text: //===- DAGISelMatcherOpt.cpp - Optimize a DAG Matcher ---------------------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This file implements the DAG Matcher optimizer.
  //
  //===----------------------------------------------------------------------===//
  
  #define DEBUG_TYPE "isel-opt"
  #include "DAGISelMatcher.h"
  #include "CodeGenDAGPatterns.h"
  #include "llvm/ADT/DenseSet.h"
  #include "llvm/ADT/StringSet.h"
  #include "llvm/Support/Debug.h"
  #include "llvm/Support/raw_ostream.h"
  using namespace llvm;
  
  /// ContractNodes - Turn multiple matcher node patterns like 'MoveChild+Record'
  /// into single compound nodes like RecordChild.
  static void ContractNodes(OwningPtr<Matcher> &MatcherPtr,
                            const CodeGenDAGPatterns &CGP) {
    // If we reached the end of the chain, we're done.
    Matcher *N = MatcherPtr.get();
    if (N == 0) return;
    
    // If we have a scope node, walk down all of the children.
    if (ScopeMatcher *Scope = dyn_cast<ScopeMatcher>(N)) {
      for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) {
        OwningPtr<Matcher> Child(Scope->takeChild(i));
        ContractNodes(Child, CGP);
        Scope->resetChild(i, Child.take());
      }
      return;
    }
    
    // If we found a movechild node with a node that comes in a 'foochild' form,
    // transform it.
    if (MoveChildMatcher *MC = dyn_cast<MoveChildMatcher>(N)) {
      Matcher *New = 0;
      if (RecordMatcher *RM = dyn_cast<RecordMatcher>(MC->getNext()))
        if (MC->getChildNo() < 8)  // Only have RecordChild0...7
          New = new RecordChildMatcher(MC->getChildNo(), RM->getWhatFor(),
                                       RM->getResultNo());
      
      if (CheckTypeMatcher *CT = dyn_cast<CheckTypeMatcher>(MC->getNext()))
        if (MC->getChildNo() < 8 &&  // Only have CheckChildType0...7
            CT->getResNo() == 0)     // CheckChildType checks res #0
          New = new CheckChildTypeMatcher(MC->getChildNo(), CT->getType());
  
      if (CheckSameMatcher *CS = dyn_cast<CheckSameMatcher>(MC->getNext()))
        if (MC->getChildNo() < 4)  // Only have CheckChildSame0...3
          New = new CheckChildSameMatcher(MC->getChildNo(), CS->getMatchNumber());
  
      if (New) {
        // Insert the new node.
        New->setNext(MatcherPtr.take());
        MatcherPtr.reset(New);
        // Remove the old one.
        MC->setNext(MC->getNext()->takeNext());
        return ContractNodes(MatcherPtr, CGP);
      }
    }
    
    // Zap movechild -> moveparent.
    if (MoveChildMatcher *MC = dyn_cast<MoveChildMatcher>(N))
      if (MoveParentMatcher *MP = 
            dyn_cast<MoveParentMatcher>(MC->getNext())) {
        MatcherPtr.reset(MP->takeNext());
        return ContractNodes(MatcherPtr, CGP);
      }
  
    // Turn EmitNode->MarkFlagResults->CompleteMatch into
    // MarkFlagResults->EmitNode->CompleteMatch when we can to encourage
    // MorphNodeTo formation.  This is safe because MarkFlagResults never refers
    // to the root of the pattern.
    if (isa<EmitNodeMatcher>(N) && isa<MarkGlueResultsMatcher>(N->getNext()) &&
        isa<CompleteMatchMatcher>(N->getNext()->getNext())) {
      // Unlink the two nodes from the list.
      Matcher *EmitNode = MatcherPtr.take();
      Matcher *MFR = EmitNode->takeNext();
      Matcher *Tail = MFR->takeNext();
          
      // Relink them.
      MatcherPtr.reset(MFR);
      MFR->setNext(EmitNode);
      EmitNode->setNext(Tail);
      return ContractNodes(MatcherPtr, CGP);
    }
  
    // Turn EmitNode->CompleteMatch into MorphNodeTo if we can.
    if (EmitNodeMatcher *EN = dyn_cast<EmitNodeMatcher>(N))
      if (CompleteMatchMatcher *CM =
            dyn_cast<CompleteMatchMatcher>(EN->getNext())) {
        // We can only use MorphNodeTo if the result values match up.
        unsigned RootResultFirst = EN->getFirstResultSlot();
        bool ResultsMatch = true;
        for (unsigned i = 0, e = CM->getNumResults(); i != e; ++i)
          if (CM->getResult(i) != RootResultFirst+i)
            ResultsMatch = false;
        
