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 "CodeGenDAGPatterns.h"
15#include "DAGISelMatcher.h"
16#include "llvm/Support/Debug.h"
17#include "llvm/TableGen/Record.h"
18#include "llvm/TableGen/TableGenBackend.h"
19using namespace llvm;
20
21#define DEBUG_TYPE "dag-isel-emitter"
22
23namespace {
24/// DAGISelEmitter - The top-level class which coordinates construction
25/// and emission of the instruction selector.
26class DAGISelEmitter {
27  CodeGenDAGPatterns CGP;
28public:
29  explicit DAGISelEmitter(RecordKeeper &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.
41static 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.
60static 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
74namespace {
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.
78struct PatternSortingPredicate {
79  PatternSortingPredicate(CodeGenDAGPatterns &cgp) : CGP(cgp) {}
80  CodeGenDAGPatterns &CGP;
81
82  bool operator()(const PatternToMatch *LHS, const PatternToMatch *RHS) {
83    const TreePatternNode *LHSSrc = LHS->getSrcPattern();
84    const TreePatternNode *RHSSrc = RHS->getSrcPattern();
85
86    MVT LHSVT = (LHSSrc->getNumTypes() != 0 ? LHSSrc->getType(0) : MVT::Other);
87    MVT RHSVT = (RHSSrc->getNumTypes() != 0 ? RHSSrc->getType(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    unsigned LHSSize = LHS->getPatternComplexity(CGP);
98    unsigned 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, giving us a deterministic ordering
114    // if all other sorting conditions fail.
115    assert(LHS == RHS || LHS->ID != RHS->ID);
116    return LHS->ID < RHS->ID;
117  }
118};
119} // End anonymous namespace
120
121
122void DAGISelEmitter::run(raw_ostream &OS) {
123  emitSourceFileHeader("DAG Instruction Selector for the " +
124                       CGP.getTargetInfo().getName() + " target", OS);
125
126  OS << "// *** NOTE: This file is #included into the middle of the target\n"
127     << "// *** instruction selector class.  These functions are really "
128     << "methods.\n\n";
129
130  DEBUG(errs() << "\n\nALL PATTERNS TO MATCH:\n\n";
131        for (CodeGenDAGPatterns::ptm_iterator I = CGP.ptm_begin(),
132             E = CGP.ptm_end(); I != E; ++I) {
133          errs() << "PATTERN: ";   I->getSrcPattern()->dump();
134          errs() << "\nRESULT:  "; I->getDstPattern()->dump();
135          errs() << "\n";
136        });
137
138  // Add all the patterns to a temporary list so we can sort them.
139  std::vector<const PatternToMatch*> Patterns;
140  for (CodeGenDAGPatterns::ptm_iterator I = CGP.ptm_begin(), E = CGP.ptm_end();
141       I != E; ++I)
142    Patterns.push_back(&*I);
143
144  // We want to process the matches in order of minimal cost.  Sort the patterns
145  // so the least cost one is at the start.
146  std::sort(Patterns.begin(), Patterns.end(), PatternSortingPredicate(CGP));
147
148
149  // Convert each variant of each pattern into a Matcher.
150  std::vector<Matcher*> PatternMatchers;
151  for (unsigned i = 0, e = Patterns.size(); i != e; ++i) {
152    for (unsigned Variant = 0; ; ++Variant) {
153      if (Matcher *M = ConvertPatternToMatcher(*Patterns[i], Variant, CGP))
154        PatternMatchers.push_back(M);
155      else
156        break;
157    }
158  }
159
160  Matcher *TheMatcher = new ScopeMatcher(PatternMatchers);
161
162  TheMatcher = OptimizeMatcher(TheMatcher, CGP);
163  //Matcher->dump();
164  EmitMatcherTable(TheMatcher, CGP, OS);
165  delete TheMatcher;
166}
167
168namespace llvm {
169
170void EmitDAGISel(RecordKeeper &RK, raw_ostream &OS) {
171  DAGISelEmitter(RK).run(OS);
172}
173
174} // End llvm namespace
175