[clang] [llvm] [OpenMP]Generate implicit default mapper for mapping array section. (PR #101101)

[Alexey Bataev via cfe-commits]

================
@@ -20796,6 +20796,204 @@ struct MappableVarListInfo {
 };
 } // namespace
 
+static DeclRefExpr *buildImplicitMap(Sema &S, QualType BaseType,
+                                     DSAStackTy *Stack,
+                                     SmallVectorImpl<OMPClause *> &Maps) {
+
+  const RecordDecl *RD = BaseType->getAsRecordDecl();
+  SourceRange Range = RD->getSourceRange();
+  DeclarationNameInfo ImplicitName;
+  // Dummy variable _s for Mapper.
+  VarDecl *VD = buildVarDecl(S, Range.getEnd(), BaseType, "_s");
+  DeclRefExpr *MapperVarRef =
+      buildDeclRefExpr(S, VD, BaseType, SourceLocation());
+
+  // Create implicit map clause for mapper.
+  SmallVector<Expr *, 4> SExprs;
+  for (auto *FD : RD->fields()) {
+    Expr *BE = S.BuildMemberExpr(
+        MapperVarRef, /*IsArrow=*/false, Range.getBegin(),
+        NestedNameSpecifierLoc(), Range.getBegin(), FD,
+        DeclAccessPair::make(FD, FD->getAccess()),
+        /*HadMultipleCandidates=*/false,
+        DeclarationNameInfo(FD->getDeclName(), FD->getSourceRange().getBegin()),
+        FD->getType(), VK_LValue, OK_Ordinary);
+    SExprs.push_back(BE);
+  }
+  CXXScopeSpec MapperIdScopeSpec;
+  DeclarationNameInfo MapperId;
+  OpenMPDirectiveKind DKind = Stack->getCurrentDirective();
+
+  OMPClause *MapClause = S.OpenMP().ActOnOpenMPMapClause(
+      nullptr, OMPC_MAP_MODIFIER_unknown, SourceLocation(), MapperIdScopeSpec,
+      MapperId, DKind == OMPD_target_enter_data ? OMPC_MAP_to : OMPC_MAP_tofrom,
+      /*IsMapTypeImplicit=*/true, SourceLocation(), SourceLocation(), SExprs,
+      OMPVarListLocTy());
+  Maps.push_back(MapClause);
+  return MapperVarRef;
+}
+
+static ExprResult buildImplicitMapper(Sema &S, QualType BaseType,
+                                      DSAStackTy *Stack) {
+
+  // Build impilicit map for mapper
+  SmallVector<OMPClause *, 4> Maps;
+  DeclRefExpr *MapperVarRef = buildImplicitMap(S, BaseType, Stack, Maps);
+
+  const RecordDecl *RD = BaseType->getAsRecordDecl();
+  // AST context is RD's ParentASTContext().
+  ASTContext &Ctx = RD->getParentASTContext();
+  // DeclContext is RD's DeclContext.
+  DeclContext *DCT = const_cast<DeclContext *>(RD->getDeclContext());
+
+  // Create implicit default mapper for "RD".
+  DeclarationName MapperId;
+  auto &DeclNames = Ctx.DeclarationNames;
+  MapperId = DeclNames.getIdentifier(&Ctx.Idents.get("default"));
+  auto *DMD = OMPDeclareMapperDecl::Create(Ctx, DCT, SourceLocation(), MapperId,
+                                           BaseType, MapperId, Maps, nullptr);
+  Scope *Scope = S.getScopeForContext(DCT);
+  if (Scope)
+    S.PushOnScopeChains(DMD, Scope, /*AddToContext*/ false);
+  DCT->addDecl(DMD);
+  DMD->setAccess(clang::AS_none);
+  auto *VD = cast<DeclRefExpr>(MapperVarRef)->getDecl();
+  VD->setDeclContext(DMD);
+  VD->setLexicalDeclContext(DMD);
+  DMD->addDecl(VD);
+  DMD->setMapperVarRef(MapperVarRef);
+  FieldDecl *FD = *RD->field_begin();
+  // create mapper refence.
+  return DeclRefExpr::Create(Ctx, NestedNameSpecifierLoc{}, FD->getLocation(),
