llvm/utils/TableGen/DAGISelEmitter.cpp

   1 //===- DAGISelEmitter.cpp - Generate an instruction selector --------------===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // This tablegen backend emits a DAG instruction selector.
  10 //
  11 //===----------------------------------------------------------------------===//
  12
  13 #include "CodeGenDAGPatterns.h"
  14 #include "DAGISelMatcher.h"
  15 #include "llvm/Support/Debug.h"
  16 #include "llvm/TableGen/Record.h"
  17 #include "llvm/TableGen/TableGenBackend.h"
  18 using namespace llvm;
  19
  20 #define DEBUG_TYPE "dag-isel-emitter"
  21
  22 namespace {
  23 /// DAGISelEmitter - The top-level class which coordinates construction
  24 /// and emission of the instruction selector.
  25 class DAGISelEmitter {
  26   RecordKeeper &Records; // Just so we can get at the timing functions.
  27   CodeGenDAGPatterns CGP;
  28 public:
  29   explicit DAGISelEmitter(RecordKeeper &R) : Records(R), CGP(R) {}
  30   void run(raw_ostream &OS);
  31 };
  32 } // End anonymous namespace
  33
  34 //===----------------------------------------------------------------------===//
  35 // DAGISelEmitter Helper methods
  36 //
  37
  38 /// getResultPatternCost - Compute the number of instructions for this pattern.
  39 /// This is a temporary hack.  We should really include the instruction
  40 /// latencies in this calculation.
  41 static unsigned getResultPatternCost(TreePatternNode *P,
  42                                      CodeGenDAGPatterns &CGP) {
  43   if (P->isLeaf()) return 0;
  44
  45   unsigned Cost = 0;
  46   Record *Op = P->getOperator();
  47   if (Op->isSubClassOf("Instruction")) {
  48     Cost++;
  49     CodeGenInstruction &II = CGP.getTargetInfo().getInstruction(Op);
  50     if (II.usesCustomInserter)
  51       Cost += 10;
  52   }
  53   for (unsigned i = 0, e = P->getNumChildren(); i != e; ++i)
  54     Cost += getResultPatternCost(P->getChild(i), CGP);
  55   return Cost;
  56 }
  57
  58 /// getResultPatternCodeSize - Compute the code size of instructions for this
  59 /// pattern.
  60 static unsigned getResultPatternSize(TreePatternNode *P,
  61                                      CodeGenDAGPatterns &CGP) {
  62   if (P->isLeaf()) return 0;
  63
  64   unsigned Cost = 0;
  65   Record *Op = P->getOperator();
  66   if (Op->isSubClassOf("Instruction")) {
  67     Cost += Op->getValueAsInt("CodeSize");
  68   }
  69   for (unsigned i = 0, e = P->getNumChildren(); i != e; ++i)
  70     Cost += getResultPatternSize(P->getChild(i), CGP);
  71   return Cost;
  72 }
  73
  74 namespace {
  75 // PatternSortingPredicate - return true if we prefer to match LHS before RHS.
  76 // In particular, we want to match maximal patterns first and lowest cost within
  77 // a particular complexity first.
  78 struct PatternSortingPredicate {
  79   PatternSortingPredicate(CodeGenDAGPatterns &cgp) : CGP(cgp) {}
  80   CodeGenDAGPatterns &CGP;
  81
  82   bool operator()(const PatternToMatch *LHS, const PatternToMatch *RHS) {
  83     const TreePatternNode *LT = LHS->getSrcPattern();
  84     const TreePatternNode *RT = RHS->getSrcPattern();
  85
  86     MVT LHSVT = LT->getNumTypes() != 0 ? LT->getSimpleType(0) : MVT::Other;
  87     MVT RHSVT = RT->getNumTypes() != 0 ? RT->getSimpleType(0) : MVT::Other;
  88     if (LHSVT.isVector() != RHSVT.isVector())
  89       return RHSVT.isVector();
  90
  91     if (LHSVT.isFloatingPoint() != RHSVT.isFloatingPoint())
  92       return RHSVT.isFloatingPoint();
  93
  94     // Otherwise, if the patterns might both match, sort based on complexity,
  95     // which means that we prefer to match patterns that cover more nodes in the
  96     // input over nodes that cover fewer.
