Level argument controls whether Combine is allowed to produce nodes and
    458   /// types that are illegal on the target.
    459   void Combine(CombineLevel Level, AliasAnalysis *AA,
    460                CodeGenOpt::Level OptLevel);
    461 
    462   /// This transforms the SelectionDAG into a SelectionDAG that
    463   /// only uses types natively supported by the target.
    464   /// Returns "true" if it made any changes.
    465   ///
    466   /// Note that this is an involved process that may invalidate pointers into
    467   /// the graph.
    468   bool LegalizeTypes();
    469 
    470   /// This transforms the SelectionDAG into a SelectionDAG that is
    471   /// compatible with the target instruction selector, as indicated by the
    472   /// TargetLowering object.
    473   ///
    474   /// Note that this is an involved process that may invalidate pointers into
    475   /// the graph.
    476   void Legalize();
    477 
    478   /// \brief Transforms a SelectionDAG node and any operands to it into a node
    479   /// that is compatible with the target instruction selector, as indicated by
    480   /// the TargetLowering object.
    481   ///
    482   /// \returns true if \c N is a valid, legal node after calling this.
    483   ///
    484   /// This essentially runs a single recursive walk of the \c Legalize process
    485   /// over the given node (and its operands). This can be used to incrementally
    486   /// legalize the DAG. All of the nodes which are directly replaced,
    487   /// potentially including N, are added to the output parameter \c
    488   /// UpdatedNodes so that the delta to the DAG can be understood by the
    489   /// caller.
    490   ///
    491   /// When this returns false, N has been legalized in a way that make the
    492   /// pointer passed in no longer valid. It may have even been deleted from the
    493   /// DAG, and so it shouldn't be used further. When this returns true, the
    494   /// N passed in is a legal node, and can be immediately processed as such.
    495   /// This may still have done some work on the DAG, and will still populate
    496   /// UpdatedNodes with any new nodes replacing those originally in the DAG.
    497   bool LegalizeOp(SDNode *N, SmallSetVector<SDNode *, 16> &UpdatedNodes);
    498 
    499   /// This transforms the SelectionDAG into a SelectionDAG
    500   /// that only uses vector math operations supported by the target.  This is
    501   /// necessary as a separate step from Legalize because unrolling a vector
    502   /// operation can introduce illegal types, which requires running
    503   /// LegalizeTypes again.
    504   ///
    505   /// This returns true if it made any changes; in that case, LegalizeTypes
    506   /// is called again before Legalize.
    507   ///
    508   /// Note that this is an involved process that may invalidate pointers into
    509   /// the graph.
    510   bool LegalizeVectors();
    511 
    512   /// This method deletes all unreachable nodes in the SelectionDAG.
    513   void RemoveDeadNodes();
    514 
    515   /// Remove the specified node from the system.  This node must
    516   /// have no referrers.
    517   void DeleteNode(SDNode *N);
    518 
    519   /// Return an SDVTList that represents the list of values specified.
    520   SDVTList getVTList(EVT VT);
    521   SDVTList getVTList(EVT VT1, EVT VT2);
    522   SDVTList getVTList(EVT VT1, EVT VT2, EVT VT3);
    523   SDVTList getVTList(EVT VT1, EVT VT2, EVT VT3, EVT VT4);
    524   SDVTList getVTList(ArrayRef<EVT> VTs);
    525 
    526   //===--------------------------------------------------------------------===//
    527   // Node creation methods.
    528 
    529   /// \brief Create a ConstantSDNode wrapping a constant value.
    530   /// If VT is a vector type, the constant is splatted into a BUILD_VECTOR.
    531   ///
    532   /// If only legal types can be produced, this does the necessary
    533   /// transformations (e.g., if the vector element type is illegal).
    534   /// @{
    535   SDValue getConstant(uint64_t Val, const SDLoc &DL, EVT VT,
    536                       bool isTarget = false, bool isOpaque = false);
    537   SDValue getConstant(const APInt &Val, const SDLoc &DL, EVT VT,
    538                       bool isTarget = false, bool isOpaque = false);
    539 
    540   SDValue getAllOnesConstant(const SDLoc &DL, EVT VT, bool IsTarget = false,
    541                              bool IsOpaque = false) {
    542     return getConstant(APInt::getAllOnesValue(VT.getScalarSizeInBits()), DL,
    543                        VT, IsTarget, IsOpaque);
    544   }
    545 
    546   SDValue getConstant(const ConstantInt &Val, const SDLoc &DL, EVT VT,
    547                       bool isTarget = false, bool isOpaque = false);
    548   SDValue getIntPtrConstant(uint64_t Val, const SDLoc &DL,
    549                             bool isTarget = false);
    550   SDValue getTargetConstant(uint64_t Val, const SDLoc &DL, EVT VT,
    551                             bool isOpaque = false) {
    552     return getConstant(Val, DL, VT, true, isOpaque);
    553   }
    554   SDValue getTargetConstant(const APInt &Val, const SDLoc &DL, EVT VT,
    555                             bool isOpaque = false) {
    556     return getConstant(Val, DL, VT, true, isOpaque);
    557   }
    558   SDValue getTargetConstant(const ConstantInt &Val, const SDLoc &DL, EVT VT,
    559                             bool isOpaque = false) {
    560     return getConstant(Val, DL, VT, true, isOpaque);
    561   }
    562   /// @}
    563 
    564   /// \brief Create a ConstantFPSDNode wrapping a constant value.
    565   /// If VT is a vector type, the constant is splatted into a BUILD_VECTOR.
    566   ///
    567   /// If only legal types can be produced, this does the necessary
    568   /// transformations (e.g., if the vector element type is illegal).
    569   /// The forms that take a double should only be used for simple constants
    570   /// that can be exactly represented in VT.  No checks are made.
    571   /// @{
    572   SDValue getConstantFP(double Val, const SDLoc &DL, EVT VT,
    573                         bool isTarget = false);
    574   SDValue getConstantFP(const APFloat &Val, const SDLoc &DL, EVT VT,
    575                         bool isTarget = false);
    576   SDValue getConstantFP(const ConstantFP &CF, const SDLoc &DL, EVT VT,
    577                         bool isTarget = false);
    578   SDValue getTargetConstantFP(double Val, const SDLoc &DL, EVT VT) {
    579     return getConstantFP(Val, DL, VT, true);
    580   }
    581   SDValue getTargetConstantFP(const APFloat &Val, const SDLoc &DL, EVT VT) {
    582     return getConstantFP(Val, DL, VT, true);
    583   }
    584   SDValue getTargetConstantFP(const ConstantFP &Val, const SDLoc &DL, EVT VT) {
    585     return getConstantFP(Val, DL, VT, true);
    586   }
    587   /// @}
    588 
    589   SDValue getGlobalAddress(const GlobalValue *GV, const SDLoc &DL, EVT VT,
    590                            int64_t offset = 0, bool isTargetGA = false,
    591                            unsigned char TargetFlags = 0);
    592   SDValue getTargetGlobalAddress(const GlobalValue *GV, const SDLoc &DL, EVT VT,
    593                                  int64_t offset = 0,
    594                                  unsigned char TargetFlags = 0) {
    595     return getGlobalAddress(GV, DL, VT, offset, true, TargetFlags);
    596   }
    597   SDValue getFrameIndex(int FI, EVT VT, bool isTarget = false);
    598   SDValue getTargetFrameIndex(int FI, EVT VT) {
    599     return getFrameIndex(FI, VT, true);
    600   }
    601   SDValue getJumpTable(int JTI, EVT VT, bool isTarget = false,
    602                        unsigned char TargetFlags = 0);
    603   SDValue getTargetJumpTable(int JTI, EVT VT, unsigned char TargetFlags = 0) {
    604     return getJumpTable(JTI, VT, true, TargetFlags);
    605   }
    606   SDValue getConstantPool(const Constant *C, EVT VT,
    607                           unsigned Align = 0, int Offs = 0, bool isT=false,
    608                           unsigned char TargetFlags = 0);
    609   SDValue getTargetConstantPool(const Constant *C, EVT VT,
    610                                 unsigned Align = 0, int Offset = 0,
    611                                 unsigned char TargetFlags = 0) {
    612     return getConstantPool(C, VT, Align, Offset, true, TargetFlags);
    613   }
    614   SDValue getConstantPool(MachineConstantPoolValue *C, EVT VT,
    615                           unsigned Align = 0, int Offs = 0, bool isT=false,
    616                           unsigned char TargetFlags = 0);
    617   SDValue getTargetConstantPool(MachineConstantPoolValue *C,
    618                                   EVT VT, unsigned Align = 0,
    619                                   int Offset = 0, unsigned char TargetFlags=0) {
    620     return getConstantPool(C, VT, Align, Offset, true, TargetFlags);
    621   }
    622   SDValue getTargetIndex(int Index, EVT VT, int64_t Offset = 0,
    623                          unsigned char TargetFlags = 0);
    624   // When generating a branch to a BB, we don't in general know enough
    625   // to provide debug info for the BB at that time, so keep this one around.
