default clause replaced by otherwise clause for metadirective in OpenMP 5.2 (#125648)

This PR replaces the `default` clause with the `otherwise` clause for
the `metadirective` in OpenMP. The `otherwise` clause serves as a
fallback condition when no directive from the `when` clauses is
selected. In the `when` clause, context selectors define traits
evaluated to determine the directive to be applied.

Author: ravurvi20

clang/include/clang/Basic/DiagnosticParseKinds.td

@@ -1657,6 +1657,10 @@ def err_omp_expected_colon : Error<"missing ':' in %0">;
 def err_omp_missing_comma : Error< "missing ',' after %0">;
 def err_omp_expected_context_selector
     : Error<"expected valid context selector in %0">;
+def err_omp_unknown_clause
+    : Error<"unknown clause '%0' in %1">;
+def warn_omp_default_deprecated : Warning<"'default' clause for"
+  " 'metadirective' is deprecated; use 'otherwise' instead">, InGroup<Deprecated>;
 def err_omp_requires_out_inout_depend_type : Error<
   "reserved locator 'omp_all_memory' requires 'out' or 'inout' "
   "dependency types">;

clang/lib/Parse/ParseOpenMP.cpp

@@ -2759,6 +2759,19 @@ StmtResult Parser::ParseOpenMPDeclarativeOrExecutableDirective(
       OpenMPClauseKind CKind = Tok.isAnnotation()
                                    ? OMPC_unknown
                                    : getOpenMPClauseKind(PP.getSpelling(Tok));
+      // Check if the clause is unrecognized.
+      if (getLangOpts().OpenMP < 52 &&
+          (CKind == OMPC_unknown || CKind == OMPC_otherwise)) {
+        Diag(Tok, diag::err_omp_unknown_clause)
+            << PP.getSpelling(Tok) << "metadirective";
+      }
+      if (getLangOpts().OpenMP >= 52 && CKind == OMPC_unknown) {
+        Diag(Tok, diag::err_omp_unknown_clause)
+            << PP.getSpelling(Tok) << "metadirective";
+      }
+      if (CKind == OMPC_default && getLangOpts().OpenMP >= 52) {
+        Diag(Tok, diag::warn_omp_default_deprecated);
+      }
       SourceLocation Loc = ConsumeToken();
 
       // Parse '('.
@@ -2785,6 +2798,13 @@ StmtResult Parser::ParseOpenMPDeclarativeOrExecutableDirective(
           return Directive;
         }
       }
+      if (CKind == OMPC_otherwise) {
+        // Check for 'otherwise' keyword.
+        if (Tok.is(tok::identifier) &&
+            Tok.getIdentifierInfo()->getName() == "otherwise") {
+          ConsumeToken(); // Consume 'otherwise'
+        }
+      }
       // Skip Directive for now. We will parse directive in the second iteration
       int paren = 0;
       while (Tok.isNot(tok::r_paren) || paren != 0) {

clang/test/OpenMP/metadirective_messages.cpp

@@ -2,21 +2,48 @@
 
 // RUN: %clang_cc1 -triple=x86_64-pc-linux-gnu -verify -fopenmp-simd -x c++ -std=c++14 -fexceptions -fcxx-exceptions %s
 
