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 "Common/CodeGenDAGPatterns.h"
14 #include "Common/CodeGenInstruction.h"
15 #include "Common/CodeGenTarget.h"
16 #include "Common/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
31 public:
DAGISelEmitter(RecordKeeper & R)32 explicit DAGISelEmitter(RecordKeeper &R) : Records(R), CGP(R) {}
33 void run(raw_ostream &OS);
34 };
35 } // End anonymous namespace
36
37 //===----------------------------------------------------------------------===//
38 // DAGISelEmitter Helper methods
39 //
40
41 /// Compute the number of instructions for this pattern.
42 /// This is a temporary hack. We should really include the instruction
43 /// latencies in this calculation.
getResultPatternCost(TreePatternNode & P,const CodeGenDAGPatterns & CGP)44 static unsigned getResultPatternCost(TreePatternNode &P,
45 const CodeGenDAGPatterns &CGP) {
46 if (P.isLeaf())
47 return 0;
48
49 unsigned Cost = 0;
50 Record *Op = P.getOperator();
51 if (Op->isSubClassOf("Instruction")) {
52 Cost++;
53 CodeGenInstruction &II = CGP.getTargetInfo().getInstruction(Op);
54 if (II.usesCustomInserter)
55 Cost += 10;
56 }
57 for (unsigned i = 0, e = P.getNumChildren(); i != e; ++i)
58 Cost += getResultPatternCost(P.getChild(i), CGP);
59 return Cost;
60 }
61
62 /// getResultPatternCodeSize - Compute the code size of instructions for this
63 /// pattern.
getResultPatternSize(TreePatternNode & P,const CodeGenDAGPatterns & CGP)64 static unsigned getResultPatternSize(TreePatternNode &P,
65 const CodeGenDAGPatterns &CGP) {
66 if (P.isLeaf())
67 return 0;
68
69 unsigned Cost = 0;
70 Record *Op = P.getOperator();
71 if (Op->isSubClassOf("Instruction")) {
72 Cost += Op->getValueAsInt("CodeSize");
73 }
74 for (unsigned i = 0, e = P.getNumChildren(); i != e; ++i)
75 Cost += getResultPatternSize(P.getChild(i), CGP);
76 return Cost;
77 }
78
79 namespace {
80 // PatternSortingPredicate - return true if we prefer to match LHS before RHS.
81 // In particular, we want to match maximal patterns first and lowest cost within
82 // a particular complexity first.
83 struct PatternSortingPredicate {
PatternSortingPredicate__anonae03922e0211::PatternSortingPredicate84 PatternSortingPredicate(CodeGenDAGPatterns &cgp) : CGP(cgp) {}
85 CodeGenDAGPatterns &CGP;
86
operator ()__anonae03922e0211::PatternSortingPredicate87 bool operator()(const PatternToMatch *LHS, const PatternToMatch *RHS) {
88 const TreePatternNode < = LHS->getSrcPattern();
89 const TreePatternNode &RT = RHS->getSrcPattern();
90
91 MVT LHSVT = LT.getNumTypes() != 0 ? LT.getSimpleType(0) : MVT::Other;
92 MVT RHSVT = RT.getNumTypes() != 0 ? RT.getSimpleType(0) : MVT::Other;
93 if (LHSVT.isVector() != RHSVT.isVector())
94 return RHSVT.isVector();
95
96 if (LHSVT.isFloatingPoint() != RHSVT.isFloatingPoint())
97 return RHSVT.isFloatingPoint();
98
99 // Otherwise, if the patterns might both match, sort based on complexity,
100 // which means that we prefer to match patterns that cover more nodes in the
101 // input over nodes that cover fewer.