    626   SDValue getBasicBlock(MachineBasicBlock *MBB);
    627   SDValue getBasicBlock(MachineBasicBlock *MBB, SDLoc dl);
    628   SDValue getExternalSymbol(const char *Sym, EVT VT);
    629   SDValue getExternalSymbol(const char *Sym, const SDLoc &dl, EVT VT);
    630   SDValue getTargetExternalSymbol(const char *Sym, EVT VT,
    631                                   unsigned char TargetFlags = 0);
    632   SDValue getMCSymbol(MCSymbol *Sym, EVT VT);
    633 
    634   SDValue getValueType(EVT);
    635   SDValue getRegister(unsigned Reg, EVT VT);
    636   SDValue getRegisterMask(const uint32_t *RegMask);
    637   SDValue getEHLabel(const SDLoc &dl, SDValue Root, MCSymbol *Label);
    638   SDValue getLabelNode(unsigned Opcode, const SDLoc &dl, SDValue Root,
    639                        MCSymbol *Label);
    640   SDValue getBlockAddress(const BlockAddress *BA, EVT VT,
    641                           int64_t Offset = 0, bool isTarget = false,
    642                           unsigned char TargetFlags = 0);
    643   SDValue getTargetBlockAddress(const BlockAddress *BA, EVT VT,
    644                                 int64_t Offset = 0,
    645                                 unsigned char TargetFlags = 0) {
    646     return getBlockAddress(BA, VT, Offset, true, TargetFlags);
    647   }
    648 
    649   SDValue getCopyToReg(SDValue Chain, const SDLoc &dl, unsigned Reg,
    650                        SDValue N) {
    651     return getNode(ISD::CopyToReg, dl, MVT::Other, Chain,
    652                    getRegister(Reg, N.getValueType()), N);
    653   }
    654 
    655   // This version of the getCopyToReg method takes an extra operand, which
    656   // indicates that there is potentially an incoming glue value (if Glue is not
    657   // null) and that there should be a glue result.
    658   SDValue getCopyToReg(SDValue Chain, const SDLoc &dl, unsigned Reg, SDValue N,
    659                        SDValue Glue) {
    660     SDVTList VTs = getVTList(MVT::Other, MVT::Glue);
    661     SDValue Ops[] = { Chain, getRegister(Reg, N.getValueType()), N, Glue };
    662     return getNode(ISD::CopyToReg, dl, VTs,
    663                    makeArrayRef(Ops, Glue.getNode() ? 4 : 3));
    664   }
    665 
    666   // Similar to last getCopyToReg() except parameter Reg is a SDValue
    667   SDValue getCopyToReg(SDValue Chain, const SDLoc &dl, SDValue Reg, SDValue N,
    668                        SDValue Glue) {
    669     SDVTList VTs = getVTList(MVT::Other, MVT::Glue);
    670     SDValue Ops[] = { Chain, Reg, N, Glue };
    671     return getNode(ISD::CopyToReg, dl, VTs,
    672                    makeArrayRef(Ops, Glue.getNode() ? 4 : 3));
    673   }
    674 
    675   SDValue getCopyFromReg(SDValue Chain, const SDLoc &dl, unsigned Reg, EVT VT) {
    676     SDVTList VTs = getVTList(VT, MVT::Other);
    677     SDValue Ops[] = { Chain, getRegister(Reg, VT) };
    678     return getNode(ISD::CopyFromReg, dl, VTs, Ops);
    679   }
    680 
    681   // This version of the getCopyFromReg method takes an extra operand, which
    682   // indicates that there is potentially an incoming glue value (if Glue is not
    683   // null) and that there should be a glue result.
    684   SDValue getCopyFromReg(SDValue Chain, const SDLoc &dl, unsigned Reg, EVT VT,
    685                          SDValue Glue) {
    686     SDVTList VTs = getVTList(VT, MVT::Other, MVT::Glue);
    687     SDValue Ops[] = { Chain, getRegister(Reg, VT), Glue };
    688     return getNode(ISD::CopyFromReg, dl, VTs,
    689                    makeArrayRef(Ops, Glue.getNode() ? 3 : 2));
    690   }
    691 
    692   SDValue getCondCode(ISD::CondCode Cond);
    693 
    694   /// Return an ISD::VECTOR_SHUFFLE node. The number of elements in VT,
    695   /// which must be a vector type, must match the number of mask elements
    696   /// NumElts. An integer mask element equal to -1 is treated as undefined.
    697   SDValue getVectorShuffle(EVT VT, const SDLoc &dl, SDValue N1, SDValue N2,
    698                            ArrayRef<int> Mask);
    699 
    700   /// Return an ISD::BUILD_VECTOR node. The number of elements in VT,
    701   /// which must be a vector type, must match the number of operands in Ops.
    702   /// The operands must have the same type as (or, for integers, a type wider
    703   /// than) VT's element type.
    704   SDValue getBuildVector(EVT VT, const SDLoc &DL, ArrayRef<SDValue> Ops) {
    705     // VerifySDNode (via InsertNode) checks BUILD_VECTOR later.
    706     return getNode(ISD::BUILD_VECTOR, DL, VT, Ops);
    707   }
    708 
    709   /// Return an ISD::BUILD_VECTOR node. The number of elements in VT,
    710   /// which must be a vector type, must match the number of operands in Ops.
    711   /// The operands must have the same type as (or, for integers, a type wider
    712   /// than) VT's element type.
    713   SDValue getBuildVector(EVT VT, const SDLoc &DL, ArrayRef<SDUse> Ops) {
    714     // VerifySDNode (via InsertNode) checks BUILD_VECTOR later.
    715     return getNode(ISD::BUILD_VECTOR, DL, VT, Ops);
    716   }
    717 
    718   /// Return a splat ISD::BUILD_VECTOR node, consisting of Op splatted to all
    719   /// elements. VT must be a vector type. Op's type must be the same as (or,
    720   /// for integers, a type wider than) VT's element type.
    721   SDValue getSplatBuildVector(EVT VT, const SDLoc &DL, SDValue Op) {
    722     // VerifySDNode (via InsertNode) checks BUILD_VECTOR later.
    723     if (Op.getOpcode() == ISD::UNDEF) {
    724       assert((VT.getVectorElementType() == Op.getValueType() ||
    725               (VT.isInteger() &&
    726                VT.getVectorElementType().bitsLE(Op.getValueType()))) &&
    727              "A splatted value must have a width equal or (for integers) "
    728              "greater than the vector element type!");
    729       return getNode(ISD::UNDEF, SDLoc(), VT);
    730     }
    731 
    732     SmallVector<SDValue, 16> Ops(VT.getVectorNumElements(), Op);
    733     return getNode(ISD::BUILD_VECTOR, DL, VT, Ops);
    734   }
    735 
    736   /// \brief Returns an ISD::VECTOR_SHUFFLE node semantically equivalent to
    737   /// the shuffle node in input but with swapped operands.
    738   ///
    739   /// Example: shuffle A, B, <0,5,2,7> -> shuffle B, A, <4,1,6,3>
    740   SDValue getCommutedVectorShuffle(const ShuffleVectorSDNode &SV);
    741 
    742   /// Convert Op, which must be of float type, to the
    743   /// float type VT, by either extending or rounding (by truncation).
    744   SDValue getFPExtendOrRound(SDValue Op, const SDLoc &DL, EVT VT);
    745 
    746   /// Convert Op, which must be of integer type, to the
    747   /// integer type VT, by either any-extending or truncating it.
    748   SDValue getAnyExtOrTrunc(SDValue Op, const SDLoc &DL, EVT VT);
    749 
    750   /// Convert Op, which must be of integer type, to the
    751   /// integer type VT, by either sign-extending or truncating it.
