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 #define DEBUG_TYPE "dag-isel-emitter"
22
23 namespace {
24 /// DAGISelEmitter - The top-level class which coordinates construction
25 /// and emission of the instruction selector.
26 class DAGISelEmitter {
27 CodeGenDAGPatterns CGP;
28 public:
DAGISelEmitter(RecordKeeper & R)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.
getResultPatternCost(TreePatternNode * P,CodeGenDAGPatterns & CGP)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.
getResultPatternSize(TreePatternNode * P,CodeGenDAGPatterns & CGP)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 {
PatternSortingPredicate__anon65a71a470211::PatternSortingPredicate79 PatternSortingPredicate(CodeGenDAGPatterns &cgp) : CGP(cgp) {}
80 CodeGenDAGPatterns &CGP;
81
operator ()__anon65a71a470211::PatternSortingPredicate82 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
run(raw_ostream & OS)122 void 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
168 namespace llvm {
169
EmitDAGISel(RecordKeeper & RK,raw_ostream & OS)170 void EmitDAGISel(RecordKeeper &RK, raw_ostream &OS) {
171 DAGISelEmitter(RK).run(OS);
172 }
173
174 } // End llvm namespace
175