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 "DAGISelEmitter.h"
15 #include "DAGISelMatcher.h"
16 #include "llvm/TableGen/Record.h"
17 #include "llvm/Support/Debug.h"
18 using namespace llvm;
19 
20 //===----------------------------------------------------------------------===//
21 // DAGISelEmitter Helper methods
22 //
23 
24 /// getResultPatternCost - Compute the number of instructions for this pattern.
25 /// This is a temporary hack.  We should really include the instruction
26 /// latencies in this calculation.
27 static unsigned getResultPatternCost(TreePatternNode *P,
28                                      CodeGenDAGPatterns &CGP) {
29   if (P->isLeaf()) return 0;
30 
31   unsigned Cost = 0;
32   Record *Op = P->getOperator();
33   if (Op->isSubClassOf("Instruction")) {
34     Cost++;
35     CodeGenInstruction &II = CGP.getTargetInfo().getInstruction(Op);
36     if (II.usesCustomInserter)
37       Cost += 10;
38   }
39   for (unsigned i = 0, e = P->getNumChildren(); i != e; ++i)
40     Cost += getResultPatternCost(P->getChild(i), CGP);
41   return Cost;
42 }
43 
44 /// getResultPatternCodeSize - Compute the code size of instructions for this
45 /// pattern.
46 static unsigned getResultPatternSize(TreePatternNode *P,
47                                      CodeGenDAGPatterns &CGP) {
48   if (P->isLeaf()) return 0;
49 
50   unsigned Cost = 0;
51   Record *Op = P->getOperator();
52   if (Op->isSubClassOf("Instruction")) {
53     Cost += Op->getValueAsInt("CodeSize");
54   }
55   for (unsigned i = 0, e = P->getNumChildren(); i != e; ++i)
56     Cost += getResultPatternSize(P->getChild(i), CGP);
57   return Cost;
58 }
59 
60 namespace {
61 // PatternSortingPredicate - return true if we prefer to match LHS before RHS.
62 // In particular, we want to match maximal patterns first and lowest cost within
63 // a particular complexity first.
64 struct PatternSortingPredicate {
65   PatternSortingPredicate(CodeGenDAGPatterns &cgp) : CGP(cgp) {}
66   CodeGenDAGPatterns &CGP;
67 
68   bool operator()(const PatternToMatch *LHS, const PatternToMatch *RHS) {
69     const TreePatternNode *LHSSrc = LHS->getSrcPattern();
70     const TreePatternNode *RHSSrc = RHS->getSrcPattern();
71 
72     if (LHSSrc->getNumTypes() != 0 && RHSSrc->getNumTypes() != 0 &&
73         LHSSrc->getType(0) != RHSSrc->getType(0)) {
74       MVT::SimpleValueType V1 = LHSSrc->getType(0), V2 = RHSSrc->getType(0);
75       if (MVT(V1).isVector() != MVT(V2).isVector())
76         return MVT(V2).isVector();
77 
78       if (MVT(V1).isFloatingPoint() != MVT(V2).isFloatingPoint())
79         return MVT(V2).isFloatingPoint();
80     }
81 
82     // Otherwise, if the patterns might both match, sort based on complexity,
83     // which means that we prefer to match patterns that cover more nodes in the
84     // input over nodes that cover fewer.
85     unsigned LHSSize = LHS->getPatternComplexity(CGP);
86     unsigned RHSSize = RHS->getPatternComplexity(CGP);
87     if (LHSSize > RHSSize) return true;   // LHS -> bigger -> less cost
88     if (LHSSize < RHSSize) return false;
89 
90     // If the patterns have equal complexity, compare generated instruction cost
91     unsigned LHSCost = getResultPatternCost(LHS->getDstPattern(), CGP);
92     unsigned RHSCost = getResultPatternCost(RHS->getDstPattern(), CGP);
93     if (LHSCost < RHSCost) return true;
94     if (LHSCost > RHSCost) return false;
95 
96     unsigned LHSPatSize = getResultPatternSize(LHS->getDstPattern(), CGP);
97     unsigned RHSPatSize = getResultPatternSize(RHS->getDstPattern(), CGP);
98     if (LHSPatSize < RHSPatSize) return true;
99     if (LHSPatSize > RHSPatSize) return false;
100 
101     // Sort based on the UID of the pattern, giving us a deterministic ordering
102     // if all other sorting conditions fail.
103     assert(LHS == RHS || LHS->ID != RHS->ID);
104     return LHS->ID < RHS->ID;
105   }
106 };
107 }
108 
109 
110 void DAGISelEmitter::run(raw_ostream &OS) {
111   EmitSourceFileHeader("DAG Instruction Selector for the " +
112                        CGP.getTargetInfo().getName() + " target", OS);
113 
114   OS << "// *** NOTE: This file is #included into the middle of the target\n"
115      << "// *** instruction selector class.  These functions are really "
116      << "methods.\n\n";
117 
118   DEBUG(errs() << "\n\nALL PATTERNS TO MATCH:\n\n";
119         for (CodeGenDAGPatterns::ptm_iterator I = CGP.ptm_begin(),
120              E = CGP.ptm_end(); I != E; ++I) {
121           errs() << "PATTERN: ";   I->getSrcPattern()->dump();
122           errs() << "\nRESULT:  "; I->getDstPattern()->dump();
123           errs() << "\n";
124         });
125 
126   // Add all the patterns to a temporary list so we can sort them.
127   std::vector<const PatternToMatch*> Patterns;
128   for (CodeGenDAGPatterns::ptm_iterator I = CGP.ptm_begin(), E = CGP.ptm_end();
129        I != E; ++I)
130     Patterns.push_back(&*I);
131 
132   // We want to process the matches in order of minimal cost.  Sort the patterns
133   // so the least cost one is at the start.
134   std::sort(Patterns.begin(), Patterns.end(), PatternSortingPredicate(CGP));
135 
136 
137   // Convert each variant of each pattern into a Matcher.
138   std::vector<Matcher*> PatternMatchers;
139   for (unsigned i = 0, e = Patterns.size(); i != e; ++i) {
140     for (unsigned Variant = 0; ; ++Variant) {
141       if (Matcher *M = ConvertPatternToMatcher(*Patterns[i], Variant, CGP))
142         PatternMatchers.push_back(M);
143       else
144         break;
145     }
146   }
147 
148   Matcher *TheMatcher = new ScopeMatcher(&PatternMatchers[0],
149                                          PatternMatchers.size());
150 
151   TheMatcher = OptimizeMatcher(TheMatcher, CGP);
152   //Matcher->dump();
153   EmitMatcherTable(TheMatcher, CGP, OS);
154   delete TheMatcher;
155 }
156