102 int LHSSize = LHS->getPatternComplexity(CGP);
103 int RHSSize = RHS->getPatternComplexity(CGP);
104 if (LHSSize > RHSSize)
105 return true; // LHS -> bigger -> less cost
106 if (LHSSize < RHSSize)
107 return false;
108
109 // If the patterns have equal complexity, compare generated instruction cost
110 unsigned LHSCost = getResultPatternCost(LHS->getDstPattern(), CGP);
111 unsigned RHSCost = getResultPatternCost(RHS->getDstPattern(), CGP);
112 if (LHSCost < RHSCost)
113 return true;
114 if (LHSCost > RHSCost)
115 return false;
116
117 unsigned LHSPatSize = getResultPatternSize(LHS->getDstPattern(), CGP);
118 unsigned RHSPatSize = getResultPatternSize(RHS->getDstPattern(), CGP);
119 if (LHSPatSize < RHSPatSize)
120 return true;
121 if (LHSPatSize > RHSPatSize)
122 return false;
123
124 // Sort based on the UID of the pattern, to reflect source order.
125 // Note that this is not guaranteed to be unique, since a single source
126 // pattern may have been resolved into multiple match patterns due to
127 // alternative fragments. To ensure deterministic output, always use
128 // std::stable_sort with this predicate.
129 return LHS->getID() < RHS->getID();
130 }
131 };
132 } // End anonymous namespace
133
run(raw_ostream & OS)134 void DAGISelEmitter::run(raw_ostream &OS) {
135 Records.startTimer("Parse patterns");
136 emitSourceFileHeader("DAG Instruction Selector for the " +
137 CGP.getTargetInfo().getName().str() + " target",
138 OS);
139
140 OS << "// *** NOTE: This file is #included into the middle of the target\n"
141 << "// *** instruction selector class. These functions are really "
142 << "methods.\n\n";
143
144 OS << "// If GET_DAGISEL_DECL is #defined with any value, only function\n"
145 "// declarations will be included when this file is included.\n"
146 "// If GET_DAGISEL_BODY is #defined, its value should be the name of\n"
147 "// the instruction selector class. Function bodies will be emitted\n"
148 "// and each function's name will be qualified with the name of the\n"
149 "// class.\n"
150 "//\n"
151 "// When neither of the GET_DAGISEL* macros is defined, the functions\n"
152 "// are emitted inline.\n\n";
153
154 LLVM_DEBUG(errs() << "\n\nALL PATTERNS TO MATCH:\n\n";
155 for (CodeGenDAGPatterns::ptm_iterator I = CGP.ptm_begin(),
156 E = CGP.ptm_end();
157 I != E; ++I) {
158 errs() << "PATTERN: ";
159 I->getSrcPattern().dump();
160 errs() << "\nRESULT: ";
161 I->getDstPattern().dump();
162 errs() << "\n";
163 });
164
165 // Add all the patterns to a temporary list so we can sort them.
166 Records.startTimer("Sort patterns");
167 std::vector<const PatternToMatch *> Patterns;
168 for (const PatternToMatch &PTM : CGP.ptms())
169 Patterns.push_back(&PTM);
170
171 // We want to process the matches in order of minimal cost. Sort the patterns
172 // so the least cost one is at the start.
173 llvm::stable_sort(Patterns, PatternSortingPredicate(CGP));
174
175 // Convert each variant of each pattern into a Matcher.
176 Records.startTimer("Convert to matchers");
177 SmallVector<Matcher *, 0> PatternMatchers;
178 for (const PatternToMatch *PTM : Patterns) {
179 for (unsigned Variant = 0;; ++Variant) {
180 if (Matcher *M = ConvertPatternToMatcher(*PTM, Variant, CGP))
181 PatternMatchers.push_back(M);
182 else
183 break;
184 }
185 }
186
187 std::unique_ptr<Matcher> TheMatcher =
188 std::make_unique<ScopeMatcher>(std::move(PatternMatchers));
189
190 Records.startTimer("Optimize matchers");
191 OptimizeMatcher(TheMatcher, CGP);
192
193 // Matcher->dump();
194
195 Records.startTimer("Emit matcher table");
196 EmitMatcherTable(TheMatcher.get(), CGP, OS);
197 }
198
199 static TableGen::Emitter::OptClass<DAGISelEmitter>
200 X("gen-dag-isel", "Generate a DAG instruction selector");
201