        // If the selected node defines a subset of the glue/chain results, we
        // can't use MorphNodeTo.  For example, we can't use MorphNodeTo if the
        // matched pattern has a chain but the root node doesn't.
        const PatternToMatch &Pattern = CM->getPattern();
        
        if (!EN->hasChain() &&
            Pattern.getSrcPattern()->NodeHasProperty(SDNPHasChain, CGP))
          ResultsMatch = false;
  
        // If the matched node has glue and the output root doesn't, we can't
        // use MorphNodeTo.
        //
        // NOTE: Strictly speaking, we don't have to check for glue here
        // because the code in the pattern generator doesn't handle it right.  We
        // do it anyway for thoroughness.
        if (!EN->hasOutFlag() &&
            Pattern.getSrcPattern()->NodeHasProperty(SDNPOutGlue, CGP))
          ResultsMatch = false;
        
        
        // If the root result node defines more results than the source root node
        // *and* has a chain or glue input, then we can't match it because it
        // would end up replacing the extra result with the chain/glue.
  #if 0
        if ((EN->hasGlue() || EN->hasChain()) &&
            EN->getNumNonChainGlueVTs() > ... need to get no results reliably ...)
          ResultMatch = false;
  #endif
            
        if (ResultsMatch) {
          const SmallVectorImpl<MVT::SimpleValueType> &VTs = EN->getVTList();
          const SmallVectorImpl<unsigned> &Operands = EN->getOperandList();
          MatcherPtr.reset(new MorphNodeToMatcher(EN->getOpcodeName(),
                                                  VTs.data(), VTs.size(),
                                                  Operands.data(),Operands.size(),
                                                  EN->hasChain(), EN->hasInFlag(),
                                                  EN->hasOutFlag(),
                                                  EN->hasMemRefs(),
                                                  EN->getNumFixedArityOperands(),
                                                  Pattern));
          return;
        }
  
        // FIXME2: Kill off all the SelectionDAG::SelectNodeTo and getMachineNode
        // variants.
      }
    
    ContractNodes(N->getNextPtr(), CGP);
    
    
    // If we have a CheckType/CheckChildType/Record node followed by a
    // CheckOpcode, invert the two nodes.  We prefer to do structural checks
    // before type checks, as this opens opportunities for factoring on targets
    // like X86 where many operations are valid on multiple types.
    if ((isa<CheckTypeMatcher>(N) || isa<CheckChildTypeMatcher>(N) ||
         isa<RecordMatcher>(N)) &&
        isa<CheckOpcodeMatcher>(N->getNext())) {
      // Unlink the two nodes from the list.
      Matcher *CheckType = MatcherPtr.take();
      Matcher *CheckOpcode = CheckType->takeNext();
      Matcher *Tail = CheckOpcode->takeNext();
      
      // Relink them.
      MatcherPtr.reset(CheckOpcode);
      CheckOpcode->setNext(CheckType);
      CheckType->setNext(Tail);
      return ContractNodes(MatcherPtr, CGP);
    }
  }
  
  /// SinkPatternPredicates - Pattern predicates can be checked at any level of
  /// the matching tree.  The generator dumps them at the top level of the pattern
  /// though, which prevents factoring from being able to see past them.  This
  /// optimization sinks them as far down into the pattern as possible.
  ///
  /// Conceptually, we'd like to sink these predicates all the way to the last
  /// matcher predicate in the series.  However, it turns out that some
  /// ComplexPatterns have side effects on the graph, so we really don't want to
  /// run a the complex pattern if the pattern predicate will fail.  For this
  /// reason, we refuse to sink the pattern predicate past a ComplexPattern.
  ///
  static void SinkPatternPredicates(OwningPtr<Matcher> &MatcherPtr) {
    // Recursively scan for a PatternPredicate.
    // If we reached the end of the chain, we're done.
    Matcher *N = MatcherPtr.get();
    if (N == 0) return;
    
