[SYCL] Introduce IntegerExprArgument

New attribute argument class is intended to provide functionality to
evaluate and cache value of ExprArgument which holds an integer value

Updated IntelReqdSubGroupSizeAttr to use new argument type

Author: AlexeySachkov

clang/include/clang/Basic/Attr.td

@@ -174,6 +174,10 @@ class IdentifierArgument<string name, bit opt = 0> : Argument<name, opt>;
 class IntArgument<string name, bit opt = 0> : Argument<name, opt>;
 class StringArgument<string name, bit opt = 0> : Argument<name, opt>;
 class ExprArgument<string name, bit opt = 0> : Argument<name, opt>;
+class IntegerExprArgument<string name, int undef = 0, bit opt = 0>
+    : ExprArgument<name, opt> {
+  int UndefValue = undef;
+}
 class DeclArgument<DeclNode kind, string name, bit opt = 0, bit fake = 0>
     : Argument<name, opt, fake> {
   DeclNode Kind = kind;
@@ -1289,28 +1293,11 @@ def LoopUnrollHint : InheritableAttr {
 
 def IntelReqdSubGroupSize: InheritableAttr {
   let Spellings = [GNU<"intel_reqd_sub_group_size">, CXX11<"cl", "intel_reqd_sub_group_size">];
-  let Args = [ExprArgument<"SubGroupSizeExpr">];
+  let Args = [IntegerExprArgument<"SubGroupSize", /* UndefValue = */ 0>];
   let Subjects = SubjectList<[Function, CXXMethod], ErrorDiag>;
   let Documentation = [IntelReqdSubGroupSizeDocs];
   let LangOpts = [OpenCL, SYCLIsDevice, SYCLIsHost];
   let PragmaAttributeSupport = 0;
-  let AdditionalMembers = [{
-  private:
-    int SubGroupSize = 0;
-
-  public:
-    int getSubGroupSizeEvaluated(ASTContext &Ctx) {
-      if (SubGroupSize != 0)
-        return SubGroupSize;
-      llvm::APSInt Val(32);
-      bool Succeedded =
-          this->getSubGroupSizeExpr()->isIntegerConstantExpr(Val, Ctx);
-      assert(Succeedded && "expression must be constant integer");
-      SubGroupSize = Val.getSExtValue();
-      assert(SubGroupSize >= 0 && "invalid value of the attribute");
-      return SubGroupSize;
-    }
-  }];
 }
 
 // This attribute is both a type attribute, and a declaration attribute (for

clang/lib/Sema/SemaTemplateInstantiateDecl.cpp

@@ -547,7 +547,7 @@ static void instantiateIntelReqdSubGroupSizeAttr(
   // The SubGroupSize expression is a constant expression.
   EnterExpressionEvaluationContext Unevaluated(
       S, Sema::ExpressionEvaluationContext::ConstantEvaluated);
-  ExprResult Result = S.SubstExpr(Attr->getSubGroupSizeExpr(), TemplateArgs);
+  ExprResult Result = S.SubstExpr(Attr->getSubGroupSize(), TemplateArgs);
   if (!Result.isInvalid())
     S.addIntelReqdSubGroupSizeAttr(New, *Attr, Result.getAs<Expr>());
 }

clang/utils/TableGen/ClangAttrEmitter.cpp

@@ -1161,6 +1161,36 @@ namespace {
     void writeHasChildren(raw_ostream &OS) const override { OS << "true"; }
   };
 
+  class IntegerExprArgument : public ExprArgument {
+  private:
+    int UndefValue;
+
+  public:
+    IntegerExprArgument(const Record &Arg, StringRef Attr)
+        : ExprArgument(Arg, Attr),
+          UndefValue(Arg.getValueAsInt("UndefValue")) {}
+
+    void writeAccessors(raw_ostream &OS) const override {
+      OS << "  " << getType() << " get" << getUpperName() << "() const {\n";
+      OS << "    return " << getLowerName() << ";\n";
+      OS << "  }\n";
+      OS << "private:\n";
+      OS << "  int " << getLowerName() << "Value = " << UndefValue << ";\n";
+      OS << "public:\n";
+      OS << "  int get" << getUpperName() << "Evaluated(ASTContext &Ctx) {\n";
+      OS << "    if (" << getLowerName() << "Value != " << UndefValue << ")\n";
+      OS << "      return " << getLowerName() << "Value;\n";
+      OS << "    llvm::APSInt Val(32);\n";
+      OS << "    bool Succeedded = " << getLowerName()
+         << "->isIntegerConstantExpr(Val, Ctx);\n";
+      OS << "    assert(Succeedded && \"expression must be constant "
+            "integer\");\n";
+      OS << "    " << getLowerName() << "Value = Val.getSExtValue();\n";
+      OS << "    return " << getLowerName() << "Value;\n";
+      OS << "  }";
+    }
+  };
+
   class VariadicExprArgument : public VariadicArgument {
   public:
     VariadicExprArgument(const Record &Arg, StringRef Attr)
@@ -1299,6 +1329,8 @@ createArgument(const Record &Arg, StringRef Attr,
     Ptr = std::make_unique<EnumArgument>(Arg, Attr);
   else if (ArgName == "ExprArgument")
     Ptr = std::make_unique<ExprArgument>(Arg, Attr);
+  else if (ArgName == "IntegerExprArgument")
+    Ptr = std::make_unique<IntegerExprArgument>(Arg, Attr);
   else if (ArgName == "DeclArgument")
     Ptr = std::make_unique<SimpleArgument>(
         Arg, Attr, (Arg.getValueAsDef("Kind")->getName() + "Decl *").str());