  97     int LHSSize = LHS->getPatternComplexity(CGP);
  98     int RHSSize = RHS->getPatternComplexity(CGP);
  99     if (LHSSize > RHSSize) return true;   // LHS -> bigger -> less cost
 100     if (LHSSize < RHSSize) return false;
 101
 102     // If the patterns have equal complexity, compare generated instruction cost
 103     unsigned LHSCost = getResultPatternCost(LHS->getDstPattern(), CGP);
 104     unsigned RHSCost = getResultPatternCost(RHS->getDstPattern(), CGP);
 105     if (LHSCost < RHSCost) return true;
 106     if (LHSCost > RHSCost) return false;
 107
 108     unsigned LHSPatSize = getResultPatternSize(LHS->getDstPattern(), CGP);
 109     unsigned RHSPatSize = getResultPatternSize(RHS->getDstPattern(), CGP);
 110     if (LHSPatSize < RHSPatSize) return true;
 111     if (LHSPatSize > RHSPatSize) return false;
 112
 113     // Sort based on the UID of the pattern, to reflect source order.
 114     // Note that this is not guaranteed to be unique, since a single source
 115     // pattern may have been resolved into multiple match patterns due to
 116     // alternative fragments.  To ensure deterministic output, always use
 117     // std::stable_sort with this predicate.
 118     return LHS->getID() < RHS->getID();
 119   }
 120 };
 121 } // End anonymous namespace
 122
 123
 124 void DAGISelEmitter::run(raw_ostream &OS) {
 125   emitSourceFileHeader("DAG Instruction Selector for the " +
 126                        CGP.getTargetInfo().getName().str() + " target", OS);
 127
 128   OS << "// *** NOTE: This file is #included into the middle of the target\n"
 129      << "// *** instruction selector class.  These functions are really "
 130      << "methods.\n\n";
 131
 132   OS << "// If GET_DAGISEL_DECL is #defined with any value, only function\n"
 133         "// declarations will be included when this file is included.\n"
 134         "// If GET_DAGISEL_BODY is #defined, its value should be the name of\n"
 135         "// the instruction selector class. Function bodies will be emitted\n"
 136         "// and each function's name will be qualified with the name of the\n"
 137         "// class.\n"
 138         "//\n"
 139         "// When neither of the GET_DAGISEL* macros is defined, the functions\n"
 140         "// are emitted inline.\n\n";
 141
 142   LLVM_DEBUG(errs() << "\n\nALL PATTERNS TO MATCH:\n\n";
 143              for (CodeGenDAGPatterns::ptm_iterator I = CGP.ptm_begin(),
 144                   E = CGP.ptm_end();
 145                   I != E; ++I) {
 146                errs() << "PATTERN: ";
 147                I->getSrcPattern()->dump();
 148                errs() << "\nRESULT:  ";
 149                I->getDstPattern()->dump();
 150                errs() << "\n";
 151              });
 152
 153   // Add all the patterns to a temporary list so we can sort them.
 154   Records.startTimer("Sort patterns");
 155   std::vector<const PatternToMatch*> Patterns;
 156   for (const PatternToMatch &PTM : CGP.ptms())
 157     Patterns.push_back(&PTM);
 158
 159   // We want to process the matches in order of minimal cost.  Sort the patterns
 160   // so the least cost one is at the start.
 161   llvm::stable_sort(Patterns, PatternSortingPredicate(CGP));
 162
 163   // Convert each variant of each pattern into a Matcher.
 164   Records.startTimer("Convert to matchers");
 165   std::vector<Matcher*> PatternMatchers;
 166   for (const PatternToMatch *PTM : Patterns) {
 167     for (unsigned Variant = 0; ; ++Variant) {
 168       if (Matcher *M = ConvertPatternToMatcher(*PTM, Variant, CGP))
 169         PatternMatchers.push_back(M);
 170       else
 171         break;
 172     }
 173   }
 174
 175   std::unique_ptr<Matcher> TheMatcher =
 176     std::make_unique<ScopeMatcher>(PatternMatchers);
 177
 178   Records.startTimer("Optimize matchers");
 179   OptimizeMatcher(TheMatcher, CGP);
 180
 181   //Matcher->dump();
 182
 183   Records.startTimer("Emit matcher table");
 184   EmitMatcherTable(TheMatcher.get(), CGP, OS);
 185 }
 186
 187 namespace llvm {
 188
 189 void EmitDAGISel(RecordKeeper &RK, raw_ostream &OS) {
 190   RK.startTimer("Parse patterns");
 191   DAGISelEmitter(RK).run(OS);
 192 }
 193
 194 } // End llvm namespace