[OpenMP] Parse and Sema support for declare target in local scope (#83223)

- adds Parse and Sema support for the `declare target` directive inside
a function scope.

Author: sandeepkosuri

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -11352,6 +11352,8 @@ def err_omp_device_type_mismatch : Error<
 def err_omp_wrong_device_function_call : Error<
   "function with 'device_type(%0)' is not available on %select{device|host}1">;
 def note_omp_marked_device_type_here : Note<"marked as 'device_type(%0)' here">;
+def err_omp_declare_target_has_local_vars : Error<
+  "local variable '%0' should not be used in 'declare target' directive; ">;
 def warn_omp_declare_target_after_first_use : Warning<
   "declaration marked as declare target after first use, it may lead to incorrect results">,
   InGroup<OpenMPTarget>;

clang/lib/Parse/ParseOpenMP.cpp

@@ -2984,8 +2984,29 @@ StmtResult Parser::ParseOpenMPDeclarativeOrExecutableDirective(
     OMPDirectiveScope.Exit();
     break;
   }
+  case OMPD_declare_target: {
+    SourceLocation DTLoc = ConsumeAnyToken();
+    bool HasClauses = Tok.isNot(tok::annot_pragma_openmp_end);
+    Sema::DeclareTargetContextInfo DTCI(DKind, DTLoc);
+    if (HasClauses)
+      ParseOMPDeclareTargetClauses(DTCI);
+    bool HasImplicitMappings =
+        !HasClauses || (DTCI.ExplicitlyMapped.empty() && DTCI.Indirect);
+
+    if (HasImplicitMappings) {
+      Diag(Tok, diag::err_omp_unexpected_directive)
+          << 1 << getOpenMPDirectiveName(DKind);
+      SkipUntil(tok::annot_pragma_openmp_end);
+      break;
+    }
+
+    // Skip the last annot_pragma_openmp_end.
+    ConsumeAnyToken();
+
+    Actions.ActOnFinishedOpenMPDeclareTargetContext(DTCI);
+    break;
+  }
   case OMPD_declare_simd:
-  case OMPD_declare_target:
   case OMPD_begin_declare_target:
   case OMPD_end_declare_target:
   case OMPD_requires:

clang/lib/Sema/SemaOpenMP.cpp

@@ -23353,6 +23353,15 @@ void Sema::ActOnOpenMPDeclareTargetName(NamedDecl *ND, SourceLocation Loc,
           isa<FunctionTemplateDecl>(ND)) &&
          "Expected variable, function or function template.");
 
+  if (auto *VD = dyn_cast<VarDecl>(ND)) {
+    // Only global variables can be marked as declare target.
+    if (!VD->isFileVarDecl() && !VD->isStaticLocal() &&
+        !VD->isStaticDataMember()) {
+      Diag(Loc, diag::err_omp_declare_target_has_local_vars)
+          << VD->getNameAsString();
+      return;
+    }
+  }
   // Diagnose marking after use as it may lead to incorrect diagnosis and
   // codegen.
   if (LangOpts.OpenMP >= 50 &&

clang/test/OpenMP/declare_target_ast_print.cpp

@@ -360,13 +360,32 @@ int inner_link;
 // CHECK-NEXT: int inner_link;
 // CHECK-NEXT: #pragma omp end declare target
 
+void foo2() { return ;}
+// CHECK: #pragma omp declare target
+// CHECK-NEXT: void foo2() {
+// CHECK-NEXT: return;
+// CHECK-NEXT: }
+
+int x;
+// CHECK: #pragma omp declare target link
+// CHECK-NEXT: int x;
+// CHECK-NEXT: #pragma omp end declare target
+
 int main (int argc, char **argv) {
   foo();
   foo_c();
   foo_cpp();
   test1();
   baz<float>();
   baz<int>();
+
+#if _OPENMP == 202111
+#pragma omp declare target enter(foo2)
+#else
+#pragma omp declare target to (foo2)
+#endif
+
+  #pragma omp declare target link(x)
   return (0);
 }
 

clang/test/OpenMP/declare_target_messages.cpp

@@ -182,11 +182,20 @@ struct S {
 #pragma omp end declare target
 };
 
+void foo3() {
+  return;
+}
+
+int *y;
+int **w = &y;
 int main (int argc, char **argv) {
+  int a = 2;
 #pragma omp declare target // expected-error {{unexpected OpenMP directive '#pragma omp declare target'}}
   int v;
 #pragma omp end declare target // expected-error {{unexpected OpenMP directive '#pragma omp end declare target'}}
   foo(v);
+#pragma omp declare target to(foo3) link(w) // omp52-error {{unexpected 'to' clause, use 'enter' instead}} omp52-error {{expected at least one 'enter', 'link' or 'indirect' clause}}
+#pragma omp declare target to(a) //omp45-error {{local variable 'a' should not be used in 'declare target' directive}} omp5-error {{local variable 'a' should not be used in 'declare target' directive}} omp51-error {{local variable 'a' should not be used in 'declare target' directive}} omp52-error {{unexpected 'to' clause, use 'enter' instead}} omp52-error {{expected at least one 'enter', 'link' or 'indirect' clause}}
   return (0);
 }