    752   SDValue getSExtOrTrunc(SDValue Op, const SDLoc &DL, EVT VT);
    753 
    754   /// Convert Op, which must be of integer type, to the
    755   /// integer type VT, by either zero-extending or truncating it.
    756   SDValue getZExtOrTrunc(SDValue Op, const SDLoc &DL, EVT VT);
    757 
    758   /// Return the expression required to zero extend the Op
    759   /// value assuming it was the smaller SrcTy value.
    760   SDValue getZeroExtendInReg(SDValue Op, const SDLoc &DL, EVT SrcTy);
    761 
    762   /// Return an operation which will any-extend the low lanes of the operand
    763   /// into the specified vector type. For example,
    764   /// this can convert a v16i8 into a v4i32 by any-extending the low four
    765   /// lanes of the operand from i8 to i32.
    766   SDValue getAnyExtendVectorInReg(SDValue Op, const SDLoc &DL, EVT VT);
    767 
    768   /// Return an operation which will sign extend the low lanes of the operand
    769   /// into the specified vector type. For example,
    770   /// this can convert a v16i8 into a v4i32 by sign extending the low four
    771   /// lanes of the operand from i8 to i32.
    772   SDValue getSignExtendVectorInReg(SDValue Op, const SDLoc &DL, EVT VT);
    773 
    774   /// Return an operation which will zero extend the low lanes of the operand
    775   /// into the specified vector type. For example,
    776   /// this can convert a v16i8 into a v4i32 by zero extending the low four
    777   /// lanes of the operand from i8 to i32.
    778   SDValue getZeroExtendVectorInReg(SDValue Op, const SDLoc &DL, EVT VT);
    779 
    780   /// Convert Op, which must be of integer type, to the integer type VT,
    781   /// by using an extension appropriate for the target's
    782   /// BooleanContent for type OpVT or truncating it.
    783   SDValue getBoolExtOrTrunc(SDValue Op, const SDLoc &SL, EVT VT, EVT OpVT);
    784 
    785   /// Create a bitwise NOT operation as (XOR Val, -1).
    786   SDValue getNOT(const SDLoc &DL, SDValue Val, EVT VT);
    787 
    788   /// \brief Create a logical NOT operation as (XOR Val, BooleanOne).
    789   SDValue getLogicalNOT(const SDLoc &DL, SDValue Val, EVT VT);
    790 
    791   /// Return a new CALLSEQ_START node, that starts new call frame, in which
    792   /// InSize bytes are set up inside CALLSEQ_START..CALLSEQ_END sequence and
    793   /// OutSize specifies part of the frame set up prior to the sequence.
    794   SDValue getCALLSEQ_START(SDValue Chain, uint64_t InSize, uint64_t OutSize,
    795                            const SDLoc &DL) {
    796     SDVTList VTs = getVTList(MVT::Other, MVT::Glue);
    797     SDValue Ops[] = { Chain,
    798                       getIntPtrConstant(InSize, DL, true),
    799                       getIntPtrConstant(OutSize, DL, true) };
    800     return getNode(ISD::CALLSEQ_START, DL, VTs, Ops);
    801   }
    802 
    803   /// Return a new CALLSEQ_END node, which always must have a
    804   /// glue result (to ensure it's not CSE'd).
    805   /// CALLSEQ_END does not have a useful SDLoc.
    806   SDValue getCALLSEQ_END(SDValue Chain, SDValue Op1, SDValue Op2,
    807                          SDValue InGlue, const SDLoc &DL) {
    808     SDVTList NodeTys = getVTList(MVT::Other, MVT::Glue);
    809     SmallVector<SDValue, 4> Ops;
    810     Ops.push_back(Chain);
    811     Ops.push_back(Op1);
    812     Ops.push_back(Op2);
    813     if (InGlue.getNode())
    814       Ops.push_back(InGlue);
    815     return getNode(ISD::CALLSEQ_END, DL, NodeTys, Ops);
    816   }
    817 
    818   /// Return true if the result of this operation is always undefined.
    819   bool isUndef(unsigned Opcode, ArrayRef<SDValue> Ops);
    820 
    821   /// Return an UNDEF node. UNDEF does not have a useful SDLoc.
    822   SDValue getUNDEF(EVT VT) {
    823     return getNode(ISD::UNDEF, SDLoc(), VT);
    824   }
    825 
    826   /// Return a GLOBAL_OFFSET_TABLE node. This does not have a useful SDLoc.
    827   SDValue getGLOBAL_OFFSET_TABLE(EVT VT) {
    828     return getNode(ISD::GLOBAL_OFFSET_TABLE, SDLoc(), VT);
    829   }
    830 
    831   /// Gets or creates the specified node.
    832   ///
    833   SDValue getNode(unsigned Opcode, const SDLoc &DL, EVT VT,
    834                   ArrayRef<SDUse> Ops);
    835   SDValue getNode(unsigned Opcode, const SDLoc &DL, EVT VT,
    836                   ArrayRef<SDValue> Ops, const SDNodeFlags Flags = SDNodeFlags());
    837   SDValue getNode(unsigned Opcode, const SDLoc &DL, ArrayRef<EVT> ResultTys,
    838                   ArrayRef<SDValue> Ops);
    839   SDValue getNode(unsigned Opcode, const SDLoc &DL, SDVTList VTs,
    840                   ArrayRef<SDValue> Ops);
    841 
    842   // Specialize based on number of operands.
    843   SDValue getNode(unsigned Opcode, const SDLoc &DL, EVT VT);
    844   SDValue getNode(unsigned Opcode, const SDLoc &DL, EVT VT, SDValue N,
    845                   const SDNodeFlags Flags = SDNodeFlags());
    846   SDValue getNode(unsigned Opcode, const SDLoc &DL, EVT VT, SDValue N1,
    847                   SDValue N2, const SDNodeFlags Flags = SDNodeFlags());
    848   SDValue getNode(unsigned Opcode, const SDLoc &DL, EVT VT, SDValue N1,
    849                   SDValue N2, SDValue N3);
    850   SDValue getNode(unsigned Opcode, const SDLoc &DL, EVT VT, SDValue N1,
    851                   SDValue N2, SDValue N3, SDValue N4);
    852   SDValue getNode(unsigned Opcode, const SDLoc &DL, EVT VT, SDValue N1,
    853                   SDValue N2, SDValue N3, SDValue N4, SDValue N5);
    854 
    855   // Specialize again based on number of operands for nodes with a VTList
    856   // rather than a single VT.
    857   SDValue getNode(unsigned Opcode, const SDLoc &DL, SDVTList VTs);
    858   SDValue getNode(unsigned Opcode, const SDLoc &DL, SDVTList VTs, SDValue N);
    859   SDValue getNode(unsigned Opcode, const SDLoc &DL, SDVTList VTs, SDValue N1,
    860                   SDValue N2);
    861   SDValue getNode(unsigned Opcode, const SDLoc &DL, SDVTList VTs, SDValue N1,
    862                   SDValue N2, SDValue N3);
    863   SDValue getNode(unsigned Opcode, const SDLoc &DL, SDVTList VTs, SDValue N1,
    864                   SDValue N2, SDValue N3, SDValue N4);
    865   SDValue getNode(unsigned Opcode, const SDLoc &DL, SDVTList VTs, SDValue N1,
    866                   SDValue N2, SDValue N3, SDValue N4, SDValue N5);
    867 
    868   /// Compute a TokenFactor to force all the incoming stack arguments to be
    869   /// loaded from the stack. This is used in tail call lowering to protect
    870   /// stack arguments from being clobbered.
    871   SDValue getStackArgumentTokenFactor(SDValue Chain);
    872 
    873   SDValue getMemcpy(SDValue Chain, const SDLoc &dl, SDValue Dst, SDValue Src,
    874                     SDValue Size, unsigned Align, bool isVol, bool AlwaysInline,
    875                     bool isTailCall, MachinePointerInfo DstPtrInfo,
    876                     MachinePointerInfo SrcPtrInfo);
    877 
    878   SDValue getMemmove(SDValue Chain, const SDLoc &dl, SDValue Dst, SDValue Src,
    879                      SDValue Size, unsigned Align, bool isVol, bool isTailCall,
    880                      MachinePointerInfo DstPtrInfo,
    881                      MachinePointerInfo SrcPtrInfo);
    882 
    883   SDValue getMemset(SDValue Chain, const SDLoc &dl, SDValue Dst, SDValue Src,
    884                     SDValue Size, unsigned Align, bool isVol, bool isTailCall,
    885                     MachinePointerInfo DstPtrInfo);
    886 
    887   /// Helper function to make it easier to build SetCC's if you just
    888   /// have an ISD::CondCode instead of an SDValue.
