1 //===- Scope.cpp - Lexical scope information --------------------*- 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 implements the Scope class, which is used for recording
10 // information about a lexical scope.
11 //
12 //===----------------------------------------------------------------------===//
13
14 #include "clang/Sema/Scope.h"
15 #include "clang/AST/Decl.h"
16 #include "llvm/Support/raw_ostream.h"
17
18 using namespace clang;
19
setFlags(Scope * parent,unsigned flags)20 void Scope::setFlags(Scope *parent, unsigned flags) {
21 AnyParent = parent;
22 Flags = flags;
23
24 if (parent && !(flags & FnScope)) {
25 BreakParent = parent->BreakParent;
26 ContinueParent = parent->ContinueParent;
27 } else {
28 // Control scopes do not contain the contents of nested function scopes for
29 // control flow purposes.
30 BreakParent = ContinueParent = nullptr;
31 }
32
33 if (parent) {
34 Depth = parent->Depth + 1;
35 PrototypeDepth = parent->PrototypeDepth;
36 PrototypeIndex = 0;
37 FnParent = parent->FnParent;
38 BlockParent = parent->BlockParent;
39 TemplateParamParent = parent->TemplateParamParent;
40 DeclParent = parent->DeclParent;
41 MSLastManglingParent = parent->MSLastManglingParent;
42 MSCurManglingNumber = getMSLastManglingNumber();
43 if ((Flags & (FnScope | ClassScope | BlockScope | TemplateParamScope |
44 FunctionPrototypeScope | AtCatchScope | ObjCMethodScope)) ==
45 0)
46 Flags |= parent->getFlags() & OpenMPSimdDirectiveScope;
47 // transmit the parent's 'order' flag, if exists
48 if (parent->getFlags() & OpenMPOrderClauseScope)
49 Flags |= OpenMPOrderClauseScope;
50 } else {
51 Depth = 0;
52 PrototypeDepth = 0;
53 PrototypeIndex = 0;
54 MSLastManglingParent = FnParent = BlockParent = nullptr;
55 TemplateParamParent = nullptr;
56 DeclParent = nullptr;
57 MSLastManglingNumber = 1;
58 MSCurManglingNumber = 1;
59 }
60
61 // If this scope is a function or contains breaks/continues, remember it.
62 if (flags & FnScope) FnParent = this;
63 // The MS mangler uses the number of scopes that can hold declarations as
64 // part of an external name.
65 if (Flags & (ClassScope | FnScope)) {
66 MSLastManglingNumber = getMSLastManglingNumber();
67 MSLastManglingParent = this;
68 MSCurManglingNumber = 1;
69 }
70 if (flags & BreakScope) BreakParent = this;
71 if (flags & ContinueScope) ContinueParent = this;
72 if (flags & BlockScope) BlockParent = this;
73 if (flags & TemplateParamScope) TemplateParamParent = this;
74
75 // If this is a prototype scope, record that. Lambdas have an extra prototype
76 // scope that doesn't add any depth.
77 if (flags & FunctionPrototypeScope && !(flags & LambdaScope))
78 PrototypeDepth++;
79
80 if (flags & DeclScope) {
81 DeclParent = this;
82 if (flags & FunctionPrototypeScope)
83 ; // Prototype scopes are uninteresting.
84 else if ((flags & ClassScope) && getParent()->isClassScope())
85 ; // Nested class scopes aren't ambiguous.
86 else if ((flags & ClassScope) && getParent()->getFlags() == DeclScope)
87 ; // Classes inside of namespaces aren't ambiguous.
88 else if ((flags & EnumScope))
89 ; // Don't increment for enum scopes.
90 else
91 incrementMSManglingNumber();
92 }
93 }
94
Init(Scope * parent,unsigned flags)95 void Scope::Init(Scope *parent, unsigned flags) {
96 setFlags(parent, flags);
97
98 DeclsInScope.clear();
99 UsingDirectives.clear();
100 Entity = nullptr;
101 ErrorTrap.reset();
102 NRVO = std::nullopt;
103 }
104
containedInPrototypeScope() const105 bool Scope::containedInPrototypeScope() const {
106 const Scope *S = this;
107 while (S) {
108 if (S->isFunctionPrototypeScope())
109 return true;
110 S = S->getParent();
111 }
112 return false;
113 }
114
AddFlags(unsigned FlagsToSet)115 void Scope::AddFlags(unsigned FlagsToSet) {
116 assert((FlagsToSet & ~(BreakScope | ContinueScope)) == 0 &&
117 "Unsupported scope flags");
118 if (FlagsToSet & BreakScope) {
119 assert((Flags & BreakScope) == 0 && "Already set");
120 BreakParent = this;
121 }
122 if (FlagsToSet & ContinueScope) {
123 assert((Flags & ContinueScope) == 0 && "Already set");
124 ContinueParent = this;
125 }
126 Flags |= FlagsToSet;
127 }
128
129 // The algorithm for updating NRVO candidate is as follows:
130 // 1. All previous candidates become invalid because a new NRVO candidate is
131 // obtained. Therefore, we need to clear return slots for other
132 // variables defined before the current return statement in the current
133 // scope and in outer scopes.
