[flang][OpenMP] Parse cancel-directive-name as clause (llvm#130146)

The cancellable construct names on CANCEL or CANCELLATION POINT
directives are actually clauses (with the same names as the
corresponding constructs).

Instead of parsing them into a custom structure, parse them as a clause,
which will make CANCEL/CANCELLATION POINT follow the same uniform scheme
as other constructs (<directive> [(<arguments>)] [clauses]).

Author: kparzysz

flang/examples/FeatureList/FeatureList.cpp

@@ -456,8 +456,6 @@ struct NodeVisitor {
   READ_FEATURE(OmpBeginLoopDirective)
   READ_FEATURE(OmpBeginSectionsDirective)
   READ_FEATURE(OmpBlockDirective)
-  READ_FEATURE(OmpCancelType)
-  READ_FEATURE(OmpCancelType::Type)
   READ_FEATURE(OmpClause)
   READ_FEATURE(OmpClauseList)
   READ_FEATURE(OmpCriticalDirective)
@@ -551,7 +549,6 @@ struct NodeVisitor {
   READ_FEATURE(OpenMPAtomicConstruct)
   READ_FEATURE(OpenMPBlockConstruct)
   READ_FEATURE(OpenMPCancelConstruct)
-  READ_FEATURE(OpenMPCancelConstruct::If)
   READ_FEATURE(OpenMPCancellationPointConstruct)
   READ_FEATURE(OpenMPConstruct)
   READ_FEATURE(OpenMPCriticalConstruct)

flang/examples/FlangOmpReport/FlangOmpReportVisitor.cpp

@@ -265,9 +265,6 @@ void OpenMPCounterVisitor::Post(const OmpDirectiveNameModifier &c) {
   clauseDetails +=
       "name_modifier=" + llvm::omp::getOpenMPDirectiveName(c.v).str() + ";";
 }
-void OpenMPCounterVisitor::Post(const OmpCancelType::Type &c) {
-  clauseDetails += "type=" + std::string{OmpCancelType::EnumToString(c)} + ";";
-}
 void OpenMPCounterVisitor::Post(const OmpClause &c) {
   PostClauseCommon(normalize_clause_name(c.source.ToString()));
   clauseDetails.clear();

flang/examples/FlangOmpReport/FlangOmpReportVisitor.h

@@ -78,7 +78,6 @@ struct OpenMPCounterVisitor {
   void Post(const OmpMapType::Value &c);
   void Post(const OmpScheduleClause::Kind &c);
   void Post(const OmpDirectiveNameModifier &c);
-  void Post(const OmpCancelType::Type &c);
   void Post(const OmpClause &c);
   void PostClauseCommon(const ClauseInfo &ci);
 

flang/include/flang/Parser/dump-parse-tree.h

@@ -540,12 +540,11 @@ class ParseTreeDumper {
         "llvm::omp::Directive = ", llvm::omp::getOpenMPDirectiveName(x))
         .str();
   }
-  NODE(parser, OmpCancelType)
-  NODE_ENUM(OmpCancelType, Type)
   NODE(parser, OmpClause)
 #define GEN_FLANG_DUMP_PARSE_TREE_CLAUSES
 #include "llvm/Frontend/OpenMP/OMP.inc"
   NODE(parser, OmpClauseList)
+  NODE(parser, OmpCancellationConstructTypeClause)
   NODE(parser, OmpContainsClause)
   NODE(parser, OmpCriticalDirective)
   NODE(parser, OmpErrorDirective)
@@ -688,7 +687,6 @@ class ParseTreeDumper {
   NODE(parser, OpenMPAtomicConstruct)
   NODE(parser, OpenMPBlockConstruct)
   NODE(parser, OpenMPCancelConstruct)
-  NODE(OpenMPCancelConstruct, If)
   NODE(parser, OpenMPCancellationPointConstruct)
   NODE(parser, OpenMPConstruct)
   NODE(parser, OpenMPCriticalConstruct)

flang/include/flang/Parser/parse-tree.h

@@ -4047,6 +4047,12 @@ struct OmpBindClause {
   WRAPPER_CLASS_BOILERPLATE(OmpBindClause, Binding);
 };
 
+// Artificial clause to represent a cancellable construct.
+struct OmpCancellationConstructTypeClause {
+  TUPLE_CLASS_BOILERPLATE(OmpCancellationConstructTypeClause);
+  std::tuple<OmpDirectiveName, std::optional<ScalarLogicalExpr>> t;
+};
+
 // Ref: [5.2:214]
 //
 // contains-clause ->
@@ -4859,26 +4865,18 @@ struct OmpLoopDirective {
   CharBlock source;
 };
 