    889   ///
    890   SDValue getSetCC(const SDLoc &DL, EVT VT, SDValue LHS, SDValue RHS,
    891                    ISD::CondCode Cond) {
    892     assert(LHS.getValueType().isVector() == RHS.getValueType().isVector() &&
    893       "Cannot compare scalars to vectors");
    894     assert(LHS.getValueType().isVector() == VT.isVector() &&
    895       "Cannot compare scalars to vectors");
    896     assert(Cond != ISD::SETCC_INVALID &&
    897         "Cannot create a setCC of an invalid node.");
    898     return getNode(ISD::SETCC, DL, VT, LHS, RHS, getCondCode(Cond));
    899   }
    900 
    901   /// Helper function to make it easier to build Select's if you just
    902   /// have operands and don't want to check for vector.
    903   SDValue getSelect(const SDLoc &DL, EVT VT, SDValue Cond, SDValue LHS,
    904                     SDValue RHS) {
    905     assert(LHS.getValueType() == RHS.getValueType() &&
    906            "Cannot use select on differing types");
    907     assert(VT.isVector() == LHS.getValueType().isVector() &&
    908            "Cannot mix vectors and scalars");
    909     return getNode(Cond.getValueType().isVector() ? ISD::VSELECT : ISD::SELECT, DL, VT,
    910                    Cond, LHS, RHS);
    911   }
    912 
    913   /// Helper function to make it easier to build SelectCC's if you
    914   /// just have an ISD::CondCode instead of an SDValue.
    915   ///
    916   SDValue getSelectCC(const SDLoc &DL, SDValue LHS, SDValue RHS, SDValue True,
    917                       SDValue False, ISD::CondCode Cond) {
    918     return getNode(ISD::SELECT_CC, DL, True.getValueType(),
    919                    LHS, RHS, True, False, getCondCode(Cond));
    920   }
    921 
    922   /// VAArg produces a result and token chain, and takes a pointer
    923   /// and a source value as input.
    924   SDValue getVAArg(EVT VT, const SDLoc &dl, SDValue Chain, SDValue Ptr,
    925                    SDValue SV, unsigned Align);
    926 
    927   /// Gets a node for an atomic cmpxchg op. There are two
    928   /// valid Opcodes. ISD::ATOMIC_CMO_SWAP produces the value loaded and a
    929   /// chain result. ISD::ATOMIC_CMP_SWAP_WITH_SUCCESS produces the value loaded,
    930   /// a success flag (initially i1), and a chain.
    931   SDValue getAtomicCmpSwap(unsigned Opcode, const SDLoc &dl, EVT MemVT,
    932                            SDVTList VTs, SDValue Chain, SDValue Ptr,
    933                            SDValue Cmp, SDValue Swp, MachinePointerInfo PtrInfo,
    934                            unsigned Alignment, AtomicOrdering SuccessOrdering,
    935                            AtomicOrdering FailureOrdering,
    936                            SyncScope::ID SSID);
    937   SDValue getAtomicCmpSwap(unsigned Opcode, const SDLoc &dl, EVT MemVT,
    938                            SDVTList VTs, SDValue Chain, SDValue Ptr,
    939                            SDValue Cmp, SDValue Swp, MachineMemOperand *MMO);
    940 
    941   /// Gets a node for an atomic op, produces result (if relevant)
    942   /// and chain and takes 2 operands.
    943   SDValue getAtomic(unsigned Opcode, const SDLoc &dl, EVT MemVT, SDValue Chain,
    944                     SDValue Ptr, SDValue Val, const Value *PtrVal,
    945                     unsigned Alignment, AtomicOrdering Ordering,
    946                     SyncScope::ID SSID);
    947   SDValue getAtomic(unsigned Opcode, const SDLoc &dl, EVT MemVT, SDValue Chain,
    948                     SDValue Ptr, SDValue Val, MachineMemOperand *MMO);
    949 
    950   /// Gets a node for an atomic op, produces result and chain and
    951   /// takes 1 operand.
    952   SDValue getAtomic(unsigned Opcode, const SDLoc &dl, EVT MemVT, EVT VT,
    953                     SDValue Chain, SDValue Ptr, MachineMemOperand *MMO);
    954 
    955   /// Gets a node for an atomic op, produces result and chain and takes N
    956   /// operands.
    957   SDValue getAtomic(unsigned Opcode, const SDLoc &dl, EVT MemVT,
    958                     SDVTList VTList, ArrayRef<SDValue> Ops,
    959                     MachineMemOperand *MMO);
    960 
    961   /// Creates a MemIntrinsicNode that may produce a
    962   /// result and takes a list of operands. Opcode may be INTRINSIC_VOID,
    963   /// INTRINSIC_W_CHAIN, or a target-specific opcode with a value not
    964   /// less than FIRST_TARGET_MEMORY_OPCODE.
    965   SDValue getMemIntrinsicNode(unsigned Opcode, const SDLoc &dl, SDVTList VTList,
    966                               ArrayRef<SDValue> Ops, EVT MemVT,
    967                               MachinePointerInfo PtrInfo, unsigned Align = 0,
    968                               bool Vol = false, bool ReadMem = true,
    969                               bool WriteMem = true, unsigned Size = 0);
    970 
    971   SDValue getMemIntrinsicNode(unsigned Opcode, const SDLoc &dl, SDVTList VTList,
    972                               ArrayRef<SDValue> Ops, EVT MemVT,
    973                               MachineMemOperand *MMO);
    974 
    975   /// Create a MERGE_VALUES node from the given operands.
    976   SDValue getMergeValues(ArrayRef<SDValue> Ops, const SDLoc &dl);
    977 
    978   /// Loads are not normal binary operators: their result type is not
    979   /// determined by their operands, and they produce a value AND a token chain.
    980   ///
    981   /// This function will set the MOLoad flag on MMOFlags, but you can set it if
    982   /// you want.  The MOStore flag must not be set.
    983   SDValue getLoad(EVT VT, const SDLoc &dl, SDValue Chain, SDValue Ptr,
    984                   MachinePointerInfo PtrInfo, unsigned Alignment = 0,
    985                   MachineMemOperand::Flags MMOFlags = MachineMemOperand::MONone,
    986                   const AAMDNodes &AAInfo = AAMDNodes(),
    987                   const MDNode *Ranges = nullptr);
    988   SDValue getLoad(EVT VT, const SDLoc &dl, SDValue Chain, SDValue Ptr,
    989                   MachineMemOperand *MMO);
    990   SDValue
    991   getExtLoad(ISD::LoadExtType ExtType, const SDLoc &dl, EVT VT, SDValue Chain,
    992              SDValue Ptr, MachinePointerInfo PtrInfo, EVT MemVT,
    993              unsigned Alignment = 0,
    994              MachineMemOperand::Flags MMOFlags = MachineMemOperand::MONone,
    995              const AAMDNodes &AAInfo = AAMDNodes());
    996   SDValue getExtLoad(ISD::LoadExtType ExtType, const SDLoc &dl, EVT VT,
    997                      SDValue Chain, SDValue Ptr, EVT MemVT,
    998                      MachineMemOperand *MMO);
    999   SDValue getIndexedLoad(SDValue OrigLoad, const SDLoc &dl, SDValue Base,
   1000                          SDValue Offset, ISD::MemIndexedMode AM);
   1001   SDValue getLoad(ISD::MemIndexedMode AM, ISD::LoadExtType ExtType, EVT VT,
   1002                   const SDLoc &dl, SDValue Chain, SDValue Ptr, SDValue Offset,
   1003                   MachinePointerInfo PtrInfo, EVT MemVT, unsigned Alignment = 0,
   1004                   MachineMemOperand::Flags MMOFlags = MachineMemOperand::MONone,
   1005                   const AAMDNodes &AAInfo = AAMDNodes(),
   1006                   const MDNode *Ranges = nullptr);
   1007   SDValue getLoad(ISD::MemIndexedMode AM, ISD::LoadExtType ExtType, EVT VT,
   1008                   const SDLoc &dl, SDValue Chain, SDValue Ptr, SDValue Offset,
   1009                   EVT MemVT, MachineMemOperand *MMO);
   1010 
   1011   /// Helper function to build ISD::STORE nodes.