134 // 2. Store the new candidate if its return slot is available. Otherwise,
135 // there is no NRVO candidate so far.
updateNRVOCandidate(VarDecl * VD)136 void Scope::updateNRVOCandidate(VarDecl *VD) {
137 auto UpdateReturnSlotsInScopeForVD = [VD](Scope *S) -> bool {
138 bool IsReturnSlotFound = S->ReturnSlots.contains(VD);
139
140 // We found a candidate variable that can be put into a return slot.
141 // Clear the set, because other variables cannot occupy a return
142 // slot in the same scope.
143 S->ReturnSlots.clear();
144
145 if (IsReturnSlotFound)
146 S->ReturnSlots.insert(VD);
147
148 return IsReturnSlotFound;
149 };
150
151 bool CanBePutInReturnSlot = false;
152
153 for (auto *S = this; S; S = S->getParent()) {
154 CanBePutInReturnSlot |= UpdateReturnSlotsInScopeForVD(S);
155
156 if (S->getEntity())
157 break;
158 }
159
160 // Consider the variable as NRVO candidate if the return slot is available
161 // for it in the current scope, or if it can be available in outer scopes.
162 NRVO = CanBePutInReturnSlot ? VD : nullptr;
163 }
164
applyNRVO()165 void Scope::applyNRVO() {
166 // There is no NRVO candidate in the current scope.
167 if (!NRVO.has_value())
168 return;
169
170 if (*NRVO && isDeclScope(*NRVO))
171 (*NRVO)->setNRVOVariable(true);
172
173 // It's necessary to propagate NRVO candidate to the parent scope for cases
174 // when the parent scope doesn't contain a return statement.
175 // For example:
176 // X foo(bool b) {
177 // X x;
178 // if (b)
179 // return x;
180 // exit(0);
181 // }
182 // Also, we need to propagate nullptr value that means NRVO is not
183 // allowed in this scope.
184 // For example:
185 // X foo(bool b) {
186 // X x;
187 // if (b)
188 // return x;
189 // else
190 // return X(); // NRVO is not allowed
191 // }
192 if (!getEntity())
193 getParent()->NRVO = *NRVO;
194 }
195
dump() const196 LLVM_DUMP_METHOD void Scope::dump() const { dumpImpl(llvm::errs()); }
197
dumpImpl(raw_ostream & OS) const198 void Scope::dumpImpl(raw_ostream &OS) const {
199 unsigned Flags = getFlags();
200 bool HasFlags = Flags != 0;
201
202 if (HasFlags)
203 OS << "Flags: ";
204
205 std::pair<unsigned, const char *> FlagInfo[] = {
206 {FnScope, "FnScope"},
207 {BreakScope, "BreakScope"},
208 {ContinueScope, "ContinueScope"},
209 {DeclScope, "DeclScope"},
210 {ControlScope, "ControlScope"},
211 {ClassScope, "ClassScope"},
212 {BlockScope, "BlockScope"},
213 {TemplateParamScope, "TemplateParamScope"},
214 {FunctionPrototypeScope, "FunctionPrototypeScope"},
215 {FunctionDeclarationScope, "FunctionDeclarationScope"},
216 {AtCatchScope, "AtCatchScope"},
217 {ObjCMethodScope, "ObjCMethodScope"},
218 {SwitchScope, "SwitchScope"},
219 {TryScope, "TryScope"},
220 {FnTryCatchScope, "FnTryCatchScope"},
221 {OpenMPDirectiveScope, "OpenMPDirectiveScope"},
222 {OpenMPLoopDirectiveScope, "OpenMPLoopDirectiveScope"},
223 {OpenMPSimdDirectiveScope, "OpenMPSimdDirectiveScope"},
224 {EnumScope, "EnumScope"},
225 {SEHTryScope, "SEHTryScope"},
226 {SEHExceptScope, "SEHExceptScope"},
227 {SEHFilterScope, "SEHFilterScope"},
228 {CompoundStmtScope, "CompoundStmtScope"},
229 {ClassInheritanceScope, "ClassInheritanceScope"},
230 {CatchScope, "CatchScope"},
231 {ConditionVarScope, "ConditionVarScope"},
232 {OpenMPOrderClauseScope, "OpenMPOrderClauseScope"},
233 {LambdaScope, "LambdaScope"},
234 {OpenACCComputeConstructScope, "OpenACCComputeConstructScope"},
235 {TypeAliasScope, "TypeAliasScope"},
236 {FriendScope, "FriendScope"},
237 };
238
239 for (auto Info : FlagInfo) {
240 if (Flags & Info.first) {
241 OS << Info.second;
242 Flags &= ~Info.first;
243 if (Flags)
244 OS << " | ";
245 }
246 }
247
248 assert(Flags == 0 && "Unknown scope flags");
249
250 if (HasFlags)
251 OS << '\n';
252
253 if (const Scope *Parent = getParent())
254 OS << "Parent: (clang::Scope*)" << Parent << '\n';
255
256 OS << "Depth: " << Depth << '\n';
257 OS << "MSLastManglingNumber: " << getMSLastManglingNumber() << '\n';
258 OS << "MSCurManglingNumber: " << getMSCurManglingNumber() << '\n';
259 if (const DeclContext *DC = getEntity())
260 OS << "Entity : (clang::DeclContext*)" << DC << '\n';
261
262 if (!NRVO)
263 OS << "there is no NRVO candidate\n";
264 else if (*NRVO)
265 OS << "NRVO candidate : (clang::VarDecl*)" << *NRVO << '\n';
266 else
267 OS << "NRVO is not allowed\n";
268 }
269