+                             DMD, false, SourceLocation(), BaseType, VK_LValue);
+}
+
+// Look up the user-defined mapper given the mapper name and mapper type,
+// return true if found one.
+static bool hasUserDefinedMapper(Sema &SemaRef, Scope *S,
+                                 CXXScopeSpec &MapperIdScopeSpec,
+                                 const DeclarationNameInfo &MapperId,
+                                 QualType Type) {
+  // Find all user-defined mappers with the given MapperId.
+  SmallVector<UnresolvedSet<8>, 4> Lookups;
+  LookupResult Lookup(SemaRef, MapperId, Sema::LookupOMPMapperName);
+  Lookup.suppressDiagnostics();
+  if (S)
+    while (S && SemaRef.LookupParsedName(Lookup, S, &MapperIdScopeSpec,
+                                         /*ObjectType=*/QualType())) {
+      NamedDecl *D = Lookup.getRepresentativeDecl();
+      while (S && !S->isDeclScope(D))
+        S = S->getParent();
+      if (S)
+        S = S->getParent();
+      Lookups.emplace_back();
+      Lookups.back().append(Lookup.begin(), Lookup.end());
+      Lookup.clear();
+    }
+  if (SemaRef.CurContext->isDependentContext() || Type->isDependentType() ||
+      Type->isInstantiationDependentType() ||
+      Type->containsUnexpandedParameterPack() ||
+      filterLookupForUDReductionAndMapper<bool>(Lookups, [](ValueDecl *D) {
+        return !D->isInvalidDecl() &&
+               (D->getType()->isDependentType() ||
+                D->getType()->isInstantiationDependentType() ||
+                D->getType()->containsUnexpandedParameterPack());
+      }))
+    return false;
+  // Perform argument dependent lookup.
+  SourceLocation Loc = MapperId.getLoc();
+  if (SemaRef.getLangOpts().CPlusPlus && !MapperIdScopeSpec.isSet())
+    argumentDependentLookup(SemaRef, MapperId, Loc, Type, Lookups);
+  if (filterLookupForUDReductionAndMapper<ValueDecl *>(
+          Lookups, [&SemaRef, Type](ValueDecl *D) -> ValueDecl * {
+            if (!D->isInvalidDecl() &&
+                SemaRef.Context.hasSameType(D->getType(), Type))
+              return D;
+            return nullptr;
+          }))
+    return true;
+  // Find the first user-defined mapper with a type derived from the desired
+  // type.
+  if (auto *VD = filterLookupForUDReductionAndMapper<ValueDecl *>(
+          Lookups, [&SemaRef, Type, Loc](ValueDecl *D) -> ValueDecl * {
+            if (!D->isInvalidDecl() &&
+                SemaRef.IsDerivedFrom(Loc, Type, D->getType()) &&
+                !Type.isMoreQualifiedThan(D->getType()))
+              return D;
+            return nullptr;
+          })) {
+    CXXBasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/true,
+                       /*DetectVirtual=*/false);
+    if (SemaRef.IsDerivedFrom(Loc, Type, VD->getType(), Paths)) {
+      if (!Paths.isAmbiguous(SemaRef.Context.getCanonicalType(
+              VD->getType().getUnqualifiedType()))) {
+        if (SemaRef.CheckBaseClassAccess(
+                Loc, VD->getType(), Type, Paths.front(),
+                /*DiagID=*/0) != Sema::AR_inaccessible) {
+          return true;
+        }
+      }
+    }
+  }
----------------
alexey-bataev wrote:

Simplify this block by early exiting where possible.

https://github.com/llvm/llvm-project/pull/101101