   1012   ///
   1013   /// This function will set the MOStore flag on MMOFlags, but you can set it if
   1014   /// you want.  The MOLoad and MOInvariant flags must not be set.
   1015   SDValue
   1016   getStore(SDValue Chain, const SDLoc &dl, SDValue Val, SDValue Ptr,
   1017            MachinePointerInfo PtrInfo, unsigned Alignment = 0,
   1018            MachineMemOperand::Flags MMOFlags = MachineMemOperand::MONone,
   1019            const AAMDNodes &AAInfo = AAMDNodes());
   1020   SDValue getStore(SDValue Chain, const SDLoc &dl, SDValue Val, SDValue Ptr,
   1021                    MachineMemOperand *MMO);
   1022   SDValue
   1023   getTruncStore(SDValue Chain, const SDLoc &dl, SDValue Val, SDValue Ptr,
   1024                 MachinePointerInfo PtrInfo, EVT TVT, unsigned Alignment = 0,
   1025                 MachineMemOperand::Flags MMOFlags = MachineMemOperand::MONone,
   1026                 const AAMDNodes &AAInfo = AAMDNodes());
   1027   SDValue getTruncStore(SDValue Chain, const SDLoc &dl, SDValue Val,
   1028                         SDValue Ptr, EVT TVT, MachineMemOperand *MMO);
   1029   SDValue getIndexedStore(SDValue OrigStoe, const SDLoc &dl, SDValue Base,
   1030                           SDValue Offset, ISD::MemIndexedMode AM);
   1031 
   1032   /// Returns sum of the base pointer and offset.
   1033   SDValue getMemBasePlusOffset(SDValue Base, unsigned Offset, const SDLoc &DL);
   1034 
   1035   SDValue getMaskedLoad(EVT VT, const SDLoc &dl, SDValue Chain, SDValue Ptr,
   1036                         SDValue Mask, SDValue Src0, EVT MemVT,
   1037                         MachineMemOperand *MMO, ISD::LoadExtType,
   1038                         bool IsExpanding = false);
   1039   SDValue getMaskedStore(SDValue Chain, const SDLoc &dl, SDValue Val,
   1040                          SDValue Ptr, SDValue Mask, EVT MemVT,
   1041                          MachineMemOperand *MMO, bool IsTruncating = false,
   1042                          bool IsCompressing = false);
   1043   SDValue getMaskedGather(SDVTList VTs, EVT VT, const SDLoc &dl,
   1044                           ArrayRef<SDValue> Ops, MachineMemOperand *MMO);
   1045   SDValue getMaskedScatter(SDVTList VTs, EVT VT, const SDLoc &dl,
   1046                            ArrayRef<SDValue> Ops, MachineMemOperand *MMO);
   1047 
   1048   /// Return (create a new or find existing) a target-specific node.
   1049   /// TargetMemSDNode should be derived class from MemSDNode.
   1050   template <class TargetMemSDNode>
   1051   SDValue getTargetMemSDNode(SDVTList VTs, ArrayRef<SDValue> Ops,
   1052                              const SDLoc &dl, EVT MemVT,
   1053                              MachineMemOperand *MMO);
   1054 
   1055   /// Construct a node to track a Value* through the backend.
   1056   SDValue getSrcValue(const Value *v);
   1057 
   1058   /// Return an MDNodeSDNode which holds an MDNode.
   1059   SDValue getMDNode(const MDNode *MD);
   1060 
   1061   /// Return a bitcast using the SDLoc of the value operand, and casting to the
   1062   /// provided type. Use getNode to set a custom SDLoc.
   1063   SDValue getBitcast(EVT VT, SDValue V);
   1064 
   1065   /// Return an AddrSpaceCastSDNode.
   1066   SDValue getAddrSpaceCast(const SDLoc &dl, EVT VT, SDValue Ptr, unsigned SrcAS,
   1067                            unsigned DestAS);
   1068 
   1069   /// Return the specified value casted to
   1070   /// the target's desired shift amount type.
   1071   SDValue getShiftAmountOperand(EVT LHSTy, SDValue Op);
   1072 
   1073   /// Expand the specified \c ISD::VAARG node as the Legalize pass would.
   1074   SDValue expandVAArg(SDNode *Node);
   1075 
   1076   /// Expand the specified \c ISD::VACOPY node as the Legalize pass would.
   1077   SDValue expandVACopy(SDNode *Node);
   1078 
   1079   /// *Mutate* the specified node in-place to have the
   1080   /// specified operands.  If the resultant node already exists in the DAG,
   1081   /// this does not modify the specified node, instead it returns the node that
   1082   /// already exists.  If the resultant node does not exist in the DAG, the
   1083   /// input node is returned.  As a degenerate case, if you specify the same
   1084   /// input operands as the node already has, the input node is returned.
   1085   SDNode *UpdateNodeOperands(SDNode *N, SDValue Op);
   1086   SDNode *UpdateNodeOperands(SDNode *N, SDValue Op1, SDValue Op2);
   1087   SDNode *UpdateNodeOperands(SDNode *N, SDValue Op1, SDValue Op2,
   1088                                SDValue Op3);
   1089   SDNode *UpdateNodeOperands(SDNode *N, SDValue Op1, SDValue Op2,
   1090                                SDValue Op3, SDValue Op4);
   1091   SDNode *UpdateNodeOperands(SDNode *N, SDValue Op1, SDValue Op2,
   1092                                SDValue Op3, SDValue Op4, SDValue Op5);
   1093   SDNode *UpdateNodeOperands(SDNode *N, ArrayRef<SDValue> Ops);
   1094 
   1095   /// These are used for target selectors to *mutate* the
   1096   /// specified node to have the specified return type, Target opcode, and
   1097   /// operands.  Note that target opcodes are stored as
   1098   /// ~TargetOpcode in the node opcode field.  The resultant node is returned.
   1099   SDNode *SelectNodeTo(SDNode *N, unsigned TargetOpc, EVT VT);
   1100   SDNode *SelectNodeTo(SDNode *N, unsigned TargetOpc, EVT VT, SDValue Op1);
   1101   SDNode *SelectNodeTo(SDNode *N, unsigned TargetOpc, EVT VT,
   1102                        SDValue Op1, SDValue Op2);
   1103   SDNode *SelectNodeTo(SDNode *N, unsigned TargetOpc, EVT VT,
   1104                        SDValue Op1, SDValue Op2, SDValue Op3);
   1105   SDNode *SelectNodeTo(SDNode *N, unsigned TargetOpc, EVT VT,
   1106                        ArrayRef<SDValue> Ops);
   1107   SDNode *SelectNodeTo(SDNode *N, unsigned TargetOpc, EVT VT1, EVT VT2);
   1108   SDNode *SelectNodeTo(SDNode *N, unsigned TargetOpc, EVT VT1,
   1109                        EVT VT2, ArrayRef<SDValue> Ops);
   1110   SDNode *SelectNodeTo(SDNode *N, unsigned TargetOpc, EVT VT1,
   1111                        EVT VT2, EVT VT3, ArrayRef<SDValue> Ops);
   1112   SDNode *SelectNodeTo(SDNode *N, unsigned TargetOpc, EVT VT1,
   1113                        EVT VT2, SDValue Op1);
   1114   SDNode *SelectNodeTo(SDNode *N, unsigned TargetOpc, EVT VT1,
   1115                        EVT VT2, SDValue Op1, SDValue Op2);
   1116   SDNode *SelectNodeTo(SDNode *N, unsigned TargetOpc, SDVTList VTs,
   1117                        ArrayRef<SDValue> Ops);
   1118 
   1119   /// This *mutates* the specified node to have the specified
   1120   /// return type, opcode, and operands.
   1121   SDNode *MorphNodeTo(SDNode *N, unsigned Opc, SDVTList VTs,
   1122                       ArrayRef<SDValue> Ops);
   1123 
   1124   /// Mutate the specified strict FP node to its non-strict equivalent,
   1125   /// unlinking the node from its chain and dropping the metadata arguments.
   1126   /// The node must be a strict FP node.
   1127   SDNode *mutateStrictFPToFP(SDNode *Node);
   1128 
   1129   /// These are used for target selectors to create a new node
   1130   /// with specified return type(s), MachineInstr opcode, and operands.