    // Walk down all members of a scope node.
    if (ScopeMatcher *Scope = dyn_cast<ScopeMatcher>(N)) {
      for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) {
        OwningPtr<Matcher> Child(Scope->takeChild(i));
        SinkPatternPredicates(Child);
        Scope->resetChild(i, Child.take());
      }
      return;
    }
    
    // If this node isn't a CheckPatternPredicateMatcher we keep scanning until
    // we find one.
    CheckPatternPredicateMatcher *CPPM =dyn_cast<CheckPatternPredicateMatcher>(N);
    if (CPPM == 0)
      return SinkPatternPredicates(N->getNextPtr());
    
    // Ok, we found one, lets try to sink it. Check if we can sink it past the
    // next node in the chain.  If not, we won't be able to change anything and
    // might as well bail.
    if (!CPPM->getNext()->isSafeToReorderWithPatternPredicate())
      return;
    
    // Okay, we know we can sink it past at least one node.  Unlink it from the
    // chain and scan for the new insertion point.
    MatcherPtr.take();  // Don't delete CPPM.
    MatcherPtr.reset(CPPM->takeNext());
    
    N = MatcherPtr.get();
    while (N->getNext()->isSafeToReorderWithPatternPredicate())
      N = N->getNext();
    
    // At this point, we want to insert CPPM after N.
    CPPM->setNext(N->takeNext());
    N->setNext(CPPM);
  }
  
  /// FindNodeWithKind - Scan a series of matchers looking for a matcher with a
  /// specified kind.  Return null if we didn't find one otherwise return the
  /// matcher.
  static Matcher *FindNodeWithKind(Matcher *M, Matcher::KindTy Kind) {
    for (; M; M = M->getNext())
      if (M->getKind() == Kind)
        return M;
    return 0;
  }
  
  
  /// FactorNodes - Turn matches like this:
  ///   Scope
  ///     OPC_CheckType i32
  ///       ABC
  ///     OPC_CheckType i32
  ///       XYZ
  /// into:
  ///   OPC_CheckType i32
  ///     Scope
  ///       ABC
  ///       XYZ
  ///
  static void FactorNodes(OwningPtr<Matcher> &MatcherPtr) {
    // If we reached the end of the chain, we're done.
    Matcher *N = MatcherPtr.get();
    if (N == 0) return;
    
    // If this is not a push node, just scan for one.
    ScopeMatcher *Scope = dyn_cast<ScopeMatcher>(N);
    if (Scope == 0)
      return FactorNodes(N->getNextPtr());
    
    // Okay, pull together the children of the scope node into a vector so we can
    // inspect it more easily.  While we're at it, bucket them up by the hash
    // code of their first predicate.
    SmallVector<Matcher*, 32> OptionsToMatch;
    
    for (unsigned i = 0, e = Scope->getNumChildren(); i != e; ++i) {
      // Factor the subexpression.
      OwningPtr<Matcher> Child(Scope->takeChild(i));
      FactorNodes(Child);
      
      if (Matcher *N = Child.take())
        OptionsToMatch.push_back(N);
    }
    
    SmallVector<Matcher*, 32> NewOptionsToMatch;
    
    // Loop over options to match, merging neighboring patterns with identical
    // starting nodes into a shared matcher.
    for (unsigned OptionIdx = 0, e = OptionsToMatch.size(); OptionIdx != e;) {
      // Find the set of matchers that start with this node.
      Matcher *Optn = OptionsToMatch[OptionIdx++];
  
      if (OptionIdx == e) {
        NewOptionsToMatch.push_back(Optn);
        continue;
      }
      
      // See if the next option starts with the same matcher.  If the two
      // neighbors *do* start with the same matcher, we can factor the matcher out
      // of at least these two patterns.  See what the maximal set we can merge
      // together is.
      SmallVector<Matcher*, 8> EqualMatchers;
      EqualMatchers.push_back(Optn);
      
      // Factor all of the known-equal matchers after this one into the same
      // group.
      while (OptionIdx != e && OptionsToMatch[OptionIdx]->isEqual(Optn))
        EqualMatchers.push_back(OptionsToMatch[OptionIdx++]);
  
      // If we found a non-equal matcher, see if it is contradictory with the
      // current node.  If so, we know that the ordering relation between the
      // current sets of nodes and this node don't matter.  Look past it to see if
      // we can merge anything else into this matching group.
      unsigned Scan = OptionIdx;
      while (1) {
        // If we ran out of stuff to scan, we're done.
        if (Scan == e) break;
        
