[clang] [HLSL] Implement HLSL intialization list support (PR #123141)

[Chris B via cfe-commits]

================
@@ -2576,3 +2576,162 @@ void SemaHLSL::processExplicitBindingsOnDecl(VarDecl *VD) {
     }
   }
 }
+
+static bool CastInitializer(Sema &S, ASTContext &Ctx, Expr *E,
+                            llvm::SmallVectorImpl<Expr *> &List,
+                            llvm::SmallVectorImpl<QualType> &DestTypes) {
+  if (List.size() >= DestTypes.size())
+    return false;
+  InitializedEntity Entity =
+      InitializedEntity::InitializeParameter(Ctx, DestTypes[List.size()], false);
+  ExprResult Res =
+      S.PerformCopyInitialization(Entity, E->getBeginLoc(), E);
+  if (Res.isInvalid())
+    return false;
+  Expr *Init = Res.get();
+  List.push_back(Init);
+  return true;
+}
+
+static void BuildIntializerList(Sema &S, ASTContext &Ctx, Expr *E,
+                                llvm::SmallVectorImpl<Expr *> &List,
+                                llvm::SmallVectorImpl<QualType> &DestTypes,
+                                bool &ExcessInits) {
+  if (List.size() >= DestTypes.size()) {
+    ExcessInits = true;
+    return;
+  }
+
+  // If this is an initialization list, traverse the sub initializers.
+  if (auto *Init = dyn_cast<InitListExpr>(E)) {
+    for (auto *SubInit : Init->inits())
+      BuildIntializerList(S, Ctx, SubInit, List, DestTypes, ExcessInits);
+    return;
+  }
+
+  // If this is a scalar type, just enqueue the expression.
+  QualType Ty = E->getType();
+  if (Ty->isScalarType()) {
+    (void)CastInitializer(S, Ctx, E, List, DestTypes);
+    return;
+  }
+
+  if (auto *ATy = Ty->getAs<VectorType>()) {
+    uint64_t Size = ATy->getNumElements();
+
+    if (List.size() + Size > DestTypes.size()) {
+      ExcessInits = true;
+      return;
+    }
+    QualType SizeTy = Ctx.getSizeType();
+    uint64_t SizeTySize = Ctx.getTypeSize(SizeTy);
+    for (uint64_t I = 0; I < Size; ++I) {
+      auto *Idx = IntegerLiteral::Create(Ctx, llvm::APInt(SizeTySize, I),
+                                         SizeTy, SourceLocation());
+
+      ExprResult ElExpr = S.CreateBuiltinArraySubscriptExpr(
+          E, E->getBeginLoc(), Idx, E->getEndLoc());
+      if (ElExpr.isInvalid())
+        return;
+      if (!CastInitializer(S, Ctx, ElExpr.get(), List, DestTypes))
+        return;
+    }
+    return;
+  }
+
+  if (auto *VTy = dyn_cast<ConstantArrayType>(Ty.getTypePtr())) {
+    uint64_t Size = VTy->getZExtSize();
+    QualType SizeTy = Ctx.getSizeType();
+    uint64_t SizeTySize = Ctx.getTypeSize(SizeTy);
+    for (uint64_t I = 0; I < Size; ++I) {
+      auto *Idx = IntegerLiteral::Create(Ctx, llvm::APInt(SizeTySize, I),
+                                         SizeTy, SourceLocation());
+      ExprResult ElExpr = S.CreateBuiltinArraySubscriptExpr(
+          E, E->getBeginLoc(), Idx, E->getEndLoc());
+      if (ElExpr.isInvalid())
+        return;
+      BuildIntializerList(S, Ctx, ElExpr.get(), List, DestTypes, ExcessInits);
+    }
+    return;
+  }
+
+  if (auto *RTy = Ty->getAs<RecordType>()) {
+    for (auto *FD : RTy->getDecl()->fields()) {
+      DeclAccessPair Found = DeclAccessPair::make(FD, FD->getAccess());
+      DeclarationNameInfo NameInfo(FD->getDeclName(), E->getBeginLoc());
+      ExprResult Res = S.BuildFieldReferenceExpr(
+          E, false, E->getBeginLoc(), CXXScopeSpec(), FD, Found, NameInfo);
+      if (Res.isInvalid())
+        return;
+      BuildIntializerList(S, Ctx, Res.get(), List, DestTypes, ExcessInits);
+    }
+  }
+}
+
+static Expr *GenerateInitLists(ASTContext &Ctx, QualType Ty,
+                               llvm::SmallVectorImpl<Expr *>::iterator &It) {
+  if (Ty->isScalarType()) {
+    return *(It++);
+  }
+  llvm::SmallVector<Expr *> Inits;
+  assert(!isa<MatrixType>(Ty) && "Matrix types not yet supported in HLSL");
+  if (Ty->isVectorType() || Ty->isConstantArrayType()) {
+    QualType ElTy;
+    uint64_t Size = 0;
+    if (auto *ATy = Ty->getAs<VectorType>()) {
+      ElTy = ATy->getElementType();
+      Size = ATy->getNumElements();
+    } else {
+      auto *VTy = cast<ConstantArrayType>(Ty.getTypePtr());
+      ElTy = VTy->getElementType();
+      Size = VTy->getZExtSize();
+    }
+    for (uint64_t I = 0; I < Size; ++I)
+      Inits.push_back(GenerateInitLists(Ctx, ElTy, It));
+  }
+  if (const RecordDecl *RD = Ty->getAsRecordDecl()) {
+    for (auto *FD : RD->fields()) {
+      Inits.push_back(GenerateInitLists(Ctx, FD->getType(), It));
+    }
+  }
+  auto *NewInit = new (Ctx) InitListExpr(Ctx, Inits.front()->getBeginLoc(),
+                                         Inits, Inits.back()->getEndLoc());
+  NewInit->setType(Ty);
+  return NewInit;
+}
+
+bool SemaHLSL::TransformInitList(const InitializedEntity &Entity,
+                                 const InitializationKind &Kind,
+                                 InitListExpr *Init) {
+  // If the initializer is a scalar, just return it.
+  if (Init->getType()->isScalarType())
+    return true;
+  ASTContext &Ctx = SemaRef.getASTContext();
+  llvm::SmallVector<QualType, 16> DestTypes;
+  // An initializer list might be attempting to initialize a reference or
+  // rvalue-reference. When checking the initializer we should look through the
+  // reference.
+  QualType InitTy = Entity.getType().getNonReferenceType();
+  BuildFlattenedTypeList(InitTy, DestTypes);
+
+  llvm::SmallVector<Expr *, 16> ArgExprs;
+  bool ExcessInits = false;
+  for (Expr *Arg : Init->inits())
+    BuildIntializerList(SemaRef, Ctx, Arg, ArgExprs, DestTypes, ExcessInits);
----------------
llvm-beanz wrote:

If any of those cases fail, they will generate errors, which will (eventually) stop processing. We can continue through all the arguments though and let the error be surfaced after the full initializer expression is processed.

https://github.com/llvm/llvm-project/pull/123141