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"
19 using namespace llvm;
20 
21 namespace {
22 /// DAGISelEmitter - The top-level class which coordinates construction
23 /// and emission of the instruction selector.
24 class DAGISelEmitter {
25   CodeGenDAGPatterns CGP;
26 public:
27   explicit DAGISelEmitter(RecordKeeper &R) : CGP(R) {}
28   void run(raw_ostream &OS);
29 };
30 } // End anonymous namespace
31 
32 //===----------------------------------------------------------------------===//
33 // DAGISelEmitter Helper methods
34 //
35 
36 /// getResultPatternCost - Compute the number of instructions for this pattern.
37 /// This is a temporary hack.  We should really include the instruction
38 /// latencies in this calculation.
39 static unsigned getResultPatternCost(TreePatternNode *P,
40                                      CodeGenDAGPatterns &CGP) {
41   if (P->isLeaf()) return 0;
42 
43   unsigned Cost = 0;
44   Record *Op = P->getOperator();
45   if (Op->isSubClassOf("Instruction")) {
46     Cost++;
47     CodeGenInstruction &II = CGP.getTargetInfo().getInstruction(Op);
48     if (II.usesCustomInserter)
49       Cost += 10;
50   }
51   for (unsigned i = 0, e = P->getNumChildren(); i != e; ++i)
52     Cost += getResultPatternCost(P->getChild(i), CGP);
53   return Cost;
54 }
55 
56 /// getResultPatternCodeSize - Compute the code size of instructions for this
57 /// pattern.
58 static unsigned getResultPatternSize(TreePatternNode *P,
59                                      CodeGenDAGPatterns &CGP) {
60   if (P->isLeaf()) return 0;
61 
62   unsigned Cost = 0;
63   Record *Op = P->getOperator();
64   if (Op->isSubClassOf("Instruction")) {
65     Cost += Op->getValueAsInt("CodeSize");
66   }
67   for (unsigned i = 0, e = P->getNumChildren(); i != e; ++i)
68     Cost += getResultPatternSize(P->getChild(i), CGP);
69   return Cost;
70 }
71 
72 namespace {
73 // PatternSortingPredicate - return true if we prefer to match LHS before RHS.
74 // In particular, we want to match maximal patterns first and lowest cost within
75 // a particular complexity first.
76 struct PatternSortingPredicate {
77   PatternSortingPredicate(CodeGenDAGPatterns &cgp) : CGP(cgp) {}
78   CodeGenDAGPatterns &CGP;
79 
80   bool operator()(const PatternToMatch *LHS, const PatternToMatch *RHS) {
81     const TreePatternNode *LHSSrc = LHS->getSrcPattern();
82     const TreePatternNode *RHSSrc = RHS->getSrcPattern();
83 
84     MVT LHSVT = (LHSSrc->getNumTypes() != 0 ? LHSSrc->getType(0) : MVT::Other);
85     MVT RHSVT = (RHSSrc->getNumTypes() != 0 ? RHSSrc->getType(0) : MVT::Other);
86     if (LHSVT.isVector() != RHSVT.isVector())
87       return RHSVT.isVector();
88 
89     if (LHSVT.isFloatingPoint() != RHSVT.isFloatingPoint())
90       return RHSVT.isFloatingPoint();
91 
92     // Otherwise, if the patterns might both match, sort based on complexity,
93     // which means that we prefer to match patterns that cover more nodes in the
94     // input over nodes that cover fewer.
95     unsigned LHSSize = LHS->getPatternComplexity(CGP);
96     unsigned RHSSize = RHS->getPatternComplexity(CGP);
97     if (LHSSize > RHSSize) return true;   // LHS -> bigger -> less cost
98     if (LHSSize < RHSSize) return false;
99 
100     // If the patterns have equal complexity, compare generated instruction cost
101     unsigned LHSCost = getResultPatternCost(LHS->getDstPattern(), CGP);
102     unsigned RHSCost = getResultPatternCost(RHS->getDstPattern(), CGP);
103     if (LHSCost < RHSCost) return true;
104     if (LHSCost > RHSCost) return false;
105 
106     unsigned LHSPatSize = getResultPatternSize(LHS->getDstPattern(), CGP);
107     unsigned RHSPatSize = getResultPatternSize(RHS->getDstPattern(), CGP);
108     if (LHSPatSize < RHSPatSize) return true;
109     if (LHSPatSize > RHSPatSize) return false;
110 
111     // Sort based on the UID of the pattern, giving us a deterministic ordering
112     // if all other sorting conditions fail.
113     assert(LHS == RHS || LHS->ID != RHS->ID);
114     return LHS->ID < RHS->ID;
115   }
116 };
117 } // End anonymous namespace
118 
119 
120 void DAGISelEmitter::run(raw_ostream &OS) {
121   emitSourceFileHeader("DAG Instruction Selector for the " +
122                        CGP.getTargetInfo().getName() + " target", OS);
123 
124   OS << "// *** NOTE: This file is #included into the middle of the target\n"
125      << "// *** instruction selector class.  These functions are really "
126      << "methods.\n\n";
127 
128   DEBUG(errs() << "\n\nALL PATTERNS TO MATCH:\n\n";
129         for (CodeGenDAGPatterns::ptm_iterator I = CGP.ptm_begin(),
130              E = CGP.ptm_end(); I != E; ++I) {
131           errs() << "PATTERN: ";   I->getSrcPattern()->dump();
132           errs() << "\nRESULT:  "; I->getDstPattern()->dump();
133           errs() << "\n";
134         });
135 
136   // Add all the patterns to a temporary list so we can sort them.
137   std::vector<const PatternToMatch*> Patterns;
138   for (CodeGenDAGPatterns::ptm_iterator I = CGP.ptm_begin(), E = CGP.ptm_end();
139        I != E; ++I)
140     Patterns.push_back(&*I);
141 
142   // We want to process the matches in order of minimal cost.  Sort the patterns
143   // so the least cost one is at the start.
144   std::sort(Patterns.begin(), Patterns.end(), PatternSortingPredicate(CGP));
145 
146 
147   // Convert each variant of each pattern into a Matcher.
148   std::vector<Matcher*> PatternMatchers;
149   for (unsigned i = 0, e = Patterns.size(); i != e; ++i) {
150     for (unsigned Variant = 0; ; ++Variant) {
151       if (Matcher *M = ConvertPatternToMatcher(*Patterns[i], Variant, CGP))
152         PatternMatchers.push_back(M);
153       else
154         break;
155     }
156   }
157 
158   Matcher *TheMatcher = new ScopeMatcher(&PatternMatchers[0],
159                                          PatternMatchers.size());
160 
161   TheMatcher = OptimizeMatcher(TheMatcher, CGP);
162   //Matcher->dump();
163   EmitMatcherTable(TheMatcher, CGP, OS);
164   delete TheMatcher;
165 }
166 
167 namespace llvm {
168 
169 void EmitDAGISel(RecordKeeper &RK, raw_ostream &OS) {
170   DAGISelEmitter(RK).run(OS);
171 }
172 
173 } // End llvm namespace
174