        Matcher *ScanMatcher = OptionsToMatch[Scan];
        
        // If we found an entry that matches out matcher, merge it into the set to
        // handle.
        if (Optn->isEqual(ScanMatcher)) {
          // If is equal after all, add the option to EqualMatchers and remove it
          // from OptionsToMatch.
          EqualMatchers.push_back(ScanMatcher);
          OptionsToMatch.erase(OptionsToMatch.begin()+Scan);
          --e;
          continue;
        }
        
        // If the option we're checking for contradicts the start of the list,
        // skip over it.
        if (Optn->isContradictory(ScanMatcher)) {
          ++Scan;
          continue;
        }
  
        // If we're scanning for a simple node, see if it occurs later in the
        // sequence.  If so, and if we can move it up, it might be contradictory
        // or the same as what we're looking for.  If so, reorder it.
        if (Optn->isSimplePredicateOrRecordNode()) {
          Matcher *M2 = FindNodeWithKind(ScanMatcher, Optn->getKind());
          if (M2 != 0 && M2 != ScanMatcher &&
              M2->canMoveBefore(ScanMatcher) &&
              (M2->isEqual(Optn) || M2->isContradictory(Optn))) {
            Matcher *MatcherWithoutM2 = ScanMatcher->unlinkNode(M2);
            M2->setNext(MatcherWithoutM2);
            OptionsToMatch[Scan] = M2;
            continue;
          }
        }
        
        // Otherwise, we don't know how to handle this entry, we have to bail.
        break;
      }
        
      if (Scan != e &&
          // Don't print it's obvious nothing extra could be merged anyway.
          Scan+1 != e) {
        DEBUG(errs() << "Couldn't merge this:\n";
              Optn->print(errs(), 4);
              errs() << "into this:\n";
              OptionsToMatch[Scan]->print(errs(), 4);
              if (Scan+1 != e)
                OptionsToMatch[Scan+1]->printOne(errs());
              if (Scan+2 < e)
                OptionsToMatch[Scan+2]->printOne(errs());
              errs() << "\n");
      }
      
      // If we only found one option starting with this matcher, no factoring is
      // possible.
      if (EqualMatchers.size() == 1) {
        NewOptionsToMatch.push_back(EqualMatchers[0]);
        continue;
      }
      
      // Factor these checks by pulling the first node off each entry and
      // discarding it.  Take the first one off the first entry to reuse.
      Matcher *Shared = Optn;
      Optn = Optn->takeNext();
      EqualMatchers[0] = Optn;
  
      // Remove and delete the first node from the other matchers we're factoring.
      for (unsigned i = 1, e = EqualMatchers.size(); i != e; ++i) {
        Matcher *Tmp = EqualMatchers[i]->takeNext();
        delete EqualMatchers[i];
        EqualMatchers[i] = Tmp;
      }
      
      Shared->setNext(new ScopeMatcher(&EqualMatchers[0], EqualMatchers.size()));
  
      // Recursively factor the newly created node.
      FactorNodes(Shared->getNextPtr());
      
      NewOptionsToMatch.push_back(Shared);
    }
    
    // If we're down to a single pattern to match, then we don't need this scope
    // anymore.
    if (NewOptionsToMatch.size() == 1) {
      MatcherPtr.reset(NewOptionsToMatch[0]);
      return;
    }
    
    if (NewOptionsToMatch.empty()) {
      MatcherPtr.reset(0);
      return;
    }
    
    // If our factoring failed (didn't achieve anything) see if we can simplify in
    // other ways.
    
    // Check to see if all of the leading entries are now opcode checks.  If so,
    // we can convert this Scope to be a OpcodeSwitch instead.
    bool AllOpcodeChecks = true, AllTypeChecks = true;
    for (unsigned i = 0, e = NewOptionsToMatch.size(); i != e; ++i) {
      // Check to see if this breaks a series of CheckOpcodeMatchers.
      if (AllOpcodeChecks &&
          !isa<CheckOpcodeMatcher>(NewOptionsToMatch[i])) {
  #if 0
        if (i > 3) {
          errs() << "FAILING OPC #" << i << "\n";
          NewOptionsToMatch[i]->dump();
        }
  #endif
        AllOpcodeChecks = false;
      }
  
