[clang] [OpenACC] Implement 'reduction' sema for compute constructs (PR #92808)

[Alexey Bataev via cfe-commits]

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@@ -715,6 +787,65 @@ SemaOpenACC::ActOnClause(ArrayRef<const OpenACCClause *> ExistingClauses,
   return nullptr;
 }
 
+/// OpenACC 3.3 section 2.5.15:
+/// At a mininmum, the supported data types include ... the numerical data types
+/// in C, C++, and Fortran.
+///
+/// If the reduction var is a composite variable, each
+/// member of the composite variable must be a supported datatype for the
+/// reduction operation.
+ExprResult SemaOpenACC::CheckReductionVar(Expr *VarExpr) {
+  VarExpr = VarExpr->IgnoreParenCasts();
+
+  auto TypeIsValid = [](QualType Ty) {
+    return Ty->isDependentType() || Ty->isScalarType();
+  };
+
+  if (isa<ArraySectionExpr>(VarExpr)) {
+    Expr *ASExpr = VarExpr;
+    QualType BaseTy = ArraySectionExpr::getBaseOriginalType(ASExpr);
+    QualType EltTy = getASTContext().getBaseElementType(BaseTy);
+
+    if (!TypeIsValid(EltTy)) {
+      Diag(VarExpr->getExprLoc(), diag::err_acc_reduction_type)
+          << EltTy << /*Sub array base type*/ 1;
+      return ExprError();
+    }
+  } else if (auto *RD = VarExpr->getType()->getAsRecordDecl()) {
+    if (!RD->isStruct() && !RD->isClass()) {
+      Diag(VarExpr->getExprLoc(), diag::err_acc_reduction_composite_type)
+          << /*not class or struct*/ 0 << VarExpr->getType();
+      return ExprError();
+    }
+
+    if (!RD->isCompleteDefinition()) {
+      Diag(VarExpr->getExprLoc(), diag::err_acc_reduction_composite_type)
+          << /*incomplete*/ 1 << VarExpr->getType();
+      return ExprError();
+    }
+    if (isa<CXXRecordDecl>(RD) && !cast<CXXRecordDecl>(RD)->isAggregate()) {
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alexey-bataev wrote:

`if (auto *CXXRD = dyn_cast<CXXRecordDecl>(RD); CXXRD && !CXXRD->`?

https://github.com/llvm/llvm-project/pull/92808