Address review comments and compilation failure

Author: kiranchandramohan

flang/lib/Lower/OpenMP/OpenMP.cpp

@@ -381,6 +381,9 @@ extractOmpDirective(const parser::OpenMPConstruct &ompConstruct) {
           [](const parser::OpenMPDeclarativeAllocate &c) {
             return llvm::omp::OMPD_allocate;
           },
+          [](const parser::OpenMPDispatchConstruct &c) {
+            return llvm::omp::OMPD_dispatch;
+          },
           [](const parser::OpenMPExecutableAllocate &c) {
             return llvm::omp::OMPD_allocate;
           },

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

@@ -1750,6 +1750,28 @@ void OmpStructureChecker::Enter(const parser::OmpErrorDirective &x) {
 
 void OmpStructureChecker::Enter(const parser::OpenMPDispatchConstruct &x) {
   PushContextAndClauseSets(x.source, llvm::omp::Directive::OMPD_dispatch);
+  const auto &block{std::get<parser::Block>(x.t)};
+  if (block.empty() || block.size() > 1) {
+    context_.Say(x.source,
+        "The DISPATCH construct is empty or contains more than one statement"_err_en_US);
+    return;
+  }
+
+  auto it{block.begin()};
+  bool passChecks{false};
+  if (const parser::AssignmentStmt *assignStmt{
+          parser::Unwrap<parser::AssignmentStmt>(*it)}) {
+    if (parser::Unwrap<parser::FunctionReference>(assignStmt->t)) {
+      passChecks = true;
+    }
+  } else if (parser::Unwrap<parser::CallStmt>(*it)) {
+    passChecks = true;
+  }
+
+  if (!passChecks) {
+    context_.Say(x.source,
+        "The DISPATCH construct does not contain a SUBROUTINE or FUNCTION"_err_en_US);
+  }
 }
 
 void OmpStructureChecker::Leave(const parser::OpenMPDispatchConstruct &x) {

flang/test/Lower/OpenMP/Todo/dispatch.f90

@@ -5,5 +5,8 @@ program p
   integer r
   r = 1
 !$omp dispatch nowait
-  print *,r
+  call foo()
+contains
+  subroutine foo
+  end subroutine
 end program p

flang/test/Semantics/OpenMP/dispatch.f90

@@ -0,0 +1,24 @@
+! RUN: %python %S/../test_errors.py %s %flang -fopenmp
+
+subroutine sb1
+  integer :: r
+  r = 1
+  !ERROR: The DISPATCH construct does not contain a SUBROUTINE or FUNCTION
+  !$omp dispatch nowait
+  print *,r
+end subroutine
+subroutine sb2
+  integer :: r
+!ERROR: The DISPATCH construct is empty or contains more than one statement
+  !$omp dispatch
+  call foo()
+  r = bar()
+  !$omp end dispatch
+contains
+  subroutine foo
+  end subroutine foo
+  function bar
+    integer :: bar
+    bar = 2
+  end function
+end subroutine

llvm/include/llvm/Frontend/OpenMP/OMP.td

@@ -321,7 +321,6 @@ def OMPC_Novariants : Clause<"novariants"> {
 }
 def OMPC_NoWait : Clause<"nowait"> {
   let clangClass = "OMPNowaitClause";
-  let clangClass = "OmpNowaitClause";
 }
 def OMP_NUMTASKS_Strict : ClauseVal<"strict", 1, 1> {}
 def OMP_NUMTASKS_Unknown : ClauseVal<"unknown", 2, 0> { let isDefault = 1; }