   1131   ///
   1132   /// Note that getMachineNode returns the resultant node.  If there is already
   1133   /// a node of the specified opcode and operands, it returns that node instead
   1134   /// of the current one.
   1135   MachineSDNode *getMachineNode(unsigned Opcode, const SDLoc &dl, EVT VT);
   1136   MachineSDNode *getMachineNode(unsigned Opcode, const SDLoc &dl, EVT VT,
   1137                                 SDValue Op1);
   1138   MachineSDNode *getMachineNode(unsigned Opcode, const SDLoc &dl, EVT VT,
   1139                                 SDValue Op1, SDValue Op2);
   1140   MachineSDNode *getMachineNode(unsigned Opcode, const SDLoc &dl, EVT VT,
   1141                                 SDValue Op1, SDValue Op2, SDValue Op3);
   1142   MachineSDNode *getMachineNode(unsigned Opcode, const SDLoc &dl, EVT VT,
   1143                                 ArrayRef<SDValue> Ops);
   1144   MachineSDNode *getMachineNode(unsigned Opcode, const SDLoc &dl, EVT VT1,
   1145                                 EVT VT2, SDValue Op1, SDValue Op2);
   1146   MachineSDNode *getMachineNode(unsigned Opcode, const SDLoc &dl, EVT VT1,
   1147                                 EVT VT2, SDValue Op1, SDValue Op2, SDValue Op3);
   1148   MachineSDNode *getMachineNode(unsigned Opcode, const SDLoc &dl, EVT VT1,
   1149                                 EVT VT2, ArrayRef<SDValue> Ops);
   1150   MachineSDNode *getMachineNode(unsigned Opcode, const SDLoc &dl, EVT VT1,
   1151                                 EVT VT2, EVT VT3, SDValue Op1, SDValue Op2);
   1152   MachineSDNode *getMachineNode(unsigned Opcode, const SDLoc &dl, EVT VT1,
   1153                                 EVT VT2, EVT VT3, SDValue Op1, SDValue Op2,
   1154                                 SDValue Op3);
   1155   MachineSDNode *getMachineNode(unsigned Opcode, const SDLoc &dl, EVT VT1,
   1156                                 EVT VT2, EVT VT3, ArrayRef<SDValue> Ops);
   1157   MachineSDNode *getMachineNode(unsigned Opcode, const SDLoc &dl,
   1158                                 ArrayRef<EVT> ResultTys, ArrayRef<SDValue> Ops);
   1159   MachineSDNode *getMachineNode(unsigned Opcode, const SDLoc &dl, SDVTList VTs,
   1160                                 ArrayRef<SDValue> Ops);
   1161 
   1162   /// A convenience function for creating TargetInstrInfo::EXTRACT_SUBREG nodes.
   1163   SDValue getTargetExtractSubreg(int SRIdx, const SDLoc &DL, EVT VT,
   1164                                  SDValue Operand);
   1165 
   1166   /// A convenience function for creating TargetInstrInfo::INSERT_SUBREG nodes.
   1167   SDValue getTargetInsertSubreg(int SRIdx, const SDLoc &DL, EVT VT,
   1168                                 SDValue Operand, SDValue Subreg);
   1169 
   1170   /// Get the specified node if it's already available, or else return NULL.
   1171   SDNode *getNodeIfExists(unsigned Opcode, SDVTList VTs, ArrayRef<SDValue> Ops,
   1172                           const SDNodeFlags Flags = SDNodeFlags());
   1173 
   1174   /// Creates a SDDbgValue node.
   1175   SDDbgValue *getDbgValue(DIVariable *Var, DIExpression *Expr, SDNode *N,
   1176                           unsigned R, bool IsIndirect, const DebugLoc &DL,
   1177                           unsigned O);
   1178 
   1179   /// Constant
   1180   SDDbgValue *getConstantDbgValue(DIVariable *Var, DIExpression *Expr,
   1181                                   const Value *C, const DebugLoc &DL,
   1182                                   unsigned O);
   1183 
   1184   /// FrameIndex
   1185   SDDbgValue *getFrameIndexDbgValue(DIVariable *Var, DIExpression *Expr,
   1186                                     unsigned FI, const DebugLoc &DL,
   1187                                     unsigned O);
   1188 
   1189   /// Remove the specified node from the system. If any of its
   1190   /// operands then becomes dead, remove them as well. Inform UpdateListener
   1191   /// for each node deleted.
   1192   void RemoveDeadNode(SDNode *N);
   1193 
   1194   /// This method deletes the unreachable nodes in the
   1195   /// given list, and any nodes that become unreachable as a result.
   1196   void RemoveDeadNodes(SmallVectorImpl<SDNode *> &DeadNodes);
   1197 
   1198   /// Modify anything using 'From' to use 'To' instead.
   1199   /// This can cause recursive merging of nodes in the DAG.  Use the first
   1200   /// version if 'From' is known to have a single result, use the second
   1201   /// if you have two nodes with identical results (or if 'To' has a superset
   1202   /// of the results of 'From'), use the third otherwise.
   1203   ///
   1204   /// These methods all take an optional UpdateListener, which (if not null) is
   1205   /// informed about nodes that are deleted and modified due to recursive
   1206   /// changes in the dag.
   1207   ///
   1208   /// These functions only replace all existing uses. It's possible that as
   1209   /// these replacements are being performed, CSE may cause the From node
   1210   /// to be given new uses. These new uses of From are left in place, and
   1211   /// not automatically transferred to To.
   1212   ///
   1213   void ReplaceAllUsesWith(SDValue From, SDValue Op);
   1214   void ReplaceAllUsesWith(SDNode *From, SDNode *To);
   1215   void ReplaceAllUsesWith(SDNode *From, const SDValue *To);
   1216 
   1217   /// Replace any uses of From with To, leaving
   1218   /// uses of other values produced by From.Val alone.
   1219   void ReplaceAllUsesOfValueWith(SDValue From, SDValue To);
   1220 
   1221   /// Like ReplaceAllUsesOfValueWith, but for multiple values at once.
   1222   /// This correctly handles the case where
   1223   /// there is an overlap between the From values and the To values.
   1224   void ReplaceAllUsesOfValuesWith(const SDValue *From, const SDValue *To,
   1225                                   unsigned Num);
   1226 
   1227   /// If an existing load has uses of its chain, create a token factor node with
   1228   /// that chain and the new memory node's chain and update users of the old
   1229   /// chain to the token factor. This ensures that the new memory node will have
   1230   /// the same relative memory dependency position as the old load. Returns the
   1231   /// new merged load chain.
   1232   SDValue makeEquivalentMemoryOrdering(LoadSDNode *Old, SDValue New);
   1233 
   1234   /// Topological-sort the AllNodes list and a
   1235   /// assign a unique node id for each node in the DAG based on their
   1236   /// topological order. Returns the number of nodes.
   1237   unsigned AssignTopologicalOrder();
   1238 
   1239   /// Move node N in the AllNodes list to be immediately
   1240   /// before the given iterator Position. This may be used to update the
   1241   /// topological ordering when the list of nodes is modified.
   1242   void RepositionNode(allnodes_iterator Position, SDNode *N) {
   1243     AllNodes.insert(Position, AllNodes.remove(N));
   1244   }
   1245 
   1246   /// Returns an APFloat semantics tag appropriate for the given type. If VT is
   1247   /// a vector type, the element semantics are returned.
   1248   static const fltSemantics &EVTToAPFloatSemantics(EVT VT) {
   1249     switch (VT.getScalarType().getSimpleVT().SimpleTy) {
   1250     default: llvm_unreachable("Unknown FP format");
   1251     case MVT::f16:     return APFloat::IEEEhalf();
   1252     case MVT::f32:     return APFloat::IEEEsingle();
   1253     case MVT::f64:     return APFloat::IEEEdouble();
   1254     case MVT::f80:     return APFloat::x87DoubleExtended();
   1255     case MVT::f128:    return APFloat::IEEEquad();
   1256     case MVT::ppcf128: return APFloat::PPCDoubleDouble();
   1257     }
   1258   }
   1259 
   1260   /// Add a dbg_value SDNode. If SD is non-null that means the
   1261   /// value is produced by SD.
   1262   void AddDbgValue(SDDbgValue *DB, SDNode *SD, bool isParameter);
   1263 
   1264   /// Get the debug values which reference the given SDNode.