-// 2.14.1 construct-type-clause -> PARALLEL | SECTIONS | DO | TASKGROUP
-struct OmpCancelType {
-  ENUM_CLASS(Type, Parallel, Sections, Do, Taskgroup)
-  WRAPPER_CLASS_BOILERPLATE(OmpCancelType, Type);
-  CharBlock source;
-};
-
 // 2.14.2 cancellation-point -> CANCELLATION POINT construct-type-clause
 struct OpenMPCancellationPointConstruct {
   TUPLE_CLASS_BOILERPLATE(OpenMPCancellationPointConstruct);
   CharBlock source;
-  std::tuple<Verbatim, OmpCancelType> t;
+  std::tuple<Verbatim, OmpClauseList> t;
 };
 
 // 2.14.1 cancel -> CANCEL construct-type-clause [ [,] if-clause]
 struct OpenMPCancelConstruct {
   TUPLE_CLASS_BOILERPLATE(OpenMPCancelConstruct);
-  WRAPPER_CLASS(If, ScalarLogicalExpr);
   CharBlock source;
-  std::tuple<Verbatim, OmpCancelType, std::optional<If>> t;
+  std::tuple<Verbatim, OmpClauseList> t;
 };
 
 // Ref: [5.0:254-255], [5.1:287-288], [5.2:322-323]

flang/lib/Parser/openmp-parsers.cpp

@@ -50,6 +50,20 @@ template <typename Parser> constexpr auto unwrap(const Parser &p) {
   return UnwrapParser<Parser>(p);
 }
 
+// Check (without advancing the parsing location) if the next thing in the
+// input would be accepted by the "checked" parser, and if so, run the "parser"
+// parser.
+// The intended use is with the "checker" parser being some token, followed
+// by a more complex parser that consumes the token plus more things, e.g.
+// "PARALLEL"_id >= Parser<OmpDirectiveSpecification>{}.
+//
+// The >= has a higher precedence than ||, so it can be used just like >>
+// in an alternatives parser without parentheses.
+template <typename PA, typename PB>
+constexpr auto operator>=(PA checker, PB parser) {
+  return lookAhead(checker) >> parser;
+}
+
 /// Parse OpenMP directive name (this includes compound directives).
 struct OmpDirectiveNameParser {
   using resultType = OmpDirectiveName;
@@ -575,6 +589,9 @@ TYPE_PARSER(construct<OmpAffinityClause>(
     maybe(nonemptyList(Parser<OmpAffinityClause::Modifier>{}) / ":"),
     Parser<OmpObjectList>{}))
 
+TYPE_PARSER(construct<OmpCancellationConstructTypeClause>(
+    OmpDirectiveNameParser{}, maybe(parenthesized(scalarLogicalExpr))))
+
 // 2.15.3.1 DEFAULT (PRIVATE | FIRSTPRIVATE | SHARED | NONE)
 TYPE_PARSER(construct<OmpDefaultClause::DataSharingAttribute>(
     "PRIVATE" >> pure(OmpDefaultClause::DataSharingAttribute::Private) ||
@@ -804,8 +821,9 @@ TYPE_PARSER(construct<OmpAbsentClause>(many(maybe(","_tok) >>
 TYPE_PARSER(construct<OmpContainsClause>(many(maybe(","_tok) >>
     construct<llvm::omp::Directive>(unwrap(OmpDirectiveNameParser{})))))
 
-TYPE_PARSER("ABSENT" >> construct<OmpClause>(construct<OmpClause::Absent>(
-                            parenthesized(Parser<OmpAbsentClause>{}))) ||
+TYPE_PARSER( //
+    "ABSENT" >> construct<OmpClause>(construct<OmpClause::Absent>(
+                    parenthesized(Parser<OmpAbsentClause>{}))) ||
     "ACQUIRE" >> construct<OmpClause>(construct<OmpClause::Acquire>()) ||
     "ACQ_REL" >> construct<OmpClause>(construct<OmpClause::AcqRel>()) ||
     "AFFINITY" >> construct<OmpClause>(construct<OmpClause::Affinity>(
@@ -982,7 +1000,20 @@ TYPE_PARSER("ABSENT" >> construct<OmpClause>(construct<OmpClause::Absent>(
     "UPDATE" >> construct<OmpClause>(construct<OmpClause::Update>(
                     parenthesized(Parser<OmpUpdateClause>{}))) ||
     "WHEN" >> construct<OmpClause>(construct<OmpClause::When>(
-                  parenthesized(Parser<OmpWhenClause>{}))))
+                  parenthesized(Parser<OmpWhenClause>{}))) ||
+    // Cancellable constructs
+    "DO"_id >=
+        construct<OmpClause>(construct<OmpClause::CancellationConstructType>(
+            Parser<OmpCancellationConstructTypeClause>{})) ||
+    "PARALLEL"_id >=
+        construct<OmpClause>(construct<OmpClause::CancellationConstructType>(
+            Parser<OmpCancellationConstructTypeClause>{})) ||
+    "SECTIONS"_id >=
+        construct<OmpClause>(construct<OmpClause::CancellationConstructType>(
+            Parser<OmpCancellationConstructTypeClause>{})) ||
+    "TASKGROUP"_id >=
+        construct<OmpClause>(construct<OmpClause::CancellationConstructType>(
+            Parser<OmpCancellationConstructTypeClause>{})))
 
