[clang] Add method 'backupStr' to ASTContext (#99417)

Summary:
Method 'backupStr' extracts common code of dynamically allocating memory
with ASTContext to hold a copy of a string's contents.

Test Plan: 

Reviewers: 

Subscribers: 

Tasks: 

Tags: 


Differential Revision: https://phabricator.intern.facebook.com/D60251287

Author: JOE1994

clang/include/clang/AST/ASTContext.h

@@ -738,6 +738,12 @@ class ASTContext : public RefCountedBase<ASTContext> {
   }
   void Deallocate(void *Ptr) const {}
 
+  llvm::StringRef backupStr(llvm::StringRef S) const {
+    char *Buf = new (*this) char[S.size()];
+    std::copy(S.begin(), S.end(), Buf);
+    return llvm::StringRef(Buf, S.size());
+  }
+
   /// Allocates a \c DeclListNode or returns one from the \c ListNodeFreeList
   /// pool.
   DeclListNode *AllocateDeclListNode(clang::NamedDecl *ND) {

clang/lib/AST/ASTConcept.cpp

@@ -28,11 +28,9 @@ CreateUnsatisfiedConstraintRecord(const ASTContext &C,
   else {
     auto &SubstitutionDiagnostic =
         *Detail.get<std::pair<SourceLocation, StringRef> *>();
-    unsigned MessageSize = SubstitutionDiagnostic.second.size();
-    char *Mem = new (C) char[MessageSize];
-    memcpy(Mem, SubstitutionDiagnostic.second.data(), MessageSize);
+    StringRef Message = C.backupStr(SubstitutionDiagnostic.second);
     auto *NewSubstDiag = new (C) std::pair<SourceLocation, StringRef>(
-        SubstitutionDiagnostic.first, StringRef(Mem, MessageSize));
+        SubstitutionDiagnostic.first, Message);
     new (TrailingObject) UnsatisfiedConstraintRecord(NewSubstDiag);
   }
 }

clang/lib/Sema/SemaTemplateInstantiate.cpp

@@ -2576,16 +2576,12 @@ createSubstDiag(Sema &S, TemplateDeductionInfo &Info,
   } else {
     ErrorLoc = Info.getLocation();
   }
-  char *MessageBuf = new (S.Context) char[Message.size()];
-  std::copy(Message.begin(), Message.end(), MessageBuf);
   SmallString<128> Entity;
   llvm::raw_svector_ostream OS(Entity);
   Printer(OS);
-  char *EntityBuf = new (S.Context) char[Entity.size()];
-  std::copy(Entity.begin(), Entity.end(), EntityBuf);
-  return new (S.Context) concepts::Requirement::SubstitutionDiagnostic{
-      StringRef(EntityBuf, Entity.size()), ErrorLoc,
-      StringRef(MessageBuf, Message.size())};
+  const ASTContext &C = S.Context;
+  return new (C) concepts::Requirement::SubstitutionDiagnostic{
+      C.backupStr(Entity), ErrorLoc, C.backupStr(Message)};
 }
 
 concepts::Requirement::SubstitutionDiagnostic *
@@ -2594,10 +2590,9 @@ concepts::createSubstDiagAt(Sema &S, SourceLocation Location,
   SmallString<128> Entity;
   llvm::raw_svector_ostream OS(Entity);
   Printer(OS);
-  char *EntityBuf = new (S.Context) char[Entity.size()];
-  llvm::copy(Entity, EntityBuf);
-  return new (S.Context) concepts::Requirement::SubstitutionDiagnostic{
-      /*SubstitutedEntity=*/StringRef(EntityBuf, Entity.size()),
+  const ASTContext &C = S.Context;
+  return new (C) concepts::Requirement::SubstitutionDiagnostic{
+      /*SubstitutedEntity=*/C.backupStr(Entity),
       /*DiagLoc=*/Location, /*DiagMessage=*/StringRef()};
 }
 
