utils/TableGen/DAGISelEmitter.cpp

   1 //===- DAGISelEmitter.cpp - Generate an instruction selector --------------===//
   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 tablegen backend emits a DAG instruction selector.
  11 //
  12 //===----------------------------------------------------------------------===//
  13
  14 #include "DAGISelEmitter.h"
  15 #include "DAGISelMatcher.h"
  16 #include "Record.h"
  17 #include "llvm/Support/Debug.h"
  18 using namespace llvm;
  19
  20 //===----------------------------------------------------------------------===//
  21 // DAGISelEmitter Helper methods
  22 //
  23
  24 /// getResultPatternCost - Compute the number of instructions for this pattern.
  25 /// This is a temporary hack.  We should really include the instruction
  26 /// latencies in this calculation.
  27 static unsigned getResultPatternCost(TreePatternNode *P,
  28                                      CodeGenDAGPatterns &CGP) {
  29   if (P->isLeaf()) return 0;
  30
  31   unsigned Cost = 0;
  32   Record *Op = P->getOperator();
  33   if (Op->isSubClassOf("Instruction")) {
  34     Cost++;
  35     CodeGenInstruction &II = CGP.getTargetInfo().getInstruction(Op);
  36     if (II.usesCustomInserter)
  37       Cost += 10;
  38   }
  39   for (unsigned i = 0, e = P->getNumChildren(); i != e; ++i)
  40     Cost += getResultPatternCost(P->getChild(i), CGP);
  41   return Cost;
  42 }
  43
  44 /// getResultPatternCodeSize - Compute the code size of instructions for this
  45 /// pattern.
  46 static unsigned getResultPatternSize(TreePatternNode *P,
  47                                      CodeGenDAGPatterns &CGP) {
  48   if (P->isLeaf()) return 0;
  49
  50   unsigned Cost = 0;
  51   Record *Op = P->getOperator();
  52   if (Op->isSubClassOf("Instruction")) {
  53     Cost += Op->getValueAsInt("CodeSize");
  54   }
  55   for (unsigned i = 0, e = P->getNumChildren(); i != e; ++i)
  56     Cost += getResultPatternSize(P->getChild(i), CGP);
  57   return Cost;
  58 }
  59
  60 namespace {
  61 // PatternSortingPredicate - return true if we prefer to match LHS before RHS.
  62 // In particular, we want to match maximal patterns first and lowest cost within
  63 // a particular complexity first.
  64 struct PatternSortingPredicate {
  65   PatternSortingPredicate(CodeGenDAGPatterns &cgp) : CGP(cgp) {}
  66   CodeGenDAGPatterns &CGP;
  67
  68   bool operator()(const PatternToMatch *LHS, const PatternToMatch *RHS) {
  69     const TreePatternNode *LHSSrc = LHS->getSrcPattern();
  70     const TreePatternNode *RHSSrc = RHS->getSrcPattern();
  71
  72     if (LHSSrc->getNumTypes() != 0 && RHSSrc->getNumTypes() != 0 &&
  73         LHSSrc->getType(0) != RHSSrc->getType(0)) {
  74       MVT::SimpleValueType V1 = LHSSrc->getType(0), V2 = RHSSrc->getType(0);
  75       if (MVT(V1).isVector() != MVT(V2).isVector())
  76         return MVT(V2).isVector();
  77
  78       if (MVT(V1).isFloatingPoint() != MVT(V2).isFloatingPoint())
  79         return MVT(V2).isFloatingPoint();
  80     }
  81
  82     // Otherwise, if the patterns might both match, sort based on complexity,
  83     // which means that we prefer to match patterns that cover more nodes in the
  84     // input over nodes that cover fewer.
  85     unsigned LHSSize = LHS->getPatternComplexity(CGP);
  86     unsigned RHSSize = RHS->getPatternComplexity(CGP);
  87     if (LHSSize > RHSSize) return true;   // LHS -> bigger -> less cost
  88     if (LHSSize < RHSSize) return false;
  89
  90     // If the patterns have equal complexity, compare generated instruction cost
  91     unsigned LHSCost = getResultPatternCost(LHS->getDstPattern(), CGP);
  92     unsigned RHSCost = getResultPatternCost(RHS->getDstPattern(), CGP);
  93     if (LHSCost < RHSCost) return true;
  94     if (LHSCost > RHSCost) return false;
  95
  96     unsigned LHSPatSize = getResultPatternSize(LHS->getDstPattern(), CGP);
  97     unsigned RHSPatSize = getResultPatternSize(RHS->getDstPattern(), CGP);
  98     if (LHSPatSize < RHSPatSize) return true;
  99     if (LHSPatSize > RHSPatSize) return false;
 100
 101     // Sort based on the UID of the pattern, giving us a deterministic ordering
 102     // if all other sorting conditions fail.
 103     assert(LHS == RHS || LHS->ID != RHS->ID);
 104     return LHS->ID < RHS->ID;
 105   }
 106 };
 107 }
 108
 109
 110 void DAGISelEmitter::run(raw_ostream &OS) {
 111   EmitSourceFileHeader("DAG Instruction Selector for the " +
 112                        CGP.getTargetInfo().getName() + " target", OS);
 113
 114   OS << "// *** NOTE: This file is #included into the middle of the target\n"
 115      << "// *** instruction selector class.  These functions are really "
 116      << "methods.\n\n";
 117
 118   DEBUG(errs() << "\n\nALL PATTERNS TO MATCH:\n\n";
 119         for (CodeGenDAGPatterns::ptm_iterator I = CGP.ptm_begin(),
 120              E = CGP.ptm_end(); I != E; ++I) {
 121           errs() << "PATTERN: ";   I->getSrcPattern()->dump();
 122           errs() << "\nRESULT:  "; I->getDstPattern()->dump();
 123           errs() << "\n";
 124         });
 125
 126   // Add all the patterns to a temporary list so we can sort them.
 127   std::vector<const PatternToMatch*> Patterns;
 128   for (CodeGenDAGPatterns::ptm_iterator I = CGP.ptm_begin(), E = CGP.ptm_end();
 129        I != E; ++I)
 130     Patterns.push_back(&*I);
 131
 132   // We want to process the matches in order of minimal cost.  Sort the patterns
 133   // so the least cost one is at the start.
 134   std::sort(Patterns.begin(), Patterns.end(), PatternSortingPredicate(CGP));
 135
 136
 137   // Convert each variant of each pattern into a Matcher.
 138   std::vector<Matcher*> PatternMatchers;
 139   for (unsigned i = 0, e = Patterns.size(); i != e; ++i) {
 140     for (unsigned Variant = 0; ; ++Variant) {
 141       if (Matcher *M = ConvertPatternToMatcher(*Patterns[i], Variant, CGP))
 142         PatternMatchers.push_back(M);
 143       else
 144         break;
 145     }
 146   }
 147
 148   Matcher *TheMatcher = new ScopeMatcher(&PatternMatchers[0],
 149                                          PatternMatchers.size());
 150
 151   TheMatcher = OptimizeMatcher(TheMatcher, CGP);
 152   //Matcher->dump();
 153   EmitMatcherTable(TheMatcher, CGP, OS);
 154   delete TheMatcher;
 155 }