+// RUN: %clang_cc1 -verify=expected,omp52 -fopenmp -fopenmp-version=52 -ferror-limit 100 -o - %s -Wuninitialized
+
 void foo() {
-#pragma omp metadirective // expected-error {{expected expression}}
-  ;
-#pragma omp metadirective when() // expected-error {{expected valid context selector in when clause}} expected-error {{expected expression}} expected-warning {{expected identifier or string literal describing a context set; set skipped}} expected-note {{context set options are: 'construct' 'device' 'target_device' 'implementation' 'user'}} expected-note {{the ignored set spans until here}}
-  ;
-#pragma omp metadirective when(device{}) // expected-warning {{expected '=' after the context set name "device"; '=' assumed}} expected-warning {{expected identifier or string literal describing a context selector; selector skipped}} expected-note {{context selector options are: 'kind' 'arch' 'isa'}} expected-note {{the ignored selector spans until here}} expected-error {{expected valid context selector in when clause}} expected-error {{expected expression}}
-  ;
-#pragma omp metadirective when(device{arch(nvptx)}) // expected-error {{missing ':' in when clause}} expected-error {{expected expression}} expected-warning {{expected '=' after the context set name "device"; '=' assumed}}
-  ;
-#pragma omp metadirective when(device{arch(nvptx)}: ) default() // expected-warning {{expected '=' after the context set name "device"; '=' assumed}}
-  ;
-#pragma omp metadirective when(device = {arch(nvptx)} : ) default(xyz) // expected-error {{expected an OpenMP directive}} expected-error {{use of undeclared identifier 'xyz'}}
-  ;
-#pragma omp metadirective when(device = {arch(nvptx)} : parallel default() // expected-error {{expected ',' or ')' in 'when' clause}} expected-error {{expected expression}}
-  ;
-#pragma omp metadirective when(device = {isa("some-unsupported-feature")} : parallel) default(single) // expected-warning {{isa trait 'some-unsupported-feature' is not known to the current target; verify the spelling or consider restricting the context selector with the 'arch' selector further}}
-  ;
+#if _OPENMP >= 202111
+  #pragma omp metadirective // omp52-error {{expected expression}}
+    ;
+  #pragma omp metadirective when() // omp52-error {{expected valid context selector in when clause}} expected-error {{expected expression}} expected-warning {{expected identifier or string literal describing a context set; set skipped}} expected-note {{context set options are: 'construct' 'device' 'target_device' 'implementation' 'user'}} expected-note {{the ignored set spans until here}}
+    ;
+  #pragma omp metadirective when(device{}) // omp52-warning {{expected '=' after the context set name "device"; '=' assumed}} expected-warning {{expected identifier or string literal describing a context selector; selector skipped}} expected-note {{context selector options are: 'kind' 'arch' 'isa'}} expected-note {{the ignored selector spans until here}} expected-error {{expected valid context selector in when clause}} expected-error {{expected expression}}
+    ;
+  #pragma omp metadirective when(device{arch(nvptx)}) // omp52-error {{missing ':' in when clause}} expected-error {{expected expression}} expected-warning {{expected '=' after the context set name "device"; '=' assumed}}
+    ;
+  #pragma omp metadirective when(device{arch(nvptx)}: ) otherwise() // omp52-warning {{expected '=' after the context set name "device"; '=' assumed}}
+    ;
+  #pragma omp metadirective when(device = {arch(nvptx)} : ) otherwise(xyz) // omp52-error {{expected an OpenMP directive}} expected-error {{use of undeclared identifier 'xyz'}}
+    ;
+  #pragma omp metadirective when(device = {arch(nvptx)} : parallel otherwise() // omp52-error {{expected ',' or ')' in 'when' clause}} expected-error {{expected expression}}
+    ;
+  #pragma omp metadirective when(device = {isa("some-unsupported-feature")} : parallel) otherwise(single) // omp52-warning {{isa trait 'some-unsupported-feature' is not known to the current target; verify the spelling or consider restricting the context selector with the 'arch' selector further}}
+    ;
+  #pragma omp metadirective when(device = {arch(nvptx)} : parallel) default() // omp52-warning {{'default' clause for 'metadirective' is deprecated; use 'otherwise' instead}}
+    ;
+  #pragma omp metadirective when(device = {arch(nvptx)} : parallel) xyz() //omp52-error {{unknown clause 'xyz' in metadirective}} 
+    ;
+#else
+  #pragma omp metadirective // expected-error {{expected expression}}
+    ;
+  #pragma omp metadirective when() // expected-error {{expected valid context selector in when clause}} expected-error {{expected expression}} expected-warning {{expected identifier or string literal describing a context set; set skipped}} expected-note {{context set options are: 'construct' 'device' 'target_device' 'implementation' 'user'}} expected-note {{the ignored set spans until here}}
+    ;
+  #pragma omp metadirective when(device{}) // expected-warning {{expected '=' after the context set name "device"; '=' assumed}} expected-warning {{expected identifier or string literal describing a context selector; selector skipped}} expected-note {{context selector options are: 'kind' 'arch' 'isa'}} expected-note {{the ignored selector spans until here}} expected-error {{expected valid context selector in when clause}} expected-error {{expected expression}}
+    ;
+  #pragma omp metadirective when(device{arch(nvptx)}) // expected-error {{missing ':' in when clause}} expected-error {{expected expression}} expected-warning {{expected '=' after the context set name "device"; '=' assumed}}
+    ;
+  #pragma omp metadirective when(device{arch(nvptx)}: ) default() // expected-warning {{expected '=' after the context set name "device"; '=' assumed}}
+    ;
+  #pragma omp metadirective when(device = {arch(nvptx)} : ) default(xyz) // expected-error {{expected an OpenMP directive}} expected-error {{use of undeclared identifier 'xyz'}}
+    ;
+  #pragma omp metadirective when(device = {arch(nvptx)} : parallel default() // expected-error {{expected ',' or ')' in 'when' clause}} expected-error {{expected expression}}
+    ;
+  #pragma omp metadirective when(device = {isa("some-unsupported-feature")} : parallel) default(single) // expected-warning {{isa trait 'some-unsupported-feature' is not known to the current target; verify the spelling or consider restricting the context selector with the 'arch' selector further}}
+    ;
+  #pragma omp metadirective when(device = {arch(nvptx)} : parallel) xyz() //expected-error {{unknown clause 'xyz' in metadirective}} 
+    ;
+#endif
 }