[flang-commits] [flang] [llvm] [flang][OpenMP]Add support for fail clause (PR #118683)

[Kiran Chandramohan via flang-commits]

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@@ -114,6 +114,11 @@ class SemanticsVisitor : public virtual BaseChecker, public virtual C... {
     context_.set_location(std::nullopt);
   }
 
+  // This is necessary to avoid "walking" into the Fail clause,
+  // which confuses the CheckAllowed into thinking there's another
+  // memoryorder, when it's actually the argument to the fail clause.
+  bool Pre(const parser::OmpFailClause &) { return false; }
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kiranchandramohan wrote:

I was asking whether this solution will prevent the ability to perform the following semantic check from the OpenMP 5.2 standard.

-> `acq_rel` and `release` cannot be specified as arguments to the `fail` clause.

If you do not want to change the parse-tree representation, an alternative solution could be to remember whether we are visiting the FailClause and only call `CheckAllowedClause` for the MemoryOrder clauses if we are not inside  the FailClause. Something like the following (only done for Release MemoryOrder clause).

```
+void OmpStructureChecker::Enter(const parser::OmpFailClause &) {
+  CheckAllowedClause(llvm::omp::Clause::OMPC_fail);
+  isFailClause = true;
+}
+
+void OmpStructureChecker::Leave(const parser::OmpFailClause &) {
+  isFailClause = false;
+}
+
+void OmpStructureChecker::Enter(const parser::OmpClause::Release &) {
+  if(!isFailClause) {
+    CheckAllowedClause(llvm::omp::Clause::OMPC_release);
+  }
+}
```

Note: The above code will also involve removing the CHECK_SIMPLE_CLAUSE entries for the Release MemoryOrder clause, adding isFailClause as a member of OmpStructureChecker, and adding the Enter and Leave signatures in OmpStructureChecker for the OmpFailClause.

https://github.com/llvm/llvm-project/pull/118683