@@ -2773,23 +2768,21 @@ TemplateInstantiator::TransformNestedRequirement(
     assert(!Trap.hasErrorOccurred() && "Substitution failures must be handled "
                                        "by CheckConstraintSatisfaction.");
   }
+  ASTContext &C = SemaRef.Context;
   if (TransConstraint.isUsable() &&
       TransConstraint.get()->isInstantiationDependent())
-    return new (SemaRef.Context)
-        concepts::NestedRequirement(TransConstraint.get());
+    return new (C) concepts::NestedRequirement(TransConstraint.get());
   if (TransConstraint.isInvalid() || !TransConstraint.get() ||
       Satisfaction.HasSubstitutionFailure()) {
     SmallString<128> Entity;
     llvm::raw_svector_ostream OS(Entity);
     Req->getConstraintExpr()->printPretty(OS, nullptr,
                                           SemaRef.getPrintingPolicy());
-    char *EntityBuf = new (SemaRef.Context) char[Entity.size()];
-    std::copy(Entity.begin(), Entity.end(), EntityBuf);
-    return new (SemaRef.Context) concepts::NestedRequirement(
-        SemaRef.Context, StringRef(EntityBuf, Entity.size()), Satisfaction);
+    return new (C) concepts::NestedRequirement(
+        SemaRef.Context, C.backupStr(Entity), Satisfaction);
   }
-  return new (SemaRef.Context) concepts::NestedRequirement(
-      SemaRef.Context, TransConstraint.get(), Satisfaction);
+  return new (C)
+      concepts::NestedRequirement(C, TransConstraint.get(), Satisfaction);
 }
 
 TypeSourceInfo *Sema::SubstType(TypeSourceInfo *T,

clang/lib/Serialization/ASTReaderStmt.cpp

@@ -785,29 +785,22 @@ void ASTStmtReader::VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr *E) {
   E->setRParenLoc(readSourceLocation());
 }
 
-static StringRef saveStrToCtx(const std::string &S, ASTContext &Ctx) {
-  char *Buf = new (Ctx) char[S.size()];
-  std::copy(S.begin(), S.end(), Buf);
-  return StringRef(Buf, S.size());
-}
-
 static ConstraintSatisfaction
 readConstraintSatisfaction(ASTRecordReader &Record) {
   ConstraintSatisfaction Satisfaction;
   Satisfaction.IsSatisfied = Record.readInt();
   Satisfaction.ContainsErrors = Record.readInt();
+  const ASTContext &C = Record.getContext();
   if (!Satisfaction.IsSatisfied) {
     unsigned NumDetailRecords = Record.readInt();
     for (unsigned i = 0; i != NumDetailRecords; ++i) {
       if (/* IsDiagnostic */Record.readInt()) {
         SourceLocation DiagLocation = Record.readSourceLocation();
-        StringRef DiagMessage =
-            saveStrToCtx(Record.readString(), Record.getContext());
+        StringRef DiagMessage = C.backupStr(Record.readString());
 
         Satisfaction.Details.emplace_back(
-            new (Record.getContext())
-                ConstraintSatisfaction::SubstitutionDiagnostic(DiagLocation,
-                                                               DiagMessage));
+            new (C) ConstraintSatisfaction::SubstitutionDiagnostic(
+                DiagLocation, DiagMessage));
       } else
         Satisfaction.Details.emplace_back(Record.readExpr());
     }
@@ -828,12 +821,10 @@ void ASTStmtReader::VisitConceptSpecializationExpr(
 
 static concepts::Requirement::SubstitutionDiagnostic *
 readSubstitutionDiagnostic(ASTRecordReader &Record) {
-  StringRef SubstitutedEntity =
-      saveStrToCtx(Record.readString(), Record.getContext());
-
+  const ASTContext &C = Record.getContext();
+  StringRef SubstitutedEntity = C.backupStr(Record.readString());
   SourceLocation DiagLoc = Record.readSourceLocation();
-  StringRef DiagMessage =
-      saveStrToCtx(Record.readString(), Record.getContext());
+  StringRef DiagMessage = C.backupStr(Record.readString());
 
   return new (Record.getContext())
       concepts::Requirement::SubstitutionDiagnostic{SubstitutedEntity, DiagLoc,
@@ -919,22 +910,21 @@ void ASTStmtReader::VisitRequiresExpr(RequiresExpr *E) {
                   std::move(*Req));
       } break;
       case concepts::Requirement::RK_Nested: {
+        ASTContext &C = Record.getContext();
         bool HasInvalidConstraint = Record.readInt();
         if (HasInvalidConstraint) {
-          StringRef InvalidConstraint =
-              saveStrToCtx(Record.readString(), Record.getContext());
-          R = new (Record.getContext()) concepts::NestedRequirement(
+          StringRef InvalidConstraint = C.backupStr(Record.readString());
+          R = new (C) concepts::NestedRequirement(
               Record.getContext(), InvalidConstraint,
               readConstraintSatisfaction(Record));
           break;
         }
         Expr *E = Record.readExpr();
         if (E->isInstantiationDependent())
-          R = new (Record.getContext()) concepts::NestedRequirement(E);
+          R = new (C) concepts::NestedRequirement(E);
         else
-          R = new (Record.getContext())
-              concepts::NestedRequirement(Record.getContext(), E,
-                                          readConstraintSatisfaction(Record));
+          R = new (C) concepts::NestedRequirement(
+              C, E, readConstraintSatisfaction(Record));
       } break;
     }
     if (!R)