[flang-commits] [flang] [flang][OpenMP] Support omx/ompx extension sentinels (PR #218475)

[Krzysztof Parzyszek via flang-commits]

================
@@ -2833,7 +2849,23 @@ static constexpr llvm::omp::DirectiveSet GetAllDirectives() {
 TYPE_PARSER(construct<OpenMPMisplacedEndDirective>(
     OmpEndDirectiveParser{GetAllDirectives()}))
 
-TYPE_PARSER(startOmpLine >>
-    sourced(construct<OpenMPInvalidDirective>(
-        maybe("BEGIN"_sptok) >> !OmpDirectiveNameParser{} >> SkipTo<'\n'>{})))
+// A string following an OpenMP sentinel that is not a recognized directive.
+// When it follows an implementation-defined extension sentinel (!$omx / !$ompx)
+// the node is flagged (true) so that semantics ignores it with a warning rather
+// than reporting an error, allowing portable use of vendor extensions
+// (OpenMP 5.2, section 3.1).
+//
+// This is a fallback that is attempted before the enclosing program unit is
+// reparsed as an execution-part construct, so the standard "!$omp" branch uses
+// the strict "_id" spelling: it must not prefix-match the "!$omp" that begins
+// "!$ompx" line, otherwise a valid extension directive such as "!$ompx barrier"
+// would be misreported as an invalid "!$omp" directive instead of being handled
+// as a real construct.
+TYPE_PARSER(skipStuffBeforeStatement >>
+    ((ompxSentinel >>
+         sourced(construct<OpenMPInvalidDirective>(maybe("BEGIN"_sptok) >>
+             !OmpDirectiveNameParser{} >> SkipTo<'\n'>{} >> pure(true)))) ||
+        ("!$OMP"_id >>
+            sourced(construct<OpenMPInvalidDirective>(maybe("BEGIN"_sptok) >>
+                !OmpDirectiveNameParser{} >> SkipTo<'\n'>{} >> pure(false))))))
----------------
kparzysz wrote:

```suggestion
static constexpr auto skipUnrecognized{
    maybe("BEGIN"_sptok) >> !OmpDirectiveNameParser{} >> SkipTo<'\n'>{}};

static constexpr auto unrecognizedExtension{ompxSentinel >>
    construct<OpenMPInvalidDirective>(skipUnrecognized >> pure(true))};
static constexpr auto invalidDirective{"!$OMP"_id >>
    construct<OpenMPInvalidDirective>(skipUnrecognized >> pure(false))};

TYPE_PARSER(sourced(
    skipStuffBeforeStatement >> (unrecognizedExtension || invalidDirective)))
```


https://github.com/llvm/llvm-project/pull/218475