 // [Clause, [Clause], ...]
 TYPE_PARSER(sourced(construct<OmpClauseList>(
@@ -1096,20 +1127,13 @@ TYPE_PARSER(sourced(construct<OmpLoopDirective>(first(
 TYPE_PARSER(sourced(construct<OmpBeginLoopDirective>(
     sourced(Parser<OmpLoopDirective>{}), Parser<OmpClauseList>{})))
 
-// 2.14.1 construct-type-clause -> PARALLEL | SECTIONS | DO | TASKGROUP
-TYPE_PARSER(sourced(construct<OmpCancelType>(
-    first("PARALLEL" >> pure(OmpCancelType::Type::Parallel),
-        "SECTIONS" >> pure(OmpCancelType::Type::Sections),
-        "DO" >> pure(OmpCancelType::Type::Do),
-        "TASKGROUP" >> pure(OmpCancelType::Type::Taskgroup)))))
-
 // 2.14.2 Cancellation Point construct
 TYPE_PARSER(sourced(construct<OpenMPCancellationPointConstruct>(
-    verbatim("CANCELLATION POINT"_tok), Parser<OmpCancelType>{})))
+    verbatim("CANCELLATION POINT"_tok), Parser<OmpClauseList>{})))
 
 // 2.14.1 Cancel construct
-TYPE_PARSER(sourced(construct<OpenMPCancelConstruct>(verbatim("CANCEL"_tok),
-    Parser<OmpCancelType>{}, maybe("IF" >> parenthesized(scalarLogicalExpr)))))
+TYPE_PARSER(sourced(construct<OpenMPCancelConstruct>(
+    verbatim("CANCEL"_tok), Parser<OmpClauseList>{})))
 
 TYPE_PARSER(sourced(construct<OmpFailClause>(
     parenthesized(indirect(Parser<OmpMemoryOrderClause>{})))))
@@ -1193,9 +1217,10 @@ TYPE_PARSER(
     sourced(construct<OpenMPStandaloneConstruct>(
                 Parser<OpenMPSimpleStandaloneConstruct>{}) ||
         construct<OpenMPStandaloneConstruct>(Parser<OpenMPFlushConstruct>{}) ||
-        construct<OpenMPStandaloneConstruct>(Parser<OpenMPCancelConstruct>{}) ||
+        // Try CANCELLATION POINT before CANCEL.
         construct<OpenMPStandaloneConstruct>(
             Parser<OpenMPCancellationPointConstruct>{}) ||
+        construct<OpenMPStandaloneConstruct>(Parser<OpenMPCancelConstruct>{}) ||
         construct<OpenMPStandaloneConstruct>(
             Parser<OmpMetadirectiveDirective>{}) ||
         construct<OpenMPStandaloneConstruct>(Parser<OpenMPDepobjConstruct>{})) /

flang/lib/Parser/unparse.cpp

@@ -2851,15 +2851,14 @@ class UnparseVisitor {
   void Unparse(const OpenMPCancellationPointConstruct &x) {
     BeginOpenMP();
     Word("!$OMP CANCELLATION POINT ");
-    Walk(std::get<OmpCancelType>(x.t));
+    Walk(std::get<OmpClauseList>(x.t));
     Put("\n");
     EndOpenMP();
   }
   void Unparse(const OpenMPCancelConstruct &x) {
     BeginOpenMP();
     Word("!$OMP CANCEL ");
-    Walk(std::get<OmpCancelType>(x.t));
-    Walk(std::get<std::optional<OpenMPCancelConstruct::If>>(x.t));
+    Walk(std::get<OmpClauseList>(x.t));
     Put("\n");
     EndOpenMP();
   }
@@ -3034,7 +3033,6 @@ class UnparseVisitor {
       OmpDeviceTypeClause, DeviceTypeDescription) // OMP device_type
   WALK_NESTED_ENUM(OmpReductionModifier, Value) // OMP reduction-modifier
   WALK_NESTED_ENUM(OmpExpectation, Value) // OMP motion-expectation
-  WALK_NESTED_ENUM(OmpCancelType, Type) // OMP cancel-type
   WALK_NESTED_ENUM(OmpOrderClause, Ordering) // OMP ordering
   WALK_NESTED_ENUM(OmpOrderModifier, Value) // OMP order-modifier
   WALK_NESTED_ENUM(OmpPrescriptiveness, Value) // OMP prescriptiveness