   1265   ArrayRef<SDDbgValue*> GetDbgValues(const SDNode* SD) {
   1266     return DbgInfo->getSDDbgValues(SD);
   1267   }
   1268 
   1269 private:
   1270   /// Transfer SDDbgValues. Called via ReplaceAllUses{OfValue}?With
   1271   void TransferDbgValues(SDValue From, SDValue To);
   1272 
   1273 public:
   1274   /// Return true if there are any SDDbgValue nodes associated
   1275   /// with this SelectionDAG.
   1276   bool hasDebugValues() const { return !DbgInfo->empty(); }
   1277 
   1278   SDDbgInfo::DbgIterator DbgBegin() { return DbgInfo->DbgBegin(); }
   1279   SDDbgInfo::DbgIterator DbgEnd()   { return DbgInfo->DbgEnd(); }
   1280 
   1281   SDDbgInfo::DbgIterator ByvalParmDbgBegin() {
   1282     return DbgInfo->ByvalParmDbgBegin();
   1283   }
   1284 
   1285   SDDbgInfo::DbgIterator ByvalParmDbgEnd()   {
   1286     return DbgInfo->ByvalParmDbgEnd();
   1287   }
   1288 
   1289   void dump() const;
   1290 
   1291   /// Create a stack temporary, suitable for holding the specified value type.
   1292   /// If minAlign is specified, the slot size will have at least that alignment.
   1293   SDValue CreateStackTemporary(EVT VT, unsigned minAlign = 1);
   1294 
   1295   /// Create a stack temporary suitable for holding either of the specified
   1296   /// value types.
   1297   SDValue CreateStackTemporary(EVT VT1, EVT VT2);
   1298 
   1299   SDValue FoldSymbolOffset(unsigned Opcode, EVT VT,
   1300                            const GlobalAddressSDNode *GA,
   1301                            const SDNode *N2);
   1302 
   1303   SDValue FoldConstantArithmetic(unsigned Opcode, const SDLoc &DL, EVT VT,
   1304                                  SDNode *Cst1, SDNode *Cst2);
   1305 
   1306   SDValue FoldConstantArithmetic(unsigned Opcode, const SDLoc &DL, EVT VT,
   1307                                  const ConstantSDNode *Cst1,
   1308                                  const ConstantSDNode *Cst2);
   1309 
   1310   SDValue FoldConstantVectorArithmetic(unsigned Opcode, const SDLoc &DL, EVT VT,
   1311                                        ArrayRef<SDValue> Ops,
   1312                                        const SDNodeFlags Flags = SDNodeFlags());
   1313 
   1314   /// Constant fold a setcc to true or false.
   1315   SDValue FoldSetCC(EVT VT, SDValue N1, SDValue N2, ISD::CondCode Cond,
   1316                     const SDLoc &dl);
   1317 
   1318   /// See if the specified operand can be simplified with the knowledge that only
   1319   /// the bits specified by Mask are used.  If so, return the simpler operand,
   1320   /// otherwise return a null SDValue.
   1321   ///
   1322   /// (This exists alongside SimplifyDemandedBits because GetDemandedBits can
   1323   /// simplify nodes with multiple uses more aggressively.)
   1324   SDValue GetDemandedBits(SDValue V, const APInt &Mask);
   1325 
   1326   /// Return true if the sign bit of Op is known to be zero.
   1327   /// We use this predicate to simplify operations downstream.
   1328   bool SignBitIsZero(SDValue Op, unsigned Depth = 0) const;
   1329 
   1330   /// Return true if 'Op & Mask' is known to be zero.  We
   1331   /// use this predicate to simplify operations downstream.  Op and Mask are
   1332   /// known to be the same type.
   1333   bool MaskedValueIsZero(SDValue Op, const APInt &Mask, unsigned Depth = 0)
   1334     const;
   1335 
   1336   /// Determine which bits of Op are known to be either zero or one and return
   1337   /// them in Known. For vectors, the known bits are those that are shared by
   1338   /// every vector element.
   1339   /// Targets can implement the computeKnownBitsForTargetNode method in the
   1340   /// TargetLowering class to allow target nodes to be understood.
   1341   void computeKnownBits(SDValue Op, KnownBits &Known, unsigned Depth = 0) const;
   1342 
   1343   /// Determine which bits of Op are known to be either zero or one and return
   1344   /// them in Known. The DemandedElts argument allows us to only collect the
   1345   /// known bits that are shared by the requested vector elements.
   1346   /// Targets can implement the computeKnownBitsForTargetNode method in the
   1347   /// TargetLowering class to allow target nodes to be understood.
   1348   void computeKnownBits(SDValue Op, KnownBits &Known, const APInt &DemandedElts,
   1349                         unsigned Depth = 0) const;
   1350 
   1351   /// Used to represent the possible overflow behavior of an operation.
   1352   /// Never: the operation cannot overflow.
   1353   /// Always: the operation will always overflow.
   1354   /// Sometime: the operation may or may not overflow.
   1355   enum OverflowKind {
   1356     OFK_Never,
   1357     OFK_Sometime,
   1358     OFK_Always,
   1359   };
   1360 
   1361   /// Determine if the result of the addition of 2 node can overflow.
   1362   OverflowKind computeOverflowKind(SDValue N0, SDValue N1) const;
   1363 
   1364   /// Test if the given value is known to have exactly one bit set. This differs
   1365   /// from computeKnownBits in that it doesn't necessarily determine which bit
   1366   /// is set.
   1367   bool isKnownToBeAPowerOfTwo(SDValue Val) const;
   1368 
   1369   /// Return the number of times the sign bit of the register is replicated into
   1370   /// the other bits. We know that at least 1 bit is always equal to the sign
   1371   /// bit (itself), but other cases can give us information. For example,
   1372   /// immediately after an "SRA X, 2", we know that the top 3 bits are all equal
   1373   /// to each other, so we return 3. Targets can implement the
   1374   /// ComputeNumSignBitsForTarget method in the TargetLowering class to allow
   1375   /// target nodes to be understood.
   1376   unsigned ComputeNumSignBits(SDValue Op, unsigned Depth = 0) const;
   1377 
   1378   /// Return the number of times the sign bit of the register is replicated into
   1379   /// the other bits. We know that at least 1 bit is always equal to the sign
   1380   /// bit (itself), but other cases can give us information. For example,
   1381   /// immediately after an "SRA X, 2", we know that the top 3 bits are all equal
   1382   /// to each other, so we return 3. The DemandedElts argument allows
   1383   /// us to only collect the minimum sign bits of the requested vector elements.
   1384   /// Targets can implement the ComputeNumSignBitsForTarget method in the
   1385   /// TargetLowering class to allow target nodes to be understood.
   1386   unsigned ComputeNumSignBits(SDValue Op, const APInt &DemandedElts,
   1387                               unsigned Depth = 0) const;
   1388 
   1389   /// Return true if the specified operand is an ISD::ADD with a ConstantSDNode
   1390   /// on the right-hand side, or if it is an ISD::OR with a ConstantSDNode that
   1391   /// is guaranteed to have the same semantics as an ADD. This handles the
   1392   /// equivalence:
   1393   ///     X|Cst == X+Cst iff X&Cst = 0.
   1394   bool isBaseWithConstantOffset(SDValue Op) const;
   1395 
   1396   /// Test whether the given SDValue is known to never be NaN.
   1397   bool isKnownNeverNaN(SDValue Op) const;
   1398 
   1399   /// Test whether the given SDValue is known to never be positive or negative
   1400   /// zero.
   1401   bool isKnownNeverZero(SDValue Op) const;
   1402 
   1403   /// Test whether two SDValues are known to compare equal. This
   1404   /// is true if they are the same value, or if one is negative zero and the
   1405   /// other positive zero.
   1406   bool isEqualTo(SDValue A, SDValue B) const;
   1407 
   1408   /// Return true if A and B have no common bits set. As an example, this can
   1409   /// allow an 'add' to be transformed into an 'or'.
   1410   bool haveNoCommonBitsSet(SDValue A, SDValue B) const;
   1411 
   1412   /// Utility function used by legalize and lowering to
   1413   /// "unroll" a vector operation by splitting out the scalars and operating
   1414   /// on each element individually.  If the ResNE is 0, fully unroll the vector
   1415   /// op. If ResNE is less than the width of the vector op, unroll up to ResNE.