      // Check to see if this breaks a series of CheckTypeMatcher's.
      if (AllTypeChecks) {
        CheckTypeMatcher *CTM =
          cast_or_null<CheckTypeMatcher>(FindNodeWithKind(NewOptionsToMatch[i],
                                                          Matcher::CheckType));
        if (CTM == 0 ||
            // iPTR checks could alias any other case without us knowing, don't
            // bother with them.
            CTM->getType() == MVT::iPTR ||
            // SwitchType only works for result #0.
            CTM->getResNo() != 0 ||
            // If the CheckType isn't at the start of the list, see if we can move
            // it there.
            !CTM->canMoveBefore(NewOptionsToMatch[i])) {
  #if 0
          if (i > 3 && AllTypeChecks) {
            errs() << "FAILING TYPE #" << i << "\n";
            NewOptionsToMatch[i]->dump();
          }
  #endif
          AllTypeChecks = false;
        }
      }
    }
    
    // If all the options are CheckOpcode's, we can form the SwitchOpcode, woot.
    if (AllOpcodeChecks) {
      StringSet<> Opcodes;
      SmallVector<std::pair<const SDNodeInfo*, Matcher*>, 8> Cases;
      for (unsigned i = 0, e = NewOptionsToMatch.size(); i != e; ++i) {
        CheckOpcodeMatcher *COM = cast<CheckOpcodeMatcher>(NewOptionsToMatch[i]);
        assert(Opcodes.insert(COM->getOpcode().getEnumName()) &&
               "Duplicate opcodes not factored?");
        Cases.push_back(std::make_pair(&COM->getOpcode(), COM->getNext()));
      }
      
      MatcherPtr.reset(new SwitchOpcodeMatcher(&Cases[0], Cases.size()));
      return;
    }
    
    // If all the options are CheckType's, we can form the SwitchType, woot.
    if (AllTypeChecks) {
      DenseMap<unsigned, unsigned> TypeEntry;
      SmallVector<std::pair<MVT::SimpleValueType, Matcher*>, 8> Cases;
      for (unsigned i = 0, e = NewOptionsToMatch.size(); i != e; ++i) {
        CheckTypeMatcher *CTM =
          cast_or_null<CheckTypeMatcher>(FindNodeWithKind(NewOptionsToMatch[i],
                                                          Matcher::CheckType));
        Matcher *MatcherWithoutCTM = NewOptionsToMatch[i]->unlinkNode(CTM);
        MVT::SimpleValueType CTMTy = CTM->getType();
        delete CTM;
        
        unsigned &Entry = TypeEntry[CTMTy];
        if (Entry != 0) {
          // If we have unfactored duplicate types, then we should factor them.
          Matcher *PrevMatcher = Cases[Entry-1].second;
          if (ScopeMatcher *SM = dyn_cast<ScopeMatcher>(PrevMatcher)) {
            SM->setNumChildren(SM->getNumChildren()+1);
            SM->resetChild(SM->getNumChildren()-1, MatcherWithoutCTM);
            continue;
          }
          
          Matcher *Entries[2] = { PrevMatcher, MatcherWithoutCTM };
          Cases[Entry-1].second = new ScopeMatcher(Entries, 2);
          continue;
        }
        
        Entry = Cases.size()+1;
        Cases.push_back(std::make_pair(CTMTy, MatcherWithoutCTM));
      }
      
      if (Cases.size() != 1) {
        MatcherPtr.reset(new SwitchTypeMatcher(&Cases[0], Cases.size()));
      } else {
        // If we factored and ended up with one case, create it now.
        MatcherPtr.reset(new CheckTypeMatcher(Cases[0].first, 0));
        MatcherPtr->setNext(Cases[0].second);
      }
      return;
    }
    
  
    // Reassemble the Scope node with the adjusted children.
    Scope->setNumChildren(NewOptionsToMatch.size());
    for (unsigned i = 0, e = NewOptionsToMatch.size(); i != e; ++i)
      Scope->resetChild(i, NewOptionsToMatch[i]);
  }
  
  Matcher *llvm::OptimizeMatcher(Matcher *TheMatcher,
                                 const CodeGenDAGPatterns &CGP) {
    OwningPtr<Matcher> MatcherPtr(TheMatcher);
    ContractNodes(MatcherPtr, CGP);
    SinkPatternPredicates(MatcherPtr);
    FactorNodes(MatcherPtr);
    return MatcherPtr.take();
  }
  