1 //===- ComparisonCategories.cpp - Three Way Comparison Data -----*- C++ -*-===//
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 file defines the Comparison Category enum and data types, which
10 // store the types and expressions needed to support operator<=>
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "clang/AST/ComparisonCategories.h"
15 #include "clang/AST/ASTContext.h"
16 #include "clang/AST/Decl.h"
17 #include "clang/AST/DeclCXX.h"
18 #include "clang/AST/Type.h"
19 #include "llvm/ADT/SmallVector.h"
20
21 using namespace clang;
22
23 Optional<ComparisonCategoryType>
getComparisonCategoryForBuiltinCmp(QualType T)24 clang::getComparisonCategoryForBuiltinCmp(QualType T) {
25 using CCT = ComparisonCategoryType;
26
27 if (T->isIntegralOrEnumerationType())
28 return CCT::StrongOrdering;
29
30 if (T->isRealFloatingType())
31 return CCT::PartialOrdering;
32
33 // C++2a [expr.spaceship]p8: If the composite pointer type is an object
34 // pointer type, p <=> q is of type std::strong_ordering.
35 // Note: this assumes neither operand is a null pointer constant.
36 if (T->isObjectPointerType())
37 return CCT::StrongOrdering;
38
39 // TODO: Extend support for operator<=> to ObjC types.
40 return llvm::None;
41 }
42
hasValidIntValue() const43 bool ComparisonCategoryInfo::ValueInfo::hasValidIntValue() const {
44 assert(VD && "must have var decl");
45 if (!VD->isUsableInConstantExpressions(VD->getASTContext()))
46 return false;
47
48 // Before we attempt to get the value of the first field, ensure that we
49 // actually have one (and only one) field.
50 auto *Record = VD->getType()->getAsCXXRecordDecl();
51 if (std::distance(Record->field_begin(), Record->field_end()) != 1 ||
52 !Record->field_begin()->getType()->isIntegralOrEnumerationType())
53 return false;
54
55 return true;
56 }
57
58 /// Attempt to determine the integer value used to represent the comparison
59 /// category result by evaluating the initializer for the specified VarDecl as
60 /// a constant expression and retreiving the value of the class's first
61 /// (and only) field.
62 ///
63 /// Note: The STL types are expected to have the form:
64 /// struct X { T value; };
65 /// where T is an integral or enumeration type.
getIntValue() const66 llvm::APSInt ComparisonCategoryInfo::ValueInfo::getIntValue() const {
67 assert(hasValidIntValue() && "must have a valid value");
68 return VD->evaluateValue()->getStructField(0).getInt();
69 }
70
lookupValueInfo(ComparisonCategoryResult ValueKind) const71 ComparisonCategoryInfo::ValueInfo *ComparisonCategoryInfo::lookupValueInfo(
72 ComparisonCategoryResult ValueKind) const {
73 // Check if we already have a cache entry for this value.
74 auto It = llvm::find_if(
75 Objects, [&](ValueInfo const &Info) { return Info.Kind == ValueKind; });
76 if (It != Objects.end())
77 return &(*It);
78
79 // We don't have a cached result. Lookup the variable declaration and create
80 // a new entry representing it.
81 DeclContextLookupResult Lookup = Record->getCanonicalDecl()->lookup(
82 &Ctx.Idents.get(ComparisonCategories::getResultString(ValueKind)));
83 if (Lookup.empty() || !isa<VarDecl>(Lookup.front()))
84 return nullptr;
85 Objects.emplace_back(ValueKind, cast<VarDecl>(Lookup.front()));
86 return &Objects.back();
87 }
88
lookupStdNamespace(const ASTContext & Ctx,NamespaceDecl * & StdNS)89 static const NamespaceDecl *lookupStdNamespace(const ASTContext &Ctx,
90 NamespaceDecl *&StdNS) {
91 if (!StdNS) {
92 DeclContextLookupResult Lookup =
93 Ctx.getTranslationUnitDecl()->lookup(&Ctx.Idents.get("std"));
94 if (!Lookup.empty())
95 StdNS = dyn_cast<NamespaceDecl>(Lookup.front());
96 }
97 return StdNS;
98 }
99
lookupCXXRecordDecl(const ASTContext & Ctx,const NamespaceDecl * StdNS,ComparisonCategoryType Kind)100 static CXXRecordDecl *lookupCXXRecordDecl(const ASTContext &Ctx,
101 const NamespaceDecl *StdNS,
102 ComparisonCategoryType Kind) {
103 StringRef Name = ComparisonCategories::getCategoryString(Kind);
104 DeclContextLookupResult Lookup = StdNS->lookup(&Ctx.Idents.get(Name));
105 if (!Lookup.empty())
106 if (CXXRecordDecl *RD = dyn_cast<CXXRecordDecl>(Lookup.front()))
107 return RD;
108 return nullptr;
109 }
110
111 const ComparisonCategoryInfo *
lookupInfo(ComparisonCategoryType Kind) const112 ComparisonCategories::lookupInfo(ComparisonCategoryType Kind) const {
113 auto It = Data.find(static_cast<char>(Kind));
114 if (It != Data.end())
115 return &It->second;
116
117 if (const NamespaceDecl *NS = lookupStdNamespace(Ctx, StdNS))
118 if (CXXRecordDecl *RD = lookupCXXRecordDecl(Ctx, NS, Kind))
119 return &Data.try_emplace((char)Kind, Ctx, RD, Kind).first->second;
120
121 return nullptr;
122 }
123
124 const ComparisonCategoryInfo *
lookupInfoForType(QualType Ty) const125 ComparisonCategories::lookupInfoForType(QualType Ty) const {
126 assert(!Ty.isNull() && "type must be non-null");
127 using CCT = ComparisonCategoryType;
128 auto *RD = Ty->getAsCXXRecordDecl();
129 if (!RD)
130 return nullptr;
131
132 // Check to see if we have information for the specified type cached.
