text: //===- DAGISelEmitter.cpp - Generate an instruction selector --------------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This tablegen backend emits a DAG instruction selector.
  //
  //===----------------------------------------------------------------------===//
  
  #include "DAGISelEmitter.h"
  #include "DAGISelMatcher.h"
  #include "llvm/TableGen/Record.h"
  #include "llvm/Support/Debug.h"
  using namespace llvm;
  
  //===----------------------------------------------------------------------===//
  // DAGISelEmitter Helper methods
  //
  
  /// getResultPatternCost - Compute the number of instructions for this pattern.
  /// This is a temporary hack.  We should really include the instruction
  /// latencies in this calculation.
  static unsigned getResultPatternCost(TreePatternNode *P,
                                       CodeGenDAGPatterns &CGP) {
    if (P->isLeaf()) return 0;
  
    unsigned Cost = 0;
    Record *Op = P->getOperator();
    if (Op->isSubClassOf("Instruction")) {
      Cost++;
      CodeGenInstruction &II = CGP.getTargetInfo().getInstruction(Op);
      if (II.usesCustomInserter)
        Cost += 10;
    }
    for (unsigned i = 0, e = P->getNumChildren(); i != e; ++i)
      Cost += getResultPatternCost(P->getChild(i), CGP);
    return Cost;
  }
  
  /// getResultPatternCodeSize - Compute the code size of instructions for this
  /// pattern.
  static unsigned getResultPatternSize(TreePatternNode *P,
                                       CodeGenDAGPatterns &CGP) {
    if (P->isLeaf()) return 0;
  
    unsigned Cost = 0;
    Record *Op = P->getOperator();
    if (Op->isSubClassOf("Instruction")) {
      Cost += Op->getValueAsInt("CodeSize");
    }
    for (unsigned i = 0, e = P->getNumChildren(); i != e; ++i)
      Cost += getResultPatternSize(P->getChild(i), CGP);
    return Cost;
  }
  
  namespace {
  // PatternSortingPredicate - return true if we prefer to match LHS before RHS.
  // In particular, we want to match maximal patterns first and lowest cost within
  // a particular complexity first.
  struct PatternSortingPredicate {
    PatternSortingPredicate(CodeGenDAGPatterns &cgp) : CGP(cgp) {}
    CodeGenDAGPatterns &CGP;
  
    bool operator()(const PatternToMatch *LHS, const PatternToMatch *RHS) {
      const TreePatternNode *LHSSrc = LHS->getSrcPattern();
      const TreePatternNode *RHSSrc = RHS->getSrcPattern();
  
      if (LHSSrc->getNumTypes() != 0 && RHSSrc->getNumTypes() != 0 &&
          LHSSrc->getType(0) != RHSSrc->getType(0)) {
        MVT::SimpleValueType V1 = LHSSrc->getType(0), V2 = RHSSrc->getType(0);
        if (MVT(V1).isVector() != MVT(V2).isVector())
          return MVT(V2).isVector();
  
        if (MVT(V1).isFloatingPoint() != MVT(V2).isFloatingPoint())
          return MVT(V2).isFloatingPoint();
      }
  
      // Otherwise, if the patterns might both match, sort based on complexity,
      // which means that we prefer to match patterns that cover more nodes in the
      // input over nodes that cover fewer.
      unsigned LHSSize = LHS->getPatternComplexity(CGP);
      unsigned RHSSize = RHS->getPatternComplexity(CGP);
      if (LHSSize > RHSSize) return true;   // LHS -> bigger -> less cost
      if (LHSSize < RHSSize) return false;
  
      // If the patterns have equal complexity, compare generated instruction cost
      unsigned LHSCost = getResultPatternCost(LHS->getDstPattern(), CGP);
      unsigned RHSCost = getResultPatternCost(RHS->getDstPattern(), CGP);
      if (LHSCost < RHSCost) return true;
      if (LHSCost > RHSCost) return false;
  
      unsigned LHSPatSize = getResultPatternSize(LHS->getDstPattern(), CGP);
      unsigned RHSPatSize = getResultPatternSize(RHS->getDstPattern(), CGP);
      if (LHSPatSize < RHSPatSize) return true;
      if (LHSPatSize > RHSPatSize) return false;
  
      // Sort based on the UID of the pattern, giving us a deterministic ordering
      // if all other sorting conditions fail.
      assert(LHS == RHS || LHS->ID != RHS->ID);
      return LHS->ID < RHS->ID;
    }
  };
  }
  
  
  void DAGISelEmitter::run(raw_ostream &OS) {
    EmitSourceFileHeader("DAG Instruction Selector for the " +
                         CGP.getTargetInfo().getName() + " target", OS);
  
    OS << "// *** NOTE: This file is #included into the middle of the target\n"
       << "// *** instruction selector class.  These functions are really "
       << "methods.\n\n";
  
    DEBUG(errs() << "\n\nALL PATTERNS TO MATCH:\n\n";
          for (CodeGenDAGPatterns::ptm_iterator I = CGP.ptm_begin(),
               E = CGP.ptm_end(); I != E; ++I) {
            errs() << "PATTERN: ";   I->getSrcPattern()->dump();
            errs() << "\nRESULT:  "; I->getDstPattern()->dump();
            errs() << "\n";
          });
  
    // Add all the patterns to a temporary list so we can sort them.
    std::vector<const PatternToMatch*> Patterns;
    for (CodeGenDAGPatterns::ptm_iterator I = CGP.ptm_begin(), E = CGP.ptm_end();
         I != E; ++I)
      Patterns.push_back(&*I);
  
    // We want to process the matches in order of minimal cost.  Sort the patterns
    // so the least cost one is at the start.
    std::sort(Patterns.begin(), Patterns.end(), PatternSortingPredicate(CGP));
  
  
    // Convert each variant of each pattern into a Matcher.
    std::vector<Matcher*> PatternMatchers;
    for (unsigned i = 0, e = Patterns.size(); i != e; ++i) {
      for (unsigned Variant = 0; ; ++Variant) {
        if (Matcher *M = ConvertPatternToMatcher(*Patterns[i], Variant, CGP))
          PatternMatchers.push_back(M);
        else
          break;
      }
    }
  
    Matcher *TheMatcher = new ScopeMatcher(&PatternMatchers[0],
                                           PatternMatchers.size());
  
    TheMatcher = OptimizeMatcher(TheMatcher, CGP);
    //Matcher->dump();
    EmitMatcherTable(TheMatcher, CGP, OS);
    delete TheMatcher;
  }
  