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