[LLVM-Flang][OpenMP] Add some semantic checks for Linear clause based on the OpenMP 5.2 restrictions

Author: Thirumalai-Shaktivel

flang/lib/Semantics/check-omp-structure.cpp

@@ -383,6 +383,21 @@ void OmpStructureChecker::CheckMultListItems() {
     CheckMultipleOccurrence(
         listVars, nontempNameList, clause->source, "NONTEMPORAL");
   }
+
+  // Linear clause
+  for (auto [_, clause] : FindClauses(llvm::omp::Clause::OMPC_linear)) {
+    const auto &linearClause{std::get<parser::OmpClause::Linear>(clause->u)};
+    std::list<parser::Name> nameList;
+    common::visit(
+        common::visitors{
+            [&](const auto &u) {
+              std::copy(
+                  u.names.begin(), u.names.end(), std::back_inserter(nameList));
+            },
+        },
+        linearClause.v.u);
+    CheckMultipleOccurrence(listVars, nameList, clause->source, "LINEAR");
+  }
 }
 
 bool OmpStructureChecker::HasInvalidWorksharingNesting(
@@ -2686,12 +2701,12 @@ void OmpStructureChecker::Leave(const parser::OmpClauseList &) {
         }
       }
     }
-
-    // Sema checks related to presence of multiple list items within the same
-    // clause
-    CheckMultListItems();
   } // SIMD
 
+  // Semantic checks related to presence of multiple list items within the same
+  // clause
+  CheckMultListItems();
+
   // 2.7.3 Single Construct Restriction
   if (GetContext().directive == llvm::omp::Directive::OMPD_end_single) {
     CheckNotAllowedIfClause(
@@ -3542,16 +3557,88 @@ void OmpStructureChecker::Enter(const parser::OmpClause::If &x) {
 void OmpStructureChecker::Enter(const parser::OmpClause::Linear &x) {
   CheckAllowedClause(llvm::omp::Clause::OMPC_linear);
 
+  parser::CharBlock source{GetContext().clauseSource};
   // 2.7 Loop Construct Restriction
   if ((llvm::omp::allDoSet | llvm::omp::allSimdSet)
           .test(GetContext().directive)) {
     if (std::holds_alternative<parser::OmpLinearClause::WithModifier>(x.v.u)) {
-      context_.Say(GetContext().clauseSource,
+      context_.Say(source,
           "A modifier may not be specified in a LINEAR clause "
           "on the %s directive"_err_en_US,
           ContextDirectiveAsFortran());
+      return;
     }
   }
+
+  auto checkForValidLinearClause_01 = [&](const parser::Name &name,
+                                          bool is_ref) {
+    std::string listItemName{name.ToString()};
+    if (!is_ref && !name.symbol->GetType()->IsNumeric(TypeCategory::Integer)) {
+      context_.Say(source,
+          "The list item `%s` specified with other than linear-modifier `REF`"
+          " must be of type INTEGER"_err_en_US,
+          listItemName);
+    }
+    if (GetContext().directive == llvm::omp::Directive::OMPD_declare_simd &&
+        !IsDummy(*name.symbol)) {
+      context_.Say(source,
+          "The list item `%s` must be a dummy argument"_err_en_US,
+          listItemName);
+    }
+    if (IsPointer(*name.symbol) ||
+        name.symbol->test(Symbol::Flag::CrayPointer)) {
+      context_.Say(source,
+          "The list item `%s` in a LINEAR clause must not be Cray Pointer "
+          "or a variable with POINTER attribute"_err_en_US,
+          listItemName);
+    }
+    if (FindCommonBlockContaining(*name.symbol)) {
+      context_.Say(source,
+          "'%s' is a common block name and must not appear in an "
+          "LINEAR clause"_err_en_US,
+          listItemName);
+    }
+  };
+
+  auto checkForValidLinearClause_02 = [&](const parser::Name &name,
+                                          const parser::OmpLinearModifier::Value
+                                              &modifierValue) {
+    std::string listItemName{name.ToString()};
+    checkForValidLinearClause_01(
+        name, (modifierValue == parser::OmpLinearModifier::Value::Ref));
+    if (modifierValue != parser::OmpLinearModifier::Value::Val &&
+        IsDummy(*name.symbol) && IsValue(*name.symbol)) {
+      context_.Say(source,
+          "The list item `%s` specified with the linear-modifier `REF` or "
+          "`UVAL` must be a dummy argument without `VALUE` attribute"_err_en_US,
+          listItemName);
+    }
+    if (modifierValue == parser::OmpLinearModifier::Value::Ref &&
+        !(IsAllocatable(*name.symbol) || IsAssumedShape(*name.symbol) ||
+            IsPolymorphic(*name.symbol))) {
+      context_.Say(source,
+          "The list item `%s` specified with the linear-modifier `REF` "
+          "must be polymorphic variable, assumed-shape array, or a variable"
+          " with the `ALLOCATABLE` attribute"_err_en_US,
+          listItemName);
+    }
+  };
+
+  // OpenMP 5.2: Linear clause Restrictions
+  common::visit(
+      common::visitors{
+          [&](const parser::OmpLinearClause::WithoutModifier &withoutModifier) {
+            for (const auto &name : withoutModifier.names)
+              if (name.symbol)
+                checkForValidLinearClause_01(name, false);
+          },
+          [&](const parser::OmpLinearClause::WithModifier &withModifier) {
+            for (const auto &name : withModifier.names)
+              if (name.symbol)
+                checkForValidLinearClause_02(name, withModifier.modifier.v);
+          },
+      },
+      x.v.u);
 }
 
 void OmpStructureChecker::CheckAllowedMapTypes(