   1416   /// If the  ResNE is greater than the width of the vector op, unroll the
   1417   /// vector op and fill the end of the resulting vector with UNDEFS.
   1418   SDValue UnrollVectorOp(SDNode *N, unsigned ResNE = 0);
   1419 
   1420   /// Return true if loads are next to each other and can be
   1421   /// merged. Check that both are nonvolatile and if LD is loading
   1422   /// 'Bytes' bytes from a location that is 'Dist' units away from the
   1423   /// location that the 'Base' load is loading from.
   1424   bool areNonVolatileConsecutiveLoads(LoadSDNode *LD, LoadSDNode *Base,
   1425                                       unsigned Bytes, int Dist) const;
   1426 
   1427   /// Infer alignment of a load / store address. Return 0 if
   1428   /// it cannot be inferred.
   1429   unsigned InferPtrAlignment(SDValue Ptr) const;
   1430 
   1431   /// Compute the VTs needed for the low/hi parts of a type
   1432   /// which is split (or expanded) into two not necessarily identical pieces.
   1433   std::pair<EVT, EVT> GetSplitDestVTs(const EVT &VT) const;
   1434 
   1435   /// Split the vector with EXTRACT_SUBVECTOR using the provides
   1436   /// VTs and return the low/high part.
   1437   std::pair<SDValue, SDValue> SplitVector(const SDValue &N, const SDLoc &DL,
   1438                                           const EVT &LoVT, const EVT &HiVT);
   1439 
   1440   /// Split the vector with EXTRACT_SUBVECTOR and return the low/high part.
   1441   std::pair<SDValue, SDValue> SplitVector(const SDValue &N, const SDLoc &DL) {
   1442     EVT LoVT, HiVT;
   1443     std::tie(LoVT, HiVT) = GetSplitDestVTs(N.getValueType());
   1444     return SplitVector(N, DL, LoVT, HiVT);
   1445   }
   1446 
   1447   /// Split the node's operand with EXTRACT_SUBVECTOR and
   1448   /// return the low/high part.
   1449   std::pair<SDValue, SDValue> SplitVectorOperand(const SDNode *N, unsigned OpNo)
   1450   {
   1451     return SplitVector(N->getOperand(OpNo), SDLoc(N));
   1452   }
   1453 
   1454   /// Append the extracted elements from Start to Count out of the vector Op
   1455   /// in Args. If Count is 0, all of the elements will be extracted.
   1456   void ExtractVectorElements(SDValue Op, SmallVectorImpl<SDValue> &Args,
   1457                              unsigned Start = 0, unsigned Count = 0);
   1458 
   1459   /// Compute the default alignment value for the given type.
   1460   unsigned getEVTAlignment(EVT MemoryVT) const;
   1461 
   1462   /// Test whether the given value is a constant int or similar node.
   1463   SDNode *isConstantIntBuildVectorOrConstantInt(SDValue N);
   1464 
   1465   /// Test whether the given value is a constant FP or similar node.
   1466   SDNode *isConstantFPBuildVectorOrConstantFP(SDValue N);
   1467 
   1468   /// \returns true if \p N is any kind of constant or build_vector of
   1469   /// constants, int or float. If a vector, it may not necessarily be a splat.
   1470   inline bool isConstantValueOfAnyType(SDValue N) {
   1471     return isConstantIntBuildVectorOrConstantInt(N) ||
   1472            isConstantFPBuildVectorOrConstantFP(N);
   1473   }
   1474 
   1475 private:
   1476   void InsertNode(SDNode *N);
   1477   bool RemoveNodeFromCSEMaps(SDNode *N);
   1478   void AddModifiedNodeToCSEMaps(SDNode *N);
   1479   SDNode *FindModifiedNodeSlot(SDNode *N, SDValue Op, void *&InsertPos);
   1480   SDNode *FindModifiedNodeSlot(SDNode *N, SDValue Op1, SDValue Op2,
   1481                                void *&InsertPos);
   1482   SDNode *FindModifiedNodeSlot(SDNode *N, ArrayRef<SDValue> Ops,
   1483                                void *&InsertPos);
   1484   SDNode *UpdateSDLocOnMergeSDNode(SDNode *N, const SDLoc &loc);
   1485 
   1486   void DeleteNodeNotInCSEMaps(SDNode *N);
   1487   void DeallocateNode(SDNode *N);
   1488 
   1489   void allnodes_clear();
   1490 
   1491   /// Look up the node specified by ID in CSEMap.  If it exists, return it.  If
   1492   /// not, return the insertion token that will make insertion faster.  This
   1493   /// overload is for nodes other than Constant or ConstantFP, use the other one
   1494   /// for those.
   1495   SDNode *FindNodeOrInsertPos(const FoldingSetNodeID &ID, void *&InsertPos);
   1496 
   1497   /// Look up the node specified by ID in CSEMap.  If it exists, return it.  If
   1498   /// not, return the insertion token that will make insertion faster.  Performs
   1499   /// additional processing for constant nodes.
   1500   SDNode *FindNodeOrInsertPos(const FoldingSetNodeID &ID, const SDLoc &DL,
   1501                               void *&InsertPos);
   1502 
   1503   /// List of non-single value types.
   1504   FoldingSet<SDVTListNode> VTListMap;
   1505 
   1506   /// Maps to auto-CSE operations.
   1507   std::vector<CondCodeSDNode*> CondCodeNodes;
   1508 
   1509   std::vector<SDNode*> ValueTypeNodes;
   1510   std::map<EVT, SDNode*, EVT::compareRawBits> ExtendedValueTypeNodes;
   1511   StringMap<SDNode*> ExternalSymbols;
   1512 
   1513   std::map<std::pair<std::string, unsigned char>,SDNode*> TargetExternalSymbols;
   1514   DenseMap<MCSymbol *, SDNode *> MCSymbols;
   1515 };
   1516 
   1517 template <> struct GraphTraits<SelectionDAG*> : public GraphTraits<SDNode*> {
   1518   using nodes_iterator = pointer_iterator<SelectionDAG::allnodes_iterator>;
   1519 
   1520   static nodes_iterator nodes_begin(SelectionDAG *G) {
   1521     return nodes_iterator(G->allnodes_begin());
   1522   }
   1523 
   1524   static nodes_iterator nodes_end(SelectionDAG *G) {
   1525     return nodes_iterator(G->allnodes_end());
   1526   }
   1527 };
   1528 
   1529 template <class TargetMemSDNode>
   1530 SDValue SelectionDAG::getTargetMemSDNode(SDVTList VTs,
   1531                                          ArrayRef<SDValue> Ops,
   1532                                          const SDLoc &dl, EVT MemVT,
   1533                                          MachineMemOperand *MMO) {
   1534   /// Compose node ID and try to find an existing node.
   1535   FoldingSetNodeID ID;
   1536   unsigned Opcode =
   1537     TargetMemSDNode(dl.getIROrder(), DebugLoc(), VTs, MemVT, MMO).getOpcode();
   1538   ID.AddInteger(Opcode);
   1539   ID.AddPointer(VTs.VTs);
   1540   for (auto& Op : Ops) {
   1541     ID.AddPointer(Op.getNode());
   1542     ID.AddInteger(Op.getResNo());
   1543   }
   1544   ID.AddInteger(MemVT.getRawBits());
   1545   ID.AddInteger(MMO->getPointerInfo().getAddrSpace());
   1546   ID.AddInteger(getSyntheticNodeSubclassData<TargetMemSDNode>(
   1547     dl.getIROrder(), VTs, MemVT, MMO));
   1548 
   1549   void *IP = nullptr;
   1550   if (SDNode *E = FindNodeOrInsertPos(ID, dl, IP)) {
   1551     cast<TargetMemSDNode>(E)->refineAlignment(MMO);
   1552     return SDValue(E, 0);
   1553   }
   1554 
   1555   /// Existing node was not found. Create a new one.
   1556   auto *N = newSDNode<TargetMemSDNode>(dl.getIROrder(), dl.getDebugLoc(), VTs,
   1557                                        MemVT, MMO);
   1558   createOperands(N, Ops);
   1559   CSEMap.InsertNode(N, IP);
   1560   InsertNode(N);
   1561   return SDValue(N, 0);
   1562 }
   1563 
   1564 } // end namespace llvm
   1565 
   1566 #endif // LLVM_CODEGEN_SELECTIONDAG_H
   1567