133 const auto *CanonRD = RD->getCanonicalDecl();
134 for (auto &KV : Data) {
135 const ComparisonCategoryInfo &Info = KV.second;
136 if (CanonRD == Info.Record->getCanonicalDecl())
137 return &Info;
138 }
139
140 if (!RD->getEnclosingNamespaceContext()->isStdNamespace())
141 return nullptr;
142
143 // If not, check to see if the decl names a type in namespace std with a name
144 // matching one of the comparison category types.
145 for (unsigned I = static_cast<unsigned>(CCT::First),
146 End = static_cast<unsigned>(CCT::Last);
147 I <= End; ++I) {
148 CCT Kind = static_cast<CCT>(I);
149
150 // We've found the comparison category type. Build a new cache entry for
151 // it.
152 if (getCategoryString(Kind) == RD->getName())
153 return &Data.try_emplace((char)Kind, Ctx, RD, Kind).first->second;
154 }
155
156 // We've found nothing. This isn't a comparison category type.
157 return nullptr;
158 }
159
getInfoForType(QualType Ty) const160 const ComparisonCategoryInfo &ComparisonCategories::getInfoForType(QualType Ty) const {
161 const ComparisonCategoryInfo *Info = lookupInfoForType(Ty);
162 assert(Info && "info for comparison category not found");
163 return *Info;
164 }
165
getType() const166 QualType ComparisonCategoryInfo::getType() const {
167 assert(Record);
168 return QualType(Record->getTypeForDecl(), 0);
169 }
170
getCategoryString(ComparisonCategoryType Kind)171 StringRef ComparisonCategories::getCategoryString(ComparisonCategoryType Kind) {
172 using CCKT = ComparisonCategoryType;
173 switch (Kind) {
174 case CCKT::PartialOrdering:
175 return "partial_ordering";
176 case CCKT::WeakOrdering:
177 return "weak_ordering";
178 case CCKT::StrongOrdering:
179 return "strong_ordering";
180 }
181 llvm_unreachable("unhandled cases in switch");
182 }
183
getResultString(ComparisonCategoryResult Kind)184 StringRef ComparisonCategories::getResultString(ComparisonCategoryResult Kind) {
185 using CCVT = ComparisonCategoryResult;
186 switch (Kind) {
187 case CCVT::Equal:
188 return "equal";
189 case CCVT::Equivalent:
190 return "equivalent";
191 case CCVT::Less:
192 return "less";
193 case CCVT::Greater:
194 return "greater";
195 case CCVT::Unordered:
196 return "unordered";
197 }
198 llvm_unreachable("unhandled case in switch");
199 }
200
201 std::vector<ComparisonCategoryResult>
getPossibleResultsForType(ComparisonCategoryType Type)202 ComparisonCategories::getPossibleResultsForType(ComparisonCategoryType Type) {
203 using CCT = ComparisonCategoryType;
204 using CCR = ComparisonCategoryResult;
205 std::vector<CCR> Values;
206 Values.reserve(4);
207 bool IsStrong = Type == CCT::StrongOrdering;
208 Values.push_back(IsStrong ? CCR::Equal : CCR::Equivalent);
209 Values.push_back(CCR::Less);
210 Values.push_back(CCR::Greater);
211 if (Type == CCT::PartialOrdering)
212 Values.push_back(CCR::Unordered